HANDBOOK ON EARTHQUAKES HAZARDS AND DISASTERS Contents 1. Introduction 2. Causes of earthquakes Interior Structure of the earth Plate tectonics movements 3. General Characteristics Earthquake Vibrations Depth of earthquakes Measurement Scales Frequency of occurrence of Earthquakes Earthquake hazards Fault Displacement and ground shaking Landslides and avalanches Ground failure Liquefaction Tsunami 4. Typical Effects Physical damage Casualties Public Health Water Supply Food supplies Transport Networks Electricity and Communication 5. Predictability 6. Indian Earthquakes Great earthquakes in India Earthquake risk in Himalayas Datasheet of Earthquakes in India Zones of earthquakes of India Case Studies 7. Factors contributing to vulnerability 8. Preparedness Measures Community Preparedness Public Education Planning 9. Typical Disaster assistance needed Damage and needs assessment survey 10. Earthquake response plan 11. Possible risk reduction measures Resources and references
1. Introduction Earthquakes are one of the most destructive of natural hazards. Earthquake occurs due to sudden transient motion of the ground as a result of release of elastic energy in a matter of few seconds. The impact of the event is most traumatic because it affects large area, occurs all on a sudden and unpredictable. They can cause large scale loss of life and property and disrupts essential services such as water supply, sewerage systems, communication and power, transport etc. They not only destroy villages, towns and cities but the aftermath leads to destabilize the economic and social structure of the nation. 1
2. Causes of Earthquakes An Earthquake is a series of underground shock waves and movements on the earth’s surface caused by natural processes within the earth’s crust. To learn more on the occurrence of this event lets know more about the interior of the earth. Interior Structure of the Earth By analyzing the seismograms from many earthquakes, scientists have discovered that three main levels or shells exist shells exist within the Earth (see Figure 1): CRUST Fig 1: Internal Structure of Earth The Earth's outermost surface is called the crust. The crust is relatively light and brittle. Most earthquakes occur within the crust. Scientists believe that below the lithosphere is a relatively narrow, mobile zone in the mantle called the asthenosphere (from asthenosphere (from asthenes, Greek for weak). Mantle The region just below the crust and extending all the way down to the Earth's core is called the mantle. The mantle, a dense, hot layer of semisolid rock approximately 2,900 km thick. The part of the mantle near the crust, about 50-100 Source: http://pubs.usgs.gov/publications//text/inside.html km Figure 2: Local Convective Currents down, is especially soft and plastic, and is called the in the Mantle asthenosphere. The rigid lithosphere is thought to "float" or move about on the slowly flowing asthenosphere(Figure 2). 2). CORE Beneath the mantle is the Earth's core. The Earth's core consists of a fluid outer core and a solid inner core. core. Convection currents develop in the viscous Mantle, because of prevailing high temperature and pressure gradients between the Crust and the Core (Figure 2). The energy for the above circulations is derived from the heat produced from the incessant 1
Source: Earthquake Tip 1, Learning Earthquake Design and Construction, IITK- BMPTC.
decay of radioactive elements in the rocks throughout the Earth’s interior. These convection currents result in a circulation of circulation of the earth’s mass; hot molten lava comes out and the cold rock mass goes into the Earth. The mass absorbed eventually melts under high temperature and pressure and becomes a part of the Mantle, only to come out again from another location, someday. Many such local circulations are taking place at different regions underneath the Earth’s surface, leading to different portions of the Earth undergoing different directions of movements along the surface. Plate Tectonics Movements The convective flows of Mantle material cause the Crust and some portion of the Mantle, to slide on the hot molten outer core. This sliding of Earth’s mass takes place in pieces called Tectonic Plates . The surface of the Earth consists of seven major tectonic plates (North American Plate, South America Plate, Antarctic Plate, African Plate, Australian Plate, Eurasian Plate and Pacific Plate) and many smaller ones (Figure 3). These plates move in different directions and at different speeds from those of the neighbouring ones. Sometimes, the plate in Source: http://pubs.usgs.gov/publications//text/slabs.html the front is slower; then, the plate behind it comes and collides (and mountains are mountains are formed). On the other hand, sometimes two plates move away from one another (and rifts are rifts are created). In another case, two plates move side-by-side, along the same direction or in opposite directions. These three types of inter-plate interactions are the convergent , divergent and transform boundaries transform boundaries (Figure 4), respectively. Figure 4: Types of Inter-plate Boundaries Divergent - where new crust is generated as the plates pull away from each other.
Convergent - where crust is destroyed as one plate dives under another.
Transformational - where crust is neither produced nor destroyed as the plates slide horizontally past each other.
The convergent boundary has a peculiarity (like at the Himalayas) that sometimes neither of the colliding plates wants to sink. The relative movement of Elastic Strain Build-Up and Brittle Rupture these plate boundaries varies across the Earth; on an average, it is of the order of a couple to tens of centimeters per year . Rocks are made of elastic material, and so elastic strain energy is stored in them during the deformations that occur due to the gigantic tectonic plate actions that occur in the Earth. But, the material contained in rocks is also very brittle. Thus, when the rocks along a weak region in the Earth’s Crust reach their strength, a sudden movement takes place there Fig. 5); opposite sides of the fault (a crack in the rocks where movement has taken place) suddenly slip release the large elastic strain energy stored in the interface rocks. For example, the energy released during the 2001 Bhuj (India) earthquake is about 400 times (or more) that released by the 1945 Atom Bomb dropped on Hiroshima!!
Elastic Rebound Theory The sudden slip at the fault causes the earthquake ….a ….a violent shaking of the Earth when large elastic strain energy released spreads out through seismic waves that travel through the body and along the surface of the Earth. And, after the earthquake is over, the process of strain build-up at this modified interface between the rocks starts all over again (Figure 6). Earth scientists know this as the Elastic Rebound Theory . The material points at the fault over which slip occurs usually constitute an oblong threedimensional volume, with its long dimension often running into tens of kilometers.
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3. General Characteristics i. Earthquake Vibrations •
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Earthquake vibrations occur in a variety of frequencies and velocities. The actual rupture process may last from a few seconds to as long as one minute for a major earthquake. Seismic waves generated by the rupture can last from several seconds to a few minutes. Ground shaking is caused by body waves and surface waves. Body waves (P waves (P and S waves) penetrate the body of the earth, vibrating fast. P waves traveling at about 6 km per hour, provide the initial jolt and cause buildings to vibrate in an up and down motion. S waves, traveling about 4 km per second in a movement similar to a rope snapped like a whip, cause a typically sharper jolt that vibrates structures from side to side and typically causes even greater damage. damage. S waves are usually the most destructive. Surface waves vibrate waves vibrate the ground horizontally and vertically. These long-period waves cause swaying of tall buildings and slight wave motion in bodies of water even at great distances from the epicenter.
ii. Depth of Earthquakes Earthquake focus depth is an important factor in shaping the characteristics of the waves and the damage they inflict. The focal depth can be deep (from 300 to 700 km), intermediate (60 to 300 km) or shallow (less than 60 km). Deep focus earthquakes are rarely destructive because the wave amplitude is greatly attenuated by the time it reaches the surface. Shallow focus earthquakes are more common and are extremely damaging because of their close proximity to the surface. Figure 8 shows the seismicity in India in terms of depth of occurrence. Note here that many of the earthquakes shown fall in the region of shallow focus which can be more damaging during an event.
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iii. Measurement Scales Earthquakes can be described by use of two distinctly different scales of measurement demonstrating magnitude and intensity. Earthquake magnitude or amount of energy released is determined by use of a seismograph, and instrument that continuously records ground vibrations. A scale developed by a seismologist named Charles Richter mathematically adjusts the readings for the distance of the instrument from the epicenter. The Richter scale is logarithmic. An increase of one magnitude signifies a 10-fold increase in ground motion or roughly an increase of 30 times the energy (see Table 2). Thus, an earthquake with a magnitude of 7.5 releases 30 times more energy than one with a 6.5 magnitude, and approximately 900 times that of a 5.5 magnitude earthquake. A quake of magnitude 3 is the smallest normally felt by humans. The largest earthquakes that have been recorded under this system are 9.25 (Alaska, 1969) and 9.5 (Chile, 1960).
Table 2: Richter magnitude and its effects Richter Magnitude Earthquake Effects Less than 3.5 3.4-5.4 Under 6.0 6.1-6.9 7.0-7.9 8 or greater
Generally not felt, but recorded. Often felt, but rarely causes damage. At most slight damage to well-designed buildings. Can cause major damage to poorly constructed buildings over small regions. Can be destructive in areas up to about 100 kilometers across where people live. Major earthquake. Can cause serious damage over larger areas. Great earthquake. Can cause serious damage in areas several hundred kilometers across.
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A second type of scale, the earthquake intensity scale, measures the effects of an earthquake where it occurs. To elaborate this distinction, consider the analogy of an electric bulb (Figure 9). The illumination at a location near a 100-Watt bulb is higher than that farther away from it. While the bulb releases 100 Watts of energy, the intensity of light (or illumination, measured in lumens) at a location depends on on the wattage of the bulb and its distance from the bulb. Here, the size of the bulb (100-Watt) is like the magnitude of an earthquake, and the illumination at a location like the intensity of shaking at that location.The most widely used scale of this type was developed in 1902 by Mercalli, an Italian seismologist. The scale was extended and modified to suit modern times. Called the Modified Mercalli Scale, it expresses the intensity of earthquake effects on people, structures and the earth’s surface in values from I to XII. A second even more explicit scale, the Medvedev-Sponheuer-Karnik (MSK) Scale is used in India. (add Annexure on MSK) The distribution of intensity at different places during an earthquake is shown graphically using isoseismals, lines joining places with equal seismic intensity (Figure 10). iv Frequency of occurrence of earthquakes The United States Geological Survey (USGS) estimates that several million earthquakes occur in the world each year
Descriptor
Magnitude
Average Annually
Great
8 and higher
1¹
Major
7 - 7.9
17 ²
Strong
6 - 6.9
134 ²
Moderate
5 - 5.9
1319 ²
Light
4 - 4.9
13,000 estimated
Minor
3 - 3.9
130,000 estimated
Very Minor
2 - 2.9
1,300,000 (estimated)
¹ Based on observations since 1900. ² Based on observations since 1990.
v. Earthquake Hazards The primary hazards associated with earthquakes are fault displacement and ground shaking. Secondary hazards include ground failure, liquefaction, landslides and avalanches, and tsunamis and seiches. Fault Displacement and ground shaking (ADD PHOTOGRAPHS) Fault displacement, either rapid or gradual, may damage foundations of buildings on or near the fault area, or may displace the land, creating troughs and ridges. Ground shaking causes more widespread damage, particularly to the built environment. The extent of the damage is related to the size of the earthquake, the closeness of the focus to the surface, the buffering power of the location’s rocks and soils, and the type of buildings being shaken. Secondary tremors that follow the main shock of an earthquake, called aftershocks, may cause further damage. Such tremors may recur for weeks or even years after the initial event. Landslides and avalanches Slope instability may cause landslides and snow avalanches during an earthquake. Steepness, weak soils and presence of water may contribute to vulnerability from landslides. Liquefaction of soils on slopes may lead to disastrous slides. The most abundant types of earthquake-induced landslides are rock falls and rock slides usually originating on steep slopes. Ground failure Seismic vibrations may cause settlement beneath buildings when soils consolidate or compact. Certain types of soils, such as alluvial or sandy silts are more likely to fail during an earthquake. Liquefaction Liquefaction is a type of ground failure which occurs when saturated soil loses its strength and collapses or becomes liquefied. During the 1964 earthquake in Niigata, Japan, ground beneath buildings that were earthquake resistant became liquefied, causing the buildings to lean or topple down sideways. Another type
of ground failure that may result from earthquakes is subsidence or vertically downward earth movement caused by reduction in soil water pressure Tsunami Tsunami is a Japanese word meaning “harbor wave”. Tsunamis are popularly called tidal waves but they actually have nothing to do with the tides. These waves, which often affect distant shores, originate from undersea or coastal seismic activity, landslides, and volcanic eruptions. Whatever the cause, sea water is displaced with a violent motion and swells up, ultimately surging over land with great destructive power. In 1883, the violent explosion of the famous volcano, Krakatoa in Indonesia, produced tsunamis measuring 40 meters which crashed upon Java and Sumatra. over 36,000 people lost their lives as a result of tsunami waves from Krakatoa. 4. Typical Effects Physical Damage – Damage occurs to human settlements, buildings, structures and infrastructure, especially bridges, elevated roads, railways, water towers, water treatment facilities, utility lines, pipelines, electrical generating facilities and transformer stations. Aftershocks can do much damage to already weakened structures. Significant secondary effects include fires, dam failures, and landslides, which may block waterways and also cause flooding. Damage may occur to facilities using or manufacturing dangerous materials resulting in possible chemical spills. There may be a breakdown of communications facilities. Destruction of property may have a serious impact on shelter needs, economic production and living standards of local populations. Depending on the vulnerability of the affected community, large numbers of people may be homeless in the aftermath of an earthquake. Casualties – Casualties – The casualty rate is often high, especially when earthquakes occur in areas: a) Of high population density, particularly when streets between buildings are narrow and buildings themselves are not earthquake resistant, and/ the ground is sloping and unstable; b) Where adobe or dry-stone construction is common with heavy upper floors and roofs. Casualty rates may be high when quakes occur at night because the preliminary tremors are not felt in sleep and people are not tuned in to media to receive warnings. In daytime, people are particularly vulnerable if in unsafe structures such as schools and offices and casualties may be very high. Casualties generally decrease with distance from the epicenter. As a very rough rule of thumb, there are three times as many injured survivors as persons killed. The proportion of dead may, however, be higher if there major landslides and other hazards, such as tsunamis. In areas where houses are of light-weight construction, especially with wood frames, casualties generally very much lower although fires may spread rapidly causing injuries and deaths. Public health health – multiple fracture injuries and number of severely and moderately injured is the most widespread problem, breakdown in sanitary conditions pose a threat and fear of epidemic due to large deaths The most widespread medical problems are fracture injuries. Other health threats may occur if: a) There is secondary flooding b) Water supplies are disrupted and contaminated water is used (although to date no documented significant outbreaks of water-borne diseases have followed an earthquake); or c) People are concentrated into high-density relief camps.
Although an earthquake is unlikely to cause any new outbreaks, endemic diseases may become virulent if control measures break down and unsanitary conditions develop. The psychological consequences of experiencing an earthquake, including trauma and depression, often last for several months. Water supply – severe problems due to failure of the water supply and distribution network and storage reservoirs • • • • • •
Severe problems are likely because: Piped (municipal) water systems may be seriously damaged or become Contaminated, especially if sewage systems have also been damaged. Reservoir dams may be broken. Open wells may be blocked by debris. Earthquakes can change levels in the water table with the possible effect of drying up wells and surface springs.
Transport network – network – severely affected due to failure of roads and bridges, turns in railway track alignment, failure of runway Electricity and Communication – all links affected. Tower collapse, transponders collapse, transformers collapse Food Supplies Food distribution and marketing systems may be disrupted. Irrigation works may be damaged. In areas where earthquakes give rise to flooding or a tsunami strikes, food stocks and standing crops may be lost. Typically, however, earthquakes do not reduce the local food supply. 4. Predictability Although some scientists claim ability to predict earthquakes, the methods are controversial. For example, the 1995 earthquake in Kobe, Japan was not predicted. Accurate and exact predictions of sudden fault displacements and the resultant earthquakes are still not possible, however mechanical observation systems make it possible to issue warnings to nearby populations immediately after detection of an earthquake. Reasonable risk assessments of potential earthquake activity can be made with confidence based upon: 1. Knowledge of seismic zones zones or areas most at risk, gained gained through study of historical incidence and and plate tectonics. 2. Monitoring of seismic activity by use of seismographs and other instruments. 3. Use of community-based community-based scientifically sound observations such as as elevation and turbidity of water in wells and recording radon gas escape into well water. (Use of animal behavior as an indicator is subject to controversy as it is often difficult to interpret.) 5. Indian Earthquakes The Indian sub-continent is highly prone to multiple natural disasters including earthquakes, which is one of the most destructive natural hazards with the potentiality of inflicting huge loss to lives and property. Earthquakes pose a real threat to India with 59% of its geographical area vulnerable to seismic disturbance of varying intensities including the capital city of the country. Almost the entire Northeast region, Northern Bihar, Himachal Pradesh, Jammu & Kashmir and some parts of Kutch are in seismic zone V, while the entire Gangetic plain and some parts of Rajasthan are in seismic zone IV.
India has experienced some of the most intense earthquakes in the world and is also one of the most earthquake prone countries in the world. Data from 1897-1991 shows that an average of three earthquakes of magnitude 6.0 or more, occur in India every year and the high degree of seismic vulnerability of the country poses a real threat to the millions of its people. In the span of last 15 years, India has experienced six earthquakes of moderate intensity. Although moderate in intensity, these earthquakes caused considerably high degree of losses to human life and property, which highlights the vulnerability of the population and infrastructure to earthquakes and the inadequacy of preparedness measures in the country. The Lattur earthquake of 1993 and the Bhuj earthquake of 2001 which caused extensive damage to lives and properties further highlighted the need to focus upon long-term seismic mitigation and preparedness in order to reduce the human and economic losses due to earthquakes. However, the September 1993 earthquake that struck Maharashtra State in Central West India that claimed nearly 12,000 lives, was not a particularly strong event, but caused such devastation because of other factors. Another earthquake also struck Central India in May 1997, but fortunately not on such a devastating scale. th The 26 January Bhuj Earthquake was the most devastating one which scaled very high in terms of loss of life and property. 13,805 human lives were lost, and over 1,67,000 persons were injured in the earthquake. This earthquake is the first major earthquake to hit an urban area of India in the last 50 yrs. Great Earthquakes in India Strong and damaging earthquakes have been felt in all parts of the Indian Sub-continent. The most seismically active areas are those in the northern regions of the sub-continent and in the Andaman and Nicobar Islands. This is where the Indian plate is thrusting (diving below) under the Eurasian plate. In the Andaman & Nicobar Islands, the Indian plate subducts (dives) beneath the Burmese. Micro-plate. The deadliest earthquake in earthquake in Indian history so far has been the M7.8 Kangra earthquake in Himachal Pradesh in 1905, which left 19,700 people dead. If was often believed that Kolkata was destroyed in an earthquake in 1737, that left 3,00,000 dead. The largest earthquake recorded earthquake recorded was an earthquake in Arunachal Pradesh in 1950. It had a magnitude of 8.6 (Mw) and was the 6th largest earthquake in the world, in the 20th century.The century.The most widely felt earthquake in earthquake in India to date, has been the M7.6 Bhuj earthquake in 2001. Shaking was experienced as far away as Chennai in the south, Shillong in the east, Quetta in the west and Kashmir in the north. After the Kangra earthquake, this is the next earthquake to have caused heavy casualties. More than 13,000 people were killed in Gujarat. The peninsula area was generally though to be "seismically safe". But recent large earthquakes in this area, have proven this statement wrong. Apart from the M 6.2 Khilari (1993) and M6.6 Koyna (1967) earthquakes, several damaging shocks have hit this region, in historical and ancient times. Earthquake Risk in the Himalayas Earthquakes are a great threat to environmental stability and life in the Himalayan region as almost the entire region is prone to high seismic activity. The region has been hit by earthquakes of varying intensities in the past and similar threats remain imminent. The Himalayas were formed by a head on collision of the Indian and Eurasian plates, and the Indian plate continues to push the Asian plate northward at the rate of about 2 cm per year. This means that in every 100 years India moves 200 cm north against the Asian plate, and this colliding force builds up pressure continually for several years and is released in the form of earthquakes. Four great earthquakes of Himalaya i.e., Assam earthquake of 1897, Kangra earthquake of 1905, Nepal-Bihar earthquake of 1934 and Assam earthquake of 1950 rocked the Himalayan Kingdom of Nepal whose
magnitude exceeds 8.0 Richter scale. The earthquake of 1833 with magnitude 7.8 occurring at a distance of 50kms NE of Kathmandu also affected the Kathmandu Valley. In the last few decades, the major amongst them are the Kinnaur earthquake of 1975, Dharchula earthquake of 1980 and the Uttarkashi earthquake of 1991, which resulted in tremendous loss of life and property. Himalayan Seismicity Plate tectonics studies reveal that the Himalayan mountain ranges were formed when Indo-Australian plate collided with the Eurasian plate. The Indian subcontinent, once part of the supercontinent called Gondwanaland, which consisted also of present-day Africa and Antartica, broke away about 100 million years ago and crawled northwards across the Tethys Sea before ramming into Asia. Figure 10 shows the plate tectonics of the Hmalayas. Figure 10: The Himalayan Plate Tectonics Around 45ma, during the Eocene, India collided with Eurasia; this was the end result of India's northward migration caused by the subduction of the Tethyan Ocean beneath the Eurasian Plate. The Indian plate slid under the Asian landmass. Its upper layers peeled and thrust upward, forming the Himalayan ranges. Giant cracks (fault zones) formed along its northern perimeter. Since then India has penetrated some 2000km into Asia leading to the creation of the Himalayan mountain range. Recent GPS measurements put the present convergence rate between India and Asia at 58 ± 4mm.yr-1 [Bilham et al., 1997], roughly a third of this motion (17.52 ± 2mm.yr-1) is accommodated by the Himalayan thrust system meaning that the Kingdom of Nepal is shortening by about 2cm.yr-1. The seismic zoning map of India shows that the entire Himalayan region lies in Zone IV and V, which correspond to MMI of VIII and >IX respectively. Seismic studies show that great earthquakes (M>8) tend to recur in cycles of 200 – 300 years along the length of the Himalayas.
Figure11: Himalayan uplift
Datasheet of Earthquakes in India (1819-2001) A number of significant earthquakes occurred in and around India over the past century some of these occurred in populated and urbanized areas and hence caused great damage. Many went unnoticed, as they occurred deep under the Earth’s surface or in relatively un-inhabited places. Some of the damaging and recent earthquakes are listed in Table 3. Most earthquakes occur along the Himalayan plate boundary (these are inter-plate earthquakes), but a number of earthquakes have also occurred in the peninsular region (these are intra-plate earthquakes). Four Great earthquakes (M>8) occurred in a span of 53 years from 1897 to 1950; the January 2001 Bhuj earthquake (M7.7) is almost as large. Each of these caused disasters, but also allowed us to learn about earthquakes and to advance earthquake engineering. For instance, 1819 Cutch Earthquake produced an unprecedented ~3m high uplift of the ground over 100km (called Allah Bund). The 1897 Assam Earthquake caused severe damage up to 500km radial distances; the type of damage sustained led to improvements in the intensity scale from I-X to I-XII. Extensive liquefaction of the ground took place over a length of 300km (called the Slump Belt) during 1934 Bihar-Nepal earthquake in which many buildings and structures went afloat.
Figure: Plot of Earthquakes (M>=5.0) from IMD catalogue for the period from 1800 to Sept, 2001.
Total Events: 3383 Magnitudes
M=5 M=6 M=7 M=8
Table 3: Earthquakes in India with Magnitude >6 (1819-2001)
DATE
EPICENTRE Lat(Deg N)
Long( Deg E )
1819 JUN 16
23.6
68.6
1869 JAN 10
25
93
1885 MAY 30
34.1
74.6
1897 JUN 12
26
91
1905 APR 04
32.3
1918 JUL 08
LOCATION
MAGNITUDE M >6
KUTCH,GUJARAT
8.0
NEAR CACHAR, ASSAM
7.5
SOPOR, J&K
7.0
SHILLONGPLATEAU
8.7
76.3
KANGRA, H.P
8.0
24.5
91.0
SRIMANGAL, ASSAM
7.6
1930 JUL 02
25.8
90.2
DHUBRI, ASSAM
7.1
1934JAN 15
26.6
86.8
BIHAR-NEPALBORDER
8.3
1941 JUN 26
12.4
92.5
ANDAMAN ISLANDS
8.1
1943 OCT 23
26.8
94.0
ASSAM
7.2
1950 AUG 15
28.5
96.7
ARUNACHAL PRADESH-CHINA BORDER
8.5
1956 JUL 21
23.3
70.0
ANJAR, GUJARAT
7.0
1967 DEC 10
17.37
73.75
KOYNA, MAHARASHTRA
6.5
1975 JAN 19
32.38
78.49
KINNAUR, HP
6.2
1988 AUG 06
25.13
95.15
MANIPUR-MYANMAR BORDER
6.6
1988 AUG 21
26.72
86.63
BIHAR-NEPAL BORDER
6.4
1991 OCT 20
30.75
78.86
UTTARKASHI, UP HILLS
6.6
1993 SEP 30
18.07
76.62
LATUR-OSMANABAD, MAHARASHTRA
6.3
1997 MAY 22
23.08
80.06
JABALPUR,MP
6.0
1999 MAR 29
30.41
79.42
CHAMOLI DIST, UP
6.8
2001 JAN 26
23.40
70.28
BHUJ , GUJARAT
6.9
Earthquake Zones in India The varying geology at different locations in the country implies that the likelihood of damaging earthquakes taking place at different locations is different. Thus, a seismic zone map is required so that buildings and other structures located in different regions can be designed to withstand different level of ground shaking. The current zone map divides India into four zones – II, III, IV and V. Parts of Himalayan boundary in the north and northeast, and the Kachchh area in the west are classified as zone V ( See figure 13 and Table 4) . Figure 12: History of Seismic Zone Map of India: 1962, 1966, 1970
Figure 13: Recent Map indicating Earthquakes Zones in India (IS 1893 – 2002)
Zone
Magnitude
Zone V
Very High Risk Quakes of Magnitude 8 and greater
Zone IV
High Risk Quakes upto Magnitude 7.9
Zone III
Moderate Risk Quakes upto Magnitude 6.9
Zone II
Seismic Disturbances upto Magnitude 4.9
The seismic zone maps are revised from time to time as more understanding is gained on the geology, the seismotectonics and the seismic activity in the country (see Figure 12). For instance, the Koyna earthquake of
1967 occurred in an area classified in zone I as per map of 1966. The 1970 version of code upgraded the area around Koyna to zone IV. The Killari (Latur) earthquake of 1993 occurred in zone I (now in Zone III). The new zone map places this area in zone III. The new zone map will now have only four seismic zones – II, III, IV and V. The areas falling in seismic zone I in the current map are merged with those of seismic zone II. Also, the seismic zone map in the peninsular region is being modified. Madras will come under seismic zone III as against zone II currently. The national Seismic Zone Map presents a large scale view of the seismic zones in the country. Local variations in soil type and geology cannot be represented at that scale. Therefore, for important projects, such as a major dam or a nuclear power plant, the seismic hazard is evaluated specifically for that site. Also, for the purposes of urban planning, metropolitan areas are microzoned. Seismic microzonation accounts for local variations in geology, local soil profile, etc. Table 4: Region falling in various zones of the country Zone Zone V
Zone IV
Zone III
Zone II
Damage risk and Intensity (Earthquake Very high damage risk zone areas may expect intensity maximum of MSK IX or more ) (Earthquake High damage risk zone areas may expect intensity maximum of MSK VIII ) (Earthquake Moderate damage risk zone areas may expect intensity maximum of MSK VII ) (Earthquake Low damage risk zone areas may experience intensity MSK VI )
Region The entire North-east, including all the seven sister states, the Kutch district, parts of Himachal and Jammu & Kashmir, and the Andaman and Nicobar islands. These areas may experience
Parts of the Northern belt starting from Jammu and Kashmir to Himachal Pradesh. Also including Delhi and parts of Haryana. The Koyna region of Maharashtra is also in this zone.
A large part of the country stretching from the North including some parts of Rajasthan to the South through the Konkan coast, and also the Eastern parts of the country.
These two zones are contiguous, covering parts of Karnataka, Andhra Pradesh, Orissa, Madhya Pradesh, and Rajasthan, known as low risk earthquake zones.
Case Study: Gujarat Earthquake 2001 Bhuj Earthquake: Preliminary Report from IITKanpur A Powerful Earthquake of magnitude 6.9 on Richter-Scale rocked the Western Indian State of Gujarat on the th 26 of January, 2001. It caused extensive damage to life & property. This earthquake was so devastating in its scale and suffering that the likes of it had not been experienced in past 50 years. Leaving thousands seriously injured, bruised and handicapped; both physically, psychologically and economically. The epicenter of the quake was located located at 23.6 north Latitude and 69.8 east Longitude, Longitude, about 20 km Northeast of Bhuj Town of Town of the Kutch district in Western Gujarat. At a depth of only 23 kms below surface this quake generated intense shaking which was felt in 70% region of India and far beyond in neighbouring
Pakistan and Nepal too. This was followed by intense after shocks that became a continued source of anxiety for the populace. The Seismicity of the affected Area of Kutch is a known fact with a high incidence of earthquakes in recent times and in historical past. It falls in Seismic Zone V. The only such zone outside the Himalayan Seismic Belt. In last 200 years important damaging earthquakes occurred in 1819, 1844, 1845, 1856, 1869,1956 in the same vicinity as 2001 earthquake. Twenty-one of the total 25 districts of the state was affected in this quake. Around 18 towns, 182 talukas and 7904 villages in the affected districts have seen large-scale devastation. The affected areas even spread up to 300 km from the epicentre. In the Kutch District, four major urban areas – Bhuj, Anjar, Bachau and Rapar suffered near total destruction. The rural areas in the region are also very badly affected with over 450 villages almost totally destroyed. In addition, wide spread damages also occurred in Rajkot, Jamnagar, Surendranagar, Patan and Ahmedabad districts. Other Urban areas such as Ganhidham, Morvi, Rajkot and Jamnagar have also suffered damage to major structures, infrastructure and industrial facilities. Ahmedabad the capital was also severely affected. Gujarat Earthquake is very significant from the point of view of earthquake disaster mitigation in India. The problems observed in this disaster are no different from other major recent earthquakes in the world. The issues in the recovery and reconstruction phase are: the proper understanding understanding risk among different stakeholders, training and confidence building among the professionals and masons with appropriate development planning strategies. This quake has provided numerous examples of geo-technical and structural failures. The traditional wisdom of design and construction practises of engineered buildings prevalent in this country came under criticism for 2 the first time. It has triggered comprehensive understanding on what needs to be done in this regard.
A common site of destruction of the villages in the meizoseismal area.
2
High Powered Committee Report on National Disaster Management , Ministry of Agriculture, New Delhi, 2001
Rubble of collapsed buildings being cleared at Anjaar. Narrow lanes caused significant casualties and made rescue and relief very difficult. Kudos to the rescue/relief workers for their daring efforts!!
Virtually nothing could be recovered from most RC frame buildings that collapsed. Clearing of debris from collapse of numerous multistorey RC frame buildings was an even bigger challenge.
Relief distribution after the earthquake.
Temporary shelters in the town of Morbi.
Chamoli (Himalaya, India) Earthquake of 29 March 1999 The Chamoli earthquake of 29 March 1999 in northern India is yet another important event from the viewpoint of Himalayan seismotectonics and seismic resistance of non-engineered constructions. The earthquake occurred in a part of the Central Himalaya, which is highly prone to earthquakes and has been placed in the
highest seismic zone (zone V) of India. There has been a bitter controversy during the recent years regarding the seismic safety of a 260-m-high rock-fill dam under construction at Tehri, about 80 km west of the epicenter. Fortunately, there are no major cities in the meizoseismal region and the population density is the second lowest in the state. The earthquake caused death of about 100 persons and injured hundreds more. Maximum MSK intensity was up to VIII at a few locations. The quake was felt at far-off places such as Kanpur (440 km south-east from the epicenter), Shimla (220 km north-west) and Delhi (280 km south-west). Maximum death and damage occurred in the district of Chamoli where about 63 persons died and over 200 injured; about 2,595 houses collapsed and about 10,861 houses were partially damaged. In all, about 1,256 villages were affected. A few buildings at the far away mega-city of Delhi sustained non-structural damages. No instances of liquefaction were reported. Longitudinal cracks in the ground were seen in some locations in the affected area.
Figure 5: Ground 5: Ground fissure at Telecom Hill near Gopeshwar
Ground cracks at several places also developed as part of slope failure and these pose threat to the downslope settlements. Cracks were seen in asphalt roads at some locations, indicating the possibility of failure due to ground slippage. At several sites, large-scale earthquake-induced landslide/rock falls were observed (Figure 6 ). ). Those near Gopeshwar, Chamoli and Gadi continued even after a fortnight of the event. Interestingly, these rockslides are also confined to locations along MCT-I.
Figure 6: A 6: A major landslide about 1km north of Gopeshwar. It blocked the road traffic to Okhimath for a considerable period.
Figure 7: Collapse 7: Collapse of one of the wythes in a traditional house in slate wafer masonry.
Figure 8: Partial 8: Partial collapse in a random rubble stone masonry. Note that the front portion has RC beam supported on concrete block columns and roof consists of RC slab
Figure 9: Two-storey 9: Two-storey house at Pipalkoti with no damage. Ground storey in slate wafer masonry, upper storey added later in concrete block masonry. Both storeys have RC lintel band
Figure 10: Partial 10: Partial collapse in a stone masonry house at Gadi village. Lintel band, present in the front portion, does not continue in the side wall
Figure 12: Lateral 12: Lateral buckling of the deck of a suspension bridge at Bairagna Emergency Response Fortunately, the number of fatalities in the earthquake was relatively less at about 100 as compared to about 800 in the 1991 Uttarkashi earthquake. Interestingly, at the time of earthquake a popular movie was being screened by a TV channel and many people who were awake could easily escape. The area has major Hindu shrines and draws huge tourist traffic during May to October; the timing of this earthquake was fortunately during the lean tourist season. Hence, the task of search and rescue operations was easier and was carried out by the local people. Army and paramilitary personnel were also called-in to help in relief operations the very next day. Some cash compensation, food rations, and cloth tents were provided by the state government. By March the winter is over, and hence, cloth tents were sufficient for temporary shelters. Food and other supplies had to be air-dropped to numerous villages which were normally inaccessible by motorable roads or cut-off due to landslides. Due to poor accessibility, relief operations were quite challenging and caused dissatisfaction in remote villages which could not be attended to on time. The headquarters for Chamoli district is at Gopeshwar, 10 km by road from Chamoli. Since Gopeshwar did not experience major damages, the entire administrative machinery could function effectively. However, frequent visits by senior politicians and administrators from the state and central governments may have significantly diverted attention of the district officials. Damage assessment for individual houses was initiated by the revenue officials immediately after the earthquake. This was also a difficult task due to the inaccessibility of many villages leading to some complaints about the fairness in damage assessment. Significant aftershock activity, which included a few events of M >5, created a lot of fear amongst the people and they hesitated to sleep indoors even when their dwellings had little or no damage. Speculations about an impending large earthquake added to the fear and panic. Massive forest fires, which are common during this time of the year, drove some wild animals towards the villages adding to the insecurity. Impending monsoons in the next two months remained a major concern; slope failures and additional damage to partially damaged houses were feared.
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Figure 26 Shake 26 Shake Map for 29 March 1999, Chamoli Earthquake The earthquake occurred on March 29th at 12:35 am (local time) near the town of Chamoli in the state of Uttar Pradesh in northern India (Figure 1). The earthquake magnitude was calculated as mb=6.3, MS=6.6 by USGS, and as mb=6.8, MS=6.5 by the India Meteorological Department (IMD). The preliminary locations of the epicenter by the different agencies are 30 49.2 N, 79 28.8 E by USGS; and 30 17.82 N, 79 33.84 E by IMD. Distances in this report refer to the USGS location. Recorded aftershocks and the damage pattern suggest that the zone of activity was close to Chamoli; this region also showed a maximum intensity of VIII on the MSK scale. USGS estimated the focal depth at 12 km. The quake was felt at far-off places such as Kanpur (440 km southeast of the epicenter), Shimla (220 km
northwest) and Delhi (280 km southwest). Maximum death and damage occurred in the district of Chamoli, where about 63 persons died and over 200 were injured. About 2,595 houses collapsed and more than 10,850 were partially damaged. In all, about 1,256 villages were affected. A few buildings at the distant city of Delhi sustained nonstructural damage. No instances of liquefaction were reported. Linear cracks in the ground were seen in some locations in the affected area. Nonstructural damage to some buildings in far-off Delhi clearly underlines the potential for a major disaster there. there. Considering the political and social significance of such an eventuality, efforts should be directed towards effective earthquake disaster mitigation and management in the Indian capital.
P1. P1. Partial collapse in a random rubble stone masonry building. Note that the front portion has RC beam supported on concrete block columns, and that the roof consists of an RC slab.
P2. P2. Collapse of one of the wythes in a traditional house in slate wafer masonry
P3.Tarang P3.Tarang Apartment in Delhi that sustained damage to infill walls.
The September 29, 1993, M6.4 Killari, Maharashtra Earthquake in Central India. Most of the world seismicity is concentrated along the plate boundaries. However, a significant number of earthquakes, including some large and damaging ones, do occur within the plates. Our understanding of intracratonic seismogenesis and the hazard it entails is poor, in part because data are scarce. The 1993 Killari earthquake in central peninsular India is the latest intracratonic event to be responsible for a large disaster. The positive side of this tragedy is that it will provide new insights into geologic, engineering and cultural factors that control the distribution and degree of damage, which will aid in turn the development of a more effective hazard reduction program for peninsular India and similar intrapolate environments. This report summarizes our observations during a ten-day investigation of the mesoseismal area of the 1993 Killari earthquake. Several aspects of the earthquake were investigated, ranging from the surface rupture and related deformation to the pattern of damage to engineered and traditional structures. Finally, the rescue and reconstruction efforts following the earthquake brought out important issues that are generally relevant to earthquake hazard reduction in traditional rural settings; these are also briefly discussed.
Figure 4: In 4: In some buildings, the traditional heavy clay roof was supported on a frame of wood posts and beams. In most cases, the timber columns continued to hold the roof together while the walls collapsed, generally outwards from the timber frame, saving the lives of many occupants
Figure 5: A 5: A brick masonry school building in Rajegaon collapsed. The roof of precast panels lacked adequate connections
Figure 6 : While most elevated water tanks performed well, this tank of Kautha collapsed straight down into its crumpled supports. Circumferential displacement of about 0.5m suggests that rotational vibration led to its collapse. Emergency Response The affected area does not suffer from floods and was considered Aseismic. The only natural disaster known in the area is drought. Hence, the earthquake took the people and administration by surprise. It took
the administration 2 to 4 days to effectively organize rescue and relief operations. What then followed appeared to be well-organized and effective. Civilian as well as military authorities cooperated in the effort. Since the reconnaissance team did not visit the affected areas of Karnataka, the discussion here is based on the response in the districts of Latur and Osmanabad only. Of all the villages devastated by the quake, only the village of Killari had a wireless connection with the district police headquarters at Latur. Within minutes, the information about the devastation in Killari was conveyed to Latur and from there to the state headquarters at Bombay. Immediately, about 20 policemen stationed at Ausa (28 km) were rushed to Killari, followed by district level administrators (District Collector, Superintendent of Police, etc). About 50 policemen were also dispatched from Latur (42 km). Immediate search and rescue was conducted by the survivors and the limited police rescue teams. As the day progressed, information about equally severe devastation from nearby villages started reaching Killari. By early next morning (Oct. 1), the Indian army took over the task of search and rescue. By the afternoon of the day of the earthquake, many curious onlookers had arrived in the area. This led to traffic jams and hampered the task of search and rescue. Beginning Oct. 2, entry to the affected area was controlled to allow entrance only to government personnel and members of volunteer organizations. The task of search and rescue became extremely difficult due to the heavy rains, which immediately followed the earthquake and the enormous quantities of the rubble. In places 2-3 m of rubble has to be removed to extricate the bodies. The narrow village streets were choked by fallen rubble, which further hampered rescue operations. Mass cremations that were held on the first two days after the earthquake were done without adequate record keeping. This led to confusion about the actual number of deaths. At one time, the newspapers were reporting up to 30000 dead. Later it was discovered that about 9000 fatalities actually occurred. Recovery Medical Aid: The Aid: The number of injured in Maharashtra was about 15500. About 50 mobile teams of doctors were pressed into service; at least – doctor was made available at each of the affected villages. The 125 beds civil hospital at Latur had to convert the nearby Rajasthan School into a hospital ward to care for about 300 indoor patients. On the other hand, the rural medical college and hospital at Ambe Jogai, which is only 60km from Latur, had a 510-bed capacity but only had 86 patients maximum at any given time. On the whole, in a few days, there were more government and private doctors available than could be used. Food, water, Provisions: Cooked Provisions: Cooked food was provided in the affected villages during the first fortnight by large number of voluntary agencies and the army. After 15 days the community kitchens were closed. Enough rations and other provisions to last a month were provided to the people, requiring them to cook their own food.
Figure 7: After 7: After the earthquake, water was trucked into the region. Generally, each village was assigned a truck requisitioned from unaffected neighbouring districts Drinking water was supplied regularly by mobile water carrying units, generally one for each village, requisitioned from the neighbouring districts. Water storage tanks (5000 l), donated by UNICEF/CARE, were being used for storing water in villages. In some villages, these tanks were lying upside down while quite a few were still resting in storage yards, indicating excess availability of the tanks. A total of 227 water hand pumps in the earthquake-affected areas of the Latur district were found operative. Simultaneously, a program for installation of tube wells in the temporary settlements was initiated. In the Latur district, 83 deep-bore wells at the temporary shelter sites needed to be dug. 47 of these had been completed by Oct 19. For this task, eleven deep-bore rigs were mobilized from the other districts of Maharashtra.
Figure 8: Distribution 8: Distribution of relief supplies was systematized through the issuance of 'family cards' and 'individual cards' to residents of the affected areas The government and several voluntary agencies distributed clothes and household goods like utensils, stoves, storage cans, and provisions for daily needs, either through the administration or directly. A team consisting of an officer from the administration, an officer from the police, and a local head of the village issued every affected family a “family card” and every affected person an “individual card” to record and regulate the goods distributed as a relief aid. This, to a large extent, systematized the relief distribution. Spontaneous offers of aid were received from within the country and outside. Bombay International Airport made special arrangements to receive and clear planeloads of clothes, medicine, tents and food. Within about 3 weeks, the relief material available was somewhat in excess of the needs.
Figure 9: Temporary 9: Temporary shelters of galvanised iron sheet were rapidly erected. Each provides shelter for five families Temporary Shelter: Immediate Shelter: Immediate shelter was provided by erecting temporary galvanized iron sheet houses. 2 Each shelter consisted of 5 units of about 15 m areas each; each affected family was offered one such unit. Common toilets and hand operated bore wells were provided. Some families chose to take tents and tin sheets instead and made their own shelters. Resettlement and Housing: A Housing: A large number of villages which were totally destroyed are being relocated to places not far away. Most of the sites for relocation have been identified. 2
Every affected family will be provided a housing unit with a covered area of 20, 40 or 60 m (depending on 2 the needs of the family) and an open area of 15 to 45 m for animal shelters and future extensions. The 2 government will bear the cost of only 20 m of the housing per family. For houses with a larger constructed area, the remaining cost will be treated as a long-term low-interest loan payable on terms similar to those for World Bank loans. Transportation The primary mode of transport in the area is bus. The affected area has no rail network. The nearest railway stations are at Latur and Sholapur. The nearest airports are at Hyderabad and Aurangabad. Since there was no damage to roads or bridges, the bus services were not adversely affected, even though the lanes inside the villages were blocked with the rubble of collapsed houses. Most of the villages have been temporarily shifted to new locations to the main roads.
Figure 10: Solar 10: Solar Powered Satellite Communication Towers were brought in to connect the larger villages to the outside world Communications An excellent communication network was set up after the earthquake. Initially, a number of HAM sets were called in. Later, solar powered satellite communication towers were installed in most of the bigger villages. The district collectors were provided with a hotline to the chief secretary at Bombay. This enabled the state to take immediate action on the requests from the local administrations for men and materials. Economic activity The economy of the area is primarily farm based with very few industries. The only major industry in the region was a sugar factory at Killari Pati, which had closed quite some time prior to the earthquake. It suffered no apparent damage and was being used as a relief distribution center. A large chicken farm about 15km north of the epicentral area reported that egg production fell substantially after the quake. Production was still down about 7% three weeks later. (No fluctuations in egg laying preceded the quake.) Though it is harvesting season for the Kharif crop and the sowing season the Rabi crop, the farmers have been unable to resume regular farming activity. This is due to incessant rains, unexpected at this time of year, and the non-availability of farm laborers, who do not seem concerned about daily wages due to the availability
of free relief provisions. There are reports that the government may have to help in harvesting by bringing in labor from outside the area. 6. Factors contributing to vulnerability and elements of risk Several key factors contribute to vulnerability of human populations: •
•
•
Location of settlements in seismic areas, especially on poorly consolidated soils, on ground prone to landslides or along fault lines. Building structures, such as homes, bridges, dams, which are not resistant to ground motion. Unreinforced masonry buildings with heavy roofs are more vulnerable than lightweight wood framed structures. Dense groupings of buildings with high occupancy. Lack of access to information about earthquake risks.
The above figure illustrates schematically the four elements contributing to risk (chance of loss). They are a) hazards (physical effects generated in the naturally occurring event), b) location of the hazards relative to the community at risk, c) exposure (the exposure (the value and importance of the various types of structures and lifeline systems in the community serving the populace), and d) vulnerability of vulnerability of the exposed structures and systems to the hazards expected to affect them during their useful life.
7. Preparedness measures Community preparedness – Community preparedness is vital for mitigating earthquake impact. most effective programs are formal and initiated at the community level with support by local or national governments. Figure 14 is explaining the steps of community preparedness done in the Gawhati city. Figure 14: Guwahati City Earthquake Preparedness Plan (Ward no: 48)
Social Map Showing different infrastructure present in ward no 48 of Guwahati .
Hazard Map : Engineering & Nonengineering buildings, Industries, Oil pipe Line, Power tower, Water tanks, Old and defunct infrastructures, Houses on Hill slopes or foot areas, Narrow entrance, Near to river
Risk & Vulnerable Map High rise buildings, Industrial areas, Densely populated areas, Slums and other vulnerable areas of the ward.
Public Education Preparedness includes educating the public on the causes and characteristics of an earthquake and what they should do if one occurs. Public officials and services must make contingency plans to react to the emergency. Nearly every country has a means of communicating with its most remotely located citizen either through media or informal communication networks. Public awareness programs can be designed to reach
every vulnerable person and may significantly reduce the social and material costs of an earthquake. Some examples of information to be provided include: •
causes of earthquakes and warning signs
•
awareness of earthquake risks and ways to minimize personal vulnerability practical ways to reinforce vulnerable houses what to do in the event of an earthquake (with possible
•
participation in a drill)
•
how to form teams to assist in search for injured and post-disaster recovery activities.
•
Planning Public officials and services must make contingency plans to react to the emergency. Activities the public sector may undertake include: •
•
•
Reviewing the structural soundness of facilities that are essential for disaster response such as hospitals, fire stations, communications installations and upgrading them if needed Training teams for search and rescue operations or ensuring the rapid availability of detection equipment Training teams for disaster assessment
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Identifying safe sites where vulnerable populations could be relocated. Training personnel in trauma care
•
Planning for an alternative water supply
•
• •
Preparing plans to clear streets for emergency access Preparing emergency communication systems and messages to the public regarding their security
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Training teams to determine if buildings are safe for reoccupancy Preparing flood plans for susceptible areas
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Coordinating preparations with voluntary organizations
•
8. Typical Post Disaster Assistance Needs The immediate impact of an earthquake affects all sectors of the community and local authorities should initially emphasize search and rescue of victims. Secondly, emergency medical assistance must be provided especially during the first 72 hours. Third, a damage and needs assessment survey, should be conducted to inform local and international agencies of needs. Fourth, the survivors will require relief assistance such as food, water and emergency shelter. Attention should be given to reopening roads, re-establishing communications, contacting remote areas and conducting disaster assessments. At the end of the emergency period, long-term recovery needs to take priority. The post earthquake period presents an opportunity to minimize future risks through enactment or strengthening of land use and building codes as rebuilding takes place. The focus should be on: • •
• •
repair and reconstruction of water, sewer, electrical services and roads technical, material and financial assistance for repair and reconstruction of houses and public buildings programs to rejuvenate the economy financial assistance for loans to individuals and businesses for economic recovery.
Earthquake Response Plan The emergency measures of evacuation, search, rescue and relief form important action plans plans in disaster management. Once disaster occurs, Disaster Management Machinery should plunge into action in doing rescue and relief operations. The Trigger Mechanism is Mechanism is a vital part of preparedness plan whereby the receipt of a signal of an impending disaster would simultaneously energise and activate the mechanism of response and mitigation without loss of crucial time. Other aspects are Rapid Damage/Loss Assessment for Emergency relief, Documentation of damages and losses and reconstruction.
Mitigation The golden rule is that there is no standard solution to mitigate a disaster risk. The goal is to minimize the impact of disaster. Possible risk reduction measures Engineered structures (designed and built) to withstand ground shaking. Architectural and engineering inputs put together to improve building design and construction practice. Develop earthquake resistant construction techniques.
Figure 15: Essential requirements in a Masonry building and designed for RCC building
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Source: www.nicee.org Earthquake Tips IITK-BMTPC)
Analyze soil type before construction and do not build structures on soft soil. To accommodate on weak soils adopt safety measures in design. Note: Buildings built on soft soils are more likely to get damaged even if the earthquake is not particularly strong in magnitude. Similar problem persists in the alluvial plains and conditions across the river banks. Heavy structural damages are concentrated when ground is soft. Follow Indian Standard Code for construction of buildings Enforcement of building code in the byelaws Land use control and restriction on density and heights of buildings Strengthening of important buildings, which need to be functional after a disaster. Upgrade level of safety of buildings.
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Public awareness, sensitization and training programmes for Engineers, Architects, Structural designers, Builders, Masons etc. Reduce possible damages from secondary effects. e.g., identify potential landslide sites and restrict construction in those areas. In earthquake prone areas insurance should be obtained for buildings under construction and those in use. Insurance policies for natural disasters should be made compulsory and priced specifically on available scientific data of hazards in the region.
The ranges of actions that can be taken are classified herewith: Engineering Collapse or failure of the buildings and structures has been the main causes of death and damages in the past events. This will continue to happen if the structures are built without the consideration of the hazards in the region. Engineering solutions has been one of the approaches to address the mitigation issues. The measures are of two types: those that result in stronger individual structures that are not resistant to hazards, and those that create structures whose function is primarily disaster IS 1893 (Part 1):2002 protection such as retaining walls, improvement of soil drainage, rock bolting, slope modification, engineering land fill, diversion channels for Indian Standard flood etc. Actions under the first type are mainly actions on the buildings and structures to withstand against the hazard and not cause any loss to life although the structure will undergo damage. The line that needs to be hint upon is structure should not collapse and kill people who are sheltered in it. The design and the construction of the building and other structures such as the bridges, flyovers, overhead water tanks etc should be compliant to the safety of the users and adhere to the design standards, code and performance levels during the occurrence of the event. Building codes are the most critical defence to have strong structures and this has to be backed up with an effective enforcement mechanism so that no structures are built unsafe. The codes are unlikely to result in stronger buildings still the code is implemented. Code enforcement by inspection of structures under construction is an important element of maintaining a strong building stock in hazard prone areas. Explanatory manuals and trainings have to be given to the engineers, builders and the work force of the construction industry in order to adopt better practice of disaster resistance construction. Each unsafe structures built up everyday add on
Criteria for Earthquake Resistant Design of Structures Part 1 General Provisions and Buildings (Fifth revision)
Bureau of Indian Standards June 2002
to the vulnerability of the region.
There are many buildings that are built without the consent of the engineering community and as they are not designed to the safety standards they become vulnerable to hazards. Engineered measures are not taken up in the buildings that come in the rural areas. They are built by traditional craftsmen, masons or any other individual who has turned looking for livelihood in the construction of buildings. All the buildings that come up without the incorporation of engineering features are called as “Non-engineered buildings ”. ”. All these non-engineered buildings in order to make it disaster resistant should incorporate the features in a practical way. Methods of incorporating these features exist and people have to be trained in the technology of
incorporating disaster resistant features into a non-engineered building or buildings that have less resistance to level of hazard or in places where the level of hazard has increased over a period of time. It is very important to improve the existing stock of buildings. Hazard impact from earthquake has been seen the world over and it is believed that 80% of the fatalities in an earthquakes are caused due to the structural collapse of the buildings. The vulnerability of these buildings can be reduced to some degree by regular maintenance and adding strength to the existing building for a particular hazard level. The laws should confirm that all the new buildings conform to the safety requirements. The department which looks after the passing of the house plan and give a nod for construction need to take a lead of a watch dog by checking compliance of controls on site along with penalties, closure orders for offenders.
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Important existing buildings that are to be functional during the response period as well as considered to be the lifeline for functioning purpose need to be strengthened to reduce their vulnerability to hazards. Important facilities can be strengthened, though these are generally too costly and requires expertise.
Physical planning measures for safe development With the rapid population growth the likely effect of people getting effected by disaster is large when compared to the earlier centuries. Poor people settle illegally and in hazardous areas such as flood, fire, plains, unstable slopes, hazardous industrial area etc. The old part of many cities is congested and the narrow road does not allow any rescue equipments to reach the site where help is needed the most. The population density in some localities of urban areas is very high at times and this accounts to a large number of deaths especially in events of fire and earthquakes. In major disasters essential services such as health care, fire fighting, water supply, telecommunication, electricity etc are hampered. The location of all these services and their functioning play a key role in the post-disaster phase. Proper planning measures in urban areas can greatly reduce the effects by avoiding the settlements away from the hazardous areas. This can be done if the hazard exists locally. For hazards which have a large geographical spread, land use plan is plan is the tool that can be adopted for achieving safe development.
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The planning and construction of settlements, roads and all essential services are brought in the Master Plan for the urban areas. Master Plan is prepared at regular intervals based upon the growth and the economy of the city. It’s important that the urban plan integrate with the disaster disaster risk mitigation as a normal process of development. The density of buildings can be controlled in the master plan by permitted densities of development. Indirect control is sometimes possible through simpler methods such as widening of roads, road development to limit the size of plots for development, height limitations etc. Creation of park land, developing of opening spaces by greenery can reduce urban densities and this also provides refuge areas for the population during emergency. Such open spaces can be used for setting up of field hospitals and distribution of relief materials or for storage purposes. The location of public sector services should be carefully sited as they play an important role in reducing the vulnerability. Schools, hospitals and medical care, emergency facilities and major services such
as water supply and water treatment/pumping station electrical stations and transformers, telephone exchange buildings represent a significant functioning of any geographical area whether a village, town or any major urban centre. An important principle is deconcentrating all the elements that are at risk. Replace all essential central division of the services at different locations in the city so that if one fails the other can continue its service. It becomes very essential to do in case of emergency facilities like hospitals and fire department. The design of all these facilities and services also needs to be carefully planned so as to reduce risk of failure. Shown below is the mitigation measures taken as part of implementation of risk reduction activities in a town of Gujarat after the Bhuj earthquake. Such actions generate protection against future disaster. Opportunities for mitigation should be looked during the post disaster implementation works in an affected area. Successful mitigation brings about a fundamental change in the attitude of the people at risk and modifies the earlier physical environment of the society. These changes take time and many times it’s learnt in a hard way after facing a disaster.
Proposed development of relocation site in Gujarat Plan. Emphasis is given in terms of open spaces, wider roads, less densification of buildings, building height etc.
Site Developed as per the plan. Note the width of the road. It is built wide enough to get necessary help during an emergency.
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43 Mitigation projects tend to be at the peak mainly in the aftermath of disaster. Places like Gujarat have been experiencing earthquakes and nothing much was done in terms of mitigation measures before the earthquake th hit on the 26 of January 2001. Nothing was learnt from the sufferings of the Latur Earthquake that struck on 30 Sept 1993. Look for the example in the figure below. Suppose Area A and Area B is B is earthquake prone and the following sequence as shown in the figure occurs.
Area B does B does not learn and adopt mitigation measures as done in Area A and when an event strikes it leads to a disaster. One thing has to be borne in mind that the selection of the hazard mitigation program should take into account of the multi-hazard ###$ approach. If a cyclone hits an area the general tendency is to take cyclone mitigation, but the earthquake risk may be higher. So mitigation programme should focus with the multihazard approach.
% %&% &% Institutional mechanism and management for mitigation Mitigation actions to be implemented shall require will of many agencies, community and also would need to have formal procedural measures so that it sustains for the time ahead. Bringing in changes in the physical planning, strengthening the structures make take decades of work and dedication. Policies are required to guide and see that the work is completed inspite of the change in the administration and the government. As it is a work work of continuous process, a sustained effort to look into the activities and monitoring has to be institutionalized by setting up a department or an authority. Education, training, political will are all necessary aspects for institutionalizing disaster mitigation in the forefront. Technical expertise on the subject, policy making are important for developing mitigation strategies at the national, state and local level. Decisions need to be taken in the
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Lessons learnt from one disaster struck area should be implemented as part of mitigation strategy in unaffected or far off areas of similar risk. Suitable adaptations to places will lessen the impact of the disaster.
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44 element of planning for disaster mitigation wherein basic observatories have to be established, resources in terms of manpower and fund organized for carrying out the job. The mitigation plan prepared need to be checked and implemented as per the top priority within the allocated budget. A clear organizational structure need to be set up at the sate level to implement the mitigation plans. Two states in the country Orissa and Gujarat have a well established authority named Orissa Disaster Mitigation Authority (OSDMA – A Government of Orissa Agency) and Gujarat State Disaster Management Authority (GSDMA - A Government of Gujarat Agency) which takes activity in preparedness and mitigation. The authority carries policy to implementation. The local level is to be strengthened by community based mitigation work carried out by the local institutions and the community. Training and technical support shall be given looking into the needs of the programme. Emphasis is on how a household copes with the disruptive occurrence of the hazard. Community Based Mitigation Community preparedness along with public education is vital for mitigating the earthquake impact. Earthquake drills and Public awareness programme. Community based Earthquake Risk Management Project should be developed and sustainable programmes launched. Retrofitting of schools and important buildings, purchase of emergency response equipment and facilities, establishing proper insurance can be the programmes under Earthquake Risk Management Project. A large number of local masons and engineers will be trained in disaster resistant construction techniques. A large number of masons, engineers and architects can get trained in this process.
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Societal awareness In order to effectively mitigate disasters of, joint efforts has to be made by all. By all, means the Government, the civil society organizations and the community. Since community is the first and the foremost to face the wrath of the disaster its necessary that they are aware of the threat and the steps that need to be taken. People have to be made fully aware of the hazard they face and protect themselves and support in the initiatives. The key to success for any mitigation programme lies in the participation and the dedication of the community. Involvement of the community includes meetings, workshops, trainings, plan preparation and discussions.
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45 Public awareness is generated through campaigns, literature and posters, emergency and evacuation drills, observing safety day or safety week (local and national level), newspaper and other source of media. In schools children can prepare the mock drills by getting under the desks. Such drills should be done on a regular basis thereby reinforces awareness as part of their daily life behavioral response. I our country disaster awareness is promoted through th national day, “National Disaster Reduction Day” (NDRD) every 29 October in the remembrance of the Orissa super cyclone disaster.
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Societal awareness is important for disaster mitigation. Participation of school children children in an awareness campaign organised on the eve eve of National Disaster Reduction Day – th 29 October 2003, 2003, Guwahati city. city.
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46 RESOURCES: www.nicee.org:: website of The National Information Center of Earthquake Engineering (NICEE) www.nicee.org hosted at Indian Institute of Technology Kanpur (IITK) is intended to collect and maintain information resources on Earthquake Engineering and make these available to the interested professionals, researchers, academicians and others with a view to mitigate earthquake disasters in India. The host also gives IITK-BMTPC Earthquake Tips. www.imd.ernet.in/section/seismo/static/welcome.htm Earthquake Information – India Meteorological Department, India. IMD detect and locate earthquakes and evaluates seismicity in different parts of the country. www.bmtpc.org In order to bridge the gap between research and development and large scale application of new building material technologies, the erstwhile Ministry of Urban Development, Government of India, had established the Building Materials And Technology Promotion Council in July 1990. www.earthquake.usgs.gov Source for science about the Earth, its natural and living resources, natural hazards, and the environment. www.neic.cr.usgs.gov National Earthquake Information Center (NEIC) - World Data Center for Seismology Earthquake information and observation station: The site hosts one of the most comprehensive systems. www.quake.wr.usgs.gov Earthquake Reporting Service: U.S. Geological Survey and UC Berkeley service for earthquake reporting. Earthquake basics and educational material; geological and historical information; links to professional and amateur organizations; online access to earthquake data. Current research activities and results in seismology, crystal structure and deformation, geology and borehole physics. for more www.asc-india.org Amateur Seismic Centre is a comprehensive website carrying details of state wise seismicty for the country. This also has extensive reports on various past earthquakes with rare photographs and maps.
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ANNEXURE I: DOS AND DON’TS Earthquakes An earthquake is a sudden, rapid shaking of the Earth caused by the breaking and shifting of rock beneath the Earth's surface. This shaking can cause buildings and bridges to collapse; disrupt gas, electric, and phone service; and sometimes trigger landslides, avalanches, flash floods, fires, and huge, destructive ocean waves (tsunamis). Buildings with foundations resting on unconsolidated landfill, old waterways, or other unstable soil are most at risk. BEFORE THE EARTHQUAKE STRIKES Develop a Family Disaster Plan. If you are at risk from earthquakes: •
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Pick "safe places" in each room of your home. A safe place could be under a sturdy table or desk or against an interior wall away from windows, bookcases, or tall furniture that could fall on you. The shorter the distance to move to safety, the less likely you will be injured. Injury statistics show that people moving as little as 10 feet during an earthquake's shaking are most likely to be injured. Also pick safe places, in your office, school and other buildings you are frequently in. Practice drop, cover, and hold-on in each safe place. Drop under a sturdy desk or table and hold on to one leg of the table or desk. Protect your eyes by keeping your head down. Practice these actions so that they become an automatic response. When an earthquake or other disaster occurs, many people hesitate, trying to remember what they are supposed to do. Responding quickly and automatically may help protect you from injury. Practice drop, cover, and hold-on at least twice a year. Frequent practice will help reinforce safe behavior. Wait in your safe place until the shaking stops, then check to see if you are hurt. You will be better able to help others if you take care of yourself first, then check the people around you. Move carefully and watch out for things that have fallen or broken, creating hazards. Be ready for additional earthquakes called "aftershocks." Be on the lookout for fires. Fire is the most common earthquake-related hazard, due to broken gas lines, damaged electrical lines or appliances, and previously contained fires or sparks being released. If you must leave a building after the shaking stops, use the stairs, not the elevator. Earthquakes can cause fire alarms and fire sprinklers to go off. You will not be certain whether there is a real threat of fire. As a precaution, use the stairs. If you're outside in an earthquake, stay outside. Move away from buildings, trees, streetlights, and power lines. Crouch down and cover your head. Many injuries occur within 10 feet of the entrance to buildings. Bricks, roofing, and other materials can fall from buildings, injuring persons nearby. Trees, streetlights, and power lines may also fall, causing damage or injury. Inform guests, babysitters, and caregivers of your plan. Everyone in your home should know what to do if an earthquake occurs. Assure yourself that others will respond properly even if you are not at home during the earthquake. Get training. Take a first aid class from your local Red Cross chapter. Get training on how to use a fire extinguisher from your local fire department. Keep your training current. Training will help you to keep calm and know what to do when an earthquake occurs. Discuss earthquakes with your family. Everyone should know what to do in case all family members are not together. Discussing earthquakes ahead of time helps reduce fear and anxiety and lets everyone know how to respond.
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Talk with your insurance agent. Different areas have different requirements for earthquake protection. Study locations of active faults, and if you are at risk, consider purchasing earthquake insurance.
Assemble a Disaster Supplies Kit A flashlight and sturdy shoes by each person's bedside. Disaster Supplies Kit basics Evacuation Supply Kit. PROTECT YOUR PROPERTY •
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Bolt bookcases, china cabinets, and other tall furniture to wall studs. Brace or anchor high or top-heavy objects. During an earthquake, these items can fall over, causing damage or injury. Secure items that might fall (televisions, books, computers, etc.). Falling items can cause damage or injury. Install strong latches or bolts on cabinets. The contents of cabinets can shift during the shaking of an earthquake. Latches will prevent cabinets from flying open and contents from falling out. Move large or heavy objects and fragile items (glass or china) to lower shelves. There will be less damage and less chance of injury if these items are on lower shelves. Store breakable items such as bottled foods, glass, and china in low, closed cabinets with latches. Latches will help keep contents of cabinets inside. Store weed killers, pesticides, and flammable products securely in closed cabinets with latches, on bottom shelves. Chemical products will be less likely to create hazardous situations from lower, confined locations. Hang heavy items, such as pictures and mirrors, away from beds, couches, and anywhere people sit. Earthquakes can knock things off walls, causing damage or injury. Brace overhead light fixtures. During earthquakes, overhead light fixtures are the most common items to fall, causing damage or injury. Strap the water heater to wall studs. The water heater may be your best source of drinkable water following an earthquake. Protect it from damage and leaks. Bolt down any gas appliances. After an earthquake, broken gas lines frequently create fire hazards. Install flexible pipe fittings to avoid gas or water leaks. Flexible fittings will be less likely to break. Repair any deep cracks in ceilings or foundations. Get expert advice if there are signs of structural defects. Earthquakes can turn cracks into ruptures and make smaller problems bigger. Check to see if your house is bolted to its foundation. Homes bolted to their foundations are less likely to be severely damaged during earthquakes. Homes that are not bolted have been known to slide off their foundations, and many have been destroyed because they are uninhabitable. Consider having your building evaluated by a professional structural design engineer. Ask about home repair and strengthening tips for exterior features, such as porches, front and back decks, sliding glass doors, canopies, carports, and garage doors. Learn about additional ways you can protect your home. A professional can give you advice on how to reduce potential damage. Follow local seismic building standards and safe land use codes that regulate land use along fault lines. Some municipalities, counties, and states have enacted codes and standards to protect property and occupants. Learn about your area's codes before construction.
Media and Community Education Ideas
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Ask your community to develop stronger building codes. Building codes are the public's first line of defense against earthquakes. The codes specify the levels of earthquake forces that structures must be designed to withstand. As ground lessons have been learned about how buildings are damaged in earthquakes, the minimum earthquake requirements specified in building codes have been improved. Publish a special section in your local newspaper with emergency information on earthquakes. Localize the information by printing the phone numbers of local emergency services offices, the American Red Cross, and hospitals. Conduct a week-long newspaper series on locating hazards in the home and how to fix them. Work with local emergency services and Deputy commissioner office to prepare appropriate information for people with mobility impairments about what to do during an earthquake.
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Provide tips on conducting earthquake drills in the home.
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Interview representatives of the gas, electric, and water companies about shutting off utilities.
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Drop, cover, and hold on! Move only a few steps to a nearby safe place. It is very dangerous to try to leave a building during an earthquake because objects can fall on you. Many fatalities occur when people run outside of buildings, only to be killed by falling debris from collapsing walls. In U.S. buildings, you are safer to stay where you are. If you are in bed, hold on and stay there, protecting your head with a pillow. You are less likely to be injured staying where you are. Broken glass on the floor has caused injury to those who have rolled to the floor or tried to get to doorways. If you are outdoors, find a clear spot away from buildings, trees, streetlights, and power lines. Drop to the ground and stay there until the shaking stops. Injuries can occur from falling trees, street-lights and power lines, or building debris. If you are in a vehicle, pull over to a clear location, stop and stay there with your seatbelt fastened until the shaking has stopped. Trees, power lines, poles, street signs, and other overhead items may fall during earthquakes. Stopping will help reduce your risk, and a hard-topped vehicle will help protect you from flying or falling objects. Once the shaking has stopped, proceed with caution. Avoid bridges or ramps that might have been damaged by the quake. Stay indoors until the shaking stops and you're sure it's safe to exit. More injuries happen when people move during the shaking of an earthquake. After the shaking has stopped, if you go outside, move quickly away from the building to prevent injury from falling debris. Stay away from windows and falling objects. Windows can shatter with such force that you can be injured several feet away. In a high-rise building, expect the fire alarms and sprinklers to go off during a quake. Earthquakes frequently cause fire alarm and fire sprinkler systems to go off even if there is no fire. Check for and extinguish small fires, and, if exiting, use the stairs. If you are in a coastal area, move to higher ground. Tsunamis are often created by earthquakes. If you are in a mountainous area or near unstable slopes or cliffs, be alert for falling rocks and other debris that could be loosened by the earthquake. Landslides commonly happen after earthquakes.
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Check yourself for injuries. Often people tend to others without checking their own injuries. You will be better able to care for others if you are not injured or if you have received first aid for your injuries.
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Protect yourself from further danger by putting on long pants, a long-sleeved shirt, sturdy shoes, and work gloves. This will protect your from further injury by broken objects. After you have taken care of yourself, help injured or trapped persons. If you have it in your area, call 9-1-1, then give first aid when appropriate. Don't try to move seriously injured people unless they are in immediate danger of further injury. Look for and extinguish small fires. Eliminate fire hazards. Putting out small fires quickly, using available resources, will prevent them from spreading. Fire is the most common hazard following earthquakes. Fires followed the San Francisco earthquake of 1906 for three days, creating more damage than the earthquake. Turn off gas on supply from the cylinder. cylinder. Explosions have caused injury and death when homeowners have improperly turned their gas back on by themselves. Switch off all electrical appliances. appliances. Clean up spilled medicines, bleaches, gasoline, or other flammable liquids immediately and carefully. Avoid the hazard of a chemical emergency. Open closet and cabinet doors cautiously. Contents may have shifted during the shaking of an earthquake and could fall, creating further damage or injury. Inspect your home for damage. Get everyone out if your home is unsafe. Aftershocks following earthquakes can cause further damage to unstable buildings. If your home has experienced damage, get out before aftershocks happen. Help neighbors who may require special assistance. Elderly people and people with disabilities may require additional assistance. People who care for them or who have large families may need additional assistance in emergency situations. Listen to a portable, battery-operated radio (or television) for updated emergency information and instructions. If the electricity is out, this may be your main source of information. Local radio and local officials provide the most appropriate advice for your particular situation. Expect aftershocks. Each time you feel one, drop, cover, and hold on! Aftershocks frequently occur minutes, days, weeks, and even months following an earthquake. Watch out for fallen power lines or broken gas lines, and stay out of damaged areas. Hazards caused by earthquakes are often difficult to see, and you could be easily injured. Stay out of damaged buildings. If you are away from home, return only when authorities say it is safe. Damaged buildings may be destroyed by aftershocks following the main quake. Use battery-powered lanterns or flashlights to inspect your home. Kerosene lanterns, torches, candles, and matches may tip over or ignite flammables inside. Inspect the entire length of chimneys carefully for damage. Unnoticed damage could lead to fire or injury from falling debris during an aftershock. Cracks in chimneys can be the cause of a fire years later. Take pictures of the damage, both to the house and its contents, for insurance claims. Avoid smoking inside buildings. Smoking in confined areas can cause fires. When entering buildings, use extreme caution. Building damage may have occurred where you least expect it. Carefully watch every step you take. o Examine walls, floor, doors, staircases, and windows to make sure that the building is not in danger of collapsing. o Check for gas leaks. If you smell gas or hear a blowing or hissing noise, open a window and quickly leave the building. Turn off the gas, using the outside main valve if you can, and call the gas company from a neighbor's home. If you turn off the gas for any reason, it must be turned back on by a professional. o Look for electrical system damage. If you see sparks or broken or frayed wires, or if you smell burning insulation, turn off the electricity at the main fuse box or circuit breaker. If you
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have to step in water to get to the fuse box or circuit breaker, call an electrician first for advice. Check for sewage and water line damage. If you suspect sewage lines are damaged, avoid using the toilets and call a plumber. If water pipes are damaged, contact the water company and avoid using water from the tap. You can obtain safe water from undamaged water heaters or by melting ice cubes. Watch for loose plaster, drywall, and ceilings that could fall.
Use the telephone only to report life-threatening emergencies. Telephone lines are frequently overwhelmed in disaster situations. They need to be clear for emergency calls to get through. Watch animals closely. Leash dogs and place them in a fenced yard. The behavior of pets may change dramatically after an earthquake. Normally quiet and friendly cats and dogs may become aggressive or defensive.
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