EarthquakesDo we need seismic design in Bahrain?
Dr. Dr. Faisal M. Falih
Tectonic activities A fold occurs when one or a stack of originally flat and planar surfaces, such as sedimentary strata , are bent or curved as a result of permanent deformation. A fault is a planar fracture or discontinuity in a volume of rock which may range in length from less than a meter to many hundreds of kilometers , across which there has been significant as a result displacement along the fractures of earth movement. The presence of such faults indicates that, at some time in the past, movements took place along them. A volcano is an opening, or rupture, in a planet's surface or crust, which allows hot magma, volcanic ash and gases to escape from the magma chamber below the surface.
Plate tectonics theory Plate tectonics theory visualizes the earth as consisting of a viscous, molten magma core with a number of lower-density rock plates floating on it. The exposed surfaces of the plates form the continents and the bottoms of the oceans. The crust of the earth is composed of many tectonic plates, and most of the major earthquakes occur at the plate boundaries . As time goes by, the plates move relative to each other, breaking apart in some areas and jamming together in others. Geodesy, the science of measuring the Earth's shape and positions on it, lets us measure plate motions directly using GPS, the Global Positioning System.
Tectonic Plates of the earth
Tectonic Plate Interactions Divergent boundaries are areas where plates move away from each other, forming either mid-oceanic ridges or rift valleys. •Convergent boundaries are areas where plates move toward each other and collide. These are also known as compressional or destructive boundaries. •Transform boundaries occur when two plates grind past each other with only limited convergent or divergent activity •
List of earthquakes in the region Saudi Arabia In January 11 1941, earthquake of M6.25 took place east of Jizan near Abu Arish. In October 17 1965, earthquake of M5.5 took place east of Abu Arish near Saudi Yemeni border. Gulf of Aqaba is an area where large damaging earthquakes occur quite regularly. The last major event was the 1995 Haql earthquake in the Gulf of Aqaba (M7.3) which caused significant damage on both sides of the Gulf and was felt hundreds of kilometers away. Earthquakes of M6 are common along the spreading axis of the Red Sea but generally they are not felt onshore and appear to pose little risk to infrastructure. On 19 May, 2009, 19 earthquakes of M4.0 or greater took place in the volcanic area of Harrat Lunayyir to the north of Yanbu, including a M5.4 event that caused minor damage to structures in the town of Al Ays (40 km to the SE). The maximum actual dip-slip offset on the fault in the hard rock in the nearby hills was about 90 cm.
Yemen In 13 December 1982, earthquake of M6.2 took place in Dhamar (depth 7 Km & epicenter 14.7 °N and 44.2°E) resulted in 2,500 deaths and injured 15000 people and destroyed about 1,500 settlements.
In November 22, 1991,earthquake took place in the Al-“Udain and Hazm Al-“Udain (Ibb), of M4.5 & epicenter 13.9 N, 44.1 E. Preliminary surveys indicate that 7,150 buildings were damaged and 1,578 were destroyed. However, the reinforced concrete structures in the epicentral area suffered no structural damage indicating the high vulnerability of traditional buildings, especially those constructed on slopes without proper foundation.
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Many of small earthquakes of magnitude less than M4.2 occurred on the period (1995-2012 ) highly felt by most of peoples.
Earthquakes in Iran( 21st century ) Date
Magnitude
Fatalities
6.5[10]
262[2]
Bou'in35 40′ 8.4″N48 55 2002 Zahra ′ 58.8″E earthquake
6.6[9]
At least 30,000[9]
29 0′ 14.4″N58 20 2003 Bam ′ 13.2″E earthquake
May 28, 2004
12:38:46 Māzandarā 6.3[8] n
At least 35[8]
36 16′ 12″N51 34′ 2004 Māzandarān 30″E earthquake
February 22, 2005
02:25:22 Zarand
6.4[6]
At least 602[7]
30 44′ 27.6″N56 5 2005 Zarand 2′ 37.2″E earthquake
November 10:22:19 Qeshm 27, 2005
6.0[5]
13[5]
26 47′ 2.4″N55 50 2005 Qeshm earthquake ′ 49.2″E
une 22, 2002
Time
Epicenter
02:58:21 Qazvin
December 01:56:52 Bam 26, 2003
Coordinates
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Name
°
°
Date
Time
Epicenter
Magnitude
Fatalities
June 22, 02:58:21 Qazvin 2002
6.5[10]
262[2]
Decembe 01:56:52 Bam r 26, 2003
6.6[9]
At least 30,000[9]
May 28, 2004
6.3[8]
At least 35[8]
February 02:25:22 Zarand 22, 2005 Novembe 10:22:19 Qeshm r 27, 2005 March 31, 01:17:01 Borujerd 2006
6.4[6]
At least 602[7]
6.0[5]
13[5]
6.1[4]
70[4]
Sep 10, 2008
11:00:34
6.1
7
Aug 27, 2010
23:56:34 Damghan
5.9
19
Dec 20, 2010
22:12:01 Hosseinabad 6.5
Jun 15, 2011 Aug 11, 2012 Apr 9, 2013
01:05:30 Kahnooj
5.3
12:23:18 Tabriz
6.4 and 6.3
16:22:50 Bushehr
6.3
Apr 16, 2013
10:44:13 Khash, Iran
7.8
12:38:46
Māzandarān
Qeshm
Coordinates
Name Bou'in35 40′ 8.4″N48 55′ 5 2002 Zahra 8.8″E earthquake 29 0′ 14.4″N58 20′ 1 2003 Bam 3.2″E earthquake 36 16′ 12″N51 34′ 3 2004 Māzandarān 0″E earthquake 30 44′ 27.6″N56 52′ 2005 Zarand 37.2″E earthquake 26 47′ 2.4″N55 50′ 4 2005 Qeshm 9.2″E earthquake 33 34′ 51.6″N48 47′ 2006 Borujerd 38.4″E earthquake 2008 Bandar 26 44′ 34.8″N55 49′ Abbas 40.8″E earthquake °
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26 44′ 34.8″N55 49′ 2010 Damghan 40.8″E earthquake 2010 11 28.491 N 59.117 E Hosseinabad earthquake Kahnooj 2 27.976 N 57.574 E 2011 earthquake Tabriz 306 38.324 N 46.759 E 2012 earthquakes 30 (early 2013 Bushehr 28.50 N 51.59 E estimate) earthquake 2013 Sistan 1 (Nonand residential area, due to 28.06 N 62.08 E Baluchestan earthquake landslide) °
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NOAA is : National Atmospheric and Oceanic Administration
USGS-Seismic Hazard-Iran-Iraq & Gulf region-16-04-2013
Conclusions and Recommendations 1. All available scientific data shows that Bahrain lies in a low-risk zone, so there is little chance of a major earthquake to occur. 2. It is recommended to establish a Program of Assessment of Earthquake Risk in Bahrain by collecting information for historical and instrumental seismicity in Bahrain, in the Arabian Gulf and in neighboring countries. 3. It is recommended to acquire as soon as possible portable seismographs to carry out a survey of ground vibrations in different locations in Bahrain aiming at choosing permanent seismological stations.
4- After recommendation 3 as above is accomplished, then it is recommended to establish Bahrain Seismological Network (BSN) consisting of a number of Remote Sensing Permanent Stations with one Central Data Acquisition System (CDAS) and a communication link through a satellite hub. 5- The main aims of the recommended BSN as in 4 above is monitoring and analysis of earthquakes at the Arabian Gulf region, studying Hazard and Risk Assessment in Bahrain in PGA terms and to study any future seismic requirements for design of buildings in Bahrain (if necessary).
Thank you
