PADANG EARTHQUAKE, WEST SUMATRA ON MARCH 6, 2007

Transcription

1 PADANG EARTHQUAKE, WEST SUMATRA ON MARCH 6, 2007 EARTHQUAKE DETAILS The U. S. Geological Survey (USGS) informed a strong earthquake struck west Sumatra on Tuesday March 6, 2007 at 10:49 with a magnitude of 6.4 followed by another earthquake 2 hours later with a magnitude of 6.3. According to The Indonesian Meteorological and Geophysical Agency (BMG) the earthquake was measured at 5,8 SR (Skala Richter). The epicenter of the earthquake located inland approximately 16 Km South West of Batusangkar-West Sumatra. The quakes were also felt in Singapore and Malaysia. Earthquake details are as follows: Magnitude : 6.4 Date-Time : Tuesday, March 6, 2007 at 03:49:39 (UTC) = Coordinated Universal Time Tuesday, March 6, 2007 at 10:49:39 AM = local time at epicenter Location : 0.55 LS BT Epicentrum located inland approximately 16 km South West of Batusangkar West Sumatra. Depth : 19 km (11.8 miles) set by location program Region : Southern Sumatra, Indonesia Distances : 50 km (30 miles) NNE of Padang, Sumatra, Indonesia 155 km (95 miles) SW of Pekanbaru, Sumatra, Indonesia 425 km (265 miles) SSW of Kuala Lumpur, Malaysia 930 km (580 miles) NW of Jakarta, Java, Indonesia Source : USGS NEIC (WDCS-D) & BMG.Go.Id TECTONIC DETAILS The locations and focal-mechanisms of the Sumatra earthquakes of March 6, 2007, are consistent with these shocks occurring on the Sumatran fault, a 1900 km-long strike-slip fault that extends the length of the island. At the latitude of the earthquake, the average long-term rate of displacement on the fault is about 20 mm/yr. The exact position of the 2007 earthquakes with respect to earlier historic earthquakes on the Sumatran fault will not be known until detailed studies have been conducted of the recent earthquakes. Two earthquakes having magnitudes of 7.2 and 7.5 respectively, occurred within seven hours of each other on June 8-9, 1943, with epicenters assigned to the section of the fault immediately to the southeast of the epicenters of the 2007 earthquakes. The magnitude 7.5 shock was among the largest earthquakes to have occurred on the Sumatran fault since the late nineteenth century. Two earthquakes that occurred within three hours of each other on June 28, 1926, which have been assigned magnitudes of 6 ½ and 6 ¾ respectively, have been assigned epicenters virtually identical to the epicenters of the 2007 earthquakes. Padang Earthquake 1

2 Image Source : Image Source : The two figures below show the location of the fault and some of its historical earthquakes. These figures are from a presentation being given at the National University of Singapore on March 7th by Dr. Danny Hilman Natawidjaja of the Indonesian Institute of Sciences (LIPI) in Bandung, Indonesia. The earthquakes of March 6th originated from the fault zone near the north end of Singkarak Lake, about 45 km north of Padang. Image Source : The tectonics of west-central Sumatra are dominated by the motion of the Australia plate northward with respect to the Sunda plate at a velocity of about 50 mm/yr. The principal plate boundary is taken to be the axis of the Sunda trench, but significant plate-boundary deformation occurs in a zone that extends hundreds of kilometers inland from the Sunda trench. The component of motion of relative plate motion that is perpendicular to the trend of the plate-boundary is mostly accommodated by underthrusting along the Sumatra subduction zone, which dips eastward from the Sunda trench and is seismically active to depths of over 200 km in west-central Java. Padang Earthquake 2

3 The Sumatra subduction zone has historically produced great thrust-fault earthquakes. The component of relative plate motion that is parallel to the plate-boundary is substantially accommodated by strike-slip faulting on the Sumatra fault, which is about 300 km inland of the Sunda trench. The part of the Sunda plate that lies to the west of the Sumatra fault and east of the principal plate boundary at the Sunda trench is sometimes called the forearc sliver of the Sunda plate, being distinguished from the rest of the Sunda plate because of its relative motion with respect to the plate's interior. PROPERTY DAMAGE AND CASUALTIES A report of Badan Koordinasi Nasional Penanggulangan Bencana dan Penanganan Pengungsi (Bakornas PBP) on March 8, 2007 states: casualties persons heavy injured peoples lightly injured persons displaced dwelling houses badly damaged dwelling houses lightly damaged school buildings seriously damaged office buildings seriously damaged public facilities suffered serious and light damage mosques completely damaged. Bakornas PBP also states that Padang earthquake hit almost 10 cities at West Sumatra, i.e. Kabupaten Solok, Kabupaten Tanah Datar, Kabupaten Padang Pariaman, Kabupaten Agam, Kabupaten Lima Puluh Kota, Kota Solok, Kota Payakumbuh, Kota Padang Panjang, Kota Bukittinggi and Kota Padang. Padang Earthquake 3

4 The Governor of West Sumatra Province stated in Media Indonesia dated March 18, 2007 that the estimated cost of rehabilitation for houses, office buildings and other infrastructures is IDR 1.6 trio, the major part of which is allocated as under: Kabupaten Tanah Datar IDR 541 bio Kabupaten Agam IDR 258 bio Padang Panjang IDR 224 bio Solok IDR 101 bio Bukittinggi IDR 58.9 bio Limapuluh Kota IDR 4 bio Payakumbuh IDR 6.2 bio Padang IDR 8.1 bio FIELD OBSERVATION Three days after the earthquake on March 6, 2007, MAIPARK sent a team of two staff to Padang to conduct a loss survey. The survey was intended to obtain a first hand impression of damages caused by the earthquake and was assisted by the Padang Branch Office of PT. Asuransi Wahana Tata. For 2 (two) days MAIPARK s team conducted the loss survey in several areas affected by the earthquake, i.e. Padang, Solok, Batusangkar, Bukittinggi and Payakumbuh. According to the observations made by MAIPARK s team only a few buildings seem to have suffered damage in Padang. Typical damages in Padang are cracks. Plaza Andalas (Pic. 1), when looking at the exterior walls vertical cracks can be detected, however they are not severe and no walls have caved in. Pic. 1. Plaza Andalas located at Padang Pic. 1 Pic. 2 is an example of a building in Padang which remained intact. In Bukittinggi the teams also found only a few buildings with partial damage and cracks developed on the walls. Buildings were mostly built to proper construction standards, thus withstanding major damage resulting from the disaster. Pic. 2 Pic. 2. Bank Mandiri building located at Padang Padang Earthquake 4

5 Bank BRI office building (Pic. 3 & 4), the cracks occurred only to the right side of the lower building. Pic. 3& 4. Bank BRI building located at Bukittinggi Pic. 3 Pic. 4 Pic. 5: A 4 storey shop house (still under construction) showing large & extensive cracks in the exterior walls on the upper storey. In Solok most of the buildings collapsed completely as can be seen in pic. 6 & 7. In pic. 6 the building on the right has almost collapsed completely. Pic. 5 Pic. 6. Dwelling house that almost collapse Pic.6 Pic. 7. BRI Branch office at Solok Pic.7 Padang Earthquake 5

6 Typical damage in Payakumbuh was heavy structural damage as shown in pic. 8, and pic. 9, leaving shop houses in ruins. Pic.9. More shop house ruins at Payakumbuh Pic.9 Pic.8. Shop houses in ruins at Payakumbuh Pic.8 In Batu Sangkar, the typical damage was the same as in Padang, namely cracks to the exterior walls of buildings as shown in pic. 10 & 11 below. Pic. 10. Bank BRI located at Batu Sangkar Pic. 10 Pic. 11. Football Stadium at Batu Sangkar Pic. 11 Padang Earthquake 6

7 INSURANCE LOSSES It is too early to estimate the insured loss. However, MAIPARK s projections for the affected areas are as follow: CITY OCCUPATION CUR. TSI (100%) MAIPARK's SHARE SOLOK AGRICULTURAL IDR. - - COMMERCIAL IDR. 24,424,549, ,445,637, INDUSTRIAL IDR. 45,370,000, ,585,625, RESIDENTIAL IDR. 3,356,462, ,115, ,151,011, ,870,377, NUMBER OF RISK 19 PADANG PANJANG AGRICULTURAL IDR. - - COMMERCIAL IDR. 1,090,000, ,500, INDUSTRIAL IDR. - - RESIDENTIAL IDR. 3,393,088, ,272, ,483,088, ,111,772, BUKIT TINGGI AGRICULTURAL IDR. - - COMMERCIAL IDR. 10,902,722, ,766,180, INDUSTRIAL IDR. - - RESIDENTIAL IDR. 2,792,497, ,124, ,695,219, ,464,304, PAYAKUMBUH AGRICULTURAL IDR. - - COMMERCIAL IDR. 19,341,867, ,764,315, INDUSTRIAL IDR. - - RESIDENTIAL IDR. 3,185,835, ,958, ,527,702, ,523,273, PADANG AGRICULTURAL IDR. 110,595,000, ,506,625, COMMERCIAL IDR. 822,274,645, ,999,961, INDUSTRIAL IDR. 3,320,903,282, ,749,921, RESIDENTIAL IDR. 342,368,499, ,559,099, ,596,141,426, ,815,607, T O T A L IDR. 4,709,998,449, ,785,336,613.00* ) 1,529 * ) Position as per MAIPARK's exposure data as at 31st January 2007 Padang Earthquake 7

8 Based on MAIPARK s data, the majority of risks are located in Padang (approximately 1433 risks) with the TSI (100%) of IDR 4,5 trio and MAIPARK s share of IDR 388 bio. Therefore most of the properties insured are within Padang city where insurance penetration is higher than in the other areas such as Padang Panjang, Solok and Bukittinggi. Applying 10% PML we estimate the insured loss at approximately IDR 40.8 bio. Up to date there is no official government report regarding the economic losses. Sources:- The Jakarta Post, Monday, March 12, U.S. Geological Survey Kompas Media Media Center Crisis Media Indonesia, Sunday, March 18, National Environment Agency, 2007 Private Journal,M. T. Zen, Prof. Bakornas PBP (Badan Koordinasi Nasional Penanggulangan Bencana dan Penanganan Pengungsi) Padang Earthquake 8