U.S. DEPARTMENT OF THE INTERIOR EARTHQUAKE SUMMARY MAP XXX U.S. GEOLOGICAL SURVEY Prepared in cooperation with the Global Seismographic M8.5 and 7.9 Southern Sumatra Earthquakes of 12 September 2007 Network

Southern Sumatra and M7.0 of 13 September 2007 12 September 2007 23:49:01 UTC Tectonic Setting Epicentral Region 90° 100° 110° 120° 96° 98° 100° 102° 104° 2.525° S., 1001.0966°4° E. 108° Singapore Depth 10 km Mw = 7.9 (GCMT) 1941 An earthquake occurred IN THE KEPULAUAN MENTAWAI REGION, EXPLANATION Nias 1971 Pekanbaru INDONESIA, about 185 km (115 miles) SSE of Padang, Sumatra or about 755 km (470 miles) WNW of JAKARTA, Java at 5:49 PM MDT, 10° 10° Mag ≥ 7.0 Sep 12, 2007 (Sep 13 at 6:49 AM local time in Indonesia). 1984 1881 Pini 2005 0 - 69 km 1946 2004 0° 12 September 2007 11:10:26 UTC 0° 70 - 299 1936 1935 4.517° S., 101.382° E. 300 - 600 1998 Tanahbala Depth 30 km 2007 Rupture Mw = 8.5 (GCMT) 2004 Padang 1943 2005 Rupture 1943 S u m a t r a An earthquake occurred 130 km (80 miles) SW of Bengkulu, Sumatra, 1907 2005 Indonesia and 625 km (390 miles) WNW of JAKARTA, Java, Indonesia 1969 2004 Rupture at 5:10 AM MDT, Sep 12, 2007 (6:10 PM local time in Indonesia). 1996 Siberut

0° 1935 1938 0° 2002 Rupture Jambi 1943 2000 Rupture J a v a S e a 1909 2007 1928 1833 Rupture 2° 2° EPICENTRAL 2007 1797 Rupture REGION 1914 Sipora 1943 2000 2007 Plate Boundaries Subduction N Pagai 1900 Palembang Transform 55 2006 S Pagai mm/yr 1943 Divergent 10° 1994 10° 1977 Bengkulu Convergent 4° EXPLANATION I N D O N E S I A 4° 2000 Volcanoes Main Shock M8.5 1914 1957 2000 1963 1975 Aftershocks of M8.5 2001

Main Shock M7.9 1931 I N D I A N Tanjungkarang- Telukbetung 1931 1933 1913 Aftershocks of M7.9 90° 100° 110° 120° O C E A N Enggano 1950 RELATIVE PLATE MOTIONS SCALE 1:20,000,000 at the Equator Main Shock M7.0 Kilometers Southern Sumatra 6° 6° 0 200 400 800 1,200 1,600 1949 Jakarta The broad red vector represents the motion of Earthquake Magnitude 13 September 2007 3:35:28 UTC the Australia Plate relative to the Sunda Plate 1943 in the region. The motion of the Australia 4.00 - 5.99 2.133° S., 99.622° E. J a v a Plate is generally 50 - 60 mm/yr north and Depth 22 km slightly eastward with respect to the Sunda 6.00 - 6.99 Mw = 7.0 (USGS) Bandung Plate. 7.00 - 7.99 Casualties and damage are included with the event of September 12 at 11:10 UTC. Felt (III) at Bengkulu 8.00 - 8.99 and Padang; (II) on Kapahiang Seismic Hazard and at Padangpanjang. 90° 100° 110° 120° 130° 9.00 - 9.99 KhonUdon Bassein Pegu Phitsanulok KaenThani Savannakhet 96° 98° 100° 102° 104° 106° 108° Moulmein Hue Rangoon Ubon Nakhon Da Nang Quezon Earthquake Depth Scale at the Equator 1:3,993,000 Sawan Nakhon Ratchathani Quang Ratchasima Mercator Projection Saraburi Ngai City 0 - 69 Manila Kilometers Slip (mm) Tavoy Bangkok Play Cu Qui Nhon Samut Siemreab Buon Me 70 - 299 Samut Batdambang 0 100 200 400 Prakan 0.07 - 50.00 Sakhon Thuot Nha Port Phnom Trang 300 - 700 Blair Penh Da Lat 50.01 - 100.00 Vinh Bien Hoa Long Xuyen Long Phan 100.01 - 150.00 10° Can Tho My Tho 10° Rach Gia Thiet TECTONIC SUMMARY Nakhon Si Bac Lieu Soc 150.01 - 200.00 Trang Thammarat Significant Earthquakes Mag ≥ 7.5 The magnitude 8.5 and 7.9 southern Sumatra earthquakes of September 200.01 - 250.00 Songkhla Davao Alor Yala Kota 12, 2007 occurred as the result of thrust faulting on the boundary Banda Kota Year Mon Day Time Lat Long Dep Mag Setar Kinabalu 250.01 - 300.00 Aceh Baharu between the Australia and Sunda plates. At the location of these 1914 06 25 1907 -4.500 102.500 0 7.6 Pinang Kuala Bandar Seri Terengganu Begawan earthquakes, the Australia plate moves northeast with respect to the 1935 12 28 0235 -0.345 98.147 35 7.8 5 Kuantan 300.01 - 350.00 6 Ipoh Sunda plate at a velocity of about 60 mm/year. The direction of relative 1943 06 09 0306 -1.000 101.000 50 7.5 0 Medan Kuala New Port Lumpur plate motion is oblique to the orientation of the plate boundary offshore 2000 06 04 1628 -4.762 102.007 35 7.9 350.01 - 400.00 Seremban of the west coast of Sumatra. The component of plate-motion 2002 11 02 0126 2.82 96.08 30 7.6 Melaka 2004 12 26 0058 3.30 95.98 30 9.1 400.01 - 450.00 Finite Fault Model Kuching Manado perpendicular to the boundary is accommodated by thrust faulting on the Singapore 2005 03 28 1609 2.09 97.11 30 8.6 Pekanbaru Johor offshore plate-boundary. Much of the component of plate motion Baharu Pontianak 2006 07 17 0819 -9.25 107.41 34 7.7 for M8.5 Earthquake 0° Samarinda 0° parallel to the plate boundary is accommodated by strike-skip faulting on 2007 08 08 1704 -5.91 107.67 280 7.5 Padang FINITE FAULT MODEL Balikpapan the Sumatra fault, which is inland on Sumatra proper. Jambi 2007 09 12 1110 -4.438 101.367 34 8.5 Contributed by Palangkaraya 2007 09 12 2349 -2.625 100.841 35 7.9 Chen Ji, University of Palembang Bandjermasin The magnitude 8.5 earthquake of September 12, 2007 is the fourth California at Santa Barbara Bengkulu Kendari Ambon earthquake of magnitude greater than 7.9 to have occurred in the past and Yuehua Zeng, NEIC D Tanjungkarang- decade on or near the plate boundaries offshore of western Sumatra. is ta Telukbetung Makassar n This earthquake occurred just north of the source region of the Distribution of the amplitude c Jakarta e and direction of slip for a magnitude 7.9 earthquake on June 4, 2000. The September 12, 2007 lo Bandung Semarang n magnitude 7.9 earthquake occurred about 225 km northwest of the subfault elements (small g Yogyakarta Surabaya s rectangles) of the fault rupture tr Mataram magnitude 8.5 earthquake at the northern end of the aftershock zone. ik EPICENTRAL REGION Dili model are determined from the e These two earthquakes and their aftershocks overlay the southern 3 DATA SOURCES inversion of teleseismic body 2 portion of the estimated 1833 rupture zone, which extends from 3 10° Kupang 10° waveforms. Arrows indicate ° approximately Eggano Island to the northern portion of Siberut Island. EARTHQUAKES AND SEISMIC HAZARD (N the amplitude and direction of 3 USGS, National Earthquake Information Center REFERENCES 7 The great magnitude 9.1 earthquake of December 26, 2004, which NOAA, National Geophysical Data Center slip (of the hanging wall with W produced the devastating Indian Ocean tsunami of that date, ruptured ) respect to the foot wall); the (k IASPEI, Centennial Catalog (1900 - 1999) and Bird, P., 2003, An updated digital model of plate boundaries: m much of the boundary separating the India plate and the Burma plate. extensions (Engdahl and Villaseñor, 2002) Geochem. Geophys. Geosyst., v. 4, no. 3, pp. 1027- 80. slip amount is also color-coded ) HDF (unpublished earthquake catalog) (Engdahl, 2003) as shown. The view of the -1 90° 100° 110° 120° 130° Global Seismic Hazard Assessment Program Engdahl, E.R. and Villaseñor, A., 2002, Global Seismicity: rupture plane is from above. 5 9 1900 - 1999, chap. 41 of Lee, W.H.K., and others,eds., .5 Seismic hazard is expressed as peak SCALE 1:20,000,000 at the Equator ) PLATE TECTONICS AND FAULT MODEL International Earthquake and Engineering Seismology, The strike of the fault rupture km ground acceleration (PGA) on firm Kilometers ( DISCLAIMER PB2002 (Bird, 2003) Part A: New York, N.Y., Elsevier Academeic Press, 932 p. plane is N37W and the dip is ip st rock, in meters/sec², expected to be 0 200 400 800 1,200 1,600 nd a Finite Fault Model, Chen Ji, UC Santa Barbara (2007) w he 12 NE. The dimensions of the o rt exceeded in a 50-yr period with a Engdahl, E.R., Van der Hilst, R.D., and Buland, R.P., 1998, d o Peak Ground Acceleration in m/sec**2 Base map data, such as place names and political subfault elements are 20 km in ce N probability of 10 percent. BASE MAP Global teleseismic earthquake relocation with improved trav- n 2° boundaries, are the best available but may not be the strike direction and 14.5 ta 1 NIMA and ESRI, Digital Chart of the World el times and procedures for depth determination: Bull. Seism. 0 is ip current or may contain inaccuracies and therefore km in the dip direction. 0 D DMap prepared by U.S. Geological Survey should not be regarded as having official significance. USGS, EROS Data Center Soc. Amer., v. 88, p. 722-743. National Earthquake Information Center .2 .4 .8 1.6 2.4 3.2 4.0 4.8 NOAA GEBCO and GLOBE Elevation Models 13 September 2007 Map not approved for release by Director USGS