Page 1

Map prepared by U.S. Geological SurveyNational Earthquake Information Center2 October 2009Map not approved for release by Director USGS

EARTHQUAKE SUMMARY MAP XXXU.S. DEPARTMENT OF THE INTERIORU.S. GEOLOGICAL SURVEY

DISCLAIMERBase map data, such as place names and politicalboundaries, are the best available but may not be current or may contain inaccuracies and thereforeshould not be regarded as having official significance.

Andaman Islands

ANDAMAN SEA

A n d a m a n B a s i n

Middle Andaman

South Andaman

Little Andaman

INDIACar Nicobar

S u m a t r a

J a v a

Siberut

Sipora

N PagaiS Pagai

Enggano

PiniNias

Tanahbala

I N D O N E S I A

2004

1797

2005

1833

2000 Jakarta

MelakaNegeri Sembilan

Selangor Pahang

SumateraSelatan

Songkhla

TerengganuPerak KelantanPulau Pinang

KedahNarathiwatAndaman and Nicobar

IslandsYala

PerlisPattani

JawaTimurJawa Tengah

Jakarta RayaJawa Barat

Lampung

Johor

Sumatera Barat

Bengkulu

Kalimantan Barat

Jambi KalimantanTengah

Singapore

Sumatera Utara

Aceh

Sarawak

Riau

2005

2004

2004

2004

2007

2007

2007

2007

2008

2008

A'

A

Pontianak

Padang

Jambi

Bengkulu

Tanjungkarang-Telukbetung

AlorSetar

KuantanNew Port

YalaKotaBaharu

PinangBandaAceh

KualaTerengganu

Ipoh

Seremban

Melaka

KuchingJohorBaharu

PekanbaruSingapore

SemarangBandung

Palembang

KualaLumpur

Medan

Narathiwat

KemamanHarbor

PattaniSatun Kangar

KualaLipis

ShahAlam

1907

1913

1914

1916

1900

1984

20012000

1998

1983

1976

1975

1971

1969

19631957

1955

19501949

1909

1946

1943

19431943

1943

1936

1936

19361935

1935

193319311931

1917

110°

110°

108°

108°

106°

106°

104°

104°

102°

102°

100°

100°

98°

98°

96°

96°

94°

94°

92°

92°

6° 6°

4° 4°

2° 2°

0° 0°

2° 2°

4° 4°

6° 6°

PALAWAN

TROUGH

SU NDA (J AVA) T RENCH

AUSTRALIA PLATE

BURMAPLATE

SUNDA PLATE

MOLUCCASEA

PLATE

BANDA SEAPLATE

AUSTRALIAPLATE

S O U T HC H I N A

S E A

J A VA S E A

A N D A M A NS E A

B A Y O FB E N G A L

BorneoSumatra

Java Lesser Sunda IslandsGreater Sunda Is lands

S u m a t r a F a u l t

P h i l i p p i n eF a u l t

I N D O N E S I A

S R I L A N K A

T H A I L A N D

S I N G A P O R E

MA L A Y S I A

C A M B O D I AV I E T N A M

P H I L I P P I N E S

B R U N E I

M A L A Y S I A

Gulfof

Thailand

M i d - I n d i a nB a s i n

N o r t hA u s t r a l i a n

B a s i n

Ni n

et y

Ea

s t R

i dg

e

Investigat o r Ri d g e

O s b o r nP l a t e a u

C e l e b e sB a s i n

60 mm/yr

18332000

2005

2004

1797

120°

120°

110°

110°

100°

100°

90°

90°

10° 10°

0° 0°

10° 10°

M7.6 Southern Sumatra, Indonesia, Earthquake of 30 September 2009

0 220 440 660 880110Kilometers

INDONESIA

Palembang

Surabaya

QuezonCity

Manila

PhnomPenh

Davao

Medan KualaLumpur

Singapore

Makassar

Bandung Semarang

Darwin

QuangNgai

KuantanNew Port

NakhonSawan Ubon

Ratchathani

Pinang

NakhonRatchasimaSaraburiPhra Nakhon

Si AyutthayaTavoy Play CuQui NhonSamut PrakanSamutSakhon

SiemreabBatdambangBuon Me

Thuot NhaTrang

Da LatPortBlair

Bien HoaPhanThiet

LongXuyen My Tho

VinhLongCan ThoRach Gia

SocTrang

Bac LieuNakhon SiThammarat

SongkhlaYala Kota

BaharuAlor

Setar KotaKinabaluBanda

AcehKualaTerengganu

BandarSeri

BegawanIpoh

SerembanMelaka KuchingJohorBaharu Manado

PekanbaruPontianak SamarindaPadang BalikpapanJambi

PalangkarayaBandjermasin AmbonBengkulu Kendari

Tanjungkarang-Telukbetung

YogyakartaDiliMataram

Kupang

Jakarta

Bangkok

130°

130°

120°

120°

110°

110°

100°

100°

10° 10°

0° 0°

10° 10°

DATA SOURCESEARTHQUAKES AND SEISMIC HAZARD USGS, National Earthquake Information Center NOAA, National Geophysical Data Center IASPEI, Centennial Catalog (1900 - 1999) and extensions (Engdahl and Villaseñor, 2002) HDF (unpublished earthquake catalog) (Engdahl, 2003) Global Seismic Hazard Assessment ProgramPLATE TECTONICS AND FAULT MODEL PB2002 (Bird, 2003) Finite Fault Model, Chen Ji, UC Santa Barbara (2007)BASE MAP NIMA and ESRI, Digital Chart of the World USGS, EROS Data Center NOAA GEBCO and GLOBE Elevation Models

0 410 820 1,230 1,640205Kilometers

Prepared in cooperation

with the Global Seismographic

Network

Tectonic Setting

Seismic Hazard

Epicentral Region

Southern Sumatra 30 September 2009 10:16:09 UTC 0.788° S., 99.961° E.Depth 80 kmMw = 7.6 (USGS)45 km (30 miles) WNW of Padang, Sumatra, Indonesia220 km (135 miles) SW of Pekanbaru, Sumatra, Indonesia475 km (295 miles) SSW of KUALA LUMPUR, Malaysia

TECTONIC SUMMARYThe magnitude 7.6 southern Sumatra earthquake of September 30, 2009occurred as a result of oblique-thrust faulting near the subductioninterface plate boundary between the Australian and Sunda plates. At thelocation of this earthquake, the Australian Plate moves northeast withrespect to the Sunda plate at a velocity of approximately 60 mm/yr.On the basis of the currently available fault mechanism information andearthquake depth of 80 km, it is likely that this earthquake occurredwithin the subducting Australian Plate rather than on the plate interfaceitself. The recent earthquake was deeper than typical subduction thrustearthquakes that generally occur at depths less than 50 km.The subduction zone surrounding the immediate region of this event hasnot witnessed a megathrust earthquake in the recent past, rupturing lastin an earthquake of M 8.5 or larger in 1797. Approximately 350km tothe south, a 250km section of the plate boundary slipped during an Mw8.4 earthquake in September 2007, while approximately 300km to thenorth, a 350km section slipped during the Mw 8.7 earthquake of March2005. In early 2008, the plate boundary updip of today's earthquake wasactive in a sequence of Mw 5-6 earthquakes. It is not clear how today'searthquake is related to the sequence of megathrust subduction zoneevents on the shallower section of the plate boundary.

Seismic hazard is expressed as peakground acceleration (PGA) on firmrock, in meters/sec², expected to beexceeded in a 50-yr period with aprobability of 10 percent.

EXPLANATIONMag ≥ 7.0

0 - 69 km70 - 299300 - 600

Plate BoundariesSubductionTransformDivergentOthersAndaman FaultsRupture Area (Year)

RELATIVE PLATE MOTIONSIn the region of this earthquake,the Australia Plate movesnorth-northwest with respect tothe Sunda Plate at about 65 mm/yr.

0 410 820 1,230 1,640205Kilometers

REFERENCESBird, P., 2003, An updated digital model of plate boundaries: Geochem. Geophys. Geosyst., v. 4, no. 3, pp. 1027- 80.Engdahl, E.R. and Villaseñor, A., 2002, Global Seismicity: 1900 - 1999, chap. 41 of Lee, W.H.K., and others,eds., International Earthquake and Engineering Seismology, Part A: New York, N.Y., Elsevier Academeic Press, 932 p.Engdahl, E.R., Van der Hilst, R.D., and Buland, R.P., 1998, Global teleseismic earthquake relocation with improved trav- el times and procedures for depth determination: Bull. Seism. Soc. Amer., v. 88, p. 722-743.The GEBCO_08 Grid, version 20090202, http://www.gebco.net

Significant Earthquakes Mag >= 7.0

Year Mon Day Time Lat Long Dep Mag1900 01 05 1900 -3.000 102.000 0 7.01907 01 04 0519 2.000 94.500 50 7.51909 06 03 1840 -2.000 101.000 0 7.21913 08 13 0425 -5.500 105.000 75 7.31914 06 25 1907 -4.500 102.500 0 7.61916 07 27 1152 4.000 96.500 100 7.01917 11 04 1203 4.800 96.800 0 7.11931 02 10 0634 -5.433 102.458 35 7.11931 09 25 0559 -5.178 102.511 35 7.31933 06 24 2154 -5.522 104.434 35 7.31935 08 03 0110 4.430 96.326 35 7.01935 12 28 0235 -0.345 98.147 35 7.81936 01 02 2234 -0.279 98.872 35 7.01936 08 23 2112 5.296 94.759 35 7.11936 09 19 0101 3.648 97.551 35 7.11943 04 01 1418 -6.500 105.500 0 7.11943 06 08 2042 -1.000 101.000 50 7.21943 06 09 0306 -1.000 101.000 50 7.51943 11 26 2125 -2.500 100.000 130 7.11946 05 08 0520 0.000 99.500 0 7.11949 06 24 2238 -6.200 105.700 65 7.01950 03 27 2118 -5.900 102.900 0 7.01955 05 17 1449 6.738 93.754 29.1 7.21957 04 16 0404 -4.504 107.244 600 7.21963 12 15 1934 -4.764 108.050 668 7.11969 11 21 0205 1.973 94.574 11 7.61971 02 04 1533 0.552 98.665 60 7.11975 10 01 0330 -4.859 102.145 37.2 7.01976 06 20 2053 3.437 96.254 16.2 7.01983 04 04 0251 5.724 94.694 94.5 7.01984 11 17 0649 0.179 97.959 28.7 7.11998 04 01 1756 -0.544 99.217 32 7.02000 06 04 1628 -4.762 102.007 34.6 7.92001 02 13 1928 -4.933 102.454 34 7.32004 07 25 1435 -2.427 103.981 582 7.32004 12 26 0058 3.295 95.982 30 9.02004 12 26 0421 6.910 92.958 39 7.22005 03 28 1609 2.085 97.108 30 8.62007 08 08 1705 -5.859 107.419 280 7.52007 09 12 1110 -4.438 101.367 34 8.52007 09 12 2349 -2.625 100.841 35 7.92007 09 13 0335 -2.130 99.627 22 7.02008 02 20 0808 2.768 95.964 26 7.42008 02 25 0836 -2.486 99.972 25 7.2

Peak Ground Acceleration in m/sec**2

.2 .4 .8 1.6 2.4 3.2 4.0 4.8

EPICENTRAL REGION

EXPLANATIONMain Shock

M6.6 1 Oct 2009Earthquake Magnitude

5.50 - 5.996.00 - 6.997.00 - 7.998.00 - 8.99

9.00 - 9.99

Earthquake Depth0 - 6970 - 299300 - 700Sumatra Fault

EPICENTRAL REGION

Depth

(km)

Distance (km)A A' -300

-300

-200

-200

-100

-100

0

0

100

100

200

200

-300 -300

-200 -200

-100 -100

0 0

Southern Sumatra 1 October 2009 1:52:47 UTC -2.602° S., 101.702° E.Depth 10 kmMw = 6.6 (USGS) .

-300

-300

-200

-200

-100

-100

0

0

100

100

200

200

-300 -300

-200 -200

-100 -100

0 0