U.S. DEPARTMENT OF THE INTERIORU.S. GEOLOGICAL SURVEY

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Padang

MedanKuala

Lumpur

IndianOcean

Strait ofMalacca

Sumatra

Engano

PagaSelatan

Sipura

Siberut

Tanahbasa

Tanahmasa

Nias

Simeulue

Indonesia

Malaysia

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95°

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Indonesia

Laos

Cambodia

Vietnam

Thailand

Malaysia

Christmas I.

Myanmar ParacelIs.

SpratlyIs.

India

SriLanka

Singapore

CocosIs.

AndamanSea

SouthChinaSea

Java Sea

SuluSea

CelebesSea

IndianOcean

110°

110°

100°

100°

90°

90°

80°

80°

10° 10°

0° 0°

10° 10°

M7.8 Southwest of Sumatra Earthquake of 02 March 2016

0 250 500125Kilometers_̂

Cambodia Vietnam

Thailand

Malaysia

Christmas I.

SpratlyIs.

India

SriLanka

Singapore

Indonesia

CocosIs.

110°

110°

100°

100°

90°

90°

80°

80°

10° 10°

0° 0°

10° 10°

0 500 1,000 1,500250Kilometers

Prepared in cooperation with the Global Seismographic Network

Tectonic Setting

Seismic Hazard

Epicentral Region

T ECT ONIC S U MMARYT he Ma rch 2, 2016 M 7.8 ea rthqua ke, 800 km off the west coa st of southern S uma tra , In don esia , occurred a s a result of strike-slip fa ultin g within the ocea n ic lithosphere of the In do-Austra lia pla te. T his even t isloca ted 600 km to the southwest of the ma jor sub duction zon e tha t defin es the pla te b oun da ry b etween the In dia /Austra lia a n d S un da pla tes offshore S uma tra . At this loca tion , the In dia /Austra lia pla tes move n orth-n orthea st rela tive to the S un da pla te a t a velocity of a b out 55 mm/yr. T he deforma tion zon e defin in g the defuse b oun da ry b etween the In dia a n d Austra lia pla tes is n ea rb y the Ma rch 2 ea rthqua ke.L a rge strike-slip ea rthqua kes a re n ot un preceden ted in the diffuse b oun da ry region sepa ra tin g the In dia a n d Austra lia pla tes, southwest of the S uma tra sub duction zon e. In 2012, two even ts of M 8.6 a n d M 8.2 on thesa me da y (04/12/2012) ruptured a series of ocea n ic strike-slip structures 650-850 km to the n orth of the Ma rch 3, 2016 even t. On J un e 18, 2000, a M 7.9 ea rthqua ke ruptured a n ocea n ic strike-slip structure a b out1000 km southea st of the Ma rch 3, 2016 ea rthqua ke. T he foca l mecha n isms of the a ll of these ea rthqua kes a re con sisten t in implyin g tha t ea ch even t could ha ve occurred a s the result of left-la tera l slip on a na pproxima tely n orth strikin g fa ult or right-la tera l slip on a n a pproxima tely west strikin g fa ult. T he two differen t orien ta tion s of strike-slip fa ultin g a re b oth possib le un der the sa me tecton ic stress field; perpen dicula rstrike-slip fa ults tha t a re b oth compa tib le with the sa me stress field a re ca lled "con juga te fa ults". In 2012, in -depth studies of those ma jor even ts showed tha t fa ults of b oth orien ta tion s were in volved in their ruptureprocesses, b rea kin g a n etwork of con juga te fa ults over a n a rea of ~ 200x200 km in size in the W ha rton Ba sin . Beca use of the remote loca tion s of these ocea n ic ea rthqua kes, such even ts ra rely ca use sha kin g-rela tedfa ta lities (the 2012 M 8.6 even t ca used two). S imila rly, strike-slip ea rthqua kes do n ot typica lly gen era te tsun a mis.

EXPLANATIONEarthquake Magnitude

( 5.5 - 6.5( 6.5 - 7.0

( 7.0 - 7.5

( 7.5 - 8.0

( > 8.0

Earthquake Depth (km)!( 0 - 69

!( 70 - 299

!( ≥ 300

Slab Contours (Depth)<= 20 (km)

40 - 140 (km)

160 - 200 (km)

> 200 (km)

Plate Boundaries# S ub duction

T ra n sform

Divergen t

Others

Finite Fault ModelSlip (m)

< 2

2 - 4

4 - 6

6 - 8

8 - 10

> 10

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.

EXPLANATIONMa g ≥ 7.0 !( 0 - 69 km!( 70 - 299!( 300 - 600

Plate Boundaries# S ub duction

T ra n sformDivergen tOthers

Volca n oes#*

0 500 1,000 1,500250Kilometers

Pea k Groun d Accelera tion in m/sec**2

.2 .4 .8 1.6 2.4 3.2 4.0 4.8

Epicentral Region

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Epicentral Region

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)EHB catalog (Engdahl et al., 1998)HDF (unpublished earthquake catalog, Engdahl, 2003)Global Seismic Hazard Assessment ProgramVolcanoes of the World (Siebert and Simkin, 2002)PLATE TECTONICS AND FAULT MODELPB2002 (Bird, 2003)Ji, C., D.J. Wald, and D.V. Helmberger, Source description of the 1999 Hector Mine, California earthquake; Part I: Waveletdomain inversion theory and resolution analysis, Bull. Seism. Soc. Am., Vol 92, No. 4. pp. 1192-1207, 2002.DeMets, C., Gordon, R.G., Argus, D.F., 2010.Geologically current plate motions, Geophys. J. Int. 181, 1-80.

BASE MAPNIMA and ESRI, Digital Chart of the WorldUSGS, EROS Data CenterNOAA GEBCO and GLOBE Elevation Models

REFERENCESBird, P., 2003, An updated digital model of plate boundaries: Geochem. Geophys. Geosyst., v. 4, no. 3, pp. 1027-80.

Engdahl, E.R., and Villasenor, 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 Academic Press, 932 p.Engdahl, E.R., Van der Hilst, R.D., and Buland, R.P.,1998, Global teleseismic earthquake relocation with improved travel times and procedures for depth determination;Bull. Seism. Soc. Amer., v. 88, p. 722-743.

EARTHQUAKE SUMMARY MAP

SUNDA PLATE

PAGER

DISCLAIMER

Base map data, such as place names and political boundaries, are the best available but may not be current or may contain inaccuracies and therefore should not be regarded as having official signifiance.Map updated by U.S. Geological Survey National Earthquake Information Center 02 March 2016http://earthquake.usgs.gov/ Map not approved for release by Director USGS

M7.8 Southwest of Sumatra Earthquake of 02 March 2016 02 March 2016 12:49:46 -4.905, 94.236Depth 10 km M = 7.8

INDIAPLATE

Burma

Distrib ution of the a mplitude a n d direction of slip for sub fa ult elemen ts of the fa ult rupture model a redetermin ed from the in version of teleseismic b ody wa veforms a n d lon g period surfa ce wa ves. Arrowsin dica te the a mplitude a n d direction of slip (of the ha n gin g wa ll with respect to the foot wa ll); the slip isa lso colored b y ma gn itude.T he view of the rupture pla n e is from a b ove. T he strike of the fa ult rupturepla n e is 274° a n d the dip is 84°N. T he dimen sion s of the sub fa ult elemen ts a re 9 km in the strikedirection a n d 5 km in the dip direction .T he rupture surfa ce is a pproxima tely 35 km a lon g strike a n d 20km down dip. T he seismic momen t relea se b a sed upon this pla n e is 6.0e+27 dyn e.cm.

Finite Fault Model