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

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_̂

Manizales

Ibague

Piura

Medellin

Cali

Quito

Guayaquil

PacificOcean

Colombia

Ecuador

Peru

75°

75°

85°

85°

5° 5°

5° 5°

#*

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_̂

CaribbeanSea

AtlanticOcean

PacificOcean

68 mm/yr78 mm/yr

74 mm/yr

19 mm/yr

20 mm/yr20 mm/yr

65 mm/yr

58 mm/yr

71 mm/yr

68 mm/yr

61 mm/yr

65°

65°

75°

75°

85°

85°

95°

95°

15° 15°

5° 5°

5° 5°

15° 15°

M7.8 Coastal Ecuador Earthquake of 16 April 2016

0 250 500125Kilom e te rs

_̂

65°

65°

75°

75°

85°

85°

95°

95°

5° 5°

5° 5°

0 500 1,000 1,500250Kilom e te rs

Prepared in cooperation with the Global Seismographic Network

Tectonic Setting

Seismic Hazard

Epicentral Region

TECTON IC SUMMARYThe April 16, 2016 M 7.8 e arthqua ke , offs hore of the we s t coa s t of northe rn Ecua d or, occurre d a s the re s ult of s ha llow thrus t fa ulting on or ne a r the pla te b ound a ry b e twe e n the N a zca a nd Pa cific pla te s . At theloca tion of the e a rthqua ke , the N a zca pla te sub d ucts e a s tward b e ne a th the South Am erica pla te a t a ve locity of 61 m m /yr. The loca tion a nd m e cha nis m of the e a rthqua ke a re cons is te nt with s lip on the prim a ry pla teb ound a ry inte rfa ce , or m e g a thrus t, b e twe e n the s e two m a jor pla te s . Sub d uction a long the Ecua d or Tre nch to the we s t of Ecua d or, a nd the Peru-Chile Tre nch further s outh, ha s le d to uplift of the And e s m ounta inra ng e a nd ha s prod uce d s om e of the larg e s t e a rthqua ke s in the world , includ ing the larg e s t e a rthqua ke on re cord , the 1960 M 9.5 e arthqua ke in s outhe rn Chile .While com m only plotte d a s points on m a ps , e a rthqua ke s of this s ize are m ore a ppropria te ly d e s crib e d a s s lip ove r a la rg e r fa ult a re a . Eve nts of the s ize of the April 16, 2016 e arthqua ke a re typica lly a b out 160x60 kmin s ize (le ng th x wid th).Ecua d or ha s a his tory of larg e sub d uction zone re la te d e a rthqua ke s . Se ve n m a g nitud e 7 or g re a te r e a rthqua ke s ha ve occurre d within 250 km of this e ve nt s ince 1900. On Ma y 14th, 1942, a M 7.8 e arthqua keoccurre d 43 km s outh of this April 16th, 2016 e ve nt. On Ja nuary 31s t, 1906 a M 8.3 e arthqua ke (re porte d ly a s la rg e a s M 8.8 in s om e s ource s ) nucle a te d on the s ub d uction zone inte rfa ce 90 km to the northe a s t of theApril 2016 e ve nt, a nd rupture d ove r a le ng th of a pproxim a te ly 400-500 km , re s ulting in a d a m a g ing ts una m i tha t ca us e d in the re g ion of 500-1,500 fa ta litie s . The April 2016 e arthqua ke is a t the s outhe rn e nd of thea pproxim a te rupture are a of the 1906 e ve nt. A s ha llow, upper crus ta l M 7.2 e arthqua ke 240 km e a s t of the April 2016 e ve nt on March 6th, 1987 re s ulte d in a pproxim a te ly 1,000 fa ta litie s .

EXPLANATIONMain Shock

_̂Aftershocks!(

Earthquake 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

Finite Fault ModelSlip (mm)

Ô < 50

Ô 50 - 150

Ô 150 - 250

Ô 250 - 270

Ô 270 - 340

Ô > 340

Plate Boundaries# Sub d uction

Tra ns form

Dive rg e nt

Othe rs

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# Sub d uction

Tra ns formDive rg e ntOthe rs

0 500 1,000 1,500250Kilom e te rs

Pe a k Ground Acce le ra tion in m /s e c**2

.2 .4 .8 1.6 2.4 3.2 4.0 4.8

Epicentral Region

_̂

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

NAZCAPLATE

PAGER

Dis tribution of the a m plitud e a nd d ire ction of s lip for sub fa ult e le m e nts of the fa ult rupture m od e l a re d e te rm ine dfrom the inve rs ion of te le s e is m ic bod y wa ve form s a nd long pe riod s urfa ce wa ve s . Arrows ind ica te the a m plitud ea nd d ire ction of s lip (of the ha ng ing wa ll with re s pe ct to the foot wa ll); the s lip is a ls o colore d by m a g nitud e . Thevie w of the rupture pla ne is from a b ove . The s trike of the fa ult rupture pla ne is 29° a nd the d ip is 15°ESE. Thed im e ns ions of the s ub fa ult e le m e nts a re 14 km in the s trike d ire ction a nd 10 km in the d ip d ire ction. The rupturesurfa ce is a pproxim a te ly 70 km a long s trike a nd 20 km a long d ownd ip. The s e is m ic m om e nt re le a s e b a s e dupon this pla ne is 7.1e+27 d yne .cm .

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 18 April 2016http://earthquake.usgs.gov/ Map not approved for release by Director USGS

M7.8 Coastal Ecuador Earthquake of 16 April 2016 16 April 2016 23:58:37 UTC 0.371° N., 79.94° W.Depth 19.2 kmMw = 7.8 (USGS)

COCOSPLATE

Finite Fault Model

SOUTH AMERICA PLATE

CARIBBEAN PLATE