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

Brazil

Bolivia

Peru

Argentina

Paraguay

Chile

1908

1922

1942

1959

1966

1974

1976

1994

1995

1996

2001

2001

2005

2007

2007

1913

1950

1960

1963

1987

Huancayo

Cuzco

Ica

Cochabamba Santa Cruzde LaSierra

OruroTacna

Sucre

Potosi

AntofagastaSan SalvadorDe Jujuy

Salta

San MiguelDe Tucuman

Callao

Arequipa La Paz

Lima

65°

65°

70°

70°

75°

75°

15° 15°

20° 20°

25° 25°

Brazil

Ecuador

Bolivia

Peru

Argentina

Paraguay

Uruguay

Colombia

Chile

PacificOcean

60°

60°

70°

70°

80°

80°

10° 10°

20° 20°

30° 30°

M8.2 and Aftershocks Offshore Northern Chile Earthquake of 1 April 2014

0 250 500125Kilometers

65 mm/yr

71 mm/yr

73 mm/yr

Brazil

Ecuador

Bolivia

Peru

Argentina

Paraguay

Uruguay

Colombia

Chile

60°

60°

70°

70°

80°

80°

10° 10°

20° 20°

30° 30°

0 500 1,000 1,500250Kilometers

Prepared in cooperation with the Global Seismographic Network

Tectonic Setting

Seismic Hazard

Epicentral Region

EXPLANATIONMain Shock

M7.6 Aftershock

Earthquake Magnitude5.5 - 5.996.0 - 6.997.0 - 7.99= 8.0

Earthquake Depth (km)0 - 6970 - 299= 300

AftershocksBetween M8.2 and M7.6After M7.6SubductionTransformDivergentOthers

Slab Contours (Depth)0 - 120 (20 km intervals)160 - 360 (40 km intervals)400 - 560 (40 km intervals)600 + (40 km intervals)

Finite Fault ModelSlip(cm)

0 - 100100 - 200200 - 300300 - 400400 - 500500 - 600600 - 700

Depth Profile Extent

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.

EXPLANATIONMain Shock

M7.6 Aftershock

Mag >= 6.00 - 69 km70 - 299300 - 600

Plate BoundarySubductionTransformDivergentOthers

Volcanoes

0 500 1,000 1,500250Kilometers

Significant Earthquakes Mag >= 7.5Year Mon Day Time Lat Long Dep Mag1908 12 12 1208 -14.000 -78.000 60 8.21913 08 06 2214 -17.000 -74.000 0 7.81922 10 11 1450 -16.125 -72.385 160 7.61942 08 24 2250 -14.975 -74.920 35 7.71950 12 09 2138 -23.500 -67.500 100 7.71959 06 14 0012 -20.369 -68.881 111 7.51960 01 13 1540 -15.814 -72.788 95.4 7.51963 08 15 1725 -13.742 -69.332 552 7.7

1966 12 28 0818 -25.502 -70.655 30 7.71974 10 03 1421 -12.254 -77.524 33.9 8.11976 11 30 0041 -20.472 -68.893 133 7.61983 10 04 1852 -26.539 -70.503 24.6 7.71987 03 05 0917 -24.395 -70.102 45.3 7.61994 06 09 0033 -13.856 -67.489 631 8.21995 07 30 0511 -23.285 -70.103 46 8.01996 11 12 1659 -14.950 -75.532 21 7.7

2001 06 23 2033 -16.305 -73.550 29.8 8.42001 07 07 0938 -17.522 -71.938 17.4 7.62005 06 13 2244 -19.987 -69.197 115 7.82007 08 15 2340 -13.386 -76.603 39 8.02007 11 14 1540 -22.247 -69.890 40 7.72014 04 01 2346 -19.642 -70.817 20.1 8.2

Peak Ground Acceleration in m/sec**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 ProgramPLATE TECTONICS AND FAULT MODELPB2002 (Bird, 2003)Hayes, G. P., Wald, D. J., and Johnson R. L., 2012, Athree-dimensional model of global. subduction zonegeometries: Journal of Geophysical Research, v. 117,B01302, . doi:10.1029/2011JB008524.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

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 Center3 April 2014http://earthquake.usgs.gov/Map not approved for release by Director USGS

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.

M8.2 Offshore Northern Chile Earthquake of 1 April 2014 01 April 2014 23:46:46 UTC 19.642° S., 70.817° W.Depth 20.1 kmMw = 8.2 (USGS)

EARTHQUAKE SUMMARY MAP

PAGER

NAZCAPLATE

SOUTH AMERICA PLATE

Finite Fault Model

TECTONIC SUMMARYThe April 1, 2014 M8.2 earthquake in northern Chile occurred as the result of thrust faulting at shallow depthsnear the Chilean coast. The location and mechanism of the earthquake are consistent with slip on the primaryplate boundary interface, or megathrust, between the Nazca and South America plates. At the latitude of theearthquake, the Nazca plate subducts eastward beneath the South America plate at a rate of 65 mm/yr.Subduction along the Peru-Chile Trench to the west of Chile has led to uplift of the Andes mountain range andhas produced some of the largest earthquakes in the world, including the 2010 M 8.8 Maule earthquake incentral Chile, and the largest earthquake on record, the 1960 M 9.5 earthquake in southern Chile.The April 1 earthquake occurred in a region of historic seismic quiescence – termed the northern Chile orIquique seismic gap. Historical records indicate a M 8.8 earthquake occurred within the Iquique gap in 1877,which was preceded immediately to the north by an M 8.8 earthquake in 1868.A recent increase in seismicity rates has occurred in the vicinity of the April 1 earthquake. An M6.7 earthquakewith similar faulting mechanism occurred on March 16, 2014 and was followed by 60+ earthquake of M4+, and26 earthquakes of M5+. The March 16 earthquake was also followed by three M6.2 events on March 17, March22, and March 23. The spatial distribution of seismicity following the March 16 event migrated spatially to thenorth through time, starting near 20°S and moving to ~19.5°S. The initial location of the April 1 earthquakeplaces the event near the northern end of this seismic sequence. Other recent large plate boundary rupturesbound the possible rupture area of the April 1 event, including the 2001 M 8.4 Peru earthquake adjacent to thesouth coast of Peru to the north, and the 2007 M 7.7 Tocopilla, Chile and 1995 M 8.1 Antofagasta, Chileearthquakes to the south. Other nearby events along the plate boundary interface include an M 7.4 in 1967 aswell as an M 7.7 in 2005 in the deeper portion of the subduction zone beneath inland Chile.On April 3, 2014 a M 7.6 aftershock off the west coast of northern Chile occurred as a result of thrust motion at adepth of approximately 40 km, 23 km south of the city Iquique. The location and mechanism of the earthquakeare consistent with slip on the plate boundary interface, or megathrust, between the Nazca and South Americaplates. At the latitude of the event, the Nazca plate is subducting beneath South America at a rate of ~73 mm/yr.

Depth Profile

Distribution of the amplitude and direction of slip for subfault elements of the fault rupture model aredetermined from the inversion of teleseismic body waveforms and long period surface waves. Arrowsindicate the amplitude and direction of slip (of the hanging wall with respect to the foot wall); the slip isalso colored by magnitude.The view of the rupture plane is from above. The strike of the fault ruptureplane is almost directly North (358°) and the dip is 15°E. The dimensions of the subfault elements are12 km in the strike direction and 10 km in the dip direction.The rupture surface is approximately 40 kmalong strike and 30 km downdip. The seismic moment release based upon this plane is 2.35e+28

M7.6 Offshore Northern Chile Earthquake of 3 April 2014 03 April 2014 02:43:17 UTC 20.400° S., 70.135° W.Depth 40.0 kmMw = 7.6 (USGS)