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

EARTHQUAKE SUMMARY MAP

Prepared in cooperation with the Global Seismographic Network

M8.2 Offshore Northern Chile Earthquake of 1 April 2014 Epicentral Region

Tectonic Setting 80°

70°

75°

60°

70°

65°

PAGER

Colombia

Ecuador

Lima

1974

SOUTH AMERICA PLATE

10°

Brazil

Huancayo

Callao

2007

10°

Cuzco 1994

1963 1908

Brazil

NAZCA PLATE

Ica

Peru

Peru

1942 15°

15°

1996 Bolivia

1960 1922

20°

20°

2001

Pacific Ocean Chile

EXPLANATION

Bolivia

La Paz

Arequipa 1913 Paraguay

M M aa ii nn S S hh oo cc kk

Cochabamba

2001

Mag >= 6.0

Tacna

Epicentral Region

0 - 69 km

Santa Cruz de La Sierra

Oruro

EXPLANATION

70 - 299

Earthquake Magnitude

300 - 600

Argentina

30° Plate Boundary

Sucre

5.5 - 5.99

30°

6.0 - 6.99

Subduction

Potosi

7.0 - 7.99

Transform Uruguay

Divergent

20°

Others

2005

= 8.0

20°

Earthquake Depth (km)

Volcanoes

1959

0 - 69 80°

70°

1976

60°

70 - 299 Kilometers 0

250

500

1,000

= 300

1,500

Finite Fault Model

Subduction

Seismic Hazard 80°

70°

60°

Divergent

Colombia

Ecuador

Paraguay

Transform

Others

Slab Contours (Depth) 65 mm/yr

10°

Distribution of the amplitude and direction of slip for subfault elements of the fault rupture model are determined from the inversion of teleseismic body waveforms and long period surface waves. Arrows indicate the amplitude and direction of slip (of the hanging wall with respect to the foot wall); the slip is also colored by magnitude.The view of the rupture plane is from above. The strike of the fault rupture plane is almost directly North (358°) and the dip is 15°E. The dimensions of the subfault elements are 12 km in the strike direction and 10 km in the dip direction.The rupture surface is approximately 40 km along strike and 30 km downdip. The seismic moment release based upon this plane is 2.35e+28

2007

M8.2 Offshore Northern Chile Earthquake of 1 April 2014

0 - 120 (20 km intervals)

Seismic hazard is expressed as peak ground acceleration (PGA) on firm rock, in meters/sec², expected to be exceeded in a 50-yr period with a probability of 10 percent.

01 April 2014 23:46:46 UTC

160 - 360 (40 km intervals) 400 - 560 (40 km intervals)

San Salvador De Jujuy

Finite Fault Model

Peru

Chile

Antofagasta

600 + (40 km intervals)

10°

Brazil

1950

1995

19.642° S., 70.817° W. Depth 20.1 km Mw = 8.2 (USGS)

Argentina

1987

Slip(cm) Salta

0 - 100 25°

25°

100 - 200 200 - 300

71 mm/yr

1966

300 - 400 400 - 500

0

Bolivia

500 - 600 20°

20°

600 - 700

Depth Profile Extent

San Miguel De Tucuman

Kilometers 0

125

250

500

75°

70°

65°

Paraguay Chile

TECTONIC SUMMARY

73 mm/yr

0 6154 -6113

Epicentral Region

Argentina

30°

30°

Uruguay

The April 1, 2014 M8.2 earthquake in northern Chile occurred as the result of thrust faulting at shallow depths near the Chilean coast. The location and mechanism of the earthquake are consistent with slip on the primary plate boundary interface, or megathrust, between the Nazca and South America plates. At the latitude of the earthquake, 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 and has produced some of the largest earthquakes in the world, including the 2010 M 8.8 Maule earthquake in central Chile, and the largest earthquake on record, the 1960 M 9.5 earthquake in southern Chile.

Kilometers 0

250

500

1,000

The April 1 earthquake occurred in a region of historic seismic quiescence – termed the northern Chile or Iquique 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.

1,500

80°

70°

60°

Peak Ground Acceleration in m/sec**2

.2

.4

.8

1.6

2.4

3.2

4.0

Significant Earthquakes Mag >= 7.5 Year Mon Day Time Lat 1908 12 12 1208 -14.000 1913 08 06 2214 -17.000 1922 10 11 1450 -16.125 1942 08 24 2250 -14.975 1950 12 09 2138 -23.500 1959 06 14 0012 -20.369 1960 01 13 1540 -15.814 1963 08 15 1725 -13.742

Long Dep Mag -78.000 60 8.2 -74.000 0 7.8 -72.385 160 7.6 -74.920 35 7.7 -67.500 100 7.7 -68.881 111 7.5 -72.788 95.4 7.5 -69.332 552 7.7

1966 1974 1976 1983 1987 1994 1995 1996

12 10 11 10 03 06 07 11

28 03 30 04 05 09 30 12

0818 -25.502 1421 -12.254 0041 -20.472 1852 -26.539 0917 -24.395 0033 -13.856 0511 -23.285 1659 -14.950

-70.655 -77.524 -68.893 -70.503 -70.102 -67.489 -70.103 -75.532

30 7.7 33.9 8.1 133 7.6 24.6 7.7 45.3 7.6 631 8.2 46 8.0 21 7.7

2001 2001 2005 2007 2007 2014

06 07 06 08 11 04

23 07 13 15 14 01

2033 -16.305 0938 -17.522 2244 -19.987 2340 -13.386 1540 -22.247 2346 -19.642

-73.550 -71.938 -69.197 -76.603 -69.890 -70.817

29.8 8.4 17.4 7.6 115 7.8 39 8.0 40 7.7 20.1 8.2

4.8

A recent increase in seismicity rates has occurred in the vicinity of the April 1 earthquake. An M6.7 earthquake with similar faulting mechanism occurred on March 16, 2014 and was followed by 60+ earthquake of M4+, and 26 earthquakes of M5+. The March 16 earthquake was also followed by three M6.2 events on March 17, March 22, and March 23. The spatial distribution of seismicity following the March 16 event migrated spatially to the north through time, starting near 20°S and moving to ~19.5°S. The initial location of the April 1 earthquake places the event near the northern end of this seismic sequence. Other recent large plate boundary ruptures bound the possible rupture area of the April 1 event, including the 2001 M 8.4 Peru earthquake adjacent to the south coast of Peru to the north, and the 2007 M 7.7 Tocopilla, Chile and 1995 M 8.1 Antofagasta, Chile earthquakes to the south. Other nearby events along the plate boundary interface include an M 7.4 in 1967 as well as an M 7.7 in 2005 in the deeper portion of the subduction zone beneath inland Chile.

Depth Profile

DATA SOURCES EARTHQUAKES 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 Program PLATE TECTONICS AND FAULT MODEL PB2002 (Bird, 2003) Hayes, G. P., Wald, D. J., and Johnson R. L., 2012, A three-dimensional model of globalsubduction zone geometries: 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.

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

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BASE MAP NIMA and ESRI, Digital Chart of the World USGS, EROS Data Center NOAA GEBCO and GLOBE Elevation Models

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.

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.

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.

Map updated by U.S. Geological Survey National Earthquake Information Center 2 April 2014 http://earthquake.usgs.gov/ Map not approved for release by Director USGS


M8.2 Offshore Northern Chile Earthquake of 1 April 2014