M 7.6 - 11 km ENE of Hojancha, Costa Rica
- 2012-09-05 14:42:07 (UTC)
- 10.085°N 85.315°W
- 35.0 km depth
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Estimated Intensity Map Ground Failure - Landslide Estimate
Limited area affected
Limited population exposed
- Liquefaction Estimate
Significant area affected
Significant population exposed
Origin - Review Status
- REVIEWED
- Magnitude
- 7.6 mww
- Depth
- 35.0 km
- Time
- 2012-09-05 14:42:07 UTC
Moment Tensor Fault Plane Solution Finite Fault 
Cross-section of slip distribution. View Nearby Seismicity - Time Range
± Three Weeks - Search Radius
250.0 km - Magnitude Range
≥ 4.0
Contributors US
USGS National Earthquake Information Center, PDE
Tectonic Summary
The September 5, 2012, M 7.6 earthquake beneath the Nicoya Peninsula, Costa Rica, occurred as the result of shallow thrust faulting on or near the subduction zone interface between the Cocos and Caribbean plates. At the location of this earthquake, the Cocos plate moves north-northeast with respect to the Caribbean plate at a velocity of about 77 mm/yr, and subducts beneath Central America at the Middle America Trench west of the September 5th earthquake.
While commonly plotted as points on maps, earthquakes of this size are more appropriately described as slip over a larger fault area. Thrust-faulting events of the size of the August 31, 2012, earthquake are typically about 90x45 km (length x width); modeling of this earthquake implies dimensions of about 80x90 km, predominantly surrounding and up-dip of the hypocenter.
Over the past 40 years, the region within 250 km of the September 5th earthquake has experienced approximately 30 M 6+ earthquakes; two of these were larger than M 7, neither of which caused documented fatalities. The first of these two historic M 7+ events was a M 7.2 earthquake in August 1978, 9 km to the north-northeast of the September 5th event; the second had a magnitude of 7.3 and struck a region just over 50 km to the east-southeast in March 1990. The M 7.8 earthquake of October 5, 1950, occurred in the general area of the September 5th earthquake, although the hypocenter of the earlier earthquake is not known to high precision. The 1950 earthquake caused damage in northwestern Costa Rica and in the Valle Central of Costa Rica, but no casualties were reported. The nearest earthquake to cause fatalities in recent history was the M 6.5 April 1973 earthquake, which occurred at shallow depth approximately 80 km to the northeast; the 1973 event resulted in 26 fatalities and more that 100 injuries.
Hayes et al. (2016) Tectonic summaries of magnitude 7 and greater earthquakes from 2000 to 2015, USGS Open-File Report 2016-1192. (5.2 MB PDF)
Summary Poster
