Magnitude 7.7 Earthquake in Northern Chile

Wednesday, November 14, 2007 at 15:40:53 UTC

12:40:53 PM Local time in Chile

7:40:53 AM Pacific Standard Time

 

Epicenter: Latitude 22.189°S, Longitude 69.843°W

Depth: approximately 60 kilometers.

The Chile earthquake resulted from the sudden release of strain that had accumulated due to subduction of the Nazca plate beneath the South American plate. In this area of the Peru-Chile Trench, the two plates are converging at a rate of about 80 mm per year. The red circle on the left-hand map below indicates the location of the epicenter of the earthquake. With a depth of 60 km, this earthquake probably occurred within the subducting Nazca Plate. The arrows on the Nazca Plate on the right-hand map below show the direction and rate of motion of the Nazca Plates with respect to the South American Plate. Preliminary indications are that damage was light, probably because the earthquake occurred 60 kilometers below the Earth’s surface. A similar magnitude earthquake at a shallow depth would likely have produced much greater damage.

 

 

The record of the Chile earthquake by the University of Portland seismometer is shown below. The first seismic waves to reach UP traveled through Earth’s mantle and required about 12 minutes to travel from the earthquake to Portland. The first-arriving Primary (P) and Secondary (S) waves traveled a long distance through Earth’s mantle from the earthquake to the base of the crust beneath Oregon, then traveled about 40 kilometers through the crust to the Earth’s surface at the University of Portland. The S waves required about 22 minutes to travel from the earthquake to Portland. The last package of seismic waves to arrive consisted of surface waves (Love and Rayleigh waves) that started arriving about 42 minutes after the earthquake occurred in Chile. These waves traveled the ~9000 kilometer distance from earthquake to University of Portland seismometer along the Earth’s surface.

 

Below is a SeismicEruption map of events from 1960 through today.  The region of the cross section in
the next figure is also shown.

 

Cross section through the Chile trench showing the relationship of today's event with other in the subduction zone.  547 events from 1960 through today are shown.  Distance and depth in kilometers.

 

 

Video of aftershock sequence showing the length of the rupture zone.

 

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