 |
 |
 |
|
 |
|
 |
|
|
|
Scientific files |
|
|
| |
 |
Seattle area earthquake on February 28, 2001 |
MEMORANDUM FROM THE LABORATORY FOR DETECTION AND GEOPHYSICS (LDG)
 Contents
Earthquake overview
A large earthquake occurred on February 28, 2001 at 6:54 pm UT (7:54 pm in France). Its magnitude was Mw=6.8 (USGS) and its epicenter was located 20 kilometers NE of Olympia (Washington State) on the west coast of the USA (47.15°N 122.72°W, depth: 52 kilometers). During the last century, several earthquakes with a magnitude above 6.5 occurred in this area (1946, 1949, and 1965). One of these occurred in the very same area as the last earthquake (April 13, 1949, M=7.0).
Seismicity along the north-west coast of the USA is largely related to subduction of the Juan de Fuca oceanic plate. The focal mechanisms of this earthquake were calculated by the USGS and by Harvard and indicated an extensive coseismic rupture (normal faulting). This deformation mechanism is related to the curvature of the oceanic plate which produces extension stress in the upper part of the oceanic crust (upper surface deformation).
 |
Earthquake location map |
Previous seismicity in the area
|
Previous seismicity in the area and isoseismal map |
|
|
|
