Northwest U.S. Quake of February 2001
| On February 28, 2001, at 10:54 a.m. Pacific Standard Time, a section of the Juan de Fuca Plate being subducted under the North American Plate gave way along a normal fault, producing an earthquake with an epicenter 58 kilometers southwest of Seattle, Washington. The 6.8 magnitude quake originated around 50 kilometers below the surface, and shook the western edge of the state, including the capital city of Olympia. The map here shows the relationship between perceived shaking of the ground (the Mercalli-scale intensity), and geophysical parameters, such as peak velocity (the fastest the earth moved during the quake itself). The pattern displayed on a map such as this can help geologists better understand the underlying rock profile and type, as well as improve deep fault-line mapping. Fortunately, the damage inflicted and the number of casualties and injuries reported for this earthquake were rather moderate for an earthquake of this amplitude, partly due to the depth of the tremblor's focus, and partly due to the quality of the construction of the buildings in the area. A similar earthquake rocked this area in 1941, and in 1980, the nearby volcanic mountain of Mount St. Helens erupted violently, two events also ultimately caused by the subduction of the small oceanic plate into the continental North American Plate. |
Credit: Map by the Pacific Northwest Seismograph Network (PNSN) (modified)
For more info: http://spike.geophys.washington.edu/shake/0102281854/intensity.html