A Shaky Past

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Science  30 Mar 2001:
Vol. 291, Issue 5513, pp. 2517
DOI: 10.1126/science.291.5513.2517d

The earthquake in the Pacific Northwest on 28 February 2001 underscores the potential for future damaging earthquakes in this area. It occurred beneath the southern part of Puget Sound on a normal fault in the Juan de Fuca Plate, which is being subducted eastward beneath North America.

In a timely description of historical context, Bourgeois and Johnson have conducted a study of sediments in the lower Snohomish delta in the Puget Lowland, which is near the epicenter of the recent earthquake. Sediment disturbance has been taken as evidence for tsunamis or liquefaction associated with two large tremors that struck this region during the past 1200 years; this study proposes that at least three other earthquakes also occurred during this period. Thus, this region has regularly been subject to strong shaking in the past, including events equal to or more intense than the most recent disturbance. — BH

Geol. Soc. Am. Bull.113, 482 (2001).

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