ML20151H111

Seismic Hazard from Interplate Earthquakes in Puget Sound Region, Presented at 880412-15 Meeting in Olympia,Wa

ML20151H111
Person / Time
Site:	Trojan File:Portland General Electric icon.png
Issue date:	04/12/1988
From:	Crosson R WASHINGTON, UNIV. OF, SEATTLE, WA
To:
Shared Package
ML20151H012	List: ML20151H010 ML20151H017 ML20151H028 ML20151H047 ML20151H066 ML20151H071 ML20151H077 ML20151H080 ML20151H093 ML20151H106 ML20151H111 ML20151H116 ML20151H122 ML20151H126 ML20151H138 ML20151H144 ML20151H147 ML20151H159 ML20151H170 ML20151H176 ML20151H185 ML20151H197 ML20151H213 ML20151H217 ML20151H229 ML20151H240 ML20151H253 ML20151H263 ML20151H272 ML20151H275 ML20151P543 ML20151P567 ML20151P703 ML20151P721 ML20151P744 ML20151P748 ML20151P767 ML20151P772 ML20151P775 ML20151P793 ML20151P805 ML20151P816 ML20151P819 ML20151P833 ML20151P842 ML20151P847 ML20151P854 ML20151P858 ML20151P861 ML20151P866
References
NUDOCS 8808010147
Download: ML20151H111 (1)

Text

. - - - . .

l SEIShUC HAZARD FROM INTRAPLATE EARTHQUAKES IN THE PUGET SOUND REGION by Robert S. Cmsson Geophysics Program University of Washington Seattle, Washington Although much attention has been focused on the possibility of a large subduc-tion earthquake, the known hazard due to moderate sized intraplate earthquakes along the Puget Willamette depression must not be neglected. There is much uncertainty about the possible source location, source sizes, and existence of subduction earth-quakes. None have been documented from instrumental data. On the other hand, j several moderate to large suberustal earthquakes have occurred since the availability of adequate instrumental data. Rasmussen and others have estimated a mean return period of 110 years for magnitude 7.0 earthquakes and 330 years for magnitude 7.5

' earthquakes for the Puget Sound region. 'Ihe central and south Puget Sound region 4

seems to be a particularly active source region for such earthquakes. We know this region is capable of generating earthquakes in the magnitude range 7.0 to .5 at depths of 50 to 60 km beneath major population centers of western Washington.

Until very recently, the cause of these suberustal earthquakes was basically unk-nown except that they were generally believed to lie within the subducted plate.

Recent progress in understanding the structure of the subducted plate may provide clues as to why the southern Puget Sound region is an important source area. A i

recently postulated arch in the subducted plate plunging gently to the east has its southem limb near the source zone. Bending stresses induced as the plate adjusts to i

this arch m eture in the process of subduction may contribute to the localization of seismic hazard in south Puget Sound. If such a model is correct, then we can expect a higher incidence of damaging earthquakes in this region relative to other parts of

tM Puget Willamette trough. Further observational and theoretical work must be dene in modeling the details of plate structure and stress within this zone to fully understand the earthquake hazard.

I I

!(

8808010147 88061S.

DR ADOCK 0500 g ,.

]