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The April 29, 1965, Puget Sound earthquake and the crustal and upper mantle structure of western Washington

Langston, Charles A. and Blum, David E. (1977) The April 29, 1965, Puget Sound earthquake and the crustal and upper mantle structure of western Washington. Bulletin of the Seismological Society of America, 67 (3). pp. 693-711. ISSN 0037-1106.

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Simultaneous modeling of source parameters and local layered earth structure for the April 29, 1965, Puget Sound earthquake was done using both ray and layer matrix formulations for point dislocations imbedded in layered media. The source parameters obtained are: dip 70° to the east, strike 344°, rake −75°, 63 km depth, average moment of 1.4 ± 0.6 × 10^(26) dyne-cm, and a triangular time function with a rise time of 0.5 sec and falloff of 2.5 sec. An upper mantle and crustal model for southern Puget Sound was determined from inferred reflections from interfaces above the source. The main features of the model include a distinct 15-km-thick low-velocity zone with a 2.5-km/sec P-wave-velocity contrast lower boundary situated at approximately 56-km depth. Ray calculations which allow for sources in dipping structure indicate that the inferred high contrast value can trade off significantly with interface dip provided the structure dips eastward. The effective crustal model is less than 15 km thick with a substantial sediment section near the surface. A stacking technique using the instantaneous amplitude of the analytic signal is developed for interpreting short-period teleseismic observations. The inferred reflection from the base of the low-velocity zone is recovered from short-period P and S waves. An apparent attenuation is also observed for pP from comparisons between the short- and long-period data sets. This correlates with the local surface structure of Puget Sound and yields an effective Q of approximately 65 for the crust and upper mantle.

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Additional Information:Copyright © 1977, by the Seismological Society of America. Manuscript received September 23, 1976. This research was supported by the Advanced Research Projects Agency of the Department of Defense and was monitored by the Air Force Office of Scientific Research under Contract F44620-72-C-0078 and by the National Science Foundation Grant EAR 76-06619.
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Advanced Research Projects Agency (ARPA)UNSPECIFIED
Air Force Office of Scientific Research (AFOSR)F44620-72-C-0078
NSFEAR 76-06619
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Caltech Division of Geological and Planetary Sciences2822
Issue or Number:3
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ID Code:48463
Deposited By: George Porter
Deposited On:13 Aug 2014 15:11
Last Modified:03 Oct 2019 07:04

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