EARTHQUAKE RECURRENCE AND GLACIAL LOADING IN WESTERN WASHINGTON

Authors
Citation
Rm. Thorson, EARTHQUAKE RECURRENCE AND GLACIAL LOADING IN WESTERN WASHINGTON, Geological Society of America bulletin, 108(9), 1996, pp. 1182-1191
Citations number
49
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Geosciences, Interdisciplinary
ISSN journal
0016-7606
Volume
108
Issue
9
Year of publication
1996
Pages
1182 - 1191
Database
ISI
SICI code
0016-7606(1996)108:9<1182:ERAGLI>2.0.ZU;2-C
Abstract
The tectonic setting of the Puget lowland was simpler during late Tert iary time (10(6)-10(7) yr) when the transfer of stress from subduction was not modulated by periodic glacial loading, Each advance of the Co rdilleran Ice Sheet during the Quaternary; Period created an additiona l 10-13 MPa of vertical load that may have stabilized the thrust sheet beneath the Puget lowland, causing background tectonic stresses to ac cumulate beyond the strength of active faults in their unglaciated con dition, Conversely, deglaciation mag have been accompanied by a brief episode of intense seismicity caused by decreasing overburden stress, elevated pore pressures, and elastic flexure in the shallow crust, and by viscous drag at the base of the crust during relaxation of isostat ic anomaly If accumulated tectonic stress was effectively ''erased'' d uring deglaciation, then some, or nearly all, of the present interglac ial may have been seismically quiet relative to the modern regime, Suc h a scenario would complicate the use of paleoseismic approaches to es tablish the recurrence frequency of damaging earthquakes in this heavi ly populated region.