Stress evolution following the 1999 Chi-Chi, Taiwan, earthquake: consequences for afterslip, relaxation, aftershocks and departures from Omori decay

NCUIR > College of Earth Sciences > Graduate Institute of Geophysics > journal & Dissertation > Item 987654321/27565

Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/27565

Title:	Stress evolution following the 1999 Chi-Chi, Taiwan, earthquake: consequences for afterslip, relaxation, aftershocks and departures from Omori decay
Authors:	Chan,CH;Stein,RS
Contributors:	地球物理研究所
Keywords:	SAN-ANDREAS FAULT;REGIONAL EARTHQUAKES;SOURCE PARAMETERS;SOUTHERN CALIFORNIA;JANUARY-DECEMBER;DISPLACEMENTS;DEFORMATION;SEQUENCE;MODEL
Date:	2009
Issue Date:	2010-06-29 18:41:00 (UTC+8)
Publisher:	中央大學
Abstract:	We explore how Coulomb stress transfer and viscoelastic relaxation control afterslip and aftershocks in a continental thrust fault system. The 1999 September 21 M-w = 7.6 Chi-Chi shock is typical of continental ramp-dEcollement systems throughout the world, and so inferences drawn from this uniquely well-recorded event may be widely applicable. First, we find that the spatial and depth distribution of aftershocks and their focal mechanisms are consistent with the calculated Coulomb stress changes imparted by the coseismic rupture. Some 61 per cent of the M >= 2 aftershocks and 83 per cent of the M >= 4 aftershocks lie in regions for which the Coulomb stress increased by >= 0.1 bars, and there is a 11-12 per cent gain in the percentage of aftershocks nodal planes on which the shear stress increased over the pre-Chi Chi control period. Second, we find that afterslip occurred where the calculated coseismic stress increased on the fault ramp and dEcollement, subject to the condition that friction is high on the ramp and low on the dEcollement. Third, viscoelastic relaxation is evident from the fit of the post-seismic GPS data on the footwall. Fourth, we find that the rate of seismicity began to increase during the post-seismic period in an annulus extending east of the main rupture. The spatial extent of the seismicity annulus resembles the calculated >= 0.05-bar Coulomb stress increase caused by viscoelastic relaxation and afterslip, and we find a 9-12 per cent gain in the percentage of focal mechanisms with > 0.01-bar shear stress increases imparted by the post-seismic afterslip and relaxation in comparison to the control period. Thus, we argue that post-seismic stress changes can for the first time be shown to alter the production of aftershocks, as judged by their rate, spatial distribution, and focal mechanisms.
Relation:	GEOPHYSICAL JOURNAL INTERNATIONAL
Appears in Collections:	[Graduate Institute of Geophysics] journal & Dissertation

Files in This Item:

File	Description	Size	Format
index.html		0Kb	HTML	549	View/Open

社群 sharing

Loading...