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Slip kinematics and dynamics during and after the 1995 October 9 M_w=8.0 Colima–Jalisco earthquake, Mexico, from GPS geodetic constraints

Hutton, W. and DeMets, C. and Sánchez, O. and Suárez, G. and Stock, J. (2001) Slip kinematics and dynamics during and after the 1995 October 9 M_w=8.0 Colima–Jalisco earthquake, Mexico, from GPS geodetic constraints. Geophysical Journal International, 146 (3). pp. 637-658. ISSN 0956-540X. doi:10.1046/j.1365-246X.2001.00472.x.

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We use horizontal and vertical crustal displacements derived from GPS measurements at 26 sites in western Mexico to study the coseismic and post-seismic kinematics and dynamics of the 1995 October 9 (M_w=8.0) Colima–Jalisco earthquake along the Middle America Trench. The measurements bracket the entire landward edge of the approximately 150 km long rupture zone and span a 4 yr period for most sites. We solve for the temporal evolution of slip along the subduction interface by inverting GPS displacements for the coseismic and four post-seismic intervals (March 1995–March 1999), subject to the assumption that the crust responds elastically to slip along a shallow-dipping, curved subduction interface. Coseismic rupture of up to 5 m was largely focused above depths of 20 km and was limited to a 120–140 km long segment of the subduction zone. Within one week of the earthquake, post-seismic slip migrated downdip to depths of 16–35 km, where it has since decayed logarithmically. We also find evidence for shallow aseismic slip during 1996 or early 1997 northwest of the coseismic rupture zone and increasingly widespread relocking of shallow regions of the subduction interface after early 1997. The relative lack of afterslip in shallow regions of the subduction interface suggests that the interface lies in the unstable frictional regime and hence is strongly coupled between earthquakes. By 1999, the cumulative slip moment associated with post-seismic slip equaled ∼70 per cent of the coseismic moment, with nearly all of this slip occurring downdip from the coseismic rupture zone. The migration of slip after the earthquake to a deeper and presumably velocity-strengthening area of the subduction interface and the logarithmic decay of afterslip conform to the qualitative and quantitative predictions of a model in which the fault kinematics are prescribed by rate- and state-variable frictional laws. However, misfits to the geodetic displacements exceed the average displacement uncertainties for all epochs, implying one or more of the following: (1) the elastic response is heterogeneous due to slip along unmodelled upper crustal faults or variations in the elastic properties of the crust; (2) other post-seismic mechanisms such as viscoelastic or poroelastic effects contribute to or possibly dominate the post-seismic response; (3) we have underestimated the uncertainties in the GPS displacements.

Item Type:Article
Related URLs:
URLURL TypeDescription
DeMets, C.0000-0001-7460-1165
Suárez, G.0000-0002-2011-4924
Stock, J.0000-0003-4816-7865
Additional Information:© 2001 RAS. Accepted 2001 April 6. Received 2001 April 14; in original form 2000 October 24. Article first published online: 20 Dec 2001. Numerous individuals assisted our field and modelling efforts, including students from Caltech, UC-Berkeley, University of Guadalajara, UNAM, and UW-Madison. We thank Ian Carmichael and UNAM for their foresight in funding the initial network installation and occupation. We thank Dra. Bertha Marquez-Azua for her tireless and cheerful assistance, Bill Unger for his meticulous field work, and Dr. Tim Melbourne and Dr. Pedro Zarate del Valle. We thank Bill, Ana, and Eduardo Douglass for their hospitality, personal vehicles, and memorable stays in their palapa. We thank Ken Hudnut and Sean Larsen for dispensing computer code and test cases. We thank Dr. Jaime Arturo Paz Garcia, Director General of Proteccion Civil of Jalisco, for providing vehicles and drivers, and the University of Guadalajara for providing field vehicles. Finally, we thank Brett Baker and UNAVCO for providing equipment and field assistance. Constructive reviews were given by Steve Cohen, Greg Lyzenga, and Steven Ward, and figures were produced using Generic Mapping Tool software (Wessel and Smith, 1991). This work was funded using grants from CONACYT (4933-T9406) and NSF (EAR9527810-JS; EAR9526419-CD).
Group:Seismological Laboratory, Division of Geological and Planetary Sciences
Funding AgencyGrant Number
Consejo Nacional de Ciencia y Tecnología (CONACYT)4933-T9406
Subject Keywords:crustal deformation, earthquakes, fault slip, geodesy, subduction, tectonics.
Issue or Number:3
Record Number:CaltechAUTHORS:20140415-132949940
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Official Citation:Hutton, W., DeMets, C., Sánchez, O., Suárez, G. and Stock, J. (2001), Slip kinematics and dynamics during and after the 1995 October 9 Mw=8.0 Colima–Jalisco earthquake, Mexico, from GPS geodetic constraints. Geophysical Journal International, 146: 637–658. doi: 10.1046/j.1365-246X.2001.00472.x
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:44963
Deposited By: Ruth Sustaita
Deposited On:15 Apr 2014 20:58
Last Modified:08 Nov 2022 22:17

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