HR: 14:10h
AN: T42C-03    [PDF]
TI: Aseismic Slip and Stress Transfer in Guerrero, Southern Mexico
AU: * Lowry, A R
EM: arlowry@himalaya.colorado.edu
AF: Department of Physics, University of Colorado, Boulder, CO 80309-0390 United States
AU: Larson, K M
EM: Kristine.Larson@colorado.edu
AF: Department of Aerospace Engineering Science, University of Colorado, Boulder, CO 80309-0492 United States
AU: Kostoglodov, V
EM: vladi@servidor.unam.mx
AF: Instituto de Geofisica, UNAM, Mexico D.F., 04510 Mexico
AU: Sanchez, O
EM: osvaldo@servidor.unam.mx
AF: Instituto de Geofisica, UNAM, Mexico D.F., 04510 Mexico
AU: Hudnut, K W
EM: hudnut@gps.caltech.edu
AF: U.S. Geological Survey, 525 S. Wilson Ave., Pasadena, CA 91106 United States
AB: Geodetic measurements from Guerrero, southern Mexico, show evidence for at least four large transient slip events in 1995, 1998, 2002 and 2003. Inverse modeling of the data suggests that the steady-state slip on the plate-boundary thrust includes partial frictional coupling at depths greater than 25 km, producing a slip deficit which is partially or completely relieved during aseismic slip events, and strong frictional coupling on the shallow thrust which is not relieved aseismically. Slip events have been observed down-dip of the seismogenic zone at several other subduction zones including New Zealand, Japan, Alaska and Cascadia. In many cases, these are interpreted as repeating events that activate a similar area on the thrust at regular intervals. In Guerrero, however, the behavior is more complex: Quiescent intervals range from one to four years, and moment release in these four events varies by up to an order of magnitude. Spatial distributions also vary substantially between events. Perhaps the most consistent feature of the events is the timescale: Significant anomalous slip lasted about three to four months during all three events observed by continuous GPS. The events are also characterized by widespread activation of slip. The current network of continuous GPS sites covers an area of about 480 km strike-parallel by 270 km strike-perpendicular, but in all events there remains the possibility that slip extended well beyond the instrumental coverage. In this presentation, we will examine the potential role of these slip events as agents for stress transfer, and assess the possibility that they are initiated by stress changes during seismic events of magnitude 6 and higher on or near the thrust.
DE: 1206 Crustal movements--interplate (8155)
DE: 1243 Space geodetic surveys
DE: 3260 Inverse theory
DE: 8123 Dynamics, seismotectonics
SC: Tectonophysics [T]
MN: 2003 Fall Meeting