HR: 14:40h
AN: G22D-05    [PDF]
TI: Reassessment of the 2001-2002 Aseismic Slow Slip Event in Mexico
AU: * Kostoglodov, V
EM: vladi@servidor.unam.mx
AF: Instituto de Geofisica, Universidad Nacional Autonoma de Mexico, IGF UNAM, Ciudad Universitaria, Coyoacan, Mexico, DF 04510 Mexico
AU: Franco, S I
EM: ivonne@ollin.igeofcu.unam.mx
AF: Instituto de Geofisica, Universidad Nacional Autonoma de Mexico, IGF UNAM, Ciudad Universitaria, Coyoacan, Mexico, DF 04510 Mexico
AU: Singh, S K
EM: krishna@ollin.igeofcu.unam.mx
AF: Instituto de Geofisica, Universidad Nacional Autonoma de Mexico, IGF UNAM, Ciudad Universitaria, Coyoacan, Mexico, DF 04510 Mexico
AU: Larson, K M
EM: Kristine.Larson@colorado.edu
AF: Department of Aerospace Engineering Science, University of Colorado, Campus Box 429, Boulder, CO 80309-0429 United States
AU: Lowry, A R
EM: arlowry@brennan.colorado.edu
AF: Department of Physics, University of Colorado, Campus Box 390, Boulder, CO 80309-0390 United States
AU: Santiago, J A
EM: santiago@ssn.ssn.unam.mx
AF: Instituto de Geofisica, Universidad Nacional Autonoma de Mexico, IGF UNAM, Ciudad Universitaria, Coyoacan, Mexico, DF 04510 Mexico
AB: In 2001-2002 a network of continuous GPS stations in Mexico recorded an unexpectedly large aseismic slow event (equivalent Mw ~7.4) in Guerrero and in western Oaxaca. This event lasted more than six months and the area involved in the aseismic motion was initially estimated as ~500x250 km2. The event produced a slow thrust slip of ~13-15 cm on the subduction plate interface below the central part of the State of Guerrero. Elastic dislocation models, which fit the observed data, restrict the width of the slip to 150-200 km along the plate interface. This interface was partially locked before, during the steady state interseismic phase associated with the continental plate compression. Unfortunately the GPS network coverage was not sufficient to resolve an important question: Was the seismogenic part of the plate interface involved in the slow thrust slip? A long term record from a permanent GPS station located on the Popocatepetl volcano, POSW, shows unambiguous displacements corresponding to the aseismic slip events of 1997-1998 and 2001-2002. Recent data analysis of 2001, 2002, and 2003 GPS occupation campaigns on 16 sites in Oaxaca reveals that the 2001-2002 slow aseismic slip may have extended SE along almost the entire Pacific coast of Oaxaca. These observations indicate that the total area affected by the last slow aseismic slip event is greater than ~300x700 km2. Most likely the same area was involved in a previous aseismic event of 1972, which is discovered from the analysis of tide gauge data. Frequently occurring aseismic transients should have an important bearing on the recurrence period of large subduction thrust earthquakes in Mexico.
DE: 1206 Crustal movements--interplate (8155)
DE: 3210 Modeling
DE: 7230 Seismicity and seismotectonics
DE: 8123 Dynamics, seismotectonics
DE: 8150 Plate boundary--general (3040)
SC: Geodesy [G]
MN: 2003 Fall Meeting