THE GEODETIC SIGNATURE OF THE M8.0-OCTOBER-9,-1995, JALISCO SUBDUCTION EARTHQUAKE

The October, 1995 Mw 8.0 Jalisco subduction earthquake has provided a thorough geodetic observation of the coseismic subduction process. An 11 station regional GPS network located directly onshore of the ruptur e demonstrates consistent vertical subsidence verified by tide gauge d ata and southwest-directed extension, with measured displacements reac hing 1 meter. Unusually shallow and non-uniform faulting is required t o explain the displacements. We determine that up to 5 meters of slip occurred within the upper 15 km of the thrust fault zone and 2 meters possibly as shallow as 8 km, and that slip was likely distributed in t wo main patches. The paucity of continental sediments in this subducti on zone could be responsible for the anomalously shallow faulting.