TELESEISMIC BODY-WAVE ANALYSIS OF THE 9 OCTOBER, 1995 (M-W=8.0), COLIMA-JALISCO, MEXICO EARTHQUAKE, AND ITS LARGEST FORESHOCK AND AFTERSHOCK

The source process of the October 9, 1995, Colima-Jalisco, Mexico, ear thquake (M-w=8.0), and its largest foreshock and aftershock were deter mined from teleseismic body waves, using a least-squares inversion sch eme. The three events are shallow-dipping, thrust-fault earthquakes, i n agreement with the relative plate motions for Rivera-North America a nd Cocos-North America plate boundaries. Neither the foreshock nor the largest aftershock show significant differences in focal mechanism no r centroidal depth with respect to the average mechanism of the mainsh ock. The rupture of the mainshock began near the foreshock hypocenter and propagated, with a variable rupture velocity, towards the NW. The source-time function for this event shows four distinct episodes of en ergy release. About 50% of the moment was released at the northern end of the rupture, between 90 and 110 km from the epicenter. This ruptur e geometry is in agreement with crustal deformation observed inland us ing GPS measurements. However, the scalar seismic moment of the main s hock obtained in this study (Mo=1.84x10(20)) is smaller with respect t o the lower frequency CMT results reported by Harvard (Mo=1.15x10(21)) .