RUPTURE LENGTH OF THE OCTOBER 9, 1995 COLIMA-JALISCO EARTHQUAKE (M(W)8) ESTIMATED FROM TSUNAMI DATA

We analyze tsunami data of the great 1995 Colima-Jalisco, Mexico earth quake, recorded in Cabo San Lucas, Baja California Sur, to estimate it s rupture length, L. To model the tsunami arrival time, we assume a re ctangular source area, oriented parallel to the trench, whose SE limit is fixed at the point of rupture initiation. The NW limit of the sour ce area, i.e., L, is varied between 120 and 200 km. The comparison bet ween synthetic and observed data strongly suggests that L of the earth quake was 160+/-20 km. This length agrees with those reported in vario us other studies of the earthquake. It, however, disagrees with a prev ious study, based on the same tsunami data, which suggested that the r upture may have extended 250 km NW from the epicenter [Tanioka cmd Ruf f, 1996]. The cause of this discrepancy is most likely an error in the timing of the records used by Tanioka and Ruff [1996]. We conclude th at the earthquake only partially ruptured the Rivera-North America pla te interface. A 120 km-long segment in the NW extreme of this interfac e, which apparently ruptured in 1932, remains presently unbroken.