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GEOPHYSICAL RESEARCH LETTERS, VOL. 24, NO. 9, PAGES 1019–1022, 1997

The 1995 Colima-Jalisco, Mexico, Earthquake (Mw 8): A Study of the Rupture Process

Françoise Courboulex

Instituto de Geofísica, UNAM, CU, 04510 México, D.F.


Shri K. Singh

Instituto de Geofísica, UNAM, CU, 04510 México, D.F.


Javier F. Pacheco

Instituto de Geofísica, UNAM, CU, 04510 México, D.F.


Charles J. Ammon

Saint Louis University, St Louis, Missouri


Abstract

In this study we map rupture characteristics of the great, shallow, thrust earthquake of October 9, 1995 which caused extensive damage to the coastal towns of Colima and Jalisco. To isolate the earthquake rupture details, we deconvolve surface waves with two empirical Green’s functions, the aftershock of October 12, 1995 (Mw 5.9) and the foreshock of October 6, 1995 (Mw 5.8), from the corresponding mainshock records. Specifically, we use a spectral water-level deconvolution to obtain 80 Apparent Source Time Functions (ASTF) at 62 stations (Rayleigh and Love waves). Durations of the ASTF, as a function of azimuth indicate that the rupture propagated toward N70°W. The duration of the Source Time Function (STF) is around 62 s with a large pulse at 45 s. To map the main characteristics of the rupture, we use an inverse Radon transform of the ASTFs, assuming a ribbon fault-model aligned in the direction of the rupture propagation. Our analysis indicates that the rupture initiated about 20 km offshore of Manzanillo and propagated almost unilaterally for 150 km towards N70°W, with an average rupture velocity of approximately 2.8 km/s. The earthquake was a composite of three significant subevents, the largest occurred 45 s after the initiation of the rupture and was located about 100 km away. This result is in good agreement with the inversion of deformation data, measured with GPS [Melbourne et al., 1997].

Received 6 November 1996; accepted 24 January 1997.

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Citation: Courboulex, F., S. K. Singh, J. F. Pacheco, and C. J. Ammon (1997), The 1995 Colima-Jalisco, Mexico, Earthquake (Mw 8): A Study of the Rupture Process, Geophys. Res. Lett., 24(9), 1019–1022.