The forecasting of the 1995 Colima-Jalisco, Mexico, earthquake (Mw=8): A case history

Abstract

In 1995 the Colima-Jalisco region (103.7-106°W) was identified as a zone with a high probability of occurrence of a large earthquake (M_s ≥ 7.5) before the end of 1996. This forecast was based on results from pattern recognition and from studies on seismic gaps and Weibull distribution for the recurrence of strong earthquakes along the Mexican subduction zone. On October 9, 1995, an event of magnitude M _w = 8 occurred within the forecast area. A detailed examination of the seismicity preceding the mainshock reveals that most moderate earthquakes (M_s ≥ 5.5) occurred outside the rupture area. They were located mostly onshore or trenchward. This seismicity pattern changed after the great Michoacan 1985 earthquake (M_s = 8.1) which took place to the southeast but not adjacent to the 1995 rupture. The diagnosed event may have been the result of a combination of change in seismicity pattern followed by quiescence. The forecasting of this mainshock suggests the importance of detailed studies of historical seismicity together with methods of pattern recognition to determine areas with a high probability for the occurrence of a large earthquake within a specified time interval.