Teleseismic body waves recorded for the October 25, 1981, Playa Azul and September 21, 1985, Zihuatanejo earthquakes in wester Mexico were inverted to derive the distributions and depths of coseismic slip. Broadband P wave displacements and intermediate-period records were included to incorporate a wide frequency band in the analysis. For the Zihuatanejo earthquake, digital SH records located away from the nodal directions were used in the inversion process. Nonnodal SH waveforms were not available for the Playa Azul earthquake, but additional azimuthal coverage was obtained by including selected worldwide analog P wave records. The results for the Playa Azul earthquake indicate that rupture occurred in two separate zones both updip and downdip of the point of initial nucleation with the majority of the slip concentrated in a circular region (15-km radius) downdip from the hypocenter. The maximum slip in this downdip region exceeds 3.6 m and is at a depth of about 16 km. The computed seismic moment is 7.14¿1026 dyn cm. Coseismic slip is observed to occur entirely within the area of reduced slip separating the two main shallow sources of the Michoacan earthquake that occurred almost 4 years later on September 19, 1985. For the Zihuatanejo earthquake the P and SH data suggest rupture over a larger area (30-km radius) with a lower peak slip (2 m) and encompassing depths between 12 and 26 km. Slip is concentrated in an area adjacent to one of the major sources of the Michoacan earthquake and represents the southeastern continuation of rupture along the Cocos-North America plate boundary. The corresponding seismic moment is 1.35¿1027 dyn cm. The zones of peak slip observed for the Playa Azul, Zihuatanejo, and Michoacan earthquakes are interpreted as asperity regions that control the cessation and generation of large earthquakes within the Michoacan segment of the plate boundary. The stress drops within each of these asperities are observed to be very similar and may reflect a characteristic asperity strength for this portion of the subduction zone. ¿ American Geophysical Union 1993