Stress accumulation and release since 1882 in Ometepec, Guerrero, Mexico: implications for failure mechanisms and risk assessments of a seismic gap.

Abstract

We found evidence that 4 episodes of large shallow (h < 30 km) interplate earthquakes ruptured approximately the same segment of the Middle America subduction zone in Ometepec, Guerrero, Mexico, during the last century: in 1890 (M = 7.2), 1937 (MS = 7.5), 1950 (MS = 7.3), and 1982 (MS - 6.9 and 7.0). This segment is about 70 km long, which is near the limit of resolution to define seismic gap dimensions. We synthesized the spatial, temporal, and mechanistic patterns of regional relocated seismicity (mb = or < 4.0) to investigate the mechanics of rupture within the same seismic gap for the relatively large number of times (4) offered by the Ometepec case history. Despite the similarities in source depths and geometries of the shallow main shocks, we found marked differences in their magnitudes, recurrence intervals, and rupture modes (eg degree of source complexity and event multiplicity).-from Authors