abstract

Seismic gaps and recurrence periods of large, shallow interplate earthquakes along the Mexican subduction zone are reexamined after combining information from a catalog of nineteenth century's earthquakes, some relocated epicenters of the early part of this century, source parameters of recent large earthquakes, and redetermined magnitudes of great, shallow earthquakes of this century. Tehuantepec and Michoacan gaps have not experienced a large shock in this century and perhaps none in the past century; they are either aseismic or have anomalously large repeat times. Guerrero, Jalisco, and Ometepec regions presently appear to have a high seismic potential. Observed average repeat times of large earthquakes (Ms ≳ 7.4) in six regions (east, central, and west Oaxaca, San Marcos, Petatlan, and Colima) are between 32 to 56 yr. Data of this century indicate that the strain is released mostly in large events (Ms ≳ 7.4). A simple dislocation model with parameters obtained from the studies of recent earthquakes explains the observed recurrence periods quite well. The b value for this zone is not meaningful, an observation which is of significance for seismic risk estimation. Most of seismic moment (or, equivalently, seismic energy) release since 1800 appears to occur for 15 yr followed by relative quiescence in the next 15 yr.

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