New locations of volcano-tectonic earthquakes under Popocatepetl Volcano applying a Genetic Search Algorithm

摘要

In the early 1990's, after ~70 years of quiescence, seismic activity was renewed beneath Popocatepetl Volcano, central Mexico, and a period of high volcanic activity began. This activity continues today, and has featured high emissions of volcanic gases and fumaroles, dome filling processes, and moderate eruptions. The three largest explosive eruptions occurred in 1997, 2001, and 2003. We applied a genetic search algorithm to fit arrival-time differences on an individual basis, and we obtain high precision (~200 m) relocations for 405 volcano-tectonic (VT) events from 968 events recorded by a local network from 1995 to 2006. We compare these results to relocations obtained by applying a double-difference algorithm. The objective is to characterize the seismicity, determine hypocentral parameters, and explore seismic sources. The results shed light on the distribution of seismic activity, revealing features previously hidden by location scatter. A diffuse cluster associated with a previously-identified SE-trending fault now appears to be associated with a fault system consisting of at least one NW-SE trending fault crossed by a NE-SW trending fault. Event occurrence was found to be locally time-dependent. Some aligned events coincide with previously-proposed faults. Other linear clusters may indicate hidden faults being activated by volcanic activity, such as dike intrusion or degassing of the magma body below Popocatepetl Volcano.