Spatial Distribution of Radiated Seismic Energy of Three Aftershocks Sequences at Guerrero, Mexico, Subduction Zone

Abstract

AbstractGeneral characteristics of seismic energy release of thrust earthquakes in Mexico have been reviewed in the past; however, a detailed analysis can contribute to a better understanding of the mechanisms that control its distribution along the Guerrero, Mexico, subduction zone. To address it, we obtain the source spectra of the 2012 Mw 7.5 Ometepec‐Pinotepa Nacional, the 2014 Mw 7.2 Papanoa, and the 2018 Mw 7.2 Pinotepa Nacional earthquakes, as well as of their M≥4.0 aftershocks to estimate their seismic moment M0 and radiated seismic energy ES. The first and the last sequences occurred at the southern border of the Guerrero seismic gap, a region where no significant earthquake (M>7.0) has occurred at least in the last century; whereas the second sequence was located at the northern edge of the same seismic gap. The mean value of the log of radiated seismic energy scaled with the seismic moment, log(e˜)=log(ES/M0), for this set of earthquakes is −5.05±0.25. We classify the analyzed events into four regions, two in the southern edge of the gap and two in the northern one. At both ends, there is one region that shows regular values of log(e˜) (−4.64±0.25 and −4.62±0.25), whereas the other one shows low values of log(e˜) (−5.40±0.25 and −5.55±0.25) that could be related to a possible slow‐rupture behavior. These last regions are identified near the trench at southern Guerrero coast and immediately outside the northern end of the seismic gap. The distribution of log(e˜) is spatially heterogeneous along the trench, suggesting variations on the shear strength and coupling at the interface.