Detection of Very Low Frequency Earthquakes in the Mexican Subduction Zone
Abstract
Tremors have already been detected in three different areas (Jalisco, Guerrero and Oaxaca) of the Mexican subduction zone but their moment tensor is difficult to estimate. However, Very Low Frequency (VLF) earthquakes have been shown to occur at the subduction interface in Guerrero, Mexico at the same time as tremors and their focal mechanisms have been calculated. We try to detect VLF events using the same method in Jalisco and in Oaxaca. With this aim we detect tremors using an envelope correlation method in Oaxaca and use a previously determined tremor catalog in Jalisco [Idehara et al., 2014]. Using the method of Ide and Yabe [2014], we stack waveforms, in the VLF band, at the time of occurrence of tremors. Finally, the stacked waveforms are inverted to better estimate the depth of these events and their moment tensor. This analysis is carried out for different time periods between 2005 and 2015, depending on the deployment of temporary network along the Mexican coast. In addition, permanent broadband stations of the Servicio Sismológico Nacional (Mexico) are used. The tremors detected in Oaxaca area are located farther west than previously known probably because of the more eastern location of stations. Our results show the spatial distribution of moment tensor along the Mexican subduction zone. The VLF sources are located at or close to the plate interface in Oaxaca and Jalisco as is observed in Guerrero. These events have magnitudes of about 3 and very low-angle to low-angle thrust mechanisms in agreement with the varying geometry of the subduction interface. The slip directions of VLF earthquakes are also consistent with the plates convergence vectors. In addition, some clear VLF signals are detected without any stacking using correlation methods. These individual detections confirm the results of our statistical analysis.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFM.S43D..06M
- Keywords:
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- 1207 Transient deformation;
- GEODESY AND GRAVITYDE: 7223 Earthquake interaction;
- forecasting;
- and prediction;
- SEISMOLOGYDE: 7230 Seismicity and tectonics;
- SEISMOLOGYDE: 8118 Dynamics and mechanics of faulting;
- TECTONOPHYSICS