15:30 〜 16:30
[J06-P-15] Moment tensor inversion of tectonic tremors in the Guerrero subduction zone
Slow earthquakes have exposed the actual complexity of the tectonic processes involved in subduction zones around the world. Despite different studies addressing these phenomena, its causal relationship is still debated.
Recent studies in different subduction zones suggest that tectonic tremors (TT) are caused by point dislocations at depth. Consequently, a systematic study of focal mechanisms of tremor sources turns out to be important to understand the processes that originate this phenomenon and the implications they have in the occurrence of slow earthquakes.
Cruz-Atienza et al. (2015) introduced the “Tremor Energy and Polarization" (TREP) method to locate tectonic tremors assuming horizontal point dislocations, which is a reasonable hypothesis for deep tremors in the state of Guerrero. However, this assumption could be a limitation in other cases where the fault dip is different (i.e., San Andreas Fault). The simultaneous determination of tremor locations and focal mechanisms would allow studying this phenomenon in any tectonic environment.
In this work, we generalize the TREP method employing a global inversion technique (i.e., simulated annealing) to determine simultaneously the source location and the associated moment tensor from the energy spatial distribution and the azimuth of the particle motion polarization.
Although the method has some difficulties to resolve the focal mechanims because of the ambient noise, preliminary results employing real data in Guerrero show that most of the obtained mechanisms are consistent with the geometry of the plate interface and with the plate convergence direction, which are similar to those reported for LFEs (Frank. et al 2013) and VLFs (Maury et al. 2016) in Mexico.
Recent studies in different subduction zones suggest that tectonic tremors (TT) are caused by point dislocations at depth. Consequently, a systematic study of focal mechanisms of tremor sources turns out to be important to understand the processes that originate this phenomenon and the implications they have in the occurrence of slow earthquakes.
Cruz-Atienza et al. (2015) introduced the “Tremor Energy and Polarization" (TREP) method to locate tectonic tremors assuming horizontal point dislocations, which is a reasonable hypothesis for deep tremors in the state of Guerrero. However, this assumption could be a limitation in other cases where the fault dip is different (i.e., San Andreas Fault). The simultaneous determination of tremor locations and focal mechanisms would allow studying this phenomenon in any tectonic environment.
In this work, we generalize the TREP method employing a global inversion technique (i.e., simulated annealing) to determine simultaneously the source location and the associated moment tensor from the energy spatial distribution and the azimuth of the particle motion polarization.
Although the method has some difficulties to resolve the focal mechanims because of the ambient noise, preliminary results employing real data in Guerrero show that most of the obtained mechanisms are consistent with the geometry of the plate interface and with the plate convergence direction, which are similar to those reported for LFEs (Frank. et al 2013) and VLFs (Maury et al. 2016) in Mexico.