I performed a linear least squares seismic moment tensor inversion (SMTI) for 27
crustal earthquakes that were well-recorded using at least four CHARGE stations.
I used available global data of station PEL (Geoscope) in Chile to study three events
located in Mendoza. We also determined the best focal depth. We will refer to the events
by the year and Julian day of occurrence. The SMTI technique consists of modeling the
complete three-component seismic displacement records at regional distances to obtain
the seismic moment tensor. We considered epicentral distances up to 727 km.
Accurate seismogram modeling depends upon reliable seismic locations and a seismic
velocity structure. We used the locations determined by the Argentine seismic network
(INPRES) operating in the region. In order assess the effect of mislocation on our focal
mechanisms we performed several tests using several possible locations. We also determined the
focal mechanisms with and without the closest CHARGE station data to evaluate our results.
The closer stations are more impacted by a mislocation. We used two seismic velocity structures
for the region. These structures were constrained from receiver function
analysisand Pn studies that also
used CHARGE data. Model 1 represents the eastern Sierras Pampeanas and Model 2 characterizes
western Sierras Pampeanas, Precordillera and Cordillera terranes. The main difference in the
models is the Vp/Vs ratio (Vs in the crust). Therefore, for cases involving raypaths in both
terranes we combined both structures to obtain a better fit to the data.
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