Coda waves were analyzed from events recorded by NARS seismic network deployed along both margins of the Gulf of California, Mexico, to estimate coda attenuation Qc. Sato’s (1977) single scattering model was used for a coda window of 20 to 25 s beginning at twice the S-wave travel time. Events recorded from 2003 to 2007 located in the central region of the Gulf of California were analyzed. Source-to-receiver distances are between 40 and 500 km. Assuming a power law of the form QC (f) = QO f a, QC values were averaged and a value of QO = 83±3 and a frequency-dependence α value of 1.06±0.03 in the frequency range from 1 to 7 Hz was obtained. QO value and the high frequency dependency agree with the values of other regions characterized by a high tectonic activity. Based on source-station distribution two subregions (north and south) were defined. QC values were calculated and correlated with tectonics and morphology of each area. The observed higher attenuation in the south region can be attributed to the fact that south region is more fractured since the greater earthquakes occur in central to south Gulf of California and the oceanic crust is reported to be thinner in the southern region.

Nine earthquakes occured between 2005 and 2009, with magnitudes between 4.9 and 5.5, at the zone that correspond to the triple junction of the Cocos, Rivera and North America plates were relocated. Records from RESCO seismic stations were used together with records from SSN seismic network. Source parameters were estimated: source dimension, seismic moment, stress drop, average displacement and source time.The seismic moment tensor inversion was used to estimate focal mechanism and seismic moment to compare then whit short and long period estimation of these parameters.A stress tensor inversion was also performed in order to evaluate stress state of the area of study. The results indicate a compressive stress regime, which is characteristic of a subduction zone. It is interesting however, that plunge of ?1 goes from a moderate angle in the northwest to sub-horizontal in the southeast. The existence of normal and strike-slip mechanisms is also interesting in a subduction zone. Their existence was interpreted in terms of the interaction of Cocos and Rivera plates in this tectonically complicate zone.

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