32-7 Seismotectonics of the North-Central Region of the Gulf of California, Mexico

Session: Recent Advances in the Gulf of California Oblique Rift: Offshore and Onshore Studies // Avances Recientes en el Rift Oblicuo del Golfo de California: Estudios Marinos y Terrestres (Part II)

Presenting Author:

Authors:

Abstract:

Several studies have identified in the Gulf of California (GoC), Mexico, a structural transition from continental trans-tensional in the north to oceanic spreading in the south that makes the tectonics in this region quite complex. This complexity is also observed in the seismicity patterns from north to south of the gulf. Based on reported estimates of the b value of the Gutenberg-Richter relation, a decrease in seismicity has been identified towards the center of the GoC, where changes in tectonic stress and variability of elastic properties of the crust can influence the seismicity observed in the GoC.

We analyze the spatial distribution of the seismic energy radiated by earthquakes in the GoC and the tectonic implications. Previous studies have reported low apparent stress in the northern GoC and in the south-central region. In this study, we concentrate on the north-central region and found that the apparent stress in this region is lower than in the south-central region, possibly due to the weaker frictional characteristics of the faults in the north-central region of the GoC.

We also compare focal mechanism types with apparent stress, and we did not observe a significant dependence on the type of focal mechanism. However, it seems that the apparent stress may be related to the predominant tectonic stress regime of the different regions. For instance, earthquakes in the northern region, having low apparent stress, have a predominantly normal faulting stress regime.

In general, the apparent stress of the earthquakes in the GoC is low and tends to increase from the northern to the central regions. These variations are due to the combination of various factors such as changes in the stress regime, fault friction, heat flow and presence of fluids. We conclude that earthquakes in the north of the GoC radiate less energy than those in the central region, probably because the northern faults exhibit weaker frictional properties.

Geological Society of America Abstracts with Programs. Vol. 58, No. 3, 2026

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