Abstract
Abstract. We analyzed the seismicity of oceanic earthquakes in the Pacific oceanic regime of Mexico. We used data from the earthquake catalogues of the Mexican National Service (SSN) and the International Seismological Centre (ISC) from 1967 to 2017. Events were classified into two different categories: intraplate oceanic (INT) and transform fault zone and mid-ocean ridges (TF-MOR) events, respectively. For each category, we determined statistical characteristics such as magnitude frequency distributions, the aftershocks decay rate, the nonextensivity parameters, and the regional stress field. We obtained b values of 1.17 and 0.82 for the INT and TF-MOR events, respectively. TF-MOR events also exhibit local b-value variations in the range of 0.72–1.30. TF-MOR events follow a tapered Gutenberg–Richter distribution. We also obtained a p value of 0.67 for the 1 May 1997 (Mw=6.9) earthquake. By analyzing the nonextensivity parameters, we obtained similar q values in the range of 1.39–1.60 for both types of earthquakes. On the other hand, the parameter a showed a clear differentiation, being higher for TF-MOR events than for INT events. An important implication is that more energy is released for TF-MOR events than for INT events. Stress orientations are in agreement with geodynamical models for transform fault zone and mid-ocean ridge zones. In the case of intraplate seismicity, stresses are mostly related to a normal fault regime.
Highlights
Mid-ocean ridges and transform fault zones are two of the main morphological features of oceanic environments
The magnitude completeness for oceanic earthquakes differs for different parts of the world, but in most cases, it is in the range of 4.0–5.0 on average considering most of the global catalogues
Oceanic earthquakes were classified into two different categories: intraplate oceanic (INT) and transform fault zone and mid-ocean ridge (TF-MOR) events, respectively
Summary
Mid-ocean ridges and transform fault zones are two of the main morphological features of oceanic environments. Several oceanic strikeslip events were reported as being energy deficient at high frequencies (Beroza and Jordan, 1990; Stein and Pelayo, 1991; Ihmlé and Jordan, 1994) or having high apparent stresses (Choy and Boatwright, 1995; Choy and McGarr, 2002). On another front, oceanic earthquakes occur as intraplate events but to a lesser extent. The reason is that the oceanic plate interiors do not experience significant strain over long periods of time
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