Active 650-km Long Fault System and Xolapa Sliver in Southern Mexico

Abstract

New estimates of long-term velocities of permanent GPS stations in Southern Mexico reveal that the geologically discernible ∼650-km long shear zone, which strikes parallel to the Middle America trench, is active. This left-lateral strike-slip, La Venta-Chacalapa (LVC) fault system, is apparently associated with a motion of the Xolapa terrain and at the present time is the northern boundary of a ∼110-160-km wide forearc sliver with a sinistral motion of 3-6 mm/year with respect to the North America plate. This sliver is the major tectonic feature in the Guerrero and Oaxaca regions, which accommodates most of the oblique component of the convergence between the Cocos and North America plates. Previous studies based purely on the moment tensor coseismic slips exceedingly overestimated the sliver inland extent and allocated its northern margin on or to the north of the Trans-Mexican Volcanic Belt. While the LVC fault system probably slips slowly over geologic scale time and there is not any historic evidence of large earthquakes on the fault so far, its seismic potential could be very high, assuming a feasible order of ∼10 3 years recurrence cycle. A detailed analysis of long-term position time series of permanent GPS stations in the Guerrero and Oaxaca states, Southern Mexico discards previous models and provides clear evidence of an active LVC fault zone bounding the Xolapa forearc sliver. The southeastward motion of this sliver may have persisted for the last ∼8-10 Million year and played an important role in the tectonic evolution of the region.

The Mechanisms of Tsunami Amplification and the Earthquake Source of the 2021 M7 Acapulco, Mexico, Earthquake

“…Yet, full characterization of mechanical coupling remains elusive. The question is of fundamental importance for tsunami hazards -geologic evidence of tsunami deposits up to ~5 km inland produced by the 1787 M8.6 San Sixto earthquake (Ramirez-Herrera et al, 2020) immediately east of the 2021 source region suggest that during extremely large events shallow slip is certainly a possibility.…”

“…This region of the country is a subduction zone where the Cocos plate subducts beneath North America at ~6 cm/yr with a slightly oblique convergence direction (e.g. Kazachkina et al, 2020). The margin is seismically quite active, with many large ~M7-M8 events in pre-and instrumental times (Castro et al, 2016;Sawires et al, 2019;Suarez et al, 2020).…”

Interplate Slip Rate Variation Between Closely Spaced Earthquakes in Southern Mexico: The 2012 Ometepec and 2018 Pinotepa Nacional Thrust Events

“…3 of 19 component of the subducting slab (Kazachkina et al, 2019(Kazachkina et al, , 2020. Both earthquake swarms and SSEs have been detected at the interface of this fault system in Oaxaca (Fasola et al, 2019).…”

“…Flattening of the slab is likely due to dehydration and rollback that caused a shift in the volcanic arc which lies oblique with an angle of ∼15° with respect to the trench, forming the Trans‐Mexican volcanic belt with very diverse chemical signatures (Ferrari et al., 2012, and references therein; Skinner & Clayton, 2011). Another relevant feature for the regional tectonics consists of a continental left‐lateral 650 km long fault system that extends parallel to the trench that accommodates a significant part of the oblique component of the subducting slab (Kazachkina et al., 2019, 2020). Both earthquake swarms and SSEs have been detected at the interface of this fault system in Oaxaca (Fasola et al., 2019).…”

Spatial Variations of Tectonic Uplift - Subducting Plate Effects on the Guerrero Forearc, Mexico

“…LVC fault system has been associated with a motion of the Xolapa terrain and at the present time is the northern boundary of a ∼110-160-km wide forearc sliver with a sinistral motion of 3-6 mm/year with respect to the North American plate. This sliver accommodates most of the oblique component of the convergence between the Cocos and North American plates (Kazachkina et al, 2020).…”