Source parameters of the 8 February 2016, Mw=4.2 Los Humeros earthquake by the inversion of InSAR-based ground deformation

Eszter Békési,Peter A Fokker,Joana E Martins,Gianluca Norini,Jan-Diederik Van Wees

doi:10.1016/j.geothermics.2021.102133

Abstract

We investigate ground movements induced by the 8 February 2016, Mw=4.2 earthquake at the Los Humeros Geothermal Field (Mexico) using Sentinel-1 radar interferometry. Previous estimated focal mechanism solution based on seismic data with a hypocentral depth of 1900 m could not resolve the measured coseismic surface deformation pattern. In this study, we applied inverse elastic dislocation models to estimate the source parameters of the seismic event. Our models suggest the reverse reactivation of the Los Humeros normal fault at a shallower depth (<1000 m), with a more significant left lateral component below ~400 m depth. The occurrence of such shallow events at Los Humeros pose increased risks for the neighboring communities and infrastructure. Therefore, continuous monitoring of seismicity and cautious planning of field operations are crucial.A NNW-SSE striking fault swarm, including the Los Humeros fault, acts as a major boundary of the subsiding area observed by InSAR time-series between February 2016 and May 2019. A potential explanation of the reverse reactivation of the Los Humeros fault and following downward movement of the eastern fault block is the depressurization of the whole hydrothermal system. Such depressurization can occur due to the exploitation of the geothermal field and/or due to natural pressure/temperature changes related to magmatic activity.

Highlights

Superhot Geothermal Systems (SGHS) with their high enthalpies are important geothermal reservoirs
We reproduced the coseismic surface deformation of the 8 February 2016, Mw=4.2 earthquake at Los Humeros, with a two-component rectangular dislocation model approximating the curved geometry of the fault structures of the Los Humeros Volcanic Complex (LHVC)
Modeling results suggest that fault kinematics changes with depth, with a purely reverse kinematics of the upper dislocation, and significant left lateral component of the lower dislocation

Summary

Introduction

Superhot Geothermal Systems (SGHS) with their high enthalpies are important geothermal reservoirs. These systems, with temperatures often exceeding 350◦C, are frequently marked by recent or even active tectonic or volcanotectonic deformations. This results in complex res ervoirs in which fault structures may act as prolific permeability path ways for geothermal fluids. Exploitation of such fields may yield considerable risks for induced seismicity. The understanding of fault geometry and behavior is crucial for a safe and sustainable exploitation of these important resources

Methods

Findings

Discussion

Conclusion