The cause of the 2011 Hawthorne (Nevada) earthquake swarm constrained by seismic and InSAR methods

Abstract

We used both seismic and InSAR data to investigate the mechanism behind the 2011 Hawthorne (Nevada) earthquake swarm that occurred between March 15 and August 17, 2011. Regional seismic data were used to estimate the centroid depth and focal mechanism for nine earthquakes that occurred in this swarm, with magnitudes between $$M_w$$ 3.9 and $$M_w$$ 4.8. The inferred focal mechanisms indicate that the source of these earthquakes is normal faulting with a small left-lateral strike-slip component along the southwest direction. Three InSAR displacement maps covering the epicentral zone of the 2011 Hawthorne earthquakes were inverted to get a slip model. The slip distribution shows that the deformation source is characterized by normal faulting, consistent with our inferred focal mechanisms. Our results suggest that the seismogenic zone was in the tensile stress environment. The temporal and spatial evolutions of seismicity suggest that the 2011 Hawthorne swarm might be caused by aseismic slip. Therefore, the 2011 Hawthorne earthquake swarm may have been the result of aseismic slip under the regional tectonic stress, and had nothing to do with volcanic activity. However, the quantitative evidence for aseismic slip is limited to the indication that the geodetic moment is 15% greater than the seismic moment, which is near the level of uncertainty.