Exploration of remote triggering: A survey of multiple fault structures in Haiti

Abstract

Triggering studies provide an important tool for understanding the fundamental physics of how faults slip and interact, and they also provide clues about the stress states of faults. In this study, we explore how seismic waves from the 27 February 2010 Mw8.8 Maule, Chile mainshock interact with the left lateral strike-slip Enriquillo–Plantain Garden Fault (EPGF) and surrounding reverse faults in the southern Haiti peninsula. The Chile mainshock occurred 6,000 km away and just 46 days after the 12 January 2010 Mw7.0 Haiti earthquake, a tragic event which activated multiple faults in the southern Haiti peninsula. During the surface waves of the Chile mainshock, several tectonic tremor signals were observed, originating from south of the EPGF trace. Cross-correlation of the triggered tremor and transient stresses resolved onto to the EPGF indicates that the Love wave of the Chile mainshock was the primary driving mechanism of the triggered deep shear slip and tremor signals, as opposed to dilatational stress changes generated by the Rayleigh wave. We also searched for any influence of transient stresses on Haiti aftershock activity by applying the matched filter technique to multiple days of seismic data around the time of the Chile mainshock. While we identified a slight increase in Haiti aftershock activity rate, the rate changes were significant only when small magnitude events were included in the significance tests. These observations are generally consistent with recent inferences that deep tectonic tremor is more sensitive than shallow earthquakes to external stress perturbations.