Spatiotemporal Evolution of Microseismicity and Repeating Earthquakes in Haiti

Abstract:

Haiti is located in a complex boundary between the North American and Caribbean plates, and this region is within a transition from a subduction regime to the east to a strike-slip to the west. The relative motion of the Caribbean plate is partitioned in part by two main left-lateral transform faults: the Enriquillo-Plantain Garden fault zone (EPGF) in the south and the Septentrional fault in the north. Several large devastating earthquakes have occurred in the past and the most recent one, the 12 January 2010 which have caused more than 200,000 fatalities, ruptured on a previously unmapped fault. Therefore, it is imperative to investigate if there are more unknown active structures that could further increase the seismic threat this region is already facing. A temporary seismic network, consisting of 27 broadband seismic stations, was deployed as part of the Trans-Haiti project between the period of June 2013 to June 2014 and an earthquake catalog was determined. Unfortunately, this catalog suffers from missing seismic events since small events are often buried within the noise level of seismic stations due to the low signal to noise. Detecting those missing earthquakes can be extremely useful to identify previously unknown active and dangerous faults, to find precursory activity before large earthquakes and to assess the likelihood of repeating events. In this study, we use the relocated events from the recently published catalog as template waveforms, and apply a matched filtering technique that cross-correlate those templates with the continuous data in order to detect missing events. Preliminary results show that we were able to detect ~14 times more events compared to the catalog. We observe several high event detection spikes (~20 events per day) that tend to occur at regular time intervals. The greatest number of detections (~30 detections per day) is observed in May. The detections are mostly located in the south part of Haiti, near the rupture zone of the 2010 earthquake and the Cul-de-Sac basin, implying active faulting in this area.