PRELIMINARY FORESHOCK ANALYSIS OF SUBMARINE TRANSFORM FAULT EARTHQUAKES ALONG THE EQUATORIAL MID-ATLANTIC RIDGE

The work presented here is a preliminary look at data from a much larger project during an undergraduate 10-week REU internship that R. Meyer participated in during the summer of 2015. From August 2011 to May 2015 an autonomous hydrophone array, covering a large portion of the Equatorial Atlantic Ocean, was deployed along the Mid-Atlantic Ridge (MAR) from approximately 22° N to 10° S and 53° W to 8° W, to record signals generated by submarine seismic events. During the deployment period, eighteen teleseismic earthquake events ≥ 5.4 mb recorded by land-based seismometers (USGS/NEIC) provide a basis set of larger transform events for detailed hydroacoustic processing and analysis including epicentral source locations from T-wave arrival patterns. Hydroacoustically derived origin times and epicentral locations are used to investigate the relationship between the timing and spatial distance of foreshocks prior to each mainshock event. Analysis of submarine foreshock patterns in this remote oceanic region provides insight for short-term predictability of large (mb≥5.4) seafloor transform fault earthquakes along the slow spreading (≈2.5 cm/yr.) Equatorial Mid-Atlantic Ridge (EMAR). Results are further compared with predictive methods described by McGuire et. al. (2005) along the submarine transforms of the fast spreading (6-16 cm/yr.) East Pacific Rise (EPR) to evaluate differences between these regimes