Source Parameters of Large Magnitude Subduction Zone Earthquakes Along Oaxaca, Mexico

Abstract:

Subduction zones are host to temporally and spatially varying seismogenic activity including, megathrust earthquakes, slow slip events (SSE), nonvolcanic tremor (NVT), and ultra-slow velocity layers (USL). We explore these variations by determining source parameters for large earthquakes (M > 5.5) along the Oaxaca segment of the Mexico subduction zone, an area encompasses the wide range of activity noted above. We use waveform data for 36 earthquakes that occurred between January 1, 1990 to June 1, 2014, obtained from the IRIS DMC, generate synthetic Green’s functions for the available stations, and deconvolve these from the ­­­observed records to determine a source time function for each event. From these source time functions, we measured rupture durations and scaled these by the cube root to calculate the normalized duration for each event. Within our dataset, four events located updip from the SSE, USL, and NVT areas have longer rupture durations than the other events in this analysis. Two of these four events, along with one other event, are located within the SSE and NVT areas. The results in this study show that large earthquakes just updip from SSE and NVT have slower rupture characteristics than other events along the subduction zone not adjacent to SSE, USL, and NVT zones. Based on our results, we suggest a transitional zone for the seismic behavior rather than a distinct change at a particular depth. This study will help aid in understanding seismogenic behavior that occurs along subduction zones and the rupture characteristics of earthquakes near areas of slow slip processes.