Recent discoveries that demonstrate the wide spectrum of fault slip along subduction megathrust faults prompt important questions about the relationships between large earthquakes, small earthquakes, slow slip, and non-volcanic tremor. In many areas, the deep portion of the fault that lies at the transition between the fast and slower slip mechanisms is out of view, sitting offshore, away from nearby monitoring. However, an existing seismic and geodetic network along the Oaxacan segment of the Middle America subduction zone provides an excellent dataset for use to quantify earthquake occurrence and source parameters in an area that has experienced M > 7 earthquakes, tremor, and slow slip events.
This research will address several hypotheses related to the spatial and temporal relationships between slow slip, tremor, and large earthquakes. These include determining 1) if a sharp transition in seismicity characteristics exists along the megathrust as events approach the downdip seismicity limit and the area of episodic tremor and slip, 2) if slow slip events produce stress loading in adjacent regions that lead to increased seismicity rates and changes in source characteristics of small earthquakes, and 3) if large earthquakes are associated with temporal changes in earthquake occurrence and source characteristics in adjacent regions due to stress changes. We will employ several seismological techniques, including the construction of a uniform event catalog, focal mechanism determination, rupture duration and stress drop calculations, and investigation of seismicity rates along specific fault patches, to address these hypotheses.
The overall goals of the project revolve around a better understanding of the deep roots of the earthquake-producing region of the Mexican subduction zone, with applicability to other global subduction zones. Thus the results of the study will produce societal benefits related to earthquake hazards, particularly in providing information needed for improving temporal variations in probabilistic seismic hazard. The outcome of this project will include data products disseminated to a wide international community through meeting presentations, publications, and archival in the relevant data repositories. The project will train 4 US based graduate and undergraduate students as well as provide capacity-building seismological training for 2 Mexican students. Another outcome of the project will be 2 educational lessons that will be disseminated through online educational activity portals.
