Geodetic observations at the early stage of subduction zone seismic cycle: towards complete seismic cycle coverage

University Of South Florida, Tampa FL

Investigators

Abstract

Subduction zones such as those along the Pacific ?Ring of Fire? produce Earth?s largest and most destructive earthquakes, and most tsunamis. The giant earthquakes and tsunamis of 2004 (Sumatra) and 2011 (Japan) were wake up calls that our ability to estimate future earthquake magnitude remains weak. Measurement of strain accumulation in the vicinity of subduction zones, as is now possible with high precision GPS units, has the potential to forecast the location and size of future earthquakes. The coastal Nicoya Peninsula of Costa Rica lies close to the trench (<70 km), allowing observations directly over the seismogenic zone. Here I propose to upgrade and operate a continuous high precision GPS network in the Nicoya Peninsula, and use the resulting data to investigate a number of questions related to seismic and tsunami processes in the subduction zone environment. In principle these kind of measurements could provide predictive capability in terms of location and size of future earthquakes and perhaps tsunamis (timing would still presumably be unknown). Northern Costa Rica is characterized by fast (~8 cm/yr) subduction and a short (50?60 year) earthquake cycle, producing frequent large (M>7.5) earthquakes including events in 1853, 1900, 1950 (M 7.7) and most recently September 5, 2012 (M 7.6). Previous NSF-funded studies in this region have defined the regional tectonics and quantified a number of key seismogenic parameters at the late stage of the seismic cycle, including the pattern of interseismic strain accumulation and microseismicity, and the nature and timing of slow slip events (SSE). The 2012 earthquake gives us a chance to investigate these processes at the beginning of a seismic cycle, providing the scientific community an incredible opportunity to characterize a complete seismic cycle. All data generated by the Nicoya C-GPS network are made publicly available through UNAVCO, and analyzed products (e.g, coseismic and slow slip offsets) are available on my website (http://labs.cas.usf.edu/geodesy/) to assist researchers who are unfamiliar with the details of GPS processing use the data for earthquake research.