INVESTIGATING MEGATHRUST MORPHOTECTONICS: KECK GEOLOGY CONSORTIUM UNDERGRADUATE RESEARCH ON THE 2012 MW7.6 NICOYA EARTHQUAKE, COSTA RICA, CENTRAL AMERICA

During summer 2013, ten undergraduate students, three faculty mentors, and a graduate teaching assistant participated in a month-long Keck Geology Consortium field research project on the Nicoya Peninsula, Costa Rica. The project goals were to investigate the geomorphic footprint of earthquake-generated uplift, and to examine the relationship of megathrust rupture and fore arc deformation. Students and faculty conducted fieldwork along the Nicoya coast, expanding on prior geomorphic, geodetic, and seismologic studies of fault rupture and coseismic deformation produced by the 2012 Mw7.6 Nicoya Earthquake. The students worked in three collaborative field teams (Coastal Uplift, Beachrock, Geophysics) to collect data for independent student-designed thesis projects. Together they learned research techniques of tectonic geomorphology, coastal geology, stratigraphy, geochronology, seismology, and GPS geodesy.

The Coastal Uplift Team studied earthquake impacts on beaches and rocky headlands by measuring changes in tidal levels, beach morphology, stream profiles, and mortality of intertidal organisms. The Beachrock Team examined net uplift of Holocene carbonate beachrock deposits through stratigraphic analysis, petrographic studies, and geochronology. The Geophysics Team installed a temporary local seismic and geodetic network to investigate processes of fault rupture, aftershocks, and crustal deformation.

Upon completion of Costa Rica fieldwork, the students returned to their home institutions to work on project results in consultation with department research advisors and Keck project faculty. Each student completed a senior thesis and presented results in talks and posters at the 27th Annual Keck Research Symposium in Geology. Students and faculty also wrote short papers published online in the 2014 Keck Symposium Volume. This student research project addressed key geoscience questions about how earthquake uplift impacts coastal geomorphology, and how seismic cycle motions contribute to net deformation and growth of topographic relief. The project results add to several decades of prior research on the seismotectonics and geomorphology of the Nicoya Peninsula, and provide an important contribution to the growing body of scientific knowledge on convergent margin morphotectonics.