HR: 14:55h
AN: U43A-04    [Abstracts]
TI: Stress Drop Estimates Based on Coda Wave Measures for Earthquakes Along the Nicoya Peninsula, Costa Rica
AU: * Stankova-Pursley, J
EM: janas@nmt.edu
AF: New Mexico Institute of Mining and Technology, Department of Earth and Environmental Science, 801 Leroy Place, Socorro, NM 87801, United States
AU: Bilek, S L
EM: sbilek@ees.nmt.edu
AF: New Mexico Institute of Mining and Technology, Department of Earth and Environmental Science, 801 Leroy Place, Socorro, NM 87801, United States
AU: Phillips, W S
EM: wsp@lanl.gov
AF: Los Alamos National Laboratory, MS F665, Los Alamos, NM 87545, United States
AU: Newman, A V
EM: anewman@gatech.edu
AF: Georgia Institute of Technology, School of Earth and Atmospheric Sciences, 311 Ferst Drive, Atlanta, GA 30332-0340, United States
AB: The majority of the world's largest earthquakes are confined to the subduction zone regions. Earthquake stress drop is an important parameter to characterize as it can illuminate changes in fault zone conditions. Here we determine stress drops for thrust zone earthquakes along the Nicoya Peninsula, Costa Rica to explore spatial variations in the Middle America subduction zone. This area is interesting because seismicity patterns vary along strike of the subduction zone as we see differences in the dip of the interface given by earthquake locations between the northern and southern ends of the Nicoya Peninsula, Costa Rica. We analyze seismograms from 694 well-located earthquakes that were recorded on land and ocean bottom seismometers from the 1999 CRSEIZE experiment placed on and near the Nicoya Peninsula. Earthquake source spectra are obtained from coda amplitude measurements taken in multiple frequency bands by correcting for average path effects, correcting for source excitation via an empirical Green's function technique, and shifting to absolute seismic moment based on independently known seismic moments of one or more events. The method of using coda energy in calculating earthquake magnitude tends to be more stable than using the direct arrival data because we minimize errors associated with the wave energy distortion arising from the crustal heterogeneity. We then use these values to compute stress drop for each earthquake along the fault zone. These earthquake stress drops will be compared with along-strike variations in b-value as well as structural heterogeneity to explore connections between subduction zone conditions and earthquake processes.
DE: 7240 Subduction zones (1207, 1219, 1240)
SC: Union [U]
MN: 2007 Joint Assembly