HR: 15:30h
AN: S43C-05    [Abstracts]
TI: Crustal Structure and Crustal Seismicity in the South-Central Andean Backarc
AU: * Alvarado, P
AF: CONICET-Univ. Nac. de San Juan, Meglioli 1160 S, Rivadavia, San Juan, 5400, Argentina
AU: Beck, S
AF: Univ. de Arizona, Department of Geosciences, Gould Simpson Bldg. #77, 1040 E, Tucson, AZ 85721, United States
AU: Zandt, G
AF: Univ. de Arizona, Department of Geosciences, Gould Simpson Bldg. #77, 1040 E, Tucson, AZ 85721, United States
AB: Crustal seismicity in the Andean backarc between 30°S and 33°S is responsible for the largest damaging earthquakes in Argentina. This region is characterized by the presence of a northeast elongated flat subduction of the Nazca plate at about 100-km depth, a shut off of the volcanic arc and the basement cored uplifts of the Sierras Pampeanas. The overriding South American plate is composed of accreted terranes, sometimes reactivated by Paleozoic-Mesozoic extensional processes. We have used regional broadband data recorded during the CHilean ARgentinean Geophysical Experiment (CHARGE) to characterize the crustal structure and crustal seismicity by modeling regional broadband waveforms. Our study shows differences in the backarc terrane crustal seismic parameters that may have implications for the nucleation of present-day crustal seismicity. The Cuyania terrane has a more mafic composition, thicker crust with possible partial eclogitization at lower crustal levels and exhibits large numbers of earthquakes of higher magnitudes from historic to modern times. In contrast, the Pampia terrane to the east has thinner more quartz-rich crust and is comparatively seismically quiet for moderate-sized events.
DE: 7200 SEISMOLOGY
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
DE: 7240 Subduction zones (1207, 1219, 1240)
DE: 8107 Continental neotectonics (8002)
DE: 8159 Rheology: crust and lithosphere (8031)
SC: Seismology [S]
MN: 2007 Joint Assembly