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Preliminary geologic slip rates along Andes fastest slipping crustal fault, the Liquiñe-Ofqui Fault Zone (LOFZ), Patagonia, Chile

Gregory P. De Pascale, Melanie Froude, Ivanna Penna, Reginald Hermanns, Daniel Moncada, Sergio Sepulveda, Mario Persico, David Petley, Gabriel Vargas, William Murphy, & Sebastian Pairoa

Published August 4, 2018, SCEC Contribution #8265, 2018 SCEC Annual Meeting Poster #222

Chile ́s building code is designed for subduction zone events, and not for higher intensity strong-ground motions generated when crustal faults slip. Fault slip rates are therefore important imputs for these models. In Chile, crustal fault contribution to seismic hazard is poorly characterised (with unknown geologic slip-rates) including along the Andes longest fault, ~1200-km-long Liquiñe-Ofqui fault zone (LOFZ). We studied the southern ~500 km of the LOFZ using remote sensing, field mapping, and light detection and ranging data and document for the first time document field observations regarding style of faulting and fault displacements. Importantly we are able to evaluate long term (Miocene to present) to recent (Late-Quaternary) neotectonics along the LOFZ. Our new mapping changes the location of the LOFZ from previous mapping which was validated in the field through the presence of fault rocks coincident with the geomorphic surface traces. Preliminary results suggest Late Cenozoic to Quaternary LOFZ slip rates (~5 to 19 mm/yr (geologic) and 12 to 25 mm/yr (geomorphic)). These new Geologic and Geomorphic data imply that the LOFZ is the Andes fastest slipping crustal fault with high associated seismic hazard. We prefer the Quaternary rates due to less uncertainty than the longer term Miocene to present rates. Because our Quaternary rates are less than GPS rates (at least 7 mm/yr from a limited campaign) suggesting perhaps the LOFZ is perhaps late in its seismic cycle and one of the major crustal faults on Earth.

Key Words
earthquake geology, Andes, Chile, Seismic hazard, Liquiñe-Ofqui Fault Zone (LOFZ)

De Pascale, G. P., Froude, M., Penna, I., Hermanns, R., Moncada, D., Sepulveda, S., Persico, M., Petley, D., Vargas, G., Murphy, W., & Pairoa, S. (2018, 08). Preliminary geologic slip rates along Andes fastest slipping crustal fault, the Liquiñe-Ofqui Fault Zone (LOFZ), Patagonia, Chile . Poster Presentation at 2018 SCEC Annual Meeting.

Related Projects & Working Groups
Earthquake Geology