Earthquake deformation in the northwestern Sierras Pampeanas of Argentina based on seismic waveform modelling
We investigate the seismic properties of modern crustal seismicity in the northwestern Sierras Pampeanas of the Andean retroarc region of Argentina. We modelled the complete regional seismic broadband waveforms of two crustal earthquakes that occurred in the Sierra de Velasco on 28 May 2002 and in t...
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todo:paper_02643707_v51_n4_p205_Alvarado2023-10-03T15:12:45Z Earthquake deformation in the northwestern Sierras Pampeanas of Argentina based on seismic waveform modelling Alvarado, P. Ramos, V.A. Andean foreland Crustal earthquakes Neotectonics Seismic hazard Sierras Pampeanas Andean orogeny data inversion deformation earthquake magnitude extensional tectonics faulting focal mechanism moment tensor neotectonics seismic hazard seismic property seismic wave seismicity shear zone Argentina Sierra de Valasco Sierras Pampeanas We investigate the seismic properties of modern crustal seismicity in the northwestern Sierras Pampeanas of the Andean retroarc region of Argentina. We modelled the complete regional seismic broadband waveforms of two crustal earthquakes that occurred in the Sierra de Velasco on 28 May 2002 and in the Sierra de Ambato on 7 September 2004. For each earthquake we obtained the seismic moment tensor inversion (SMTI) and tested for its focal depth. Our results indicate mainly thrust focal mechanism solutions of magnitudes Mw 5.8 and 6.2 and focal depths of 10 and 8km, respectively. These results represent the larger seismicity and shallower focal depths in the last 100 years in this region. The SMTI 2002 and 2004 solutions are consistent with previous determinations for crustal seismicity in this region that also used seismic waveform modelling. Taken together, the results for crustal seismicity of magnitudes ≥5.0 in the last 30 years are consistent with an average P-axis horizontally oriented by an azimuth of 125° and T-axis orientation of azimuth 241° and plunge 58°. This modern crustal seismicity and the historical earthquakes are associated with two active reverse faulting systems of opposite vergences bounding the eastern margin of the Sierra de Velasco in the south and the southwestern margin of the Sierra de Ambato in the north. Strain recorded by focal mechanisms of the larger seismicity is very consistent over this region and is in good agreement with neotectonic activity during the last 11,000 years by Costa (2008) and Casa et al. (in press); this shows that the dominant deformation in this part of the Sierras Pampeanas is mainly controlled by contraction. Seismic deformation related to propagation of thrusts and long-lived shear zones of this area permit to disregard previous proposals, which suggested an extensional or sinistral regime for the geomorphic evolution since Pleistocene. © 2010 Elsevier Ltd. Fil:Ramos, V.A. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. JOUR info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by/2.5/ar http://hdl.handle.net/20.500.12110/paper_02643707_v51_n4_p205_Alvarado |
| institution |
Universidad de Buenos Aires |
| institution_str |
I-28 |
| repository_str |
R-134 |
| collection |
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) |
| topic |
Andean foreland Crustal earthquakes Neotectonics Seismic hazard Sierras Pampeanas Andean orogeny data inversion deformation earthquake magnitude extensional tectonics faulting focal mechanism moment tensor neotectonics seismic hazard seismic property seismic wave seismicity shear zone Argentina Sierra de Valasco Sierras Pampeanas |
| spellingShingle |
Andean foreland Crustal earthquakes Neotectonics Seismic hazard Sierras Pampeanas Andean orogeny data inversion deformation earthquake magnitude extensional tectonics faulting focal mechanism moment tensor neotectonics seismic hazard seismic property seismic wave seismicity shear zone Argentina Sierra de Valasco Sierras Pampeanas Alvarado, P. Ramos, V.A. Earthquake deformation in the northwestern Sierras Pampeanas of Argentina based on seismic waveform modelling |
| topic_facet |
Andean foreland Crustal earthquakes Neotectonics Seismic hazard Sierras Pampeanas Andean orogeny data inversion deformation earthquake magnitude extensional tectonics faulting focal mechanism moment tensor neotectonics seismic hazard seismic property seismic wave seismicity shear zone Argentina Sierra de Valasco Sierras Pampeanas |
| description |
We investigate the seismic properties of modern crustal seismicity in the northwestern Sierras Pampeanas of the Andean retroarc region of Argentina. We modelled the complete regional seismic broadband waveforms of two crustal earthquakes that occurred in the Sierra de Velasco on 28 May 2002 and in the Sierra de Ambato on 7 September 2004. For each earthquake we obtained the seismic moment tensor inversion (SMTI) and tested for its focal depth. Our results indicate mainly thrust focal mechanism solutions of magnitudes Mw 5.8 and 6.2 and focal depths of 10 and 8km, respectively. These results represent the larger seismicity and shallower focal depths in the last 100 years in this region. The SMTI 2002 and 2004 solutions are consistent with previous determinations for crustal seismicity in this region that also used seismic waveform modelling. Taken together, the results for crustal seismicity of magnitudes ≥5.0 in the last 30 years are consistent with an average P-axis horizontally oriented by an azimuth of 125° and T-axis orientation of azimuth 241° and plunge 58°. This modern crustal seismicity and the historical earthquakes are associated with two active reverse faulting systems of opposite vergences bounding the eastern margin of the Sierra de Velasco in the south and the southwestern margin of the Sierra de Ambato in the north. Strain recorded by focal mechanisms of the larger seismicity is very consistent over this region and is in good agreement with neotectonic activity during the last 11,000 years by Costa (2008) and Casa et al. (in press); this shows that the dominant deformation in this part of the Sierras Pampeanas is mainly controlled by contraction. Seismic deformation related to propagation of thrusts and long-lived shear zones of this area permit to disregard previous proposals, which suggested an extensional or sinistral regime for the geomorphic evolution since Pleistocene. © 2010 Elsevier Ltd. |
| format |
JOUR |
| author |
Alvarado, P. Ramos, V.A. |
| author_facet |
Alvarado, P. Ramos, V.A. |
| author_sort |
Alvarado, P. |
| title |
Earthquake deformation in the northwestern Sierras Pampeanas of Argentina based on seismic waveform modelling |
| title_short |
Earthquake deformation in the northwestern Sierras Pampeanas of Argentina based on seismic waveform modelling |
| title_full |
Earthquake deformation in the northwestern Sierras Pampeanas of Argentina based on seismic waveform modelling |
| title_fullStr |
Earthquake deformation in the northwestern Sierras Pampeanas of Argentina based on seismic waveform modelling |
| title_full_unstemmed |
Earthquake deformation in the northwestern Sierras Pampeanas of Argentina based on seismic waveform modelling |
| title_sort |
earthquake deformation in the northwestern sierras pampeanas of argentina based on seismic waveform modelling |
| url |
http://hdl.handle.net/20.500.12110/paper_02643707_v51_n4_p205_Alvarado |
| work_keys_str_mv |
AT alvaradop earthquakedeformationinthenorthwesternsierraspampeanasofargentinabasedonseismicwaveformmodelling AT ramosva earthquakedeformationinthenorthwesternsierraspampeanasofargentinabasedonseismicwaveformmodelling |
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