Levantamiento cosismico e impacto del tsunami a lo largo de la costa de Chile central asociado al terremoto del Maule Mw8,8 de 2010.

Abstract

ABSTrACT. On February 27, 2010 at 03:34:08 AM an Mw8.8 earthquake, with epicenter located off Cobquecura (73.24°W; 36.29°S), severely hit Central Chile. The tsunami waves that followed this event affected the coastal regions between the cities of Valparaíso and Valdivia, with minor effects as far as Coquimbo. The earthquake occurred along the subduction of the Nazca oceanic plate beneath the South American plate. Coseismic coastal uplift was estimated through observations of bleached lithothamnioids crustose coralline algae, which were exposed after the mainshock between 34.13°S and 38.34°S, suggesting the latitudinal distribution of the earthquake rupture. The measured coastal uplift values varied between 240±20 cm at sites closer to the trench along the western coast of the Arauco peninsula and 15±10 cm at sites located farther east. A maximum value of 260±50 cm was observed at the western coast of Santa María Island, which is similar to the reported uplift associated with the 1835 earthquake at Concepción. Land subsidence values on the order of 0.5 m to 1 m evidenced a change in polarity and position of the coseismic hinge at 110-120 km from the trench. In four sites along the coast we observed a close match between coastal uplift values deduced from bleached lithothamnioids algae and GPS measurements. According to field observations tsunami heights reached ca. 14 m in the coastal area of the Maule Region immediately north of the epicenter, and diminished progressively northwards to 4-2 m near Valparaíso. Along the coast of Cobquecura, tsunami height values were inferior to 2-4 m. More variable tsunami heights of 6-8 m were measured at Dichato-Talcahuano and Tirúa-Puerto Saavedra, in the Biobío and Arauco regions, respectively, to the south of the epicenter. According to eyewitnesses, the tsunami reached the coast between 12 to 20 and 30 to 45 minutes in areas located closer and faraway from the earthquake rupture zone, respectively. Destructive tsunami waves arrived also between 2.5 and 4.5 hours after the mainshock, especially along the coast of the Biobío and Arauco regions. The tsunami effects were highly variable along the coast, as a result of geomorphological and bathymetric local conditions, besides potential complexities induced by the main shock. ; 36,29°S), afectó severamente la zona centrosur de Chile. Posteriormente un tsunami afectó las costas comprendidas entre las regiones de Valdivia y Valparaíso, con efectos menores en la costa de Coquimbo. El terremoto ocurrió a lo largo de la subducción de la placa tectónica de Nazca bajo la placa Sudamericana. Se estimó el levantamiento cosísmico de la costa a partir de observaciones de la franja de algas coralina lithothamnioideas, expuesta como producto del terremoto. Evidencias de deformación vertical se observaron entre los 34,13°S y 38,34°S, sugiriendo la extensión latitudinal de la ruptura sísmica del evento principal. El levantamiento costero observado varió entre 240±20 cm, en la costa occidental de la península de Arauco, ubicada relativamente má...

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