Crustal thickness estimation in the Maule Region (Chile) from P-wave receiver function analysis .

Dannowski, Anke , Grevemeyer, Ingo , Thorwart, Martin, Rabbel, Wolfgang and Flueh, Ernst R. (2010) Crustal thickness estimation in the Maule Region (Chile) from P-wave receiver function analysis . [Poster] In: AGU Fall Meeting 2010. , 13.-17.12.2010, San Franciso, USA .

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A temporary passive seismic network of 31 broad-band stations was deployed in the region around Talca and Constitución between 35°S to 36°S latitude and 71°W to 72.5°W longitude. The network was operated between March and October 2008. Thus, we recorded data prior the magnitude Mw=8.8 earthquake of 27 February 2010 at a latitude of the major slip and surface uplift. The experiment was conducted to address fundamental questions on deformation processes, crustal and mantle structures, and fluid flow. We present first results of a teleseismic P receiver function study that covers the coastal region and reaches to the Andes. The aim is to determine the structure and thickness of the continental crust and constrain the state of hydration of the mantle wedge. The P-wave receiver function technique requires large teleseismic earthquakes from different distances and backazimuths. A few percent of the incident P-wave energy from a teleseismic event will be converted into S-wave (Ps) at significant and relatively sharp discontinuities beneath the station. A small converted S phase is produced that arrives at the station within the P wave coda directly after the direct P-wave. The converted Ps phase and their crustal multiples contain information about crustal properties, such as Moho depth and the crustal vp/vs ratio. We use teleseismic events with magnitudes mb > 5.5 at epicentral distances between 30° and 95° to examine P-to-S converted seismic phases. Our preliminary results provide new information about the thickness of the continental crust beneath the coastal region in Central Chile. At most of the stations we observed significant energy from P to S converted waves between 4 and 5 s after the direct P-wave within a positive phase interpreted as the Moho, occurring at 35 to 40 km. Thus, the great Maule earthquake of 27 February 2010 nucleated up-dip of the continental Moho and hence ruptured along a plate contact between subducted sediments and continental crust. Further, the Moho reflection show a positive polarity, indicating that the mantle is either dry or only moderately hydrated.

Document Type: Conference or Workshop Item (Poster)
Keywords: Seismology
Research affiliation: OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-GDY Marine Geodynamics
Kiel University
Date Deposited: 10 Jan 2011 10:51
Last Modified: 23 Feb 2012 06:24

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