Comportement actuel de l'avant-arc et de l'arc du coude de Arica dans l'orogénèse des Andes centrales

TOULOUSE3-BU Sciences (315552104) / SudocTOULOUSE-Observ. Midi Pyréné (315552299) / SudocSudocFranceF

Automatic detection of P- and S- wave arrival times: new strategies based on the modified fractal method and basic matching pursuit

In this work, new strategies for automatic identification of P- and S-wave arrival times from digital recorded local seismograms are proposed and analyzed. The database of arrival times previously identified by a human reader was compared with automatic identification techniques based on the Fourier transformation in reduced time (spectrograms), fractal analysis, and the basic matching pursuit algorithm. The first two techniques were used to identify the P-wave arrival times, while the third was used for the identification of the S-wave. For validation, the results were compared with the short-time average over long-time average (STA/LTA) of Rietbrock et al., Geophys Res Lett 39(8), (2012) for the database of aftershocks of the 2010 Maule M-w = 8.8 earthquake. The identifiers proposed in this work exhibit good results that outperform the STA/LTA identifier in many scenarios. The average difference from the reference picks (times obtained by the human reader) in P- and S-wave arrival times is similar to 1 s.FONDECYT 1130071 Advanced Center for Electrical and Electronic Engineering FB000

Source parameters of the Mw = 6.3 Aroma crustal earthquake of July 24, 2001 (northern Chile), and its aftershock sequence

International audienceThe July 24, 2001, Mw = 6.3 earthquake in Aroma, Chile, is one of the few moderately shallow earthquakes to occur recently in northern Chile. This study uses different seismological data (short-period, broadband, strong-motion) to locate the event and its corresponding aftershocks. In addition, it carefully constrains the focal depth using SP phase and the focal mechanism of the main-shock. Finally, a model of the strong-motion waveforms discriminates the activated fault plane among the two nodal planes. The main-shock fault plane solution obtained from the strong-motion analysis is (strike, dip, rake) = (14° ± 10°, 53° ± 15°, −163° ± 15°), which indicates a right-lateral motion on an inclined fault, in agreement with the aftershock distribution, which also indicates a fault striking N14°E and dipping about 50°E

Delamination of southern Puna lithosphere revealed by body wave attenuation tomography

Artículo de publicación ISIThe southern Puna Plateau has been proposed to result from a major Pliocene delamination event that has previously been inferred from geochemical, geological, and some preliminary geophysical data. Seventy-five seismic stations were deployed across the southern Puna Plateau in 2007–2009 by scientists fromthe U.S., Germany, Chile, and Argentina to test the delamination model for the region. The Puna passive seismic stations were located between 25 and 28°S. Using the seismic waveform data collected from the PUNA experiment,we employ attenuation tomography methods to resolve both compressional and shear quality factors (Qp and Qs, respectively) in the crust and uppermost mantle. The images clearly show a high-Q Nazca slab subducting eastward beneath the Puna plateau and another high-Q block with a westward dip beneath the Eastern Cordillera. We suggest that the latter is a piece of delaminated South American lithosphere. A significant low-Q zone lies between the Nazca slab and the South American lithosphere and extends southward from the northernmargin of the seismic array at 25°S before vanishing around 27.5°S. This low-Q zone extends farther west in the crust and uppermost mantle at the southern end of the seismic array. The low-Q zone reaches ~100 km depth beneath the northern part of the array but only ~50 km depth in the south. Lateral variations of the low-Q zone reflect the possible mechanism conversion between mantle upwelling related to delamination and dehydration. The depth of the Nazca slab as defined by Q images decreases from north to south beneath the plateau, which is consistentwith the steep-flat transition of the angle of the subducting slab as defined by previous earthquake studies.This research is supported by the National Natural Science Foundation of China under grant 41340040, 91128210, the Continental Dynamics, National Science Foundation (USA) under grant EAR- 0538245, and by the Deutsche Forschungsgemeinschaft KI 314/27-1