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Ito, Yoichi
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- PublicationOpen AccessThe full-scale avalanche test site, Lautaret, France(2013-10-07)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;Thibert, Emmanuel; IRSTEA ;Bellot, Hervé; IRSTEA ;Ravanat, Xavier; IRSTEA ;Ousset, Frédéric; IRSTEA ;Pulfer, Gaëtan; IRSTEA ;Naaim, Mohamed; IRSTEA ;Naaim-Bouvet, Florence; IRSTEA ;Nishimura, Koichi; Nagoya University ;Ito, Yoichi; Nagoya University ;Baroudi, Djebar; Institute of Mountain Risk Engineering ;Prokop, Alexander; Institute of Mountain Risk Engineering ;Schön, Peter; Institute of Mountain Risk Engineering ;Soruco, P. Alvaro; IGEMA ;Vincent, Christian; LGGE ;Limam, Ali; INSA-Lyon ;Pesaresi, Damiano; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; ; ; ; ; ; ; ; ; ; ; ; ; ; ; The Lautaret full-scale avalanche test site in the southern French Alps has been used by IRSTEA (Cemagref) Research Institute since 1973. Over the recent years two avalanche paths are used to release small to medium avalanches 3 or 4 times each winter. Avalanche flows are generally dense, whether wet or dry, sometimes with a powder part. Main path n°2 (track length 800 m) is dedicated to avalanche dynamics. Within the flow of the avalanche, flow height and vertical profiles of pressure and velocity are measured along a 3.5 m tripod. The snow volume released in the starting zone is quantified by a differential analysis of laser scanning measurements set before and after triggering. A high rate positioning of the avalanche along the track is determined from terrestrial oblique photogrammetry. Above the dense layer, the saltation layer and the powder part are characterized by particles and air fluxes measurements. In path n°1 smaller in size, medium-size avalanches (track length 500 m) make this track of particular interest for experiments on structures. A macroscopic sensor-structure is set nearly 150 m downhill from the starting zone, that is, in the area where avalanches generally reach their maximum velocity. It consists is a one square-meter plate supported by a 3.5 m high steel cantilever fixed in the ground, facing the avalanche. Impact pressures are reconstructed from the cantilever deformations, while avalanche velocity is measured from optical sensors. Seismic signals generated by avalanches of those 2 paths are recorded by a 3-axial broadband seismometer. Around those experimental devices dedicated to the understanding of avalanche physics, a national and international partnership has been developed from years to years, including INSA de Lyon, CNRS and Université Joseph Fourier (France), Aalto University (Finland), Nagoya University (Japan), Boku University (Austria), IGEMA (Bolivia), OGS (Italy)325 187 - PublicationOpen AccessStructural control on the Tohoku earthquake rupture process investigated by 3D FEM, tsunami and geodetic data(2014-07-09)
; ; ; ; ; ; ; ; ; ; ;Romano, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Trasatti, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Lorito, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Piromallo, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Piatanesi, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Ito, Y.; Disaster Prevention Research Institute, Kyoto University, Japan ;Zhao, D.; Department of Geophysics, Tohoku University, Sendai, Japan ;Hirata, K.; National Research Institute for Earth Science and Disaster Prevention, Ibaraki, Japan ;Lanucara, P.; CINECA, SuperComputing Applications and Innovation Department - SCAI, Rome, Italy ;Cocco, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; ; ; ; ; ; ; ; ; The 2011 Tohoku earthquake (Mw = 9.1) highlighted previously unobserved features for megathrust events, such as the large slip in a relatively limited area and the shallow rupture propagation. We use a Finite Element Model (FEM), taking into account the 3D geometrical and structural complexities up to the trench zone, and perform a joint inversion of tsunami and geodetic data to retrieve the earthquake slip distribution. We obtain a close spatial correlation between the main deep slip patch and the local seismic velocity anomalies, and large shallow slip extending also to the North coherently with a seismically observed low-frequency radiation. These observations suggest that the friction controlled the rupture, initially confining the deeper rupture and then driving its propagation up to the trench, where it spreads laterally. These findings are relevant to earthquake and tsunami hazard assessment because they may help to detect regions likely prone to rupture along the megathrust, and to constrain the probability of high slip near the trench. Our estimate of ~40 m slip value around the JFAST (Japan Trench Fast Drilling Project) drilling zone contributes to constrain the dynamic shear stress and friction coefficient of the fault obtained by temperature measurements to ~0.68 MPa and ~0.10, respectively.1288 127