Browsing by Autor "Alexis Le Pichon"

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Evidence for a meteoritic origin of the September 15, 2007, Carancas crater
(Wiley, 2008) Alexis Le Pichon; K. Antier; Yves Cansi; B. Hernandez; E. Minaya; B. BURGOA; D. P. Drob; Läslo Evers; Jérémie Vaubaillon
Abstract— On September 15th, 2007, around 11:45 local time in Peru, near the Bolivian border, the atmospheric entry of a meteoroid produced bright lights in the sky and intense detonations. Soon after, a crater was discovered south of Lake Titicaca. These events have been detected by the Bolivian seismic network and two infrasound arrays operating for the Comprehensive Nuclear‐Test‐Ban Treaty Organization, situated at about 80 and 1620 km from the crater. The localization and origin time computed with the seismic records are consistent with the reported impact. The entry elevation and azimuthal angles of the trajectory are estimated from the observed signal time sequences and back‐azimuths. From the crater diameter and the airwave amplitudes, the kinetic energy, mass and explosive energy are calculated. Using the estimated velocity of the meteoroid and similarity criteria between orbital elements, an association with possible parent asteroids is attempted. The favorable setting of this event provides a unique opportunity to evaluate physical and kinematic parameters of the object that generated the first actual terrestrial meteorite impact seismically recorded.
Ground‐coupled air waves and diffracted infrasound from the Arequipa earthquake of June 23, 2001
(American Geophysical Union, 2002) Alexis Le Pichon; J. Guilbert; Ángel Javier Vega; Milton Garcés; Nicolas Brachet
On June 23, 2001, a strong earthquake measuring M w 8.4 occurred along the coast of south‐central Peru. Coherent infrasonic waves were detected over a period of one hour by the IS08 infrasound station in Bolivia. Analysis of the ground‐coupled air waves shows that the rupture propagated from the northwestern to the southeastern part of the fault with a rupture velocity of 3.3 km/s. The azimuth variation of the infrasonic waves is attributed to a distribution of secondary sources along the highest mountain ranges, which excite infrasonic waves that are diffracted to the ground. The predominant source of infrasound is likely distributed along the Andean Cordillera. Using the azimuth and arrival time determination, the horizontal scale size of the distant source regions of infrasonic waves is reconstructed over distances greater than 400 km.