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TitreGround shaking and earthquake engineering aspects of the M 8.8 Chile earthquake of 2010 - applications to Cascadia and other subduction zones
AuteurCassidy, J F; Boroschek, R; Ventura, C; Huffman, S
SourceAmerican Geophysical Union, Fall Meeting 2010, abstract volume ; 2010, 1 pages
Séries alt.Secteur des sciences de la Terre, Contribution externe 20100166
RéunionAmerican Geophysical Union Annual Fall Meeting; San Francisco, CA; US; décembre 13-17, 2010
Mediaen ligne; numérique
Sujetssecousses séismiques; études séismiques; magnitudes des séismes; mécanismes de tremblement de terre; risque sismique; interpretations sismiques; géophysique
ProgrammeÉvaluations ciblées des dangers dans l'Ouest du Canada, Géoscience pour la sécurité publique
Résumé(disponible en anglais seulement)
The M 8.8 Maule, Chile earthquake of February 27, 2010 was the fifth largest earthquake ever recorded by seismographs and provides a rare opportunity to compare strong shaking observations with earthquake rupture and damage patterns. This subduction earthquake was caused by up to 13 m of eastward slip of the Nazca plate beneath the South American plate. The rupture zone extended nearly 600 km along the Chile coast and covered the most populated region of the country - extending from south of Concepcion to just south of Valpraiso (near the latitude of Santiago). As this is the type of earthquake that is expected along the Cascadia subduction zone of western Canada and the U.S., and given that modern building codes and construction styles in Chile and Cascadia are very similar, the Canadian Association of Earthquake Engineers sent a team of 10 engineers and a seismologist to the earthquake zone to learn from this earthquake. In this presentation we focus on sites where strong ground shaking was recorded (the data available to date range from about 0.1g to 0.66g). The recorded waveforms showed strong shaking for up to 2-3 minutes, with two distinct bursts of energy that may correspond to two large asperities that ruptured. At many locations, particularly along the coast, the recorded shaking levels exceeded code values, especially at longer periods (~ 1 second and longer). There was significant damage to older hospitals and schools. Twenty-five hospitals were severely damaged (17 collapsed, 8 repairable) and in the Maule region, 45% of the hospital beds were lost. More than 2500 schools were damaged and more than 780,000 students were affected. Of about 12,000 bridges in Chile, only 40 were damaged, 20 severely (many of these were newer overpasses). Modern high-rise buildings, in general, did very well. Of the 10,000 3-storey or higher buildings constructed since 1985, only 4 collapsed, and 50-150 were badly damaged. This clearly demonstrates the importance of modern building codes to minimising damage from earthquakes. One of the key lessons learned is the importance of ground motion recordings (the value of dense strong motion networks) to understanding shaking and the effects on structures. It is these strong motion recordings that allow for improvements to codes and standards. The relevance of this set of ground motions to the Cascadia Subduction Zone and other global subduction zones will be highlighted.