San Ramon Fault - trenching
San Ramon Fault - trenching
Robin Lacassin
Directeur de recherche CNRS
Tectonique - IPGP
Estimating the potential for the occurrence of large earthquakes on slow-slip-rate faults in continental interiors, away from plate boundaries, is possible only if the long-term geological record of past events is available. However, our knowledge of strong earthquakes appears to be incomplete for thrust faults flanking large actively growing mountain ranges, such as those surrounding Tibet and the Andes Mountains. We present a paleoseismic study of a prominent fault scarp at the west flank of the Andes in Santiago, Chile. The evidence demonstrates recur- rent faulting with displacement of ~5 m in each event. With two large earthquake ruptures within the past 17–19 k.y., and the last event occurring ~8 k.y. ago, the fault appears to be ripe for another large earthquake (moment magnitude, Mw 7.5). These results emphasize the potential danger of intraplate continental faults, particularly those associated with youthful mountain fronts.
Probing large intraplate earthquakes at the west flank of the Andes
Vargas, Klinger, Rockwell, Forman, Rebolledo, Baize, Lacassin, Armijo
Geology, v. 42 no. 12 p. 1083-1086; published online on 17 October 2014 as doi:10.1130/G35741.1
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updated December 2014