Probing large intraplate earthquakes at the west flank of the Andes

G Vargas (1) , Y Klinger (2) , Tom Rockwell (3) , Steve Forman (4) , S Rebolledo (1) , S Baize (5) , R Lacassin (2) , R Armijo (2)

1 Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Santiago
2 IPGP - Institut de Physique du Globe de Paris
3 Geology SDSU - Department of Geological Sciences [San Diego State Univ]
4 Baylor University
5 IRSN - Institut de Radioprotection et de Sûreté Nucléaire

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 recurrent 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, M w 7.5). These results emphasize the potential danger of intraplate continental faults, particularly those associated with youthful mountain fronts.

Mots clés: Orogeny; San Ramon Fault; West Andean Thrust; Paleoseismological trench; Andes; Chile; Seismic Hazard; Earthquake; Paleoseismology; Tectonics

Domaines: Tectonique; Sciences de la Terre; Géomorphologie

G Vargas, Y Klinger, Tom Rockwell, Steve Forman, S Rebolledo, et al.. Probing large intraplate earthquakes at the west flank of the Andes. Geology, 2014, 42, pp.1083-1086. ⟨10.1130/G35741.1⟩. ⟨insu-01138562⟩