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

Download Article (PDF, open access, CC-BY) - Suppl. infos (PDF)

Snapshot figures on this page are linked to high-res versions

INSU-CNRS news (in french)

Please refer to the published paper and to this page while using these figures

Links to figures (high-res versions) :

Figure 1 (Andes map, 3D satellite view) – Figure 2 (3D view of San Ramon fault)
Figure 3 (trench photo mosaic and log) – Figure 4 (model)

Versions of the figures with legends in french : Andes map, San Ramon 3D view