Rates of thrust faulting at the front of the Precordillera in western Argentina: Implications for the seismic hazard in Mendoza city from surface expose dating and paleoseismology

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A significant amount of the current plate convergence between the Nazca and the South American Plate is taken up in the back-arc region of the Andes. Between latitude 28°S and 33.5°S many large historical intraplate earthquakes document that ongoing deformation is concentrated along the front of the Precordillera and the basement uplifts of the Sierra Pampeanas farther east. Long-term slip rates of active thrust faults at the mountain front of the Precordillera are not known, although these faults pose a serious threat to major cities at the front of the Precordillera. At two surface-breaking thrusts near Mendoza city we will combine geomorphic mapping, topographic surveying, exposure dating of tectonically offset river terraces, paleoseismologic investigations, and luminescence dating in order to determine (1) the long-term rates of vertical uplift and horizontal shortening and (2) the frequency of destructive earthquakes on these faults in the past. Comparison of the longterm shortening rates with short-term velocities inferred from GPS data (~5 mm/a) will provide important insight into temporal variations in the rate of faulting, i.e. changes in the frequency of earthquakes. The planned investigations will help to better constrain crustal deformation at the front of the Precordillera and thus the seismic hazard for Mendoza city.