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

纳斯卡板块和南美洲板块之间的板块汇聚的一个重要部分位于安第斯山脉的弧后区域。在南纬28°和南纬33.5°之间，许多历史上的大规模板内地震记录表明，正在进行的变形集中在沿着前科迪勒拉山脉的前缘和更东面的潘佩纳斯山脉的基底隆起。虽然这些断层对前科迪勒拉山脉前的主要城市构成严重威胁，但前科迪勒拉山脉前的活动逆冲断层的长期滑动速率尚不清楚。在门多萨市附近的两个地表断裂逆冲断层处，我们将结合联合收割机的地貌测绘、地形测量、构造偏移河流阶地的暴露年代测定、古地震调查和发光年代测定，以确定（1）垂直隆起和水平缩短的长期速率和（2）过去这些断层上破坏性地震的频率。将长期缩短率与从GPS数据推断的短期速度（~5 mm/a）进行比较，将为了解断层速率的时间变化，即地震频率的变化，提供重要的见解。计划中的调查将有助于更好地限制前心脏地带前部的地壳变形，从而减少门多萨市的地震危险。

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.