Collaborative Research: Towards a Quaternary Spatial and Temporal Deformation History at the Central Andean Thrust Front

这项多学科研究的目的是测量阿根廷安第斯中央逆冲前缘的形变速率，以便(1)更好地了解薄皮Precordilleran和厚皮潘皮亚构造带交汇处的形变运动学和几何学；以及(2)评估该地区盲目推挤对附近城市门多萨和圣胡安等人口中心构成的风险。通过将地质数据(地震线、年代地层、构造剖面)与地貌数据(变形和确定年代的阶地和风隙、排水模式)相结合，美国研究小组将与阿根廷研究人员合作，将逆冲断层的滑动速率、逆冲和盲冲背斜上盘的抬升速率以及个别构造上盘背斜支腿上的旋转速率转换为综合的空间和时间变形历史。五个构造--Barrancas背斜、El Borbollon背斜、拉斯佩纳斯逆冲断层、Montecito背斜和Cerro Salinas逆冲构造--被作为地震解释、地貌填图、宇宙成因测年和排水分析的目标。这项研究将同时涉及构造和地震灾害。研究区位于薄皮肤、东偏东的Precordillera和西偏西的Sierras Pampeanas构造域的交汇处。导致缩短作用向安第斯板块内部转移的条件，以及同时驱动厚皮和薄皮变形的条件，人们了解甚少。时间和空间上受限的变形历史对于回答以下问题至关重要：哪些构造滑动最快；变形历史是一致的，还是速率在时间上是可变的；如果速率是可变的，相邻构造之间或属于不同构造省的构造之间的关系是什么？该项目将记录安第斯前陆的三个盲目逆冲构造。盲目逆冲断层对门多萨-圣胡安走廊以及世界其他地区构成重大风险。这种类型的断层在地震危险性分析中特别重要，因为有时微妙的地貌表现使它们很难识别，特别是在被城市化改变的地区。这一区域提供了一个机会，可以调查与不同发展阶段的盲目突进有关的地貌变化，以及可能表明以前未发现的变形的水系区域变化。

This multidisciplinary research aims to measure deformation rates at the central Andean thrust front in Argentina in order to (1) better understand the kinematics and geometry of deformation at the intersection of the thin skinned Precordilleran and thick-skinned Pampean structural zones; and (2) assess the risk posed by blind-thrusts in this region for population centers such as the nearby cities of Mendoza and San Juan. By combining geologic data (seismic lines, dated stratigraphy, structural cross-sections) with geomorphic data (deformed and dated terraces and wind gaps, drainage patterns), the U.S. research team in collaboration with Argentine researchers will translate slip rates on thrust faults, uplift rates in the hanging wall of thrusts and blind-thrust anticlines, and rotation rates on the limbs of hanging wall anticlines on individual structures into an integrated spatial and temporal deformation history. Five structures - the Barrancas anticline, El Borbollon anticline, Las Penas thrust fault, Montecito anticline and Cerro Salinas thrust - are targeted for seismic interpretation, geomorphic mapping, cosmogenic dating, and drainage analysis. This study will address both tectonics and seismic hazards. The study region lies at the intersection between the thin-skinned, east-vergent Precordillera and the west-vergent, thick-skinned Sierras Pampeanas tectonic domains. The conditions that have led to the transferal of shortening far into the interior of the Andean plate and that simultaneously drive both thick- and thin-skinned deformation are poorly understood. A temporally and spatially constrained deformation history is of critical importance for answering questions such as: which structures are slipping fastest; is the deformation history uniform, or are rates temporally variable; if rates are variable, what is the relationship between adjacent structures, or between structures belonging to different structural provinces? The project will document three blind thrust structures in the Andean foreland. Blind-thrust faults pose a significant risk to the Mendoza-San Juan corridor as well as other parts of the world. This type of fault is of particular interest in seismic hazard analysis because the sometimes subtle geomorphic expression makes them difficult to identify, especially in areas that have been altered by urbanization. This region presents an opportunity to investigate changes in geomorphology associated with blind-thrusts in different stages of development, as well as regional changes in the drainage network which might indicate previously undetected deformation.