Collaborative Research: Erosional Forcing of Late Quaternary Compressive Strain, West Central Taiwan

挤压造山带的稳态增长概念是近20年来大陆构造学中最被接受的观点之一，但令人惊讶的是，几乎没有直接的数据来检验已经提出的模型。测试和完善的概念，稳定状态的造山运动需要确定的情况下，瞬态响应和动态反馈的压缩造山带，并记录的空间和时间尺度，地壳变形响应侵蚀。本计画利用台湾中西部活跃褶皱冲断带独特的自然实验，在此有足够的现代地震、大地测量、构造与地质年代学资料，以评估造山带如何回应数十公里尺度的楔体体积的快速与突变。位于台湾中西部的埔里湾比褶皱冲断带的邻近部分低约1.5公里。 地质和大地测量证据表明，逆冲作用发生在地形海湾的宽度上，而不是集中在冲断带的前部，就像冲断带南部的相邻部分那样，那里的地形保持着典型的楔形。 应变和地形梯度之间的假设的连接进行测试（a）晚第四纪滑动速率和变形模式的数据库的开发，使用结构，地质年代学和地貌方法的组合，和（B）使用三维有限元模型，以确定所需的必要和充分条件，以产生所观察到的地形和变形模式。断层滑动速率是通过对变形的河流阶地和盆地充填沉积物进行测年而获得的。年龄测定还可以测试和校准长期河流切割规律。校准的法律提供了一个定量的基础，地形派生的估计应变模式，在难以进入或约束不良的地区，如阿里山山脉的带。

The concept of steady-state growth of compressive orogens is one of the most accepted ideas in continental tectonics developed in the last two decades, yet surprisingly few direct data exist to test the models that have been advanced. Testing and refining the concept of steady-state mountain building requires identification of cases of transient response and dynamic feedback in compressive orogens, and documentation of the spatial and temporal scales at which crustal deformation responds to erosion. This project takes advantage of a unique natural experiment in the active fold-thrust belt of west-central Taiwan where enough modern seismologic, geodetic, structural and geochronologic data exist to assess how an orogen responds to rapid and abrupt changes in wedge volume at scales of tens of kilometers. The Puli embayment in the west-central Taiwan lies approximately 1.5 km lower than neighboring parts of the fold-thrust belt. Geologic and geodetic evidence suggests that thrusting occurs over the width of the topographic embayment, rather than being concentrated at the front of the thrust belt, as is the case in the adjacent part of the thrust belt to the south where the topography maintains a classic wedge shape. The hypothesized connection between strain and topographic gradients is tested by (a) development of a database of late Quaternary slip rates and deformation patterns using a combination of structural, geochronologic and geomorphic methods, and (b) use of a 3D finite element model to determine the necessary and sufficient conditions required to produce the observed topography and deformation patterns. Fault-slip rates are obtained via dating of deformed stream terrace and basin fill deposits. Age dating also enables testing and calibration of long-term stream incision laws. The calibrated laws provide a quantitative basis for topographically derived estimates of strain patterns in inaccessible or poorly constrained areas of the belt such as the Alishan Range.