SGER: Geomorphic Response to the September1999 Taiwan Earthquake: Evolution of River Profiles Across the Scarp and Inference about Earthquake Recurrence Intervals

0000893人们普遍认为，山地景观演化的迪特里希构造作用力是通过断层沿着山脉边界产生的断层点的河流网络向上游传播而发生的。 1999年9月21日发生在台湾的7.6级地震提供了一个难得的机会来研究构造隆起的信号是如何通过不断变化的景观传递的。 60公里长的地表破裂，沿着中央山脉西部山麓的底部，形成了跨越几条主要河流的2至8米高的瀑布。 在我们工作的初始勘探阶段，PI将调查初始悬崖剖面和通道几何形状，测量河床沉积物粒度分布，收集基岩样品进行强度和耐磨性测试，并记录过去隆起事件的地貌特征。 他们预计，由于下伏泥岩和砂岩较弱，年降雨量高，粗泥沙含量高，跨河道断层陡坎将迅速演化。 他们将使用现场调查和实验室测试的结果，在基岩河道切口的数值模型，以预测上游断点传播的速率和风格。 在随后的现场活动中，他们将重新调查不断变化的断层崖和河道状况，以与模型预测进行比较。 除了深入了解隆起事件如何通过景观传播外，这项工作还可能有助于限制这种震级地震的复发间隔，这些信息对研究这种灾害的工程师具有相当重要的实际意义。

0000893Dietrich Tectonic forcing of the evolution of mountainous landscapes is widely thought to occur through the upstream propagation through the river network of knickpoints created by faulting along range boundaries. The September 21, 1999, magnitude 7.6 earthquake in Taiwan offers a rare opportunity to study how the signal of tectonic uplift is transmitted through an evolving landscape. The 60 km long surface rupture, along the base of the western foothills of the Central Range, created waterfalls from 2 to 8 m high across several major rivers. In this initial exploratory phase of our work PIs will survey the initial scarp profiles and channel geometry, measure bed sediment size distributions, collect bedrock samples for strength and abrasion resistance testing, and document geomorphic features from past uplift events. They anticipate rapid evolution of the channel-crossing fault scarps because of the weak underlying mudstones and sandstones, the high annual rainfall and high coarse sediment load. They will use the results of the field surveys and laboratory testing in a numerical model of bedrock channel incision, to predict the rate and style of upstream knickpoint propagation. In subsequent field campaigns they will re-survey the evolving fault scarps and channel conditions to compare with model predictions. In addition to providing insight into how an uplift event propagates through a landscape, this work may help constrain the recurrence interval for earthquakes of this magnitude, information of considerable practical importance to engineers studying this disaster.