Toward Dynamic Models of Contemporary Plate Boundary Deformation with Application to the Taiwan Collision Zone

最近在苏门答腊岛和巴基斯坦发生的灾难性地震强调了发展识别潜在大震源的技术和提高对板块边界变形过程的理解的重要性。受大地测量、地震、古地震和地貌数据约束的地壳变形模型是探索板块边界变形物理特性的合适工具。本研究的目的是建立板块边界变形的动态模型，将GPS测量的地壳运动与台湾弧-大陆碰撞带的各种地质和地球物理数据集结合起来，台湾弧-大陆碰撞带是仪器最密集但却知之甚少的板块边界之一。这些模型是动态的，因为断层上的滑动是由一个假定的本构律控制的，该本构律将岩石圈中的应力与断层滑动联系起来。本研究所建立的模型是对相关运动学模型的扩展，在运动学模型中，断层滑动只根据岩石圈块体的运动而不考虑驱动力。激发本研究的首要问题是，如何更好地理解控制台湾和其他板块边界环境中岩石圈变形时空分布的因素：1)台湾的弧-陆快速辐合如何分布在活动断裂和褶皱中？2)爬行和锁断断段对这种变形的分布起什么作用？3)断层几何形状在形变分布中起什么作用？(3)未来哪里可能发生地震？4)如何将各种不同的数据集集成到这个正在进行的变形过程的综合3D模型中？特别是，研究的目的是将动态模型与各种数据集相结合，以获得台湾断层滑动率的估计，并确定在未来地震中可能破裂的活动断层的锁定段的空间分布。基于GPS数据的断层滑动率模型预测受到古地震、地质和地貌对长期滑动率估计的限制。活动断层的几何形状以及爬行和锁定断层块的位置受到重新定位的地震活动性、地震震源机制的分布以及小型重复地震的位置的限制。地震层析成像限制了地壳几何和流变学。

The recent catastrophic earthquakes in Sumatra and Pakistan underscore the importance of developing techniques to identify potential large seismic sources and gaining an improved understanding of plate-boundary deformation processes. Crustal deformation models constrained by geodetic, seismic, paleoseismic, and geomorphic data are the appropriate tools for probing into the physics of plate-boundary deformation. The purpose of this research is to develop dynamic models of plate-boundary deformation that incorporate GPS measurements of crustal motions with a wide variety of geologic and geophysical data sets from the Taiwan arc-continent collision zone, one of the most densely instrumented, yet poorly understood, plate boundaries. The models are dynamic in the sense that slip on faults is governed by an assumed constitutive law that relates stresses in the lithosphere to fault slip. The models being developed in this research are an extension of related kinematic models in which slip on faults is prescribed based solely on the motions of lithospheric blocks, without regard to the driving forces. The overarching questions that motivate this work are directed toward an improved understanding of factors that control the spatial and temporal distribution of lithospheric deformation in Taiwan and other plate-boundary settings: 1) How is the rapid arc-continent convergence in Taiwan distributed among the active faults and folds? 2) What role do creeping and locked fault segments play in distributing this deformation?, 3) What role does fault geometry play in distributing the deformation?, 3) Where are future earthquakes likely to occur?, and 4) How can the various disparate data sets be integrated into a comprehensive 3D model of this ongoing deformation process? In particular, the research aims to integrate the dynamic model with various data sets to obtain estimates of fault slip rates in Taiwan and determine the spatial distribution of locked sections of active faults that are likely to rupture in future earthquakes. Model predictions of fault slip rates from GPS data are constrained by paleoseismic, geologic, and geomorphic estimates of long-term slip rates. Active fault geometry and locations of creeping and locked fault patches are constrained by relocated seismicity, distributions of earthquake focal mechanisms, and locations of small repeating earthquakes. Seismic tomography constrains crustal geometry and rheology.