Constraining Non-Linear Lithospheric Viscous Flow Laws From Postseismic Surface Deformation Measurements

这个项目依靠1992年兰德斯地震和1999年赫克托雷地震后的地表形变观测来推断莫哈韦沙漠下岩石圈明显的非线性粘性流变特征的流动规律。非线性或幂律行为，其中应变率与应力的幂成正比，指数依赖于温度，已经在实验室实验中得到证明，并从莫哈韦地震后有效线性粘度的推断变化中推测出来。然而，表征莫哈韦岩石圈流变性的具体非线性流动规律尚未确定。由于缺乏足够的观测约束，非线性流变学在过去很难推断。前所未有的GPS和InSAR覆盖莫哈韦地震后的震后变形，结合复杂滑动分布和非线性流变的数值模拟能力，可以确定控制该地区大陆岩石圈行为的适当流动规律参数。这项工作包括将大地测量数据集汇编成一种有助于约束数值模型的形式，并开发兰德斯和赫克托矿井破裂的三维粘弹性有限元模型。该约束模型用于(1)划分粘性过程与余震等其他机制之间的震后变形；(2)确定粘性流动的深度分布；(3)推断适用的非线性流动规律。这些结果提供了对地球内部产生的力如何在地表表现出来以及地震引起的应力如何在震间期重新分布的见解。后者对于理解地震灾害很重要。这项研究的另一个副产品是，通过指出与走滑地震有关的最有用的仪器位置，为进行非线性岩石圈流变学的未来大地测量调查提供指导。

EAR-0207617Roland BurgmannThis project relies on observations of postseismic surface deformation following the 1992 Landers and 1999 Hector Mine earthquakes to infer the flow laws that characterize the apparent non-linear viscous rheology of the lithosphere beneath the Mojave Desert. Non-linear or power law behavior, in which strain rate is proportional to stress raised to a power and exponentially dependent on temperature, has been demonstrated in laboratory experiments and surmised from an inferred change in effective linear viscosity following the Mojave quakes. However, the specific non-linear flow laws that characterize the rheology of the Mojave lithosphere have not been determined. Non-linear rheology has been difficult to infer in the past due to a lack of sufficiently resolved observational constraints. The unprecedented GPS and InSAR coverage of postseismic deformation following the Mojave quakes, combined with the ability to numerically model complex slip distributions and non-linear rheology, allow for the determination of the appropriate flow law parameters governing continental lithospheric behavior in this region. The work consists of compiling the geodetic data sets in a form useful for constraining a numerical model and development of a 3-D viscoelastic finite element model of the Landers and Hector Mine ruptures. This constrained model is used to (1) partition postseismic deformation between viscous processes and other mechanisms such as afterslip, (2) determine the depth distribution of viscous flow, and (3) infer applicable non-linear flow laws. The results provide insight into how forces generated within the Earth's interior manifest themselves at the surface and how stresses induced by earthquakes are redistributed during interseismic periods. The latter of which is important to understanding seismic hazards. An additional byproduct of this research consists of guidelines for conducting future geodetic investigations of non-linear lithospheric rheology by noting the most useful locations for instrumentation relative to strike-slip earthquakes.