Collaborative Research: Mechanisms of Postseismic Deformation Following the 2002 Denali Fault Earthquake Sequence

2002年11月3日发生的里氏7.9级迪纳利地震为收集地表变形测量数据提供了机会，这些数据可以显著提高我们对地球岩石圈主要变形机制的认识，以及对断裂带及其周围地壳和上地幔流变参数的认识。德纳里地震的大力矩、精确的震前变形场和即时的场响应使其成为现代空间大地测量方法问世以来最有希望解决震后变形问题的目标。我们的观测策略包括在16个地点进行连续的GPS （CGPS）测量，这些地点距离破裂的距离很宽，包括一些150公里的地点，以区分深断裂带，下地壳和上地幔的过程。其中11个站点在事件发生后两周内安装完毕，此后一直在持续运行。本文研究的一个基本目标是精确地确定地震后变形信号的时间依赖性。CGPS测量将由每年两次GPS运动补充，使用现有基准，以便在空间上密集地测量震后位移场。我们还将测试InSAR测量同震和早期震后变形的能力。观测工作将辅以综合建模工作，以评估候选变形机制，如速度增强后滑、孔隙弹性反弹和下地壳和上地幔的粘性流动。描述这些机制的相对重要性是本研究项目的主要目标。我们将充分探索不同模型类型的能力（例如，下地壳和上地幔中破裂上及其以下的时间相关余震与幂律流），以拟合数据，同时与互补的地质和地球物理约束保持一致。pi: J. Freymueller（阿拉斯加大学费尔班克斯分校），R. Burgmann（加州大学伯克利分校），E. Calais（普渡大学）

Collaborative Research: Mechanisms of Postseismic Deformation Following the 2002 Denali Fault Earthquake SequenceThe occurrence of the Mw 7.9 November 3, 2002 Denali earthquake has created the opportunity to collect the surface deformation measurements needed to make significant improvements in our knowledge of the dominant deformation mechanisms in the Earth's lithosphere and the rheological parameters of the fault zone and surrounding crust and upper mantle. The large moment of the Denali earthquake, the precise pre-earthquake deformation field, and the immediate field response make this the most promising target to address postseismic deformation problems since modern space-geodetic methods became available.Our observational strategy consists of continuous GPS (CGPS) measurements at 16 sites located at a wide range of distances from the rupture, including some at 150 km, in order to distinguish processes in the deep fault zone, the lower crust and upper mantle. Eleven of these sites were installed within two weeks after the event and have since been operating continuously. A fundamental objective of the proposed research is to precisely determine the time-dependence of the postseismic deformation signal. CGPS measurements will be complemented by two GPS campaigns per year, using existing benchmarks, in order to spatially densify the postseismic displacement field. We will also test the ability of InSAR to measure the coseismic and early postseismic deformation.The observational efforts will be complemented by comprehensive modeling efforts to evaluate candidate deformation mechanisms such as velocity-strengthening afterslip, poroelastic rebound, and viscous flow in the lower crust and upper mantle. Characterization of the relative importance of each of these mechanisms is a major goal of this research project. We will fully explore the ability of the different model types (e.g., time-dependent afterslip on and below the rupture vs. powerlaw flow in the lower crust and upper mantle) to fit the data while being consistent with complementary geological and geophysical constraints. PIs: J. Freymueller (Univ. Alaska, Fairbanks), R. Burgmann (UC Berkeley), E. Calais (Purdue University)