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

合作研究：2002年德纳利断裂地震序列后的震后形变机制2002年11月3日发生的里氏7.9级地震创造了收集地表形变测量的机会，这些测量结果可以显著改善我们对地球岩石圈的主要形变机制和断裂带及其周围地壳和上地幔的流变参数的认识。德纳利地震的大时刻、精确的震前形变场和即时的场响应使其成为自现代空间大地测量方法问世以来解决震后变形问题的最有希望的目标。我们的观测策略包括在距离破裂很远的16个站点进行连续GPS(CGPS)测量，其中一些站点位于150公里处，以区分深断裂带、下地壳和上地幔的过程。其中11个地点在事发后两周内安装完毕，此后一直在持续运作。这项研究的一个基本目标是精确确定震后形变信号的时间相关性。CGPS测量将得到每年两次全球定位系统运动的补充，利用现有的基准，以便在空间上致密震后位移场。我们还将测试InSAR测量同震和早期震后变形的能力。除了观测工作外，还将进行全面的模拟工作，以评估可能的变形机制，如速度增强的余滑、孔洞弹性反弹和下地壳和上地幔的粘性流动。表征每一种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类型的模型(例如，断裂上和断裂下的随时间变化的余滑与下地壳和上地幔中的幂定律流)在与互补的地质和地球物理约束相一致的情况下对数据进行拟合的能力。PIS：J.Freymueller(大学阿拉斯加，费尔班克斯)，R.伯格曼(加州大学伯克利分校)，E.加莱(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)