Collaborative Research: Tests of Postseismic Deformation Models with Continued Absolute Gravity and GPS Measursements in Alaska, Phase I

jeffrey freymueller这个项目正在测量阿拉斯加的重力绝对值，与GPS测量一起定位。对大地震后瞬态变形的解释包括粘弹性反应、地震蠕变和两者的结合。不同的震后粘弹性松弛模型预测了1000 km长度尺度上的可观测重力变化，具有复杂的空间格局。迄今为止，黏度分布最好是通过冰期后的反弹研究来确定的。重力和GPS测量提供了获得阿拉斯加板块边界粘度剖面估计的机会。这个地区特别有趣，因为俯冲带物质的粘度可能与大陆和海洋板块中心下的物质非常不同。预测地震蠕变产生的变形比粘弹性松弛产生的变形具有更有限和明显不同的空间特征。确定地震蠕变对震后变形的贡献对于估计大地震的重复周期是很重要的。这个项目是在阿拉斯加建立一个由15个站点组成的基线重力网络。网络的大部分形成了垂直于远场最大重力变化的预测轮廓的样条。附加点位于变形近场内。重力测量与现有的GPS站同时进行。这些初步测量结果构成了测试不同地震后变形模型的基础。其他活动包括收集辅助数据，以纠正诸如地下水位变化等信号的重力数据。为了确定地震以来基奈半岛上的总重力变化，1964-1965年相对重力测量的一部分也正在重复进行。数据通过传统方式和互联网网站分发。

EAR-0207957Jeffrey FreymuellerThis project is measuring the absolute value of gravity, co-located with GPS measurements, in Alaska. Proposed explanations for the transient deformation after great earthquakes include viscoelastic response, aseismic creep and combinations of the two. Different models of postseismic viscoelastic relaxation predict observable gravity changes over 1000 km length scales, with a complex spatial pattern. To date, the viscosity profile is best determined by postglacial rebound studies. Gravity and GPS measurements offer the opportunity to obtain viscosity profile estimates for the Alaskan plate boundary. The area is especially interesting, as the viscosity of subduction zone materials may be very different from that beneath the centers of continental and oceanic plates. Aseismic creep is predicted to produce deformation of a more limited and markedly different spatial character than that of viscoelastic relaxation. Determining the contribution of aseismic creep in postseismic deformation is important in estimating recurrence intervals for great earthquakes.This project is establishing a baseline gravity network of fifteen stations in Alaska. The bulk of the network forms a transect perpendicular to the predicted contours of maximum gravity change in the far field. Additional points are located within the deformation near field. Gravity measurements are collocated with existing GPS stations. These initial measurements form the basis for testing different postseismic deformation models. Additional activities include collecting auxiliary data to correct the gravity data for signals such as water table variations. A portion of a 1964-1965 relative gravity survey is being repeated as well, in order to determine the total gravity change over the Kenai Peninsula since the earthquake. Data are distributed through traditional means and an Internet website.