Collaborative Research: Tests of Postseismic Deformation Models with Continued Absolute Gravity and GPS Measurements in Alaska, Phase 1

Zumbergeorge-0208164该项目正在测量重力的绝对值，与GPS测量位于阿拉斯加。 对大地震后瞬态变形的解释包括粘弹性响应、抗震蠕变以及两者的组合。 不同的震后粘弹性松弛模型预测可观测到的重力变化超过1000公里的长度尺度，具有复杂的空间模式。 到目前为止，粘度分布最好是由冰后反弹研究确定的。 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。这一区域特别令人感兴趣，因为俯冲带物质的粘度可能与大陆和海洋板块中心之下的粘度大不相同。 抗震蠕变预计产生的变形更有限的和显着不同的空间特性比粘弹性松弛。 确定地震蠕变在震后形变中的贡献对于估计大地震的复发间隔是很重要的。 网络的大部分形成一个垂直于远场最大重力变化预测轮廓的断面。 附加点位于变形近场内。 重力测量与现有的全球定位系统台站并置。 这些初始测量结果构成了检验不同震后变形模型的基础。 其他活动包括收集辅助数据，以纠正重力数据中的水位变化等信号。 1964-1965年相对重力测量的一部分也在重复进行，以确定自地震以来基奈半岛的总重力变化。 数据通过传统手段和互联网网站分发。

ZumbergeEAR-0208164This 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.