Collaborative Research: Modeling of 3-D Viscoelastic Stress Transfer in the California Crust: Implications for Earthquake Triggering and Seismic Hazard Migration

研究人员建议进行一组三维数值模拟实验，重点研究最近三次加利福尼亚地震序列：(1)1992年的兰德斯地震，它在引发1999年赫克托雷事件中的潜在作用，以及它们对南部圣安德烈亚斯断层的综合影响；(2) 1983年Coalinga和1985年Kettleman Hills盲逆冲地震及其对San Andreas断层Parkfield段延迟地震破裂的潜在影响；(3)洛杉矶地区最近的历史地震序列，包括1933年长滩地震、1952年克恩县地震、1971年圣费尔南多地震、1987年惠蒂尔海峡地震和1994年北岭地震，以及它们对洛杉矶地区地震危险性迁移的影响。最近，研究人员已经成功地为上述加利福尼亚序列的一小部分开发了初步的三维粘弹性模型。这个项目将允许他们通过以下方式进行更全面的调查：(1)扩展模型以包括所有相关的地震；(2)验证模型解的鲁棒性及其对地壳流变学和断层几何假设的敏感性；(3)将模型结果与大地测量结果进行比较。这次模拟研究的结果，加上空间大地测量学和地震监测能力的进步，将使我们更清楚地了解加利福尼亚地壳的地震性质、地震触发机制以及加利福尼亚地震危险性迁移的规律。这是加州大学伯克利分校（Andy Freed）和WHOI （Jian Lin）的合作项目。Freed将领导使用I-deas粘弹性建模代码的三维建模实验，而Lin将领导将I-deas解决方案与GENPro边界元素代码的独立结果进行比较的任务，并分析研究区域的大地测量和地震数据以约束建模。

Lin BurgmannThe investigators propose to perform a set of 3-D numerical modeling experiments, focusing on three recent California earthquake sequences: (1) the 1992 Landers earthquake, its potential role in triggering the 1999 Hector Mine event, and their combined effects on the southern San Andreas fault; (2) the 1983 Coalinga and 1985 Kettleman Hills blind-thrust quakes and their potential effects on delaying seismic rupture on the Parkfield segment of the San Andreas fault; and (3) the most recent sequence of historical quakes in the Los Angeles region, including the 1933 Long Beach, 1952 Kern County, 1971 San Fernando, 1987 Whittier Narrows, and 1994 Northridge events, and their implications on seismic hazard migration in the Los Angeles region. Recently the investigators have successfully developed preliminary 3-D viscoelastic models for a small subset of the above California sequences. This project will allow them to carry out a much more comprehensive investigation through (1) extending the models to include all relevant quakes, (2) verifying the robustness of the model solutions and their sensitivity to assumptions in crustal rheology and fault geometry, and (3) comparing the model results with geodetic observations. Results of this modeling investigation, together with advances in space geodesy and seismic monitoring capabilities, should provide us with a much clearer understanding of the seismic properties of the California crust, the mechanisms of earthquake triggering, and the regularities in seismic hazard migration in California. This is a collaborative project between the UC Berkeley (Andy Freed) and WHOI (Jian Lin). Freed will lead 3-D modeling experiments using the I-deas viscoelastic modeling code, while Lin will lead tasks of comparing the I-deas solutions to independent results from the GENPro boundary-element code and analyzing the geodetic and earthquake data in the study regions to constrain modeling.