The Strength of Strike-Slip Faults: Space-Geodetic Constraints for a Ridge-Transtensional System in the Gulf of California

这个项目是对加利福尼亚州海湾的巴列纳斯转换断层进行的空间大地测量研究，该断层是北美-太平洋板块边界的一部分。研究小组将获得战役GPS和干涉合成孔径雷达数据，并使用有限元建模方法研究构造应变的积累和释放，以测试沿断层的地壳强度变化。强度预计会发生变化，因为热流随着距离北部和南部两个新生的大洋中脊盆地的距离而变化，以及断层两侧地壳结构的显著差异(未变形的下加利福尼亚州与加利福尼亚州海湾伸展省)。该断裂位于大洋航道中，它为研究强度变化提供了一个特殊的机会，因为：1)转换断裂具有很高的滑动速率，约为46 mm/年：2)断裂容纳了整个北美-太平洋板块的相对运动，在其附近没有任何其他走滑断裂，因此没有重叠的应变模式；3)2009年8月的6.9级地震及其规则的地震重复时间(每55年一次)使人们能够清楚地定义断层在地震周期内的状态，这对于应变累积模型非常重要。这项研究对所有主要转换断层的地震危险性评估具有重要意义，例如更北的加利福尼亚州的圣安德烈亚斯断层系统。地震危险性估计通常基于忽略强度变化的模型。这项研究将为地壳强度变化如何影响应变积累提供新的数据。

This project is a space-geodetic study of the Ballenas Transform Fault in the Gulf of California, which is part of the North America-Pacific plate boundary. The research team will acquire campaign GPS and interferometric synthetic aperture radar data and use finite element modeling methods to study the accumulation and release of tectonic strain to test for crustal strength variations along the fault. Strength variations are expected because the heat flow varies with distance from two incipient mid-ocean ridge basins in the north and south, and because of significant variations in crustal structure on both sides of the fault (undeformed Baja California versus the Gulf of California extensional province). The fault, situated in a oceanic channel, affords a special opportunity to study strength variation for because: 1) the transform fault has a very high slip rate of approximately 46 mm/yr; 2) the fault accommodates the entire North America-Pacific plate relative motion without any other strike-slip faults in its vicinity and therefore no overlapping strain patterns; 3) the August 2009 magnitude 6.9 earthquake and its regular earthquake repeat time (every 55 years) allows for a clear definition of the state of the fault within the earthquake cycle which is very important for models of the strain accumulation.This study has important implications for seismic hazard estimates for all major transform faults such as the San Andreas Fault system in California further to the north. Seismic hazard estimates are commonly based on models that ignore strength variations. This study will provide new data on how crustal strength variations affect strain accumulation.