Collaborative Research: Testing Tectonic Geodesy from Fault Slip Rates Across the Eastern California Shear Zone

东加利福尼亚剪切带是板块边界断层系统的一个有趣的例子，在那里，已知的断层速率加起来可能与应变积累的大地测量速率不一致。这项研究通过收集新的长期滑动率数据，从一个明确的、暴露良好的、构造简单的横跨莫哈韦沙漠中部的活动断层样带收集数据，验证了地质和大地测量应变率在某种程度上必须在加州东部剪切带一致的假设。通过有针对性地获取高分辨率机载激光测绘高程数据，现场地貌和地质测绘将记录六个右侧走滑断层上第三纪至第四纪的偏移熔岩流和冲积扇。选定的偏移标记将用40Ar/39Ar、宇宙成因10Be或宇宙成因3He进行测年，以平均几个地震周期的10^5至10^6年时间尺度测量地壳变形率。如果地质确实通过一个或多个断层上的显著滑动率来解释大地应变率，那么构造大地测量学的预测能力就得到了证明。或者，如果长期地质应变速率明显慢于大地测量速率，就像现有的古地震数据所支持的那样，那么整个系统的瞬态加载过程必须对横跨东加利福尼亚剪切带的高现今应变积累负责。

The Eastern California Shear zone is an intriguing example of a plate boundary fault system where the known rates of faulting may not add up to the geodetic rate of strain accumulation. This research tests the hypothesis that geologic and geodetic strain rates must somehow agree across the Eastern California Shear zone by gathering new long-term slip rate data from a well-defined, well-exposed, and tectonically simple transect of active faulting across the central Mojave Desert. Field geomorphic and geologic mapping, augmented by targeted acquisition of high-resolution airborne laser swath mapping altimetry data, will document offset Plio-Quaternary lava flows and alluvial fans across each of six right-lateral strike-slip faults. Selected offset markers will be dated with 40Ar/39Ar, cosmogenic 10Be or cosmogenic 3He to measure crustal deformation rates at 10^5 to 10^6 year time scales that average several earthquake cycles. If the geology does account for the geodetic strain rate through significant slip rates on one or more faults, the predictive capability of tectonic geodesy is demonstrated. Alternatively, if the long-term geologic strain rate is significantly slower than the geodetic rate, as seems to be supported by existing paleoseismic data, then a system-wide transient loading process must be responsible for the high present-day strain accumulation across the Eastern California Shear zone.