Analysis of the Shallow Slip Deficit Using Sub-Pixel Image Correlation: Implications for Fault Evolution, Slip Rates, and Seismic Hazards

这一研究项目的重点是通过使用一种强大的新技术(COSI-CORR亚像素图像相关)来了解地震期间地球表面附近断层滑动的分布情况，该技术有助于更详细地跟踪沿着断层及其周围的地表形变的位置和数量，而不是使用以前可用的方法。以前的研究表明，地震期间沿着断层发生的滑动在深度上大于地表附近，导致了所谓的地表滑动赤字。确定这种地表滑动亏损的原因(S)为这项研究提供了基本的理论基础。利用COSI-CORR图像相关技术，南加州大学和加州理工大学的科学家们将研究过去几十年发生的十几次大地震中地表附近滑动的分布情况。这些结果将有助于绘制地震中断层上和断层外的形变模式，使这些观测结果与断裂带的基本特征相关联，如断层在其生命周期中容纳的总滑移量，这可能被证明是未来地震中断层上将发生的滑动百分比的良好预测。这一研究结果对理解主要断层系统造成的地震危险具有基本意义。目前，对未来发生地震的可能性的预测在很大程度上是基于断层的滑移率，即断层两侧的块体在多次地震过程中相互滑动的速度。这种速率主要来自于对偏移距表面特征的分析，通常不包括可能分布在主断层迹线周围的任何变形。因此，重大的断层外变形可能会低估断层上的移动速度，从而导致地震危险性的低估。此外，这些数据将使研究人员能够测试地震破裂可能的优先传播方向的模型，这将对提前确定强地面运动的区域分布具有深远的重要性。预期的结果还将允许对地震破裂将(或不会)通过断层沿线的复杂结构传播的可能性进行模型评估，这是预先估计未来地震规模的基本重要问题。因此，这些结果将为制定断层上与断层外滑动和破裂行为的统计措施提供基础，这些措施将用于下一代危险评估战略，以提供对未来地震危险的更准确估计。

This research project is focused on understanding the distribution of fault slip near the Earth's surface during earthquakes through the use of a powerful new technology (COSI-corr sub-pixel image correlation), which facilitates tracking of the location and amount of surface deformation along and around faults in much more detail than was possible using previously available methods. Previous studies suggest that the slip that occurs along faults during earthquakes is larger at depth than near the surface, leading to what has been termed a surface slip deficit. Determining the cause(s) of this surface slip deficit provides the basic rationale for this research. Using the COSI-corr image correlation technique, scientists from the University of Southern California and Caltech will examine the distribution of slip near the surface along more than a dozen large-magnitude earthquakes that occurred during the past few decades. The results will facilitate the mapping of on-fault versus off-fault deformation patterns in earthquakes, allowing correlation of these observations with basic features of the fault zone, such as the amount of total slip a fault has accommodated in its lifetime, which may prove to be good predictors of the percentage of slip that will occur on faults during future earthquakes.The results of this research have basic implications for the understanding of the seismic hazards posed by major fault systems. Currently, forecasts of the probability of the future occurrence of earthquakes are based largely on the slip rate of the fault, that is, the rate at which the blocks on either side of the fault slide past each other over the course of many earthquakes. Such rates are mainly derived from the analysis of offset surface features, and usually do not include any deformation that might be distributed around the main fault trace. Thus, significant off-fault deformation may yield underestimates of the rate of movements on faults, and thus on seismic hazard. In addition, these data will allow the researcher to test models of possible preferred propagation direction of seismic ruptures, which will be of profound importance for determining in advance the regional distribution of strong ground motions. The anticipated results will also allow assessment of models for the likelihood that seismic ruptures will (or will not) propagate through structural complexities along the fault, an issue of basic importance for estimating in advance the sizes of future earthquakes. The results will thus provide the basis for the development of statistical measures of on-fault versus off-fault slip and rupture behavior that will be used in next-generation hazard assessment strategies to provide more accurate estimates of future seismic hazard.