活动走滑断层累积位移量分布波峰的形成及其古地震事件识别应用的适用性的探讨研究

在走滑断层的错断地形中，有时会显现相似大小的累积位移量成组分布，各组的分布波峰很早就被用于识别系列的古地震事件。随着LiDAR等高分辨率地形数据的应用，该解译方法因为揭示精细的断层活动强度和地震重发规律，成为近年活动断层研究的常见途径。然而，其假设及应用条件尚未得到充分检验。本课题结合数值模拟和全球数据分析检验，探讨该方法的适用性。研究基于历史同震地表位移数据，正演模拟多次事件的累积位移量沿走向的分布几率，以揭示位移量分布峰值和事件之间的真实对应关系，并检验同震位移量变化率对可解译事件次数的影响。同时重编更新全球历史同震地表位移数据，检验其可能支持的事件识别次数，并探讨影响事件识别的各类因素及其所带来的解译误差，最后界定该方法的适用条件和解译要求，并探索新的校正解译路径。研究提醒对位移量波峰解译方法更为谨慎的应用，防止古地震事件过度解译造成假象，对活动断层研究以及地震灾害预测具有重要意义。

Coseismic slip distributions of repeated earthquakes are important data used to forecast magnitude and recurrence characteristicsof future earthquakes. For active strike-slip faults, many studies have attempted to identify individual paleoearthquakes from frequency histograms of geomorphic offsets. Such histograms, often expressed as a COPD (cumulative offset probability distribution), commonly show multiple peaks with similar displacements, which are interpreted to be incremental slip associated with successive paleoearthquakes. Because assumptions to link COPD peaks to individual earthquakes have not been fully explored, we combine statistical modeling with global historical coseismic surface rupture data to evaluate the conditions required for the approach. Along-fault offset accumulation and COPD formation are simulated assuming simple slip repetition. We then investigate the relation between along-fault offset variability and observable number of events. In addition, we update historical coseismic surface rupture dataset to evaluate the level of variability of field-documented offset and how it varies with fault segmentation and fault length. In this way, historical coseismic offset data are applied in the model to generate offset peaks, and we explore their link to earthquake events. Requirements for improving such interpretations are thus constraint. Finally, we try to propose a new route for a normalized COPD interpretation. This study cautions more careful COPD analyses to prevent false results caused by excessive interpretation of earthquake events.