The knowledge of the strain/stress field evolution in time is important to seismic hazard assessment and risk mitigation, and is fundamental to the understanding of the earth dynamic system. Based on the principle that past tectonic stress should have left traces in the rocks, geologists have been trying to determine the paleostress history from evidence found in rocks for decades. Recent development of techniques for automatic extraction of fracture surfaces from digital outcrop models and estimation of historical shear deformation on rock fractures provide an efficient way of quantitatively acquiring large amount of high quality fracture/fault slip data (direction and sense of slip occurs on the fault plane) from outcrops. So unlike traditional paleostress inversion methods whose data is manually collected in the field, this high quality fracture/fault slip data provide an opportunity to develop fully automatic and quantitative methods for deciphering paleostrain. In this study, for slip on each fracture, the corresponding local strain tensor is calculated, then the local strain tensors are grouped into populations corresponding to far-field strain events and local strain events using a clustering analysis technique. The applications on outcrops in the eastern Tian Shan area give a clear picture of the paleostrain variation over space and time, and also throw light on the relationship between paleostrain, fracture development and the distribution of shear displacements in a thrusting environment.

中文翻译：

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从数字露头模型定量破译古菌株及其在东天山的应用

应变/应力场随时间演化的知识对于地震灾害评估和风险缓解很重要，并且是理解地球动力系统的基础。基于过去的构造应力应该在岩石中留下痕迹的原理，地质学家几十年来一直试图根据在岩石中发现的证据来确定古应力历史。从数字露头模型中自动提取断裂面和估计岩石断裂历史剪切变形的技术的最新发展为定量获取大量高质量断裂/断层滑动数据（断层上发生滑动的方向和感觉）提供了一种有效的方法平面）从露头。所以不同于传统的古应力反演方法，其数据是在现场手动收集的，这种高质量的裂缝/断层滑动数据为开发用于破译古应变的全自动定量方法提供了机会。在这项研究中，对于每个裂缝上的滑动，计算相应的局部应变张量，然后使用聚类分析技术将局部应变张量分组为对应于远场应变事件和局部应变事件的群体。东天山地区露头的应用清楚地描绘了古应变随空间和时间的变化，也揭示了冲断环境中古应变、裂缝发育和剪切位移分布之间的关系。计算相应的局部应变张量，然后使用聚类分析技术将局部应变张量分组为对应于远场应变事件和局部应变事件的群体。东天山地区露头的应用清楚地描绘了古应变随空间和时间的变化，也揭示了古应变、裂缝发育与逆冲环境中剪切位移分布之间的关系。计算相应的局部应变张量，然后使用聚类分析技术将局部应变张量分组为对应于远场应变事件和局部应变事件的群体。东天山地区露头的应用清楚地描绘了古应变随空间和时间的变化，也揭示了古应变、裂缝发育与逆冲环境中剪切位移分布之间的关系。