CAREER: Towards a comprehensive model of seismicity throughout the seismic cycle

每天，世界各地的断层都会产生数百次小地震，这些地震太弱而感觉不到，也不会造成任何损害。卡米拉·卡塔尼亚和她的小组将调查这些小地震是否能提供大的破坏性地震可能发生的地点和时间的线索。有时候，小地震会被证明是大地震的前震--但是我们直到大地震发生之后才能知道这是真的！实验室地震实验（在大块岩石中产生“实验室地震”）已经完成，以观察在大的实验室地震发生之前，小的实验室地震是否有任何迹象。与地球上的真实的断层不同，这些实验表明，在每次大的实验室地震之前，都有一种可预测的小地震模式。卡塔尼亚和她的团队将建立复杂的断层计算机模型，试图理解为什么实验室实验似乎与真实的断层数据不一致。这些模型将使用来自加州、意大利和冰岛的地震数据进行测试，并进行调整，直到它们尽可能准确地代表真实世界的断层物理学。利用这些模型，Cattania和她的团队将确定实验室实验何时可以有效地模拟自然断层，何时不能，以及在什么条件下预计前震会发生在真实的世界中。该项目可以改善地震预报，并帮助研究人员确定安装地震监测设备以检测前震的最佳区域（这可能进一步改进地震预报）。本项目将开发一个新的地震周期模型，解释三维破坏区中断层的复杂性和离散断层之间的相互作用，来模拟整个地震周期中真实的地震活动模式。该模型将包括一个人口的断层构造和瞬态负荷，由实验室推导的摩擦定律（率态摩擦和动态削弱在高滑动速度）和嵌入在弹性介质。小断层的2.5D表示将允许以适度的计算成本对大量断层之间的真实应力相互作用进行建模。将使用基于应力转移和断裂力学的分析表达式，将地震活动模式（如频率-震级分布的变化和震群迁移）与应力的基本状态联系起来。最后，该项目将利用高分辨率地震活动目录来测试这些结果与来自加州、意大利和冰岛的观测结果。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Every day, faults worldwide produce hundreds of small earthquakes, too weak to be felt or produce any damage. Camilla Cattania and her group will be investigating whether these small earthquakes could provide clues about where and when large, destructive earthquakes might occur. Sometimes, small earthquakes turn out to be foreshocks of a larger earthquake - but we can't tell this is so until after the large earthquake has happened! Laboratory earthquake experiments (which produce "lab earthquakes" in large hunks of rock) have been done to see if there are any telltale signs from small lab earthquakes before a big lab quake occurs. Unlike real faults in the Earth, these experiments show a predictable pattern of small earthquakes before each large lab earthquake. Cattania and her team will build sophisticated computer models of faults to try to understand why the lab experiments seem to disagree with data from real faults. The models will be tested using earthquake data from California, Italy, and Iceland, and adjusted until they represent real-world fault physics as accurately as possible. Using these models, Cattania and her team will determine when laboratory experiments can be useful analogs to natural faults and when they cannot, and under what conditions foreshocks are expected to happen in the real world. This project could improve earthquake forecasts, and help researchers identify the best regions to install earthquake monitoring equipment to detect foreshocks (which may further improve earthquake forecasts).This project will explore physical processes driving microseismicity by developing a new earthquake cycle model that accounts for fault complexity and interactions between discrete faults in a three-dimensional damage zone, to simulate realistic seismicity patterns throughout the seismic cycle. The model will consist of a population of faults subject to tectonic and transient loading, governed by laboratory derived frictional laws (rate-state friction and dynamic weakening at high slip speeds) and embedded in an elastic medium. A 2.5D representation of small faults will allow modeling realistic stress interactions between a large number of faults, at a moderate computational cost. Analytical expressions based on stress transfer and fracture mechanics will be used to relate seismicity patterns (such as changes in the frequency-magnitude distribution and swarm migration) to the underlying state of stress. Finally, the project will leverage high-resolution seismicity catalogs to test these results against observations from California, Italy, and Iceland.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.