Collaborative Research: High-velocity and long-displacement stick-slips: Experimental analogs of earthquake rupture and the seismic cycle

当地球深处的岩石突然破裂时，或者当沿着先前存在的断层发生突然错位或“滑动”时，地震就会发生。地质学家缺乏对岩石破坏和断层滑动行为的详细了解，这是预测破坏性地震的努力并未完全成功的原因之一。地震断层滑动开始于地球表面以下，无法直接观测到，因此科学家们在实验室进行实验，在受控条件下模拟岩石块中的微型地震。提萨托和他们的团队将开发新的实验室技术，在实验室中产生小规模地震，并将对断层滑动速度、岩石温度、振动和断层强度等量进行详细测量，以努力更好地了解它们的机制。提萨托的实验是独一无二的，因为他们可以模拟地震的长序列，并可以看到这些地震是如何相互作用的。从这些实验中获得的知识可以使用数学方程应用于真实世界的断层，并可能使科学家能够识别可能预示即将到来的大地震的现象。目前，地震过程的实验系统一般分为两类：(A)旋转剪切仪，它在受控滑移速度下产生大位移，但不能模拟天然地震的自发成核、传播和地震复发；(B)粘滑系统，它模拟地震的自发性质，但仅限于小位移。这一建议将把这两种实验类型的能力整合到一个系统中，该系统可以模拟地震的关键特征，如自发成核和破裂传播，以及毫米到米级的滑移位移。这种独特的方法的初步结果已经产生了一系列天然发震断层的典型特征，包括由于快速破裂传播和高滑动速度而产生的高强度事件、大滑动位移、前震和慢滑事件。计划使用透明材料和高速摄像机将使人们能够观察实验室断层上发生的过程，同时监测与地震类似的声发射。实验还将在岩石样品上进行，分析结果将用于验证天然地震模型。这种方法的内在本质是为统计和机器学习算法量身定做的，这些算法可以用来创建地震预测模型。该项目还将专注于通过为本科生和高中生创建教材和提供实验室实验经验来扩大范围。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

An earthquake develops when rocks deep in the Earth suddenly break, or when sudden offset or 'slip' occurs along a pre-existing fault. Geoscientists lack detailed knowledge of rock failure and fault slip behavior, and this is one reason that efforts to forecast damaging earthquakes have not been entirely successful. Earthquake fault slip begins below the Earth's surface where it cannot be directly observed, so scientists perform laboratory experiments to simulate miniature earthquakes in blocks of rock under controlled conditions. Tisato and their team will develop new laboratory techniques to generate small earthquakes in the lab, and will take detailed measurements of quantities like fault slip speed, rock temperature, vibrations, and fault strength in an effort to better understand their mechanics. Tisato's experiments are unique in that they can simulate long sequences of earthquakes and can see how these earthquakes interact with each other. Knowledge gained from these experiments can be applied to real-world faults using mathematical equations, and may enable scientists to identify phenomena that could signal an upcoming large earthquake. Currently, experimental systems of earthquake processes belong to two general types: (A) Rotary shear apparatuses that produce large displacements under controlled slip-velocity but cannot simulate the spontaneous nucleation, propagation, and seismic recurrence of natural earthquakes, and (B) Stick-slip systems that simulate the spontaneous nature of earthquakes but are limited to small displacements. This proposal will integrate the capabilities of these two experimental types into one system that can simulate the key earthquake features of spontaneous nucleation and rupture propagation, along with millimetric to metric slip displacements. The preliminary results of this unique method already produced a gamut of typical features of natural seismogenic faults, including high-intensity events due to fast rupture propagation and high slip velocity, large slip displacements, foreshocks, and slow-slip events. The planned use of transparent materials and high-speed cameras will allow the observation of the processes happening on the laboratory fault while monitoring acoustic emissions as earthquake analogs. Experiments will also be performed on rock samples, and the analyzed results will be applied to validate natural earthquake models. The intrinsic nature of the method is well-tailored for statistical and machine-learning algorithms that could be used to create earthquake forecasting models. The project will also focus on outreach by creating educational materials and providing laboratory experiment experiences for undergraduate and high-school students.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.