Analysis of fault rupture processes by earthquake-like slipevents in the laboratory

实验室类地震滑动事件分析断层破裂过程

• 批准号: 1045414
• 负责人: Ze'ev Reches
• 金额: $ 12.95万
• 依托单位: University of Oklahoma Norman Campus
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-06-01 至 2013-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1045414&HistoricalAwards=false
• 关键词: Analysis; fault; rupture; processes; earthquake

The investigators propose to analyze experimentally the processes of initiation, acceleration and self-healing of seismic slip at a patch on the surface of a fault. The experiments will be conducted on a new rotary shear apparatus that allows testing frictional sliding along rock blocks for large slip (a few meters), slip-velocity of ~1 m/s, and normal stress up to 30 MPa. Further, the design of this apparatus allows application of a finite amount of stored energy on a fault surface (up to 107 J/m2) for a short period of time (up to 5 s). Their preliminary results show that these conditions can generate an Earthquake-Like lip Event (ELSE) along the rock sample with rise time 0.1 s, slip velocity up to 1 m/s, slip-distance up to 3 m, and self-healing (strength recovery and rupture arrest). They propose to use the unique capabilities of this apparatus for an extensive series of ELSE experiments that are analogous to earthquake processes at a fault patch under in-situ loading conditions. These experiments will allow analyzing fundamental earthquake parameters, such as rise-time, weakening, self-healing, slip velocity, slip distance, heat generation and energy dissipation under laboratory-controlled conditions.The objectives of the project is to improve the apparatus capabilities in two main aspects:1. Stiffening of the loading frame to eliminate (or significantly reduce) the unstable shattering athigh velocities.2. Develop and implement the torque control system that will allow us to simulate a wide range ofearthquake scenarios.A typical earthquake starts at a small nucleus and propagates as a fast movingrupture front along a fault surface. Every patch on the fault surface is at rest before the earthquake, it isaccelerated to slip velocity of about 1 m/s by the rupture front and it stops slipping when the elasticenergy that was stored prior to the earthquake has been dissipated. Thus, the patch experiences abruptacceleration and deceleration over periods from a fraction of a second to a few seconds. During thisperiod of intense acceleration/deceleration, the patch friction changes dramatically without steady-statevelocity. On the other hand, typical experimental studies of fault friction are designed to determine thesteady-state friction that probably does not realized during earthquakes.The proposed research eliminates this fundamental experimental limitation by utilizing the uniquecapabilities of an apparatus that was built recently in University of Oklahoma. Theapparatus is suitable to simulate earthquake-like events as it can load a laboratory rock patch by energystored in a massive flywheel (225 kg). This unique, advanced design of the our experimental systemallows simulating earthquake rupture processes under in-situ conditions of (1) high stress and highvelocity; (2) finite energy supply; and (3) stress and velocity control. The proposed experiments willprovide better links between experiments, theory and seismic concepts, and, by doing so, willsignificantly advance the understanding of earthquake rupture processes, earthquake energy balance,physics of fault weakening, and the scaling of slip rates, slip magnitude, and radiated energy.

研究人员建议通过实验分析断层表面斑块处地震滑移的引发、加速和自愈过程。实验将在新型旋转剪切装置上进行，该装置可以测试沿岩石块的大滑移（几米）、滑移速度约为 1 m/s 以及高达 30 MPa 的正应力的摩擦滑动。此外，该设备的设计允许在短时间内（最多 5 秒）在断层表面上应用有限量的存储能量（最多 107 J/m2）。他们的初步结果表明，这些条件可以沿着岩石样本产生类地震唇部事件（ELSE），上升时间为 0.1 s，滑移速度高达 1 m/s，滑移距离高达 3 m，并且具有自愈能力（强度恢复和破裂停止）。他们建议利用该设备的独特功能进行一系列广泛的 ELSE 实验，这些实验类似于原位加载条件下断层斑块的地震过程。这些实验将能够在实验室控制的条件下分析基本的地震参数，例如上升时间、减弱、自愈、滑移速度、滑移距离、热量产生和能量耗散。该项目的目标是提高地震设备的能力。主要有两个方面：1．加载框架的加固以消除（或显着减少）高速下的不稳定破碎。2．开发并实施扭矩控制系统，使我们能够模拟各种地震场景。典型的地震从一个小震核开始，并以快速移动的断裂前沿沿断层表面传播。地震前断层表面上的每个斑块都处于静止状态，被破裂前沿加速到约1m/s的滑动速度，当地震前储存的弹性能消散后，断层表面上的每个斑块就停止滑动。因此，该补丁会在几分之一秒到几秒的时间内经历突然的加速和减速。在这段剧烈的加速/减速期间，贴片摩擦力会发生剧烈变化，而没有稳态速度。另一方面，典型的断层摩擦实验研究旨在确定在地震期间可能无法实现的稳态摩擦。这项研究利用俄克拉荷马大学最近建造的设备的独特功能消除了这一基本实验限制。该装置适合模拟类似地震的事件，因为它可以通过巨大飞轮（225 公斤）中存储的能量来加载实验室岩石块。我们的实验系统的这种独特、先进的设计允许在以下原位条件下模拟地震破裂过程：（1）高应力和高速； (2)能源供应有限； (3)应力和速度控制。所提出的实验将在实验、理论和地震概念之间提供更好的联系，并且通过这样做，将显着增进对地震破裂过程、地震能量平衡、断层弱化物理学以及滑移率、滑移幅度和辐射的缩放的理解。活力。