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的地震滑移的起始，加速和自我修复的过程。实验将在新的旋转剪切设备上进行，该设备允许沿着岩石块摩擦滑动，以进行大滑动（几米），左右左右，〜1 m/s的滑道和高达30 MPa的正常应力。此外，该设备的设计允许在短时间（最高5 s）内将有限量的存储能量在断层表面（最高107 j/m2）上应用。他们的初步结果表明，这些条件可以沿着岩石样品产生地震样的唇部事件（Else），而时间为0.1 s，滑动速度高达1 m/s，滑移距离最高3 m，并进行自我修复（强度恢复和破裂滞留）。他们建议使用该设备的独特功能进行一系列广泛的实验，这些实验类似于在原位载荷条件下的断层斑块上的地震过程。这些实验将允许分析基本地震参数，例如上升时间，弱化，自我修复，滑动速度，滑动距离，距离，热产生和能量耗散在实验室控制的条件下。该项目的目标旨在提高两个主要方面的设备能力：1：1。加载载荷框架以消除（或显着减少）不稳定的震动速度。2。开发和实施扭矩控制系统，该系统将使我们能够模拟广泛的地球场景。典型的地震始于小核，并沿断层表面繁殖为快速移动的前部。断层表面上的每个斑块都处于地震前的静止状态，它会通过破裂的前部进行大约1 m/s的滑动速度，并且当地震前储存的弹性能过度时，它会停止滑动。因此，该斑块从一秒钟到几秒钟的时间内经历了突破和减速。在强度加速/减速的基础上，斑块摩擦在没有稳态的情况下发生了巨大变化。另一方面，对断层摩擦的典型实验研究旨在确定可能在地震期间未意识到的摩擦摩擦。拟议的研究通过利用最近在俄克拉荷马大学建立的设备的独立性来消除这种基本的实验限制。 Theapparatus适合模拟类似地震的事件，因为它可以通过在巨大的飞轮（225千克）中加载实验室岩石斑块。我们实验系统的独特，先进的设计在（1）高应力和高速度的原位条件下模拟地震破裂过程； （2）有限能源供应； （3）应力和速度控制。拟议的实验将在实验，理论和地震概念之间提供更好的联系，并通过这样做，将明显地促进对地震破裂过程的理解，地震能量平衡，故障的物理削弱以及滑移速率，滑移幅度的缩放，滑移幅度和辐射能量的缩放。