Experimental Study of the Role of Pore Fluid Pressure in Earthquake Nucleation

孔隙流体压力在地震成核中作用的实验研究

• 批准号: 0230170
• 负责人: Terry Tullis
• 金额: --
• 依托单位: Brown University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-01-01 至 2008-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0230170&HistoricalAwards=false
• 关键词: Experimental; Study; Role; Pore; Fluid

EAR-0230170Terry E. TullisABSTRACT We will conduct a systematic study to understand the relationship between stress change and pore pressure change in experimental fault zones. It is important to understand the mechanical contributions of pore fluid pressure change during earthquake nucleation and how pore fluid pressure change may trigger seismicity. The geophysical purpose of this research is determine to what degree changing pore fluid pressure plays a mechanical role in earthquake occurrence and under what conditions. Geologic observations show that seismic faulting occurs in the presence of crustal fluids. However rarely is fluid behavior accounted for in models of seismicity, earthquake nucleation and triggered seismicity. It is most often assumed that shear induced dilatancy during seismic slip will decrease the pore pressure, tend to stabilize the slip, and discourage earthquake occurrence. However, recent laboratory observations suggest that for slip localized within thick fault zones, elastic dilation or compaction of the fault zone with stress change is of the opposite sense and greatly exceeds shear induced dilatancy. Thus, common assumptions about the role of pore fluid pressure in earthquake source mechanics require renewed scrutiny. No laboratory experiments where stick-slip sliding occurs have been conducted in the presence of pore fluids, no laboratory measurements of the poroelastic properties of fault zones have been made, and no poroelastic measurements have been made on unfaulted (country) rock at the significant differential stresses appropriate for seismic faulting. Therefore we will conduct two series of experiments; the first designed to measure the poroelastic properties of fault zones near the failure stress, the second to determine and compare the magnitudes of shear induced dilatancy (inelastic strain) and elastic strain during stick-slip in thick gouge layers. We will develop constitutive equations for seismic fault slip based on the experimental observations and extrapolate the results to crustal conditions.

Terry E.本文将对实验断裂带的应力变化与孔隙压力变化的关系进行系统的研究。了解孔隙流体压力变化在地震成核过程中的力学贡献以及孔隙流体压力变化如何触发地震活动是非常重要的。 本研究的地球物理目的是确定变化的孔隙流体压力在何种程度上和在何种条件下对地震发生起着力学作用。地质观测表明，地震断层活动是在地壳流体存在的情况下发生的。然而，在地震活动性、地震成核和触发地震活动性的模型中很少考虑流体行为。人们通常认为，地震滑动过程中剪切引起的剪切力将降低孔隙压力，趋于稳定滑动，并阻止地震发生。然而，最近的实验室观察表明，对于位于厚断层带内的滑动，断层带随应力变化的弹性膨胀或压实具有相反的意义，并且大大超过剪切诱导的剪切力。因此，在震源力学中孔隙流体压力的作用的一般假设需要重新审查。在孔隙流体存在的情况下，没有进行粘滑滑动发生的实验室实验，没有对断层带的孔隙弹性性质进行实验室测量，也没有在适合地震断层作用的显著差异应力下对无断层（围岩）岩石进行孔隙弹性测量。因此，我们将进行两个系列的实验;第一个旨在测量断裂带附近的破坏应力的孔隙弹性性质，第二个确定和比较剪切引起的粘性（非弹性应变）和弹性应变的大小在粘滑厚断层泥层。我们将发展地震断层滑动的本构方程的基础上，实验观察和推断的结果，地壳条件。