从Parkfield SAFOD钻井现场的活性源监测中观察到的地震前速度变化
Fenglin Niu1, Paul G Silver, Thomas M Daley
1Department of Earth Science, MS-126, Rice University, 6100 Main Street, Houston, Texas 77005, USA. niu@rice.edu
Nature
|July 11, 2008
概括
科学家使用地震波速度测量了断层区域的应力变化. 他们发现,旅行时间的变化与气压相关,并且地震之前发生,这表明破裂前的应力变化.
科学领域:
- 地质物理学 地质物理学
- 地震学 地震学
- 地球科学 地球科学 地球科学
背景情况:
- 测量活跃断层区域的应力变化对于了解地震过程至关重要.
- 众所周知,地震波速度对岩石中的应力变化很敏感.
研究的目的:
- 通过使用地震波速度研究在地震活跃断层区域测量应力变化的可行性.
- 分析地震波旅行时间与环境因素或地震事件之间的关系.
主要方法:
- 在圣安德烈亚斯断层深度观测站 (SAFOD) 进行了活源跨井地震实验.
- 在两个月的时间里,在一个固定的路径上监测了剪切波的行程时间.
- 与气压和巧合的地震事件相关的旅行时间变化.
主要成果:
- 证明使用SAFOD地点的地震波速度可以测量应力变化.
- 观察到剪切波旅行时间和气压之间的反相关性.
- 确定了地震前的两个显著的旅行时间游览,这可能表明地震前的压力变化.
结论:
- 地震波速度的变化为监测活跃断层区域的应力变化提供了一种可行的方法.
- 观察到的前体旅行时间变化表明,断层区域内的裂特性受到地震前压力积累的影响.
- 这些发现与实验室研究对岩石特性压力诱导的变化一致.
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