通过富含二氧化来控制潜水区缓慢地震周期的可能
Pascal Audet1, Roland Bürgmann2
1Department of Earth Sciences, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada.
Nature
|June 20, 2014
概括
潜伏区的缓慢地震与富含的前弧地有关. 增加的二氧化含量,以地震波速度表示,与缓慢滑动事件和震的更短的复发时间相关.
科学领域:
- 地质物理学 地质物理学
- 地震学 地震学
- 构造学 构造学 构造学 构造学
背景情况:
- 缓慢的地震,包括偶尔的震动和滑动,发生在俯冲区前弓中,复发间隔从几个月到几年.
- 这些事件需要高孔液压,但控制复发时间变化的因素尚不清楚.
- 在卡斯卡迪亚,缓慢滑行细分和震动特征随深度而变化,这表明局部控制.
研究的目的:
- 为了研究前弧地特性与地震复发时间缓慢之间的关系.
- 为了确定控制缓慢地震行为在俯冲区的变化性的物理机制.
- 探索缩和流体压力在调节地震活动中的作用.
主要方法:
- 从俯冲区前收集和分析地震数据 (压缩和剪切波速度).
- 地震速度比率 (vP/vS) 与缓慢的地震复发间隔的相关性.
- 将地质和地物理观测与流体岩石相互作用的理论模型相结合.
主要成果:
- 前弧地的平均压缩 (P) 波与剪切 (S) 波速度比 (vP/vS) 和缓慢地震复发时间之间存在线性关系.
- Forearc的vP/vS值在1.6到2.0之间,与缩 (5-15%体积) 相对应.
- 在卡斯卡迪亚北部,随着深度的下降,vP/vS与更短的震复发间隔相关.
结论:
- 从板块衍生的流体中,前弧的缩控制了vP/vS值,并影响了缓慢的地震行为.
- 取决于温度的二氧化沉积和溶解-沉在断层沟中的爬行降低了透性,导致更快的流体过压积累和更短的复发时间.
- 这些过程,加上扩张强度的增强,决定了观测到的缓慢地震复发和震动活动的变化.
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