Earthquake-enhanced permeability - evidence from carbon dioxide release following the ML 3.5 earthquake in West Bohemia
Earthquake-enhanced permeability - evidence from carbon dioxide release following the ML 3.5 earthquake in West Bohemia
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DOI：
10.1016/j.epsl.2016.12.001
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发表时间：
2017-02-15
影响因子：
5.3
通讯作者：
Heinicke, J.
中科院分区：
文献类型：
--
作者：
Fischer, T.;Matyska, C.;Heinicke, J.
西波希米亚/沃格特兰地区以震群活动和地幔来源的二氧化碳脱气为特征。2014年5月，在距震中9公里的哈尔图索夫莫菲特，发生M-L 3.5级地震后的第4天，观测到了二氧化碳流量的快速增加。在接下来的150天里，流量达到了原来水平的六倍，并且一直在缓慢衰减，直到现在。在2008年的蜂群期间和之后也观察到了类似的行为，这表明从长期来看，这是一种断层阀机制。在此，我们给出了一个二维地壳模型中气体流动的模拟结果，该模型由震中深度的封闭层组成，该封闭层被地震断层穿透并从相对低渗透性的下地壳释放流体。这个简单的模型能够解释观测结果，包括从8公里深到地表的水流脉冲的短期传播时间，长期的流量增加及其随后的缓慢衰减。我们的模型与其他对2014年余震的分析是一致的，后者将余震的异常特征归因于外部流体力的指数下降。因此，我们的观测和模型从深处跟踪流体压力脉冲，在那里它是触发余震的原因，并在4天后开始显着地长期增加二氧化碳流量。(C)2016爱思唯尔B.V.保留所有权利。
The West Bohemia/Vogtland region is characterized by earthquake swarm activity and degassing of CO2 of mantle origin. A fast increase of CO2 flow rate was observed 4 days after a M-L 3.5 earthquake in May 2014 in the Hartousov mofette, 9 km from the epicentres. During the subsequent 150 days the flow reached sixfold of the original level, and has been slowly decaying until present. Similar behavior was observed during and after the swarm in 2008 pointing to a fault-valve mechanism in long-term. Here, we present the results of simulation of gas flow in a two dimensional model of Earth's crust composed of a sealing layer at the hypocentre depth which is penetrated by the earthquake fault and releases fluid from a relatively low-permeability lower crust. This simple model is capable of explaining the observations, including the short travel time of the flow pulse from 8 km depth to the surface, long-term flow increase and its subsequent slow decay. Our model is consistent with other analyse of the 2014 aftershocks which attributes their anomalous character to exponentially decreasing external fluid force. Our observations and model hence track the fluid pressure pulse from depth where it was responsible for aftershocks triggering to the surface where a significant long-term increase of CO2 flow started 4 days later. (C) 2016 Elsevier B.V. All rights reserved.