Fault zone controlled seafloor methane seepage in the rupture area of the 2010 Maule earthquake, Central Chile
Fault zone controlled seafloor methane seepage in the rupture area of the 2010 Maule earthquake, Central Chile
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DOI：
10.1002/2016gc006498
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发表时间：
2016-11-01
影响因子：
3.5
通讯作者：
Hensen, Christian
中科院分区：
文献类型：
--
作者：
Geersen, Jacob;Scholz, Florian;Hensen, Christian
在一些海洋前弧中发现了含烃流体的海底渗漏。然而，渗漏活动的时间变化以及控制渗漏的结构和构造参数往往仍然缺乏约束。例如，俯冲带地震经常被讨论为引发海底渗漏，但超出理论考虑的因果联系尚未完全确定。这主要是由于近海震中区无法进入，大地震很少发生，以及与近海大面积和充足时间段的渗漏监测有关的挑战。在这里，我们报告了位于2010兆瓦断裂区的康塞普西翁甲烷渗漏区(智利中部近海)的视觉、地球化学、地球物理和模拟结果和观测结果。8.8毛勒地震。海洋水柱中甲烷浓度较高，硫酸盐渗入海底深度较浅，表明甲烷渗漏活跃。释放气的甲烷和烃类组成的稳定碳同位素特征表明，浅源生物气和深源热源成分的混合。在海底观察到的原始裂缝和裂缝，以及在海洋前弧上地震成像的大断层，可能是甲烷迁移的有效途径。具有水力破裂和膨胀的上板块断层活动与板块边界大地震期间增加的法线库仑应力是一致的，正如2010年地震的示范模型所示。从全球的角度来看，我们的结果指出了反复发生的大型俯冲带地震在长时间尺度上驱动海洋前弧油气渗漏的可能作用。
Seafloor seepage of hydrocarbon-bearing fluids has been identified in a number of marine fore arcs. However, temporal variations in seep activity and the structural and tectonic parameters that control the seepage often remain poorly constrained. Subduction zone earthquakes, for example, are often discussed to trigger seafloor seepage but causal links that go beyond theoretical considerations have not yet been fully established. This is mainly due to the inaccessibility of offshore epicentral areas, the infrequent occurrence of large earthquakes, and challenges associated with offshore monitoring of seepage over large areas and sufficient time periods. Here we report visual, geochemical, geophysical, and modeling results and observations from the Concepcion Methane Seep Area (offshore Central Chile) located in the rupture area of the 2010 Mw. 8.8 Maule earthquake. High methane concentrations in the oceanic water column and a shallow subbottom depth of sulfate penetration indicate active methane seepage. The stable carbon isotope signature of the methane and hydrocarbon composition of the released gas indicate a mixture of shallow-sourced biogenic gas and a deeper sourced thermogenic component. Pristine fissures and fractures observed at the seafloor together with seismically imaged large faults in the marine fore arc may represent effective pathways for methane migration. Upper plate fault activity with hydraulic fracturing and dilation is in line with increased normal Coulomb stress during large plate-boundary earthquakes, as exemplarily modeled for the 2010 earthquake. On a global perspective our results point out the possible role of recurring large subduction zone earthquakes in driving hydrocarbon seepage from marine fore arcs over long timescales.