GEOCHEMICAL AND PETROPHYSICAL RESPONSES TO FLUID PROCESSES WITHIN SEISMOGENIC FAULT ZONES：IMPLICATIONS FROM MINERALOGICAL, PETRO- CHEMICAL AND PETROPHYSICAL DATA

doi:10.3969/j.issn.0253-4967.2014.03.024

Abstract

Abstract:

Earthquake fault zones are conduits of deep crustal fluids. Extensive rock-water interaction within fault zones results in distinct rock properties of fault rocks, including their mineral composition, particle size distribution, porosity, permeability and elasticity. These features are taken as responses to fluids acting on fault rocks during co- and inter-seismic periods, and can provide important information on rock formation, energetic partitioning, fluid and mass transport within the fault zones, and can also serve as constraints to deep probing results. Taking the Wenchuan earthquake fault for instance, this paper summarizes rock-physical properties of fault rocks, including permeability, porosity, P-wave velocity, particle size distribution, chemical and mineral composition. The results indicate that fault rocks seen now on the surface are definitely related to coseismic fracturing process, but their physical properties have been significantly influenced by long-term rock-water interaction; the present internal structure is not simply the product of the 2008 Wenchuan earthquake, but the cumulative nature of repeated seismic events. This can explain the large petrophysical difference from country rocks. This paper further discusses earthquake-related issues including fracturing energy, rupture propagation, formation and explanation of trapped wave.

Key words: fluid-rock interaction, mineral transition and material migration, porosity, permeability, elastic wave velocities, generalized thermal pressurization

摘要：

地震断层带是壳内深部流体的通道。流体与地震破裂带内的岩石相互作用导致其具有与地壳完整岩石完全不同的特性，包括其矿物成分、化学成分、粒度分布、孔隙度、渗透性和弹性等方面，这些特征可以视为流体与地震断层带相互作用的响应。深入研究断层岩的岩石化学和岩石物理性质将有助于准确和精细地了解地震断层岩的形成过程，分析地震能量分配，认识物质迁移的方式，解释或约束地震断层带深部探测结果等。文中以汶川地震破裂带内的断层岩为例，研究并总结了地震断层岩的渗透率、孔隙度、纵波速度、粒度分布和矿物组成等特征。结果显示，地震破裂带上的断层岩形成与地震破裂作用有关，但表现出的性质更大程度上烙有间震期流体与断层岩相互作用的印记。汶川地震破裂带上的断层岩本身并不是汶川地震破裂的直接产物，而是多次地震破裂和间震期流体与断层带相互作用的综合结果。此外，还探讨了地震破裂能、地震破裂扩展、围陷波形成及解释的问题。

关键词: 水岩相互作用, 矿物转变与物质迁移, 孔隙度, 渗透率, 弹性波速度, 热压作用

CLC Number:

P315.1

YANG Xiao-song, CHEN Jian-ye, DUAN Qing-bao, YANG Yu, CHEN Jin-yu. GEOCHEMICAL AND PETROPHYSICAL RESPONSES TO FLUID PROCESSES WITHIN SEISMOGENIC FAULT ZONES：IMPLICATIONS FROM MINERALOGICAL, PETRO- CHEMICAL AND PETROPHYSICAL DATA[J]. SEISMOLOGY AND GEOLOGY, 2014, 36(3): 862-881.

杨晓松, 陈建业, 段庆宝, 杨彧, 陈进宇. 地震断层带流体作用的岩石化学-物理响应——来自矿物学、岩石化学、岩石物理学的启示[J]. 地震地质, 2014, 36(3): 862-881.

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