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首页> 外文期刊>Tectonophysics: International Journal of Geotectonics and the Geology and Physics of the Interior of the Earth >Fluid overpressure and flow in fault zones: field measurements and models
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Fluid overpressure and flow in fault zones: field measurements and models

机译：断层带中的流体超压和流量：现场测量和模型

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Field studies of small normal faults (throws of metres to tens of metres) show that their fault cores consist of breccias that vary in thickness along the fault plane. Commonly, the down-dip variation in the breccia thickness is 0-1 in with a wavelength of 5-10 m. The breccia acts mechanically as an inclusion; soft, ductile and sometimes creeping when the fault zone is active, but stiff and brittle when the fault zone is inactive. During interseismic periods, and when the fault has become inactive, the breccia behaves as a very dense, low-permeability material that is a barrier to transverse flow of groundwater. The breccia barrier thus collects water and channels it downdip or updip along the contact between the fault core and the damage zone. For a typical I-m-thick interseismic breccia, the maximum transmissivity is estimated at T-p similar to 10(-10) m(2) s(-1). The field data, however, indicate that during the high strain rates associated with faulting, seismogenic slip may occur either along the breccia, or along its contacts with the damage zone. The resulting fractures with apertures of similar to0.3 cm may temporarily increase the transmissivity of the fault core by at least 8 orders of a magnitude, to as much as T-f similar to 10(-2) m(2) s(-1). It is suggested that slip of faults of this type is commonly associated with the flow of overpressured water into the fault plane. High water pressure lowers the critical driving shear stress needed for fault slip and may greatly increase the aperture, hence the fluid transport, of the slipping fracture. Theoretical considerations indicate that, other things being equal, fluid flow along strike-slip faults is favoured over flow along dip-slip faults and that, generally, the steeper the dip of the fault, the more effective it is for fluid transport. (C) 2001 Elsevier Science B.V. All rights reserved. [References: 51]
机译：对小型正常断层（数米至数十米）的野外研究表明，其断层芯由角砾岩组成，角砾岩沿断层平面的厚度变化。通常，角砾岩厚度的下倾变化为0-1 in，波长为5-10 m。角砾岩在机械上起包裹体的作用。当断层带处于活动状态时，它柔软，易延展，有时会蠕变;而当断层带处于非活动状态时，则是刚性而脆。在地震期间，当断层变为非活动状态时，角砾岩表现为一种非常致密，低渗透的材料，是阻碍地下水横向流动的障碍。角砾岩屏障因此收集了水，并引导水沿着断层岩心和破坏区之间的接触而下倾或上倾。对于典型的I-m厚间震角砾岩，在T-p处估计的最大透射率类似于10（-10）m（2）s（-1）。但是，现场数据表明，在与断层有关的高应变率期间，沿角砾岩或沿其与破坏带的接触可能会发生地震。所产生的孔径接近0.3厘米的裂缝可能会使断层岩心的透射率暂时增加至少8个数量级，至多等于10（-2）m（2）s（-1）的Tf。 。建议这种类型的断层滑动通常与超压水流入断层平面有关。高水压降低了断层滑动所需的临界驱动剪切应力，并可能大大增加了滑动裂缝的孔径，从而增加了流体的输送。理论上的考虑表明，在其他条件相同的情况下，沿走滑断层的流体流动要比沿倾滑断层的流体流动更为有利，并且通常，断层的倾角越陡，流体输送的有效性就越高。 （C）2001 Elsevier Science B.V.保留所有权利。 [参考：51]

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