Coseismic fluid-rock interactions at high temperatures in the Chelungpu fault
Coseismic fluid-rock interactions at high temperatures in the Chelungpu fault
复制标题
DOI：
10.1038/ngeo308
复制
发表时间：
2008-10-01
影响因子：
18.3
通讯作者：
Song, Sheng-Rong
中科院分区：
文献类型：
--
作者：
Ishikawa, Tsuyoshi;Tanimizu, Masaharu;Song, Sheng-Rong
含水流体被认为在断层和地震破裂的动态传播中起着重要作用。流体超压可以影响地震成核（1,2），在一个称为热加压的过程中，摩擦加热产生的孔隙流体压力可以减少作用在断层表面的有效正应力（3-5）。这可能导致滑动期间断层强度的显著降低。然而，流体在滑动带内的同震存在以及流体在动态断层弱化中的作用仍然是一个有争议的问题。本文介绍了台湾车隆堡断裂带三个活动带的主要和微量元素组成以及岩心样品的同位素比值，这些岩心样品代表了相对完好的和非常细粒度的变形物质。在厚度为2-15厘米的剪切最强烈带上的深度剖面显示出流体流动元素和锶同位素的尖锐组成峰。我们认为，地震过程中沉积孔隙流体加热产生的高温流体（bb0 ~ 350℃）与断裂带内的物质相互作用，使元素被调动。断裂带内低水力扩散系数(6)条件下的高温流体同震存在有利于热加压。这种效应可能导致了1999年齐齐7.6级地震期间沿车隆堡断层的摩擦动态减少。
Aqueous fluids are thought to have an essential role in faulting and the dynamic propagation of earthquake rupture. Fluid overpressure can affect earthquake nucleation(1,2) and in a process termed thermal pressurization, pore fluid pressure produced by frictional heating can reduce the effective normal stress acting on the fault surface(3-5). This may lead to a marked reduction in fault strength during slip. However, the coseismic presence of fluids within slip zones and the role of fluids in dynamic fault weakening is still a matter of debate. Here we present compositions of major and trace elements as well as isotope ratios of core samples representing relatively undamaged as well as very fine-grained deformed material from three active zones of the Chelungpu fault, Taiwan. Depth profiles across the most intensely sheared bands that range in thickness from 2-15 cm exhibit sharp compositional peaks of fluid-mobile elements and of strontium isotopes. We suggest that high-temperature fluids (>350 degrees C) derived from heating of sediment pore fluids during the earthquake interacted with material within the fault zone and mobilized the elements. The coseismic presence of high-temperature fluids under conditions of low hydraulic diffusivity(6) within the fault zone is favourable for thermal pressurization. This effect may have caused a dynamic decrease of friction along the Chelungpu fault during the 1999 magnitude 7.6 Chi-Chi earthquake.