基于Gassmann方程的流体替换方法在珊溪水库地震研究中的应用①

钟羽云, 张帆, 阚宝祥

(浙江省地震局，浙江 杭州 310013)

摘要：引入基于Gassmann方程的流体替换方法，在分析地震波P波速度、波速比与岩石孔隙度和饱和度关系的基础上，应用于珊溪水库地震波速比和P波速度变化特征研究，得到：(1)珊溪水库震中区岩石始终处于接近水饱和的饱水状态，波速比和P波速度“下降-回升”的变化实质上反映了震中区岩石“孔隙度增大(饱和度减小)-饱和度增大”的变化，每一丛地震的波速比由极小值逐渐增大为极大值是由于岩石从不饱和状态变化到饱和状态；(2)根据每一丛地震波速比的变化，计算得到珊溪水库流体扩散率αs=1.06×104 cm2 s-1，该数值与美国南卡罗莱纳水库、巴西Acu水库、广东新丰江水库的流体扩散率基本一致；(3)震源区岩石孔隙度上限值为8.7%～2.0%，该数值与华东勘测设计研究院通过室内岩石物理力学性质试验测定的珊溪水库坝址区新鲜流纹斑岩的孔隙度平均值一致。

关键词：Gassmann方程； 孔隙度； 饱和度； 珊溪水库

收稿日期：①2014-12-25

基金项目：浙江省公益技术应用研究项目(2012C23035)

作者简介：钟羽云(1966-)，男，硕士，研究员，主要从事地震预测方法、水库地震等研究。 E-mail:hzyuyun@126.com。

中图分类号:P631.4文献标志码：A

DOI:10.3969/j.issn.1000-0844.2015.03.0678

Application of Gassmann Equation-based Fluid Substitution

Method to the Research of Reservoir-induced

Earthquakes at Shanxi Reservoir

ZHONG Yu-yun, ZHANG Fan, KAN Bao-xiang

(EarthquakeAdministrationofZhejiangProvince,Hangzhou310013,Zhejiang，China)

Abstract：By analyzing the relationship between seismic P-wave velocity, velocity ratio, and rock porosity and saturation in the Shanxi reservoir, the fluid substitution equation method based on the Gassmann equation was used to estimate the rock porosity and fluid diffusion rate in the reservoir’s earthquake source region. The results show that the rock of the epicentral area is always close to the water-saturated state. The changes in P-wave velocity and the velocity ratio from decreasing to increasing reflect that the rock in the epicentral area changes from increasing porosity (decreasing saturation) to increasing saturation. The velocity ratio gradually increases from the minimum value to the maximum value because of the changes in rock conditions from unsaturated to saturated. Moreover, the fluid diffusivity of the Shanxi reservoir is 1.44 × 104 cm2 s-1 to 0.84 × 104 cm2 s-1, which is consistent with that of the South Carolina reservoir in the United States, the Acu reservoir in Brazil, and the Xinfengjiang reservoir in Guangdong, China. Further, the maximum rock porosity in the source area is 8.7%～2.0%, which is consistent with the average value of porosity of new rhyolite porphyries in the Shanxi reservoir dam site measured by the East China Investigation and Design Institute by lab testing of the physical and mechanical properties of the rock.

Key words： Gassmann equation; porosity; saturation; Shanxi reservoir

0引言

水库地震诱发机理研究表明，水库蓄水后将导致库水向下渗透，改变库基岩体的应力状态和介质性质，诱发地震活动。因此水库地震与库水向地下渗透运移有着不可分割的联系[1-2]，水在水库诱发地震中起着重要作用。……