地震研究

注水诱发地震的谱振幅相关系数及视应力研究^*

(1.四川省地震局,四川成都 610041; 2.云南省地震局,云南昆明 650224)

Study on Correlation Coefficient of Spectral Amplitude and Apparent Stress of Water Injection Induced Earthquake

ZHANG Zhi-wei¹, QIAO Hui-zhen¹, WU Peng¹,GONG Yue¹, ZHAO Xiao-yan²

(1.Earthquake Administration of Sichuan Province, Chengdu 610041,Sichuan, China)(2. Earthquake Administration of Yunnan Province, Kunming 650224,Yunnan, China)

Keywords： water injection induced earthquake; Q value; site response; correlation coefficient of spectral amplitude; apparent stress

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参考文献

以四川自贡和长宁两个注水地区为例,基于区域测震台网记录的数字地震波形资料和观测报告,分析注水诱发地震的谱振幅相关系数特征及其与当地加压注水数据的关系,并结合表征绝对应力水平的视应力综合分析研究自贡和长宁地区的应力状态。结果表明,自贡和长宁地区注水诱发地震的谱振幅相关系数均在高值波动,其均值分别为0.89和0.90,且变化过程与加压注水数据具有很好的相关性。分析认为加压注水对局部区域应力场产生扰动影响,使地下浅层裂隙呈优势取向排列,引发的中小地震震源机制表现出较好的相似性,但其视应力结果显示研究区域的应力水平并不高。

Taking Zigong and Changning which are both water injection areas in Sichuan as the study regions, based on digital seismic waveform recorded by regional seismic network and observation report, we analyze the characteristic of correlation coefficient of spectral amplitude of water injection induced earthquake and the relationship between correlation coefficient and water injection data. Then combining the apparent stress which represents the absolute stress level, we analyze the stress intensity of the two study regions. The result shows that the correlation coefficients of spectral amplitude of water injection induced earthquakes both fluctuate at high value and the average values are 0.89 and 0.90 in Zigong and Changning areas respectively, and the changing process of correlation coefficient has a good correlation with water injection data. The pressurized water injection has the disturbance influence on stress field in local region, thus the fractures of underground shallow layer arrange in predominant direction, and the focal mechanisms of water injection induced small-moderate earthquakes shows good similarity, however, the apparent stress results indicate that the stress is lower in the study region.

引言
1 资料和方法
2 谱振幅相关系数结果分析
3 地震视应力结果分析
4 结论与讨论

图1 2000年以来自贡、长宁地区注水诱发地震时空分布特征(a)研究区域; 自贡(b)、长宁(c)地区ML≥2.0地震M-T、N-T图<br/>Fig.1 Spatial and temporal distribution characteristic of water injection induced earthquakes in Zigong and Changning areas since 2000 (a)study area; M-T、N-T graph of ML≥2.0 earthquakes in Zigong(b)and Changning(c)areas since 2000

图1 2000年以来自贡、长宁地区注水诱发地震时空分布特征(a)研究区域; 自贡(b)、长宁(c)地区ML≥2.0地震M-T、N-T图
Fig.1 Spatial and temporal distribution characteristic of water injection induced earthquakes in Zigong and Changning areas since 2000 (a)study area; M-T、N-T graph of ML≥2.0 earthquakes in Zigong(b)and Changning(c)areas since 2000

图2 四川东南地区P波(a)、S波(b)的Q值随频率f的变化及其拟合曲线<br/>Fig.2 Q-value variation of P(a)and S(b)waves with frequency f and their fitted curve in the southeast area of Sichuan

图2 四川东南地区P波(a)、S波(b)的Q值随频率f的变化及其拟合曲线
Fig.2 Q-value variation of P(a)and S(b)waves with frequency f and their fitted curve in the southeast area of Sichuan

图3 川东南地区7个台站的场地响应结果<br/>Fig.3 Site responses results of 7 stations in the southeast area of Sichuan

图3 川东南地区7个台站的场地响应结果
Fig.3 Site responses results of 7 stations in the southeast area of Sichuan

图4 自贡(a)、长宁(b)地区加压注水数据与谱振幅相关系数对比图<br/>(时间分段:自贡:Ⅰ:2009-01～2010-07; Ⅱ:2010-08～2013-04; 长宁:Ⅰ:2006-04～2007-11; <br/>Ⅱ:2007-12～2013-04; min、max和mean分别表示谱振幅相关系数最小值、最大值和平均值)<br/>(a-1):加压数据;(b-1):注(出)水量及其差值;(a-2),(b-2):谱振幅相关系数<br/>(曲线)和参与相关系数计算的地震M-T图(竖线)<br/>Fig.4 The comparison diagram between pressurized water injection data and correlation coefficient of spectral amplitude in Zigong(a)and Changning(b)areas (time slicing:Ⅰis from 2009-01 to 2010-07 in Zigong area; Ⅱ is from 2010-08 to 2013-04; Ⅰis from 2006-04 to 2007-11 Ⅱ is from 2007-12 to 2013-04 in Changning area; min,max and mean represent minimum value,maximum value and mean value of spectral amplitude correlation coefficient respectively)(a-1):pressure data;(b-1):water injection(yield)rate and difference value;(a-2),(b-2):the correlation coefficient of spectral amplitude(curve)and the M-T graph(long string)of earthquakes which are used to calculate the correlation coefficient

图4 自贡(a)、长宁(b)地区加压注水数据与谱振幅相关系数对比图
(时间分段:自贡:Ⅰ:2009-01～2010-07; Ⅱ:2010-08～2013-04; 长宁:Ⅰ:2006-04～2007-11;
Ⅱ:2007-12～2013-04; min、max和mean分别表示谱振幅相关系数最小值、最大值和平均值)
(a-1):加压数据;(b-1):注(出)水量及其差值;(a-2),(b-2):谱振幅相关系数
(曲线)和参与相关系数计算的地震M-T图(竖线)
Fig.4 The comparison diagram between pressurized water injection data and correlation coefficient of spectral amplitude in Zigong(a)and Changning(b)areas (time slicing:Ⅰis from 2009-01 to 2010-07 in Zigong area; Ⅱ is from 2010-08 to 2013-04; Ⅰis from 2006-04 to 2007-11 Ⅱ is from 2007-12 to 2013-04 in Changning area; min,max and mean represent minimum value,maximum value and mean value of spectral amplitude correlation coefficient respectively)(a-1):pressure data;(b-1):water injection(yield)rate and difference value;(a-2),(b-2):the correlation coefficient of spectral amplitude(curve)and the M-T graph(long string)of earthquakes which are used to calculate the correlation coefficient

图5 川东南地区ML≥3.0地震(a)及其视应力值空间分布(b)<br/>Fig.5 Epicenter distribution of ML≥3.0 earthquakes(a)and spatial distribution of apparent stress(b)in the southeast area of Sichuan

图5 川东南地区ML≥3.0地震(a)及其视应力值空间分布(b)
Fig.5 Epicenter distribution of ML≥3.0 earthquakes(a)and spatial distribution of apparent stress(b)in the southeast area of Sichuan

图6 自贡、长宁及川东南地区ML≥3.5地震视应力与震级分布<br/>Fig.6 The distribution of apparent stress and magnitude of ML≥3.5 earthquakes in Zigong,Changning and the southeast area of Sichuan

图6 自贡、长宁及川东南地区ML≥3.5地震视应力与震级分布
Fig.6 The distribution of apparent stress and magnitude of ML≥3.5 earthquakes in Zigong,Changning and the southeast area of Sichuan

图7 自贡(a)、长宁(b)地区ML≥3.5地震视应力在不同阶段的变化(实竖线:地震震级; 虚竖线:分段间隔; 分段时间:同图4)<br/>Fig.7 The apparent stress change of ML≥3.5 earthquakes at different stages in Zigong(a)and Changning(b)areas(real vertical lines:earthquake magnitude; virtual vertical lines:section gap; time slicing is the same as Fig.4)

图7 自贡(a)、长宁(b)地区ML≥3.5地震视应力在不同阶段的变化(实竖线:地震震级; 虚竖线:分段间隔; 分段时间:同图4)
Fig.7 The apparent stress change of ML≥3.5 earthquakes at different stages in Zigong(a)and Changning(b)areas(real vertical lines:earthquake magnitude; virtual vertical lines:section gap; time slicing is the same as Fig.4)