浙江珊溪水库库区地震波衰减特征研究

朱新运; 于俊谊; 张帆

doi:10.3969/j.issn.0253-3782.2013.02.006

浙江珊溪水库库区地震波衰减特征研究

中国杭州 310013 浙江省地震局

基金项目: 中国地震局星火计划(XH12023)和中国自然科学基金(41090291)资助.

详细信息

通讯作者:
朱新运, E-mail:zhuxinyun@126.com

中图分类号: P315.3⁺1
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出版历程
- 收稿日期: 2012-02-28
- 修回日期: 2012-09-21
- 发布日期: 2013-02-28

Characteristics of seismic wave attenuation in Shanxi Reservoir area of Zhejiang Province

Earthquake Administration of Zhejiang Province, Hangzhou 310013, China

摘要

摘要: 2002—2007年发生的珊溪水库地震事件是少震、弱震的浙江省区域显著的地震事件. 搜集182次M_L>2.0地震的近场台站数字地震波形, 使用这些波形高信噪比的尾波时间域信号，根据计算尾波Q_c(f)值的Sato模型，通过滤波及去除环境噪声，计算了地震波传播路径上的尾波Q_c(f)值; 拟合Q_c(f)值与频率f之间的关系，分析了水库区域地震波衰减的时空特征. 根据信噪比及计算要求，从近场9个台站的记录中挑选出641条三分向记录，计算尾波衰减参数，得到尾波Q_c(f)与频率f的关系为: Q_c(f)=52.19±7.11f^{0.922 1±0.05}. 结果表明，本区域为低衰减区域. 震群活动使区域介质对高频率波衰减趋势性增大. 进一步对尾波衰减参数及尾波采样体之间的关系分析发现，该区域存在深部高衰减层.
- 震群 /
- 尾波 /
- 衰减参数 /
- 水库地震
Abstract: The earthquakes which occurred from 2002 to 2007 in Shanxi Reservoir area, Zhejiang Province, are very notable, because the province is not considered prone to earthquakes. We have collected waveform data of 182 M_L>2.0 earthquakes recorded at near-source stations. By using the coda time series with high signal-to-noise ratio and filtering the data to eliminate background noises based on Sato model, the coda Q_c(f) was calculated, and the relationship between Q_c(f) and frequency (f) was obtained. Then, the characteristics of seismic wave attenuation in the reservoir area were analyzed. 641 three-component records chosen from 9 stations were used for this study. Our result shows that the relationship between the coda Q_c(f) and f is: Q_c(f)=52.19±7.11f^0.9221±0.05, suggesting that the study area is a tectonically inactive zone. The attenuation coefficient for high frequency waves increases with seismic activity. Further analysis on the relationship between Q_c(f) and sampling depth reveals that high attenuation layers exist deep beneath the study area.
- earthquake swarm /
- coda /
- attenuation coefficient /
- reservoir earthquakes

HTML全文

图 1 台站、震中及射线分布图(震中引自朱新运等，2010) WEZ：温州台； JIN：景宁台； HUT：黄塘台；YUH：云湖台； TSH：泰顺台； BY：包洋台；XP：新浦台； SHX：珊溪台； LIY：联云台

Figure 1. Seismic stations (triangles),epicenters (circles) and ray-paths (blue solid lines)

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图 2 尾波衰减参数计算过程实例(a) 使用波形原始记录(仅绘EW向)，t_n表示满足信噪比条件的尾波截断点，t₁表示尾波计算实际使用的尾波截断点，t₀表示地震发震时刻(t₁-t₀=60 s)； (b) f=11(f±1/3f)数据滤波实例； (c) 主频率为f=11的数据拟合； (d) Q_c(f)与频率关系

Figure 2. Examples of coda wave attenuation parameter calculation (a) E- -W component velocity seismogram,t_n represents cutoff point of coda waves satisfying signal-to-noise ratio (SNR) condition，t₁ denotes cutoff point of coda waves used in the calculation,t₀ is the origin time (t₁-t₀=60 s); (b) Filtered seismogram (f=11(f±1/3f)); (c) Data fitting with f=11; (d) Relationship between Q_c(f) and frequency

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图 3 全区域所有台站记录的尾波衰减参数与频率关系 (a) Q_c(f)与频率关系图,星号表示实测的Q_c(f)值,实线表示衰减参数与频率的依赖关系; (b) 数据残差分布

Figure 3. Q_c(f) values versus frequency for all stations in the whole region (a) Relationship between Q_c(f) and frequency，asterisk represents measuredQ_c(f),solid line shows Q_c(f)-frequency dependency relation for the whole region; (b) Residual distribution

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图 4 TSH台获得的Q_c(f)与频率关系 (a) Q_c(f)与频率关系图,星号表示实测的Q_c(f)值,实线表示衰减参数与频率的依赖关系; (b) 数据残差分布

Figure 4. Q_c(f) obtained as a function of frequency for TSH station (a) Relationship between Q_c(f) and frequency，asterisk represents measured Q_c(f),solid line shows the Q_c(f)-frequency dependency relation for the whole region; (b) Residual distribution

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图 5
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图 7 TSH台获得的尾波衰减参数Q₀ (a)和η (b)随地震序列的变化

Figure 7. Variation of coda Q₀ (a) and η (b) values with the earthquake sequence at TSH station

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表 1 各台站数据统计结果

Table 1 Statistical results of Q value from different stations

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表 2 国内外不同区域尾波衰减参数比较

Table 2 Comparison of coda attenuation parameters obtained at home and abroad

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