地震研究

从岩石的应力和应变的本构关系出发,利用基于库仑应力触发模型的加卸载响应比计算方法,计算了天津蓟县洞体应变和小辛庄洞体应变的加卸载响应比值,并依据孕震尺度与震级关系选取震例,结合伸缩应变原始观测数据的趋势性变化特征和天津及周边地区b值扫描结果开展了综合分析。结果表明:① 2020年河北古冶M_S5.1地震前小辛庄洞体应变两分量出现了明显的拉张应变加速、震后减弱现象,加卸载响应比值在该时段内同样出现了先增大后减小的异常变化; ② 2018—2019年天津小辛庄周边区域出现了明显的低b值异常区,且上述结果在时、空上呈现出较好的一致性。

According to the stress-strain constitutive relationship of rock,the Load/Unload Response Ratio(LURR)method based on the Coulomb stress triggering model is used to calculate LURR values of the cave strain observed at Jixian seismic station and on Xiaoxinzhuang monitoring spot in Tianjin city.Earthquake cases are selected according to the relationship between the seismogenic range and the magnitude.Variation trend of the observational strain data is analyzed and b-values in Tianjin city and its vicinity are calculated.Results indicate that before the Guye M_S5.1 earthquake in Hebei province,the tension strain in NS and EW component on Xiaoxinzhuang spot sped up,then slowed down after the Guye earthquake.In the meantime,LURR values of the strain on Xiaoxinzhuang spot and its surrounding areas increased,and then decreased.In addition,there was obviously a low b-value region around Xiaoxinzhuang spot from 2018 to 2019.All these precursory anomalies were consistent in time and space.

引言
1 研究背景
2 研究方法
3 研究结果
4 结论

图1 蓟县台周边构造及MS≥4.0地震空间分布<br/>Fig.1 Distribution of structures and MS≥ 4.0 earthquakes around Jixian seismic station

图1 蓟县台周边构造及MS≥4.0地震空间分布
Fig.1 Distribution of structures and MS≥ 4.0 earthquakes around Jixian seismic station

表1 2017年以来天津蓟县台周边200 km范围内MS≥4.0地震基本信息<br/>Tab.1 MS≥4.0 earthquakes within 200 km around Jixian seismic station since 2017

表1 2017年以来天津蓟县台周边200 km范围内MS≥4.0地震基本信息
Tab.1 MS≥4.0 earthquakes within 200 km around Jixian seismic station since 2017

图2 岩石应力-应变曲线(岳冲等,2020)<br/>Fig.2 Stress-strain curve of rock(Yue et al,2020)

图2 岩石应力-应变曲线(岳冲等,2020)
Fig.2 Stress-strain curve of rock(Yue et al,2020)

图3 蓟县洞体应变(a)和小辛庄洞体应变(b)的各分量观测时序曲线<br/>Fig.3 Time series of the cave strain at Jixian seismic station(a),and the cave strain on Xiaoxinzhuang monitoring spot(b)

图3 蓟县洞体应变(a)和小辛庄洞体应变(b)的各分量观测时序曲线
Fig.3 Time series of the cave strain at Jixian seismic station(a),and the cave strain on Xiaoxinzhuang monitoring spot(b)

图4 小辛庄洞体应变LURR值时序曲线<br/>Fig.4 LURR time series of the cave strain on Xiaoxinzhuang monitoring spot

图4 小辛庄洞体应变LURR值时序曲线
Fig.4 LURR time series of the cave strain on Xiaoxinzhuang monitoring spot

图5 天津及周边地区b值扫描结果<br/>Fig.5 Temporal scanning of b-values in Tianjin and its surrounding areas

图5 天津及周边地区b值扫描结果
Fig.5 Temporal scanning of b-values in Tianjin and its surrounding areas

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备注

引言

1 研究背景

2 研究方法

3 研究结果

4 结论

期刊信息