利用基于时-空传染型余震序列(Epidemic Type Aftershock Sequence,简称ETAS)模型的随机除丛法,重新审视了2008年5月12日汶川M_S8.0地震前可能存在的长期地震活动异常,研究了川滇地区背景地震活动特征,并评估了当前的强震危险状态.对川...利用基于时-空传染型余震序列(Epidemic Type Aftershock Sequence,简称ETAS)模型的随机除丛法,重新审视了2008年5月12日汶川M_S8.0地震前可能存在的长期地震活动异常,研究了川滇地区背景地震活动特征,并评估了当前的强震危险状态.对川滇地区1 970年以来的M_L3.0以上的背景地震和丛集地震活动的研究结果表明,该地区地震丛集特征明显、时空分布很不均匀、地震序列常有前震事件.直接将概率值作为地震计数的权重,对地震丛集率空间分布图像分析表明,汶川M_S8.0地震前,龙门山断裂带中南段存在着长期、大范围的地震丛集率低值区,震前该段处于应力闭锁状态.对川滇地区地震从集率低值区内背景地震与全部地震的累积次数、b值和新定义的Δb等统计参量的分析表明,龙日坝与龙门山断裂带具有地震活动的关联性,川滇地区当前的强震潜在危险区可能是巧家地区和汶川M_S8.0地震破裂尚未穿越的龙门山断裂带南段.此外,还发现b值倾向于反映局部应力场变化,而△b能较为敏感地给出更大范围应力场的相对变化.展开更多
Influenced by the layout of seismic network and the location of earthquakes,earthquake catalogs are often incomplete;such incompleteness of earthquake catalogue directly affects the analysis of sequence activity chara...Influenced by the layout of seismic network and the location of earthquakes,earthquake catalogs are often incomplete;such incompleteness of earthquake catalogue directly affects the analysis of sequence activity characteristics.In this paper,the GPU-acceleration-based g template matching method is used to scan the continuous waveforms of Chang Island earthquake swarm in Shandong Province from February 9 to August 20,2017.In total,15,286 earthquakes events were detected,which was more than 6 times compared with those in network catalogue and thus reduced the magnitude of completeness from 1.0 to 0.5.Based on the intergrated catalogue of earthquakes,the characteristics of Chang Island earthquake swarm were then analyzed using the Epidemic Type Aftershock Sequences(ETAS)model.The stochastic components in the ETAS model are used as a proxy for possible earthquake triggered by external forces(fluids).The results show that the proportion of earthquakes triggered by external forces of Chang Island swarm increases gradually(from 31.9%to 63.5%)and then decreases.The latter stage of swarm development is mainly affected by the self-excitation of earthquakes,suggesting that the fluids play an important role in the development of the Chang Island swarm.However,the triggering intensity of fluids to microseismicity is divergent in different periods,which may be related to the process of fluid permeation.展开更多
In order to reveal the relationship between water injection in mine wells in the Zigong area and seismicity, we divide the historical earthquakes of ML ≥ 1.2 into 3 phases according to seismicity behavior, and the ET...In order to reveal the relationship between water injection in mine wells in the Zigong area and seismicity, we divide the historical earthquakes of ML ≥ 1.2 into 3 phases according to seismicity behavior, and the ETAS model parameters are then inversed by the POWELL method. The results show that phase 1 and 2, in which there is no water injection, have moderate-to-low ratio of background earthquakes （40 % - 50 % ）, and aftershocks are relatively less for a single earthquake sequence. In phase 3, where there is water injection, the aftershocks triggered by foreshocks dominate （ 93. 1% ）, and background earthquakes amount only to 6. 9 %, less than those of phase 1 and 2. The results conflict with the existing cognition. To resolve this problem, we propose that the occurrence ratio of background earthquakes in unit time, that is, the p value in ETAS model is used as an indicator of water injection triggered earthquakes. Compared to the first two phases, phase 3 has the largest u value, which illustrates that the water injection has an obvious triggering effect on earthquakes of this region.展开更多
耐震时程分析(endurance time analysis,ETA)法作为结构响应分析领域的有效简化方法,基于频域地震动反应谱合成的耐震时程曲线无法准确反映时域的脉冲特性,限制了其在近断层脉冲型地震中的应用。为将ETA法应用到近断层脉冲型地震动作用...耐震时程分析(endurance time analysis,ETA)法作为结构响应分析领域的有效简化方法,基于频域地震动反应谱合成的耐震时程曲线无法准确反映时域的脉冲特性,限制了其在近断层脉冲型地震中的应用。为将ETA法应用到近断层脉冲型地震动作用下斜拉桥动力响应分析中,基于增量动力分析(incremental dynamic analysis,IDA)法研究了不同峰值下脉冲、高频分量对斜拉桥动力响应的贡献程度,构建了考虑脉冲和强度特性的斜拉桥动力响应预测模型,利用ETA法模拟高频分量下的斜拉桥动力响应并结合预测模型,预测了近断层脉冲型地震动下斜拉桥的动力响应。结果表明:建立的预测模型可以精确表达不同强度下高频分量与原始地震动响应之间的定量关系;基于ETA模型和IDA法计算出0.6 g下的平均动力响应最大相对误差不超过10%,具有良好的预测精度。研究成果为高效合理地计算近断层脉冲型地震动下斜拉桥的动力响应提供了技术支撑。展开更多
文摘利用基于时-空传染型余震序列(Epidemic Type Aftershock Sequence,简称ETAS)模型的随机除丛法,重新审视了2008年5月12日汶川M_S8.0地震前可能存在的长期地震活动异常,研究了川滇地区背景地震活动特征,并评估了当前的强震危险状态.对川滇地区1 970年以来的M_L3.0以上的背景地震和丛集地震活动的研究结果表明,该地区地震丛集特征明显、时空分布很不均匀、地震序列常有前震事件.直接将概率值作为地震计数的权重,对地震丛集率空间分布图像分析表明,汶川M_S8.0地震前,龙门山断裂带中南段存在着长期、大范围的地震丛集率低值区,震前该段处于应力闭锁状态.对川滇地区地震从集率低值区内背景地震与全部地震的累积次数、b值和新定义的Δb等统计参量的分析表明,龙日坝与龙门山断裂带具有地震活动的关联性,川滇地区当前的强震潜在危险区可能是巧家地区和汶川M_S8.0地震破裂尚未穿越的龙门山断裂带南段.此外,还发现b值倾向于反映局部应力场变化,而△b能较为敏感地给出更大范围应力场的相对变化.
基金sponsored by the National Key R&D Program of China(2016YFE0109300)the Seismological Science and Technology Spark Program(XH18026Y)+1 种基金Natural Science Foundation of Shandong Province(ZR2017QD014)Key R&D Program of Shandong Province(2016GSF120011)
文摘Influenced by the layout of seismic network and the location of earthquakes,earthquake catalogs are often incomplete;such incompleteness of earthquake catalogue directly affects the analysis of sequence activity characteristics.In this paper,the GPU-acceleration-based g template matching method is used to scan the continuous waveforms of Chang Island earthquake swarm in Shandong Province from February 9 to August 20,2017.In total,15,286 earthquakes events were detected,which was more than 6 times compared with those in network catalogue and thus reduced the magnitude of completeness from 1.0 to 0.5.Based on the intergrated catalogue of earthquakes,the characteristics of Chang Island earthquake swarm were then analyzed using the Epidemic Type Aftershock Sequences(ETAS)model.The stochastic components in the ETAS model are used as a proxy for possible earthquake triggered by external forces(fluids).The results show that the proportion of earthquakes triggered by external forces of Chang Island swarm increases gradually(from 31.9%to 63.5%)and then decreases.The latter stage of swarm development is mainly affected by the self-excitation of earthquakes,suggesting that the fluids play an important role in the development of the Chang Island swarm.However,the triggering intensity of fluids to microseismicity is divergent in different periods,which may be related to the process of fluid permeation.
基金supported by "Study on Strong Earthquake Risk in Southern Region of Longmenshan Fault,Huayingshan Fault and Border Area of Sichuan and Yunnan Provinces",Department of Earthquake Monitoring and Prediction,China Earthquake Administration
文摘In order to reveal the relationship between water injection in mine wells in the Zigong area and seismicity, we divide the historical earthquakes of ML ≥ 1.2 into 3 phases according to seismicity behavior, and the ETAS model parameters are then inversed by the POWELL method. The results show that phase 1 and 2, in which there is no water injection, have moderate-to-low ratio of background earthquakes （40 % - 50 % ）, and aftershocks are relatively less for a single earthquake sequence. In phase 3, where there is water injection, the aftershocks triggered by foreshocks dominate （ 93. 1% ）, and background earthquakes amount only to 6. 9 %, less than those of phase 1 and 2. The results conflict with the existing cognition. To resolve this problem, we propose that the occurrence ratio of background earthquakes in unit time, that is, the p value in ETAS model is used as an indicator of water injection triggered earthquakes. Compared to the first two phases, phase 3 has the largest u value, which illustrates that the water injection has an obvious triggering effect on earthquakes of this region.
