青海祁连M_S5.2地震微震检测与目录完备性研究
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摘要
利用模板匹配方法对2015年11月23日青海省祁连县M_S5.2地震进行遗漏地震检测研究,由于主震后短时间内目录中遗漏事件较多,故对主震后1天的连续波形进行检测。主震后1天内青海测震台网记录到的余震个数(包括单台)共62个,选取主震后M_L1.0以上余震30个作为模板事件,通过匹配滤波的方式扫描出遗漏地震31个,约为台网目录给出的0.5倍。基于包络差峰值振幅与震级的线性关系估测检测事件的震级参数,最后将检测后的余震目录与台网余震目录在主震后1天内的最小完备震级进行对比分析,结果发现检测后最小完备震级从M_L1.2降到了M_L0.7,得到青海测震台网在祁连地区最小完整性震级为M_L0.7。
This paper used a template matching technique to detect missing earthquakes of the Qilian, Qinghai M_S5.2 earthquake that occurred on November 23, 2015. In existing catalogs, aftershock sequence data, especially from the short time after the main shock, are usually huge so we detected continual waveforms one day after the mainshock. In that day, the seismic network recorded 62 aftershocks, including single-station earthquakes. In this study, we chose 30 M_L>1.0 aftershocks as the templates, and finally found 31 missing earthquakes after detection, which was about 0.5 times the number given by the network catalog. According to the linear fitting relationship between frequency envelope difference amplitude and magnitude, we estimated the magnitude of detected events. We then compared the minimum magnitude of completeness(M_C) before and after detection within one day of mainshock, and found that the minimum magnitude of completeness was reduced from M_L1.2 to M_L0.7, showing that the minimum magnitude of completeness in the Qilian area of the Qinghai Seismic Network was about M_L0.7. In addition, the b value of seismicity decreased slightly after the detection, and the results showed that the b value decreased markedly within a short time after the mainshock. Using the template matching method can effectively reduce the number of loss events caused by the earthquake coda wave interference, and improve the capability of seismic detection. The b value of further accurate calculations of earthquake aftershocks can help us better track earthquake activity.
This paper used a template matching technique to detect missing earthquakes of the Qilian, Qinghai M_S5.2 earthquake that occurred on November 23, 2015. In existing catalogs, aftershock sequence data, especially from the short time after the main shock, are usually huge so we detected continual waveforms one day after the mainshock. In that day, the seismic network recorded 62 aftershocks, including single-station earthquakes. In this study, we chose 30 M_L>1.0 aftershocks as the templates, and finally found 31 missing earthquakes after detection, which was about 0.5 times the number given by the network catalog. According to the linear fitting relationship between frequency envelope difference amplitude and magnitude, we estimated the magnitude of detected events. We then compared the minimum magnitude of completeness(M_C) before and after detection within one day of mainshock, and found that the minimum magnitude of completeness was reduced from M_L1.2 to M_L0.7, showing that the minimum magnitude of completeness in the Qilian area of the Qinghai Seismic Network was about M_L0.7. In addition, the b value of seismicity decreased slightly after the detection, and the results showed that the b value decreased markedly within a short time after the mainshock. Using the template matching method can effectively reduce the number of loss events caused by the earthquake coda wave interference, and improve the capability of seismic detection. The b value of further accurate calculations of earthquake aftershocks can help us better track earthquake activity.
引文
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[15] 谭毅培,曹井泉,陈继锋,等.2013年甘肃岷县漳县MS6.6地震余震序列时域衰减特征分析[J].地球物理学报,2015,58(9):3222-3231.TAN Yipei,CAO Jingquan,CHEN Jifeng,et al.Temporal Decay Characteristics of the Aftershock Sequence of the 2013 Minxian—Zhangxian,Gansu,MS6.6 Earthquake.[J].Chinese Journal of Geophys.2015,58(9):3222-3231.
[16] SCHAFF D P.Semiempirical Statistics of Correlation-detector Performance[J].Bulletin of the Seismological Society of America,2008,98(3):1495-1507.
[17] 冯建刚,蒋长胜,韩立波,等.甘肃测震台网监测能力及地震目录完整性分析[J].地震学报,2012,34(5):646-658.FENG Jian'gang,JIANG Changsheng,HAN Libo,et al.Analysis on the Monitoring Capability of Seismic Networks and Completeness of Earthquake Catalogues in Gansuregion[J] Acta Seismologica Sinica,2012,34(5):646-658.
[18] GUTENBERG B,RICHTER C F.Frequency of Earthquakes in California[J].Bulletin of the Seismological Society of America,1944,34(4):185-188.
[19] MOGI K.Study of Elastic Shocks Caused by the Fracture of Heterogeneous Materials and Its Relations to Earthquake Phenomena[J].1962.
[19] 尹欣欣,杨立明,赵林林,等.青海门源MS6.4地震微震检测与目录完备性研究[J].大地测量与地球动力学,2018,38(7):760-764,770.YIN Xinxin,YANG Liming,ZHAO Linlin,et al.Missing Earthquakes Detection and Completeness of Earthquake Catalogues of the 2016 Menyuan,Qinghai,MS6.4 Earthquake[J].Journal of Geodesy and Geodynamics,2018,38(7):760-764,770.
[2] 张诚.地震分析基础[M].北京:地震出版社,1986.ZHANG Cheng.Foundation of Seismic Analysis[M].Beijing:Seismological Press,1986.
[3] 邹立晔.地震震相分析与测量的进展[J].国际地震动态,2004(10):1-8.ZOU Liye.Advances in Seismic Facies Analysis and Measurement[J].Recent Developments in World Seismology,2004(10):1-8.
[4] GIBBONS S J,RINGDAL F.The Detection of Low Magnitude Seismic Events Using Array-based Waveform Correlation[J].Geophysical Journal International,2006,165(1):149-166.
[5] PENG Z.ZHAO P.Migration of Early Aftershocks Following the 2004 Parkfield Earthquake[J].Nature Geoscience,2009,2(12),877-881.
[6] MENG X,PENG Z,HARDEBECK J L.Seismicity around Parkfield Correlates with Static Shear Stress Changes Following the 2003 MW6.5 San Simeon earthquake[J].Journal of Geophysical Research Solid Earth,2013,118(7):3576-3591.
[7] ZHANG M,WEN L.An Effective Method for Small Event Detection:Match and Locate (ML)[J].Geophysical Journal International,2015,200(3):1523-1537.
[8] 郭安宁,郭增建,任栋,等.2013年甘肃岷县—漳县MS6.6级地震及非传统方法的回顾性预测讨论[J].华南地震,2016,36(2):56-59.GUO Anning,GUO Zengjian,REN Dong,et al.Retrospective Discussion of Prediction by Using Non-traditional Methods for the 2013 Minxian—Zhangxian MS6.6 Earthquake in Gansu[J].South China Journal of Seismology,2016,36(2):56-59.
[9] 谭毅培,陈继锋,曹井泉,等.2013年甘肃岷县—漳县MS6.6地震余震序列目录完备性研究——基于对单台记录地震事件震中与震级的估计[J].地震学报,2015,37(5):806-819.TAN Yipei,CHEN Jifeng,CAO Jingquan,et al.2015.Catalogue Completeness Analysis on Aftershock Sequence of the 2013 Minxian—Zhangxian,Gansu,MS6.6 Earthquake Based on Location and Magnitude Estimation of Single-Station Earthquake Events[J]Acta Seismologica Sinica,2015,37(5):806-819.
[10] 尹欣欣,杨立明,陈继锋,等.甘肃地区一维速度模型计算研究[J].地震工程学报,2017,39(1):154-159.YIN Xinxin,YANG Liming,CHEN Jifeng,et al.Study on the One Dimensional Velocity Model in Gansu Area[J].China Earthquake Engineering Journal,2017,39(1):154-159.
[11] 李少华,王彦宾,梁子斌,等.甘肃东南部地壳速度结构的区域地震波形反演[J].地球物理学报,2012,55(4):1186-1197.LI Shaohua,WANG Yanbin,LIANG Zibin,et al.Crustal Structure in Southeastern Gansu from Regional Seismic Waveform Inversion[J].Chinese J Geophys,2012,55(4):1186-1197.
[12] 谭毅培,邓莉,曹井泉,等.2015年河北滦县震群发震机理分析[J].地球物理学报,2016,59(11):4113-4125.TAN Yipei,DENG Li,CAO Jingquan,et al.Seismological Mechanism Analysis of 2015 Luanxian Swarm,Hebei Province[J].Chinese J Geophys,2016,59(11):4113-4125.
[13] PENG Z,VIDALE J E,ISHII M,et al.Seismicity Rate Immediately before and after Main Shock Rupture from High-frequency Waveforms in Japan[J].Journal of Geophysical Research,2007,112(B3):485-493.
[14] WANG J,SCHWEITZER J,TILMANN F,et al.Application of the Multichannel Wiener Filter to Regional Event Detection Using NORSAR Seismic-Array Data[J].Bulletin of the Seismological Society of America,2011,101(6):2887-2896.
[15] 谭毅培,曹井泉,陈继锋,等.2013年甘肃岷县漳县MS6.6地震余震序列时域衰减特征分析[J].地球物理学报,2015,58(9):3222-3231.TAN Yipei,CAO Jingquan,CHEN Jifeng,et al.Temporal Decay Characteristics of the Aftershock Sequence of the 2013 Minxian—Zhangxian,Gansu,MS6.6 Earthquake.[J].Chinese Journal of Geophys.2015,58(9):3222-3231.
[16] SCHAFF D P.Semiempirical Statistics of Correlation-detector Performance[J].Bulletin of the Seismological Society of America,2008,98(3):1495-1507.
[17] 冯建刚,蒋长胜,韩立波,等.甘肃测震台网监测能力及地震目录完整性分析[J].地震学报,2012,34(5):646-658.FENG Jian'gang,JIANG Changsheng,HAN Libo,et al.Analysis on the Monitoring Capability of Seismic Networks and Completeness of Earthquake Catalogues in Gansuregion[J] Acta Seismologica Sinica,2012,34(5):646-658.
[18] GUTENBERG B,RICHTER C F.Frequency of Earthquakes in California[J].Bulletin of the Seismological Society of America,1944,34(4):185-188.
[19] MOGI K.Study of Elastic Shocks Caused by the Fracture of Heterogeneous Materials and Its Relations to Earthquake Phenomena[J].1962.
[19] 尹欣欣,杨立明,赵林林,等.青海门源MS6.4地震微震检测与目录完备性研究[J].大地测量与地球动力学,2018,38(7):760-764,770.YIN Xinxin,YANG Liming,ZHAO Linlin,et al.Missing Earthquakes Detection and Completeness of Earthquake Catalogues of the 2016 Menyuan,Qinghai,MS6.4 Earthquake[J].Journal of Geodesy and Geodynamics,2018,38(7):760-764,770.