西秦岭北缘断裂带断层气浓度空间分布特征与强震危险性分析
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摘要
以西秦岭北缘断裂带不同段断层气Hg、Rn浓度空间分布特征分析为基础、通过对历史大震背景、现今地震活动影像以及b值空间分布特征的对比分析,从地球化学的角度,对西秦岭北缘断裂带不同段落的活动习性进行深入探讨,并识别出该断裂带潜在大震危险区段。可为未来地震趋势判定及震情跟踪提供重要的基础资料。
The Northern Xiqinling fault zone is located at the northeast edge of the Tibet Plateau, which is one of the largest active faults in northern region of the plateau and the key earthquake hazard area in Gansu province.During the most recent decade,many large earthquakes have occurred in succession near the rim of Bayan Har Block,including the Mani MS 7.9earthquake on the western border,the KunLun MS 8.1earthquake on the northwestern border,the Wenchuan MS 8.0and Lushan MS 7.0earthquakes on the eastern border,the Yushu MS 7.1earthquake on the southern border,and the MinXian MS 6.6 earthquake on the northeast border.The spatial and temporal variation characteristics of these seismic events show that the Bayan Har Block has entered a new period of seismic activity,which has enhanced the earthquake risk of the adjacent areas including the Qaidam and Qilian blocks.Therefore,continued research of seismic hazards and background fields of the Northern Xiqinling fault zone are necessary. In this study,we surveyed the spatial distribution characteristics of fault gas concentration on the Northern Xiqinling fault zone.The hazard area was predicted according to the spatial concentration anomaly values of Hg and Rn soil gas combining with the seismotectonic background and spatiotemporal evolution characteristics of large historical and recent earthquakes.We conclude that the tectonic background of large earthquakes at the F1 and F4 segments of the Western QinLing fault zone includes few small earthquakes,a lengthy period since the most recent large earthquake,and a low gas concentration of Hg and Rn.In comparison,the F3 segment of the Northern Xiqinling fault zone showed frequent small earthquakes,a short period since the most recent large earthquake,and a high gas concentration of Hg and Rn.This research can provide vital background information for earthquake prediction.
The Northern Xiqinling fault zone is located at the northeast edge of the Tibet Plateau, which is one of the largest active faults in northern region of the plateau and the key earthquake hazard area in Gansu province.During the most recent decade,many large earthquakes have occurred in succession near the rim of Bayan Har Block,including the Mani MS 7.9earthquake on the western border,the KunLun MS 8.1earthquake on the northwestern border,the Wenchuan MS 8.0and Lushan MS 7.0earthquakes on the eastern border,the Yushu MS 7.1earthquake on the southern border,and the MinXian MS 6.6 earthquake on the northeast border.The spatial and temporal variation characteristics of these seismic events show that the Bayan Har Block has entered a new period of seismic activity,which has enhanced the earthquake risk of the adjacent areas including the Qaidam and Qilian blocks.Therefore,continued research of seismic hazards and background fields of the Northern Xiqinling fault zone are necessary. In this study,we surveyed the spatial distribution characteristics of fault gas concentration on the Northern Xiqinling fault zone.The hazard area was predicted according to the spatial concentration anomaly values of Hg and Rn soil gas combining with the seismotectonic background and spatiotemporal evolution characteristics of large historical and recent earthquakes.We conclude that the tectonic background of large earthquakes at the F1 and F4 segments of the Western QinLing fault zone includes few small earthquakes,a lengthy period since the most recent large earthquake,and a low gas concentration of Hg and Rn.In comparison,the F3 segment of the Northern Xiqinling fault zone showed frequent small earthquakes,a short period since the most recent large earthquake,and a high gas concentration of Hg and Rn.This research can provide vital background information for earthquake prediction.
引文
[1]万永革,沈正康,盛书中,等.2008年汶川大地震对周围断层的影响[J].地震学报,2009,31(2):128-139.WAN Yong-ge,SHEN Zheng-kang,SHENG Shu-zhong,et al.The Influence of 2008Wenchuan Earthquake on Surrounding Faults[J].Acta Seismologica Sinica,2009,31(2):128-139.(in Chienes)
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[6]石雅镠,张必敖.秦岭北缘大断裂断层气与地震危险性[J].西北地震学报,1990,12(2):22-26.SHI Ya-liu,ZHANG Bi-ao.The Fault Gases of Large Faults on the Northern Fringe of Qinling Mountain and Its Earthquake Risk[J].Northwester Seismological Journal,1990,12(2):22-26.(in Chienes)
[7]Pizzino L,Burrato P,Quattrocchi F,et al.Geochemical Signatures of Large Active Faults:The Example of the 5February1783,Calabrian Earthquake(Southern Italy)[J].Journal of Seismology,2004,(8):363-380.
[8]赵振燊.甘东南地震重点危险区主要活动断裂带断层气地球化学特征[D].兰州:中国地震局兰州地震研究所,2012:7-34.ZHAO Zhen-shen.The Geochemical Characteristics on Fault Gas of Main Active Faults in the Danger Earthquake Area of GanNan and LongNan[D].Lanzhou:Lanzhou Institute of Seismology,CEA,2012:7-34.(in Chienes)
[9]赵振燊,张慧,苏鹤军.玛曲断裂带土壤气汞、氡地球化学特征[J].西北地震学报,2011,33(4),376-379.ZHAO Zhen-shen,ZHANG Hui,SU He-jun.The Geochemical Features of Mercury and Radon on Maqu Active Fault[J].Northwestern Seismological Jounal,2011,33(4),376-379.(in Chienes)
[10]K Ioannides,C Papachristodoulou,K Stamoulis,et al.Soil Gas Radon:A Tool for Exploring Active Fault Zones[J].Applied Radiation and Isotopes,2003,(59):205-213.
[11]Miesch A T.Estimation of the Geochemical Threshold and Its Statistical Signifcance[J].J.Geochem.Explor,1981,(16):49-76.
[12]Wiemer S,WyssM.Mapping the Frequency-magnitude Distribution in Asperities:An Improved Technique to Calculate Recurrence Times[J].J.Geophys.Res.,1997,102(B7):15115-15128.
[13]Wyss M,Schorlemmer D,Wiemer S.Mapping Asperities by Minima of Local Recurrence Time:San Jacinto-Elsinore Fault Zones[J].J.Geophys.Res.,2000,105(B4):7829-7844.
[14]易桂喜,龙锋,苏有锦.四川及邻区强震前地震活动性参数的变化特征[J].四川地震,2007,(4):5-9.YI Gui-xi,LONG Feng,SU You-jing.Variation Characteristics of Seismicity Parameters before Strong Earthquakes in Sichuan and Its Neighboring Regions[J].Earthquake Research in Sichuan,2007,(4):5-9.(in Chienes)
[15]易桂喜,闻学泽,王思维,等.由地震活动参数分析龙门山-岷山断裂带的现今活动习性与强震危险性[J].中国地震,2006,22(2):117-125.YI Gui-xi,WEN Xue-ze,WANG Si-wei,et al.Study on Fault Sliding Behaviors and Strong earthquake Risk of the Longmenshan-Minshan Fault Zones from Current Seismicity Parameters[J].Earthquake Research in China,2006,22(2):117-125.(in Chienes)
[16]Jochen Woessner,Stefan Wiemer.Assessing the Quality of Earthquake Catalogues:Estimating the Magnitude of Completeness and Its Uncertainty[J].Bulletin of the Seismological Society of America,2005,95(2):684-698.
[17]Stefan Wiemer,Max Wyss.Minimum Magnitude of Completeness in Earthquake Catalogs:Examples from Alaska,the Western United States,and Japan[J].Bulletin of the Seismological Society of America,2000,90(4):859-869.
[18]Aki K.Asperities,Barriers,Characteristic Earthquakes and Strong Motion Prediction[J].J.Geophys.Res.,1984,89(B7):5867-5872.
[19]Scholz C H.The Frequency-magnitude Relation Tomicrofracturing in Rock and Itsrelation to Earthquakes[J].Bull.Seism.Soc.Am.,1968,58:399-415.
[2]李传友,张培震,张剑玺,等.西秦岭北缘断裂带黄香沟段晚第四纪活动表现与滑动速率[J].第四纪研究,2007,27(1):54-63.LI Chuan-you,ZHANG Pei-zhen,ZHANG Jian-xi,et al.Late-quaternary Activity and Slip Rate of The Western Qinling Fault Zone at HuangXiangGou[J].Quaternary Sciences,2007,27(1):54-63.(in Chienes)
[3]曹娟娟,刘百篪,闻学泽.西秦岭北缘断裂带特征地震平均复发间隔的确定和地震危险性评价[J].地震研究,2011,26(4):372-381.CAO Juan-juan,LIUu Bai-chi,WEN Xue-ze.Determination of the Average Recurrence Intervals of Characteristic Earthquakes and Estimate of Earthquake Risk on Northern Xiqinling Faults[J].Journal of Seismological Research,2011,26(4):372-381.(in Chienes)
[4]李延兴,胡新康.GPS测量所揭示的西秦岭北缘断裂带现今活动特征[J].中国地震,1999,15(4):295-302.LI Yan-xing,HU Xin-kang.Current Activity Characteristics of the Fault Zone Along the North Margin of West Qinling Mountain Revealed by GPS Measurements[J].Earthquake Research in China,1999,15(4):295-302.(in Chienes)
[5]康来迅,张新基,石雅镠.西秦岭北缘断裂带地震危险段的研究[J].华南地震,1999,19(1):60-65.KANG Lai-xun,ZHANG Xin-ji,SHI Ya-liu.A Study on the Earthquake Risk Segments of the North Fault Zone in West Qinling Mountain[J].South China Journal of Seismology,1999,19(1):60-65.(in Chienes)
[6]石雅镠,张必敖.秦岭北缘大断裂断层气与地震危险性[J].西北地震学报,1990,12(2):22-26.SHI Ya-liu,ZHANG Bi-ao.The Fault Gases of Large Faults on the Northern Fringe of Qinling Mountain and Its Earthquake Risk[J].Northwester Seismological Journal,1990,12(2):22-26.(in Chienes)
[7]Pizzino L,Burrato P,Quattrocchi F,et al.Geochemical Signatures of Large Active Faults:The Example of the 5February1783,Calabrian Earthquake(Southern Italy)[J].Journal of Seismology,2004,(8):363-380.
[8]赵振燊.甘东南地震重点危险区主要活动断裂带断层气地球化学特征[D].兰州:中国地震局兰州地震研究所,2012:7-34.ZHAO Zhen-shen.The Geochemical Characteristics on Fault Gas of Main Active Faults in the Danger Earthquake Area of GanNan and LongNan[D].Lanzhou:Lanzhou Institute of Seismology,CEA,2012:7-34.(in Chienes)
[9]赵振燊,张慧,苏鹤军.玛曲断裂带土壤气汞、氡地球化学特征[J].西北地震学报,2011,33(4),376-379.ZHAO Zhen-shen,ZHANG Hui,SU He-jun.The Geochemical Features of Mercury and Radon on Maqu Active Fault[J].Northwestern Seismological Jounal,2011,33(4),376-379.(in Chienes)
[10]K Ioannides,C Papachristodoulou,K Stamoulis,et al.Soil Gas Radon:A Tool for Exploring Active Fault Zones[J].Applied Radiation and Isotopes,2003,(59):205-213.
[11]Miesch A T.Estimation of the Geochemical Threshold and Its Statistical Signifcance[J].J.Geochem.Explor,1981,(16):49-76.
[12]Wiemer S,WyssM.Mapping the Frequency-magnitude Distribution in Asperities:An Improved Technique to Calculate Recurrence Times[J].J.Geophys.Res.,1997,102(B7):15115-15128.
[13]Wyss M,Schorlemmer D,Wiemer S.Mapping Asperities by Minima of Local Recurrence Time:San Jacinto-Elsinore Fault Zones[J].J.Geophys.Res.,2000,105(B4):7829-7844.
[14]易桂喜,龙锋,苏有锦.四川及邻区强震前地震活动性参数的变化特征[J].四川地震,2007,(4):5-9.YI Gui-xi,LONG Feng,SU You-jing.Variation Characteristics of Seismicity Parameters before Strong Earthquakes in Sichuan and Its Neighboring Regions[J].Earthquake Research in Sichuan,2007,(4):5-9.(in Chienes)
[15]易桂喜,闻学泽,王思维,等.由地震活动参数分析龙门山-岷山断裂带的现今活动习性与强震危险性[J].中国地震,2006,22(2):117-125.YI Gui-xi,WEN Xue-ze,WANG Si-wei,et al.Study on Fault Sliding Behaviors and Strong earthquake Risk of the Longmenshan-Minshan Fault Zones from Current Seismicity Parameters[J].Earthquake Research in China,2006,22(2):117-125.(in Chienes)
[16]Jochen Woessner,Stefan Wiemer.Assessing the Quality of Earthquake Catalogues:Estimating the Magnitude of Completeness and Its Uncertainty[J].Bulletin of the Seismological Society of America,2005,95(2):684-698.
[17]Stefan Wiemer,Max Wyss.Minimum Magnitude of Completeness in Earthquake Catalogs:Examples from Alaska,the Western United States,and Japan[J].Bulletin of the Seismological Society of America,2000,90(4):859-869.
[18]Aki K.Asperities,Barriers,Characteristic Earthquakes and Strong Motion Prediction[J].J.Geophys.Res.,1984,89(B7):5867-5872.
[19]Scholz C H.The Frequency-magnitude Relation Tomicrofracturing in Rock and Itsrelation to Earthquakes[J].Bull.Seism.Soc.Am.,1968,58:399-415.
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