由地震活动参数分析安宁河—则木河断裂带的现今活动习性及地震危险性
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摘要
利用区域台网地震资料 ,分析了川西安宁河—则木河断裂带不同段落的现今活动习性 ,进而鉴别潜在大地震危险的断裂段 .文中由异常低b值的分布圈绘出凹凸体 ,发展和应用了由多个地震活动参数值的组合判定断裂分段活动习性的方法 ,尝试了利用凹凸体段的震级 频度关系参数估计特征地震的平均复发间隔 .结果表明 ,该研究断裂带存在 5个不同现今活动习性的段落 .其中 ,安宁河断裂的冕宁—西昌段属于高应力下的闭锁段 ,其核心部分为一较大尺度的凹凸体 ;则木河断裂的西昌—普格段则表现为低应力下的微弱活动状态 .重新定位的震源深度分布 ,显示出上述闭锁段和微弱活动段的断层面轮廓 .冕宁—西昌段是未来大地震的潜在危险段 .该段从最晚的 195 2年 6 .7级地震起算 ,至未来特征地震的平均复发间隔估值为 5 5～ 6 7年 ,未来地震的震级估值为 7.0～ 7.5 .本研究也初步表明 ,同一断裂段的活动习性可随时间动态演变
Using the data of regional seismic network, this paper analyzes the current faulting behaviors of different segments of the Anninghe Zemuhe fault zone, western Sichuan, and identifies the likely risky segments for potential large earthquakes. The authors map the probable asperities from the abnormally low b value distribution, develop and employ a method for identifying current faulting behaviors of individual fault segment from the combinations of multiple seismicity parameter values, and make an effort to estimate the average recurrence intervals of characteristic earthquakes by using the parameters of magnitude frequency relationship of the asperity segment. The result suggests that the studied fault zone contains 5 segments of different current faulting behaviors. Among them, the Mianning Xichang segment of the Anninghe fault has been locked under high stress, its central part is probably an asperity with a relatively large scale. The Xichang Puge segment of the Zemuhe fault displays very low seismicity under low stress. Both the locked segment and the low seismicity segment can be outlined on the across profile of relocated hypocenter depths. The Mianning Xichang segment is identified to be the one with potential large earthquake risk, for which the average recurrence interval between the latest M =6.7 earthquake, 1952 and the next characteristic event is estimated to be 55 to 67 years, and the magnitude of the potential earthquake between 7.0 and 7.5. Also, it has been preliminarily suggested that for a certain fault segment, the faulting behaviors may change and evolve with time gradually.
Using the data of regional seismic network, this paper analyzes the current faulting behaviors of different segments of the Anninghe Zemuhe fault zone, western Sichuan, and identifies the likely risky segments for potential large earthquakes. The authors map the probable asperities from the abnormally low b value distribution, develop and employ a method for identifying current faulting behaviors of individual fault segment from the combinations of multiple seismicity parameter values, and make an effort to estimate the average recurrence intervals of characteristic earthquakes by using the parameters of magnitude frequency relationship of the asperity segment. The result suggests that the studied fault zone contains 5 segments of different current faulting behaviors. Among them, the Mianning Xichang segment of the Anninghe fault has been locked under high stress, its central part is probably an asperity with a relatively large scale. The Xichang Puge segment of the Zemuhe fault displays very low seismicity under low stress. Both the locked segment and the low seismicity segment can be outlined on the across profile of relocated hypocenter depths. The Mianning Xichang segment is identified to be the one with potential large earthquake risk, for which the average recurrence interval between the latest M =6.7 earthquake, 1952 and the next characteristic event is estimated to be 55 to 67 years, and the magnitude of the potential earthquake between 7.0 and 7.5. Also, it has been preliminarily suggested that for a certain fault segment, the faulting behaviors may change and evolve with time gradually.
引文
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UrbancicTI ,TrifuCI ,LongJM ,etal.1992.Space timecorrelationofbvalueswithstressrelease[J].PureApplGeo phys,139:449～462
WellsDL ,CoppersmithKJ .1994.Newempiricalrelationshipsamongmagnitude,rupturelength,rupturewidth,rupturearea,andsurfacedisplacement[J].BullSeismSocAmer,84:974～1002
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WyssM ,SchorlemmerD ,WiemerS .2000.Mappingasperitiesbyminimaoflocalrecurrencetime:SanJacintoElsinorefaultzones[J].JGeophysRes,105(B4):7829～7844
国家地震局震害防御司编.1995.中国历史强震目录[M].北京:地震出版社,1～514
闻学泽.2000.四川西部鲜水河—安宁河—则木河断裂带的地震破裂分段特征[J].地震地质,22(3):239～249
闻学泽,杜平山,龙德雄.2000.安宁河断裂带小相岭段古地震的新证据及最晚事件的年代[J].地震地质,22(1):1～8
闻学泽,徐锡伟,郑荣章,等.2001.磨西断裂的晚第四纪活动性与大地震复发间隔[A].见:卢演俦等主编.新构造与环境[M].北京:地震出版社,255～266
徐锡伟,闻学泽,郑荣章.2003.川滇地区活动块体最新构造变动样式及其动力来源[J].中国科学,D辑,33(增刊):151～162
易桂喜,闻学泽.2000a.时间震级可预报模式在南北地震带分段危险性评估中的应用[J].地震,20(1):71～79
易桂喜,闻学泽.2000b.活动断裂带的整体地震复发行为及其与分段地震复发行为的关系[J].地震学报,22(5):527～537
张培震,邓起东,张国民,等.2003.中国大陆的强震活动与活动地块[J].中国科学,D辑,33(增刊):12～20
中国地震局震害防御司编.1999.中国近代地震目录[M ].北京:中国科学技术出版社,1～637
AkiK .1984.Asperities,barriers,characteristicearthquakesandstrongmotionprediction[J].JGeophysRes,89(B7):5867～5872
ChenP ,ChenH .1989.Scalinglawanditsapplicationstoearthquakestatisticalrelations[J].Tectonophysics,166:53～72
MolnarP .1979.Earthquakerecurrenceintervalsandplatetectonics[J].BullSeismSocAmer,69:115～133
PapazachosBC .1992.Atime andmagnitudepredictablemodelforgenerationofshallowearthquakesintheAegeanarea[J].PureApplGeophys,138(2):287～308
PruggerAF ,GendzwillDJ.1988.Microearthquakelocation:anonlinearapproachthatmakesuseofasimplexsteppingproce dure[J].BullSeismSocAmer,78(2):799～815
ScholzCH .1968.Thefrequency magnituderelationtomicrofracturinginrockanditsrelationtoearthquakes[J].BullSeismSocAmer,58:399～415
ShimazakiK ,NakataT .1980.Time predictablerecurrenceoflargeearthquakes[J].GeophysResLett,7:279～282
UrbancicTI ,TrifuCI ,LongJM ,etal.1992.Space timecorrelationofbvalueswithstressrelease[J].PureApplGeo phys,139:449～462
WellsDL ,CoppersmithKJ .1994.Newempiricalrelationshipsamongmagnitude,rupturelength,rupturewidth,rupturearea,andsurfacedisplacement[J].BullSeismSocAmer,84:974～1002
WiemerS ,WyssM .1997.Mappingthefrequency magnitudedistributioninasperities:Animprovedtechniquetocalculatere currencetimes?[J].JGeophysRes,102(B7):15115～15128
WyssM ,SchorlemmerD ,WiemerS .2000.Mappingasperitiesbyminimaoflocalrecurrencetime:SanJacintoElsinorefaultzones[J].JGeophysRes,105(B4):7829～7844
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