对现今地壳变形资料在地震区划中应用的初步探讨
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摘要
采用汾渭地震带中段1996～2001年时段内的GPS观测数据,计算了地壳运动速度场,处理得到区内各测点相对水平运动矢量。采用均匀弹性体变形模型,计算了变形单元的主应变速率参数;引入地壳变形累积地震矩率的计算方法,探讨了其地震带内地震活动趋势和潜在震源区内大震复发间隔估计的应用问题。结果表明,汾渭地震带中段的地震矩累积速率为4.22×1017Nma,大大高于当前活动期的平均地震矩释放速率,处于地震应变累积阶段,未来地震活动性应比目前有所增强。对定襄潜在震源区和霍州潜在震源区的大震复发间隔估计结果也与采用活断层资料获得的结果相近。说明采用该估算方法具有进一步探讨的价值,特别是对于那些历史地震记录相对短暂或活动构造研究程度较低地区更有实际意义。
The authors collected the available data from 1996 to 2001 of the 40 GPS sites in the middle Fenwei seismic zone. By processing the GPS data, the relative horizontal velocity of each site was achieved, and then the principal strain rates for three selected crustal deforming units was calculated. The authors analyzed the seismic activity trend in 100 years in the middle Fenwei seismic zone and evaluated the earthquake recurrence intervals of two potential earthquake sources by adopting the method of assessing seismic moment accumulation rates using the strain rates of deforming units. The rate of seismic moment accumulation in the middle Fenwei seismic zone is 4.22×10~(17)Nm/a and mach larger than the average seismic moment release rate. This result indicates the seismic activity in the middle Fenwei seismic zone will increase in 100 years. The earthquake recurrence intervals of the Dingxiang and Hozhou potential earthquake sources deduced by strain rates are close to those by geological methods. Therefore, as long as the GPS data is sufficient enough, this method is applicable to analyze the long-time seismic activity trend in a seismic zone,and evaluate the recurrence interval of large earthquakes in potential earthquake sources. Especially for those potential earthquake sources which geological data are not available.
The authors collected the available data from 1996 to 2001 of the 40 GPS sites in the middle Fenwei seismic zone. By processing the GPS data, the relative horizontal velocity of each site was achieved, and then the principal strain rates for three selected crustal deforming units was calculated. The authors analyzed the seismic activity trend in 100 years in the middle Fenwei seismic zone and evaluated the earthquake recurrence intervals of two potential earthquake sources by adopting the method of assessing seismic moment accumulation rates using the strain rates of deforming units. The rate of seismic moment accumulation in the middle Fenwei seismic zone is 4.22×10~(17)Nm/a and mach larger than the average seismic moment release rate. This result indicates the seismic activity in the middle Fenwei seismic zone will increase in 100 years. The earthquake recurrence intervals of the Dingxiang and Hozhou potential earthquake sources deduced by strain rates are close to those by geological methods. Therefore, as long as the GPS data is sufficient enough, this method is applicable to analyze the long-time seismic activity trend in a seismic zone,and evaluate the recurrence interval of large earthquakes in potential earthquake sources. Especially for those potential earthquake sources which geological data are not available.
引文
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WorkingGrouponCaliforniaEarthquakeProbabilities.,1995,SeismichazardsinSouthernCalifornia:Probableearthquake,1994～ 2024.BullSeiSocAmer,85:379～439.
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甘卫军,2001,GPS的地球物理应用———美国加州东部及全美中部地壳变形研究,89～107,北京:中国地震局地质研究所博 士学位论文。
国家地震局《鄂尔多斯周缘活动断裂系》编写组,1988,鄂尔多斯周缘活动断裂系,290～306,北京:地震出版社。
国家地震局,1996,中国地震烈度区划图(1990)概论,129～136,北京:地震出版社。
国家地震局《一九七六年唐山地震》编写组,1987,一九七六年唐山地震,43～45,北京:地震出版社。
江娃利、邓起东、徐锡伟等,2004,1303年山西洪洞8级地震地表破裂带,地震学报,20(4),355～362。
刘 静、汪良谋,1996,运用活断层资料评价汾渭地震带中长期强震危险性,地震学报,18(4),427～436。
徐锡伟、邓起东、韩竹军,1993,霍山山前断裂晚第四纪活动和古地震研究,马宗晋主编,山西临汾地震研究与系统减灾, 136～148,北京:地震出版社。
袁志祥、丁韫玉,1993,汾渭地震带及其渭河地震亚带的中长期地震趋势综合分析,见:国家地震局震害防御司编,中国地 震区划文集,158～163,北京:地震出版社。
Kostrov,V.V.1974,Seismicmomentandenergyofearthquakesandseismicflowofrock,Izv.Acad.Sci.USSR.Phys.SolidEarth1, 23～40.
Molnar,P.,1979,Earthquakerecurrenceintervalsandplatetectonics,Bull.Seis.Soc.Amer.,69,115～123.
Savage,J.C.andR.W.Simpson,1997,Surfacestrainaccumulationandtheseismicmomenttensor,Bull.Seism.SocAm.,87,1345 ～1353.
Word,S.N.,1994,AmultidisciplinaryapproachtoseismichazardinsouthernCalifornia,Bull.Seism.Soc.Am.84,1293～1309.
Word,S.N.,1998,Ontheconsistenceofearthquakemomentrates,geologicalfaultdata,andspacegeodeticstrain:theUnitedStates, Geophys.J.Int.134,172～186.
WorkingGrouponCaliforniaEarthquakeProbabilities.,1995,SeismichazardsinSouthernCalifornia:Probableearthquake,1994～ 2024.BullSeiSocAmer,85:379～439.
WorkingGrouponCaliforniaEarthquakeProbabilities.,1999,EarthquakeProbabilitiesintheSanFranciscoBayRegion:2000to2030— ASummaryofFindings,open filereport99 517ofUSGS.
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