基于震例的前兆统计特征分析
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摘要
依据《中国震例》(1966—1999年)收录的185次震例的2500多条地震活动及前兆异常资料,研究了各学科平均异常数量、空间分布范围、异常时间等统计特征及其与主震震级的关系.结果显示,地震学、形变、流体异常数量相对较多,且平均异常数量随震级增大有加速增长的趋势,前兆平均异常数量随震级的增加尤其明显.从地震学各方法来看,频次、空区、b值、条带等方法提供的异常数占总异常数量的1/2.前兆异常分布范围数倍于地震破裂尺度,形变、流体异常平均震中距随主震震级大体上呈线性增加.各类异常出现时间与未来主震震级定性正相关,即地震越大,出现的时间越早.研究结果还显示,当目标震级不高时(例如5—6级地震),现有预测方法及手段可能不足以提供年时间尺度的地震预测依据.同时,流体和电磁等前兆学科在3年地震大形势预测研究,甚至是在年度预测研究中所能够发挥的作用,可能也不如人们所期望的那么大.本文较多震例的平均统计结果显示,随主震的临近,前兆异常空间分布向震中附近集中、收缩,同时异常数量明显增加.这一现象始于年尺度的中短期阶段而非更短时间的临震,同时本文亦未能够检测到前兆异常空间分布向外围明显的扩散过程.最后对《中国震例》前兆异常选取范围的合理性及对本文统计结果的可能影响进行了初步讨论.
Based on 185 earthquake cases with about 2500 anomalies collected in《Earthquake Cases in China》 from 1966 to 1999,the average numbers,spatial distribution ranges,average periods of the precursors,as well as the relationship between these quantities and the mainshock magnitudes,have been examined.The result shows that the seismicity,deformation and underground fluid can offer more evidences for earthquake prediction,and their average numbers of precursors increase exponentially with the mainshock magnitude,especially for deformation and fluid precursors.For seismicity,the precursor numbers of earthquake frequency,seismic gap,b value and seismic belt are about 50% of total precursor numbers.The spatial distribution range of precursors is several times of fracture size of the mainshock.Average epicentral distances of deformation and fluid precursors increase linearly with the mainshock magnitude.The anomaly periods are proportional to the magnitude of the mainshock:the larger the mainshock,the longer the anomaly period.The result also indicates that the current existing methods or observation items could not offer enough scientific evidences for yearly earthquake prediction,if the expecting mainshock is not large enough(for example,for MS5—6 earthquakes).At the same time,the effects of fluid and electromagnetic precursors on long-or middle-term(several years)earthquake prediction,even on yearly earthquake prediction,may not be so powerful as we expected.With the approach of the mainshock,the precursor distribution concentrated to the epicenter region gradually and the number of precursors increases quickly.This tendency began from middle-or short-term phase within about one year or more before the mainshock,but not in the immediate-term in a very short time period.Further more,the obvious diffusing process of the precursor distribution proposed by other authors could not be identified in this paper.Finally,the selected spatial range for precursors in《Earthquake Cases in China》and its potential influence on the conclusion of this paper have also been discussed.
Based on 185 earthquake cases with about 2500 anomalies collected in《Earthquake Cases in China》 from 1966 to 1999,the average numbers,spatial distribution ranges,average periods of the precursors,as well as the relationship between these quantities and the mainshock magnitudes,have been examined.The result shows that the seismicity,deformation and underground fluid can offer more evidences for earthquake prediction,and their average numbers of precursors increase exponentially with the mainshock magnitude,especially for deformation and fluid precursors.For seismicity,the precursor numbers of earthquake frequency,seismic gap,b value and seismic belt are about 50% of total precursor numbers.The spatial distribution range of precursors is several times of fracture size of the mainshock.Average epicentral distances of deformation and fluid precursors increase linearly with the mainshock magnitude.The anomaly periods are proportional to the magnitude of the mainshock:the larger the mainshock,the longer the anomaly period.The result also indicates that the current existing methods or observation items could not offer enough scientific evidences for yearly earthquake prediction,if the expecting mainshock is not large enough(for example,for MS5—6 earthquakes).At the same time,the effects of fluid and electromagnetic precursors on long-or middle-term(several years)earthquake prediction,even on yearly earthquake prediction,may not be so powerful as we expected.With the approach of the mainshock,the precursor distribution concentrated to the epicenter region gradually and the number of precursors increases quickly.This tendency began from middle-or short-term phase within about one year or more before the mainshock,but not in the immediate-term in a very short time period.Further more,the obvious diffusing process of the precursor distribution proposed by other authors could not be identified in this paper.Finally,the selected spatial range for precursors in《Earthquake Cases in China》and its potential influence on the conclusion of this paper have also been discussed.
引文
陈棋福(主编).2002a.中国震例(1992—1994)[M].北京:地震出版社:1--428.
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蒋海昆,苗青壮,董祥,吴琼,黎明晓,宋金.2009.中国大陆7级强震前中小地震应变释放特征[J].地震(待发表).
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中国地震局.2007.震例总结规范(DB/T24-2007)[S].北京:地震出版社:4.
中国地震局监测预报司.2005.华北地区强地震短期前兆特征与预测方法研究[M].北京:地震出版社:178--190.
Bowman D D,Ouillon G,Sammis C G,Sornette A,Sornette D.1998.An observational test of the critical earthquakeconcept[J].J Geophys Res,103:24359--24372.
Bufe C G,Varnes DJ.1993.Predictive modeling of the seismic cycle of the greater San Francisco Bay region[J].J Geo-phys Res,98:9871--9883.
JaumèR,Sykes L.1999.Evolvingtowards a critical point:Areviewof accelerating seismic moment/energy release priorto large and great earthquake[J].Pure Appl Geophys,155:279--306.
Keilis-Borok VI,Malinovskaya L N.1964.One regularity in the occurrence of strong earthquakes[J].J Geophys Res,69(14):3019--3024.
Keilis-Borok VI,Soloviev A A.2003.Nonlinear Dynamics ofthe Lithosphere and Earthquake Prediction[M].Heidel-berg:Springer-Verlag:355.
Papazachos C B,Karakaisis G F,Scordilis E M,Papazachos B C.2005.Global observational properties of the criticalearthquake model[J].Bull Seism Soc Amer,95:1841--1855.
Press F,Allen C.1995.Patterns of seismic release in the southern California region[J].J Geophys Res,100(B4):6421--6430.
Utsu T A.1961.Statistical study on the occurrence of aftershocks[J].Geophys Mag,30:521--605.
Varnes DJ.1989.Predicting earthquakes by analyzing accelerating precursory seismic activity[J].Pure Appl Geophys,130:661--686.
陈棋福(主编).2002b.中国震例(1995—1996)[M].北京:地震出版社:1--488.
陈棋福(主编).2002c.中国震例(1997—1999)[M].北京:地震出版社:1--468.
蒋海昆,苗青壮,董祥,吴琼,黎明晓,宋金.2009.中国大陆7级强震前中小地震应变释放特征[J].地震(待发表).
梅世蓉,冯德益,张国民,朱岳清,高旭,张肇诚.1993.中国地震预报概论[M].北京:地震出版社:250--256.
吴开统,焦远碧,吕培苓.1990.地震序列概论[M].北京:北京大学出版社:138--148.
张肇诚(主编).1988.中国震例(1966—1975)[M].北京:地震出版社:1--294.
张肇诚(主编).1990a.中国震例(1976—1980)[M].北京:地震出版社:1--421.
张肇诚(主编).1990b.中国震例(1981—1985)[M].北京:地震出版社:1--294.
张肇诚(主编).1999.中国震例(1986—1988)[M].北京:地震出版社:1--394.
张肇诚(主编).2000.中国震例(1989—1991)[M].北京:地震出版社:1--453.
中国地震局.2007.震例总结规范(DB/T24-2007)[S].北京:地震出版社:4.
中国地震局监测预报司.2005.华北地区强地震短期前兆特征与预测方法研究[M].北京:地震出版社:178--190.
Bowman D D,Ouillon G,Sammis C G,Sornette A,Sornette D.1998.An observational test of the critical earthquakeconcept[J].J Geophys Res,103:24359--24372.
Bufe C G,Varnes DJ.1993.Predictive modeling of the seismic cycle of the greater San Francisco Bay region[J].J Geo-phys Res,98:9871--9883.
JaumèR,Sykes L.1999.Evolvingtowards a critical point:Areviewof accelerating seismic moment/energy release priorto large and great earthquake[J].Pure Appl Geophys,155:279--306.
Keilis-Borok VI,Malinovskaya L N.1964.One regularity in the occurrence of strong earthquakes[J].J Geophys Res,69(14):3019--3024.
Keilis-Borok VI,Soloviev A A.2003.Nonlinear Dynamics ofthe Lithosphere and Earthquake Prediction[M].Heidel-berg:Springer-Verlag:355.
Papazachos C B,Karakaisis G F,Scordilis E M,Papazachos B C.2005.Global observational properties of the criticalearthquake model[J].Bull Seism Soc Amer,95:1841--1855.
Press F,Allen C.1995.Patterns of seismic release in the southern California region[J].J Geophys Res,100(B4):6421--6430.
Utsu T A.1961.Statistical study on the occurrence of aftershocks[J].Geophys Mag,30:521--605.
Varnes DJ.1989.Predicting earthquakes by analyzing accelerating precursory seismic activity[J].Pure Appl Geophys,130:661--686.
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