汶川8.0级地震前四川地区地震视应力时空变化特征
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摘要
本文根据Brune模式,在近震源条件下,利用中国数字遥测地震台网观测的波形资料,测定了2000年5月至2008年4月四川地区439次ML≥3.0地震的视应力值,给出了2008年5月12日汶川8.0级地震前四川地区视应力空间分布图象,分析了四川地区、龙门山断裂带以及龙门山断裂带上小震频次高值区视应力随时间变化过程。结果表明:①汶川地震前,视应力较高的地震主要集中在四川南部的川、滇交界地区;②2001—2006年,四川地区视应力随时间的变化表现为突升突降型变化形态,且视应力高值点有逐渐增大的现象,从2007年初至2008年初视应力在较低水平呈缓慢下降,临近汶川地震前有小幅升高变化;③龙门山断裂带上视应力在2004年中至2005年初曾出现过较为明显的、短暂的上升—下降变化过程。而Δσapp值的变化则相对复杂,出现过二次上升—下降变化过程;④龙门山断裂带上小震频次高值区视应力在2003—2005年间,曾出现过二次较为明显的上升—下降变化过程,临震前,视应力出现突然上升。而Δσapp值随时间的变化则主要表现为2003—2004年的上升和其后的下降过程。临近地震发生前,Δσapp值也有一定幅度的上升变化。
On the condition of near-source,the Brune model was employed to determine the apparent stress of 439 earthquakes with ML≥3.0 occurred in Sichuan during May 2000 to April 2008 with seismic waveform data recorded by the regional digital telemetric seismic networks in Sichuan area.The spatial distribution image of the apparent stress in Sichuan before the MS8.0 Wenchuan earthquake on May 12,2008 had been given,and the variation process of the apparent stress with time in Sichuan,the Longmenshan Fault Zone and the dense zone of small earthquakes in the Longmenshan Fault Zone was analyzed.The results were as follows: ① High apparent stress was mainly concentrated in the Sichuan-Yunnan boundary region before the Wenchuan earthquake;② Variation of the apparent stress with time in Sichuan from 2001 to 2006 showed a process of abrupt rise and fall,and the high-value points of the apparent stress increased gradually.The apparent stress declined slowly at a low level from 2007 to the beginning of 2008,and had little increase before the Wenchuan earthquake.③ Apparent stress in Longmenshan Fault Zone showed an obvious increase-decrease process from the midyear of 2004 to the beginning of 2005.The variation of Dsapp value which showed two increase-decrease processes was relatively complex.④ Apparent stress in the dense zone of small earthquakes in the Longmenshan Fault Zone showed two obvious increase-decrease processes from 2003 to 2005,and increased abruptly before the main earthquake.The Dsapp value increased at the beginning and then decreased from 2003 to 2004,and increased at a certain level before the main shock.
On the condition of near-source,the Brune model was employed to determine the apparent stress of 439 earthquakes with ML≥3.0 occurred in Sichuan during May 2000 to April 2008 with seismic waveform data recorded by the regional digital telemetric seismic networks in Sichuan area.The spatial distribution image of the apparent stress in Sichuan before the MS8.0 Wenchuan earthquake on May 12,2008 had been given,and the variation process of the apparent stress with time in Sichuan,the Longmenshan Fault Zone and the dense zone of small earthquakes in the Longmenshan Fault Zone was analyzed.The results were as follows: ① High apparent stress was mainly concentrated in the Sichuan-Yunnan boundary region before the Wenchuan earthquake;② Variation of the apparent stress with time in Sichuan from 2001 to 2006 showed a process of abrupt rise and fall,and the high-value points of the apparent stress increased gradually.The apparent stress declined slowly at a low level from 2007 to the beginning of 2008,and had little increase before the Wenchuan earthquake.③ Apparent stress in Longmenshan Fault Zone showed an obvious increase-decrease process from the midyear of 2004 to the beginning of 2005.The variation of Dsapp value which showed two increase-decrease processes was relatively complex.④ Apparent stress in the dense zone of small earthquakes in the Longmenshan Fault Zone showed two obvious increase-decrease processes from 2003 to 2005,and increased abruptly before the main earthquake.The Dsapp value increased at the beginning and then decreased from 2003 to 2004,and increased at a certain level before the main shock.
引文
[1]张国民,邵志刚,刘桂萍,等.汶川8.0级地震构造成因分析[J].地震,2008,28(1):168-177.
[2]张培震,徐锡伟,闻学泽,等.2008年汶川8.0级地震发震断裂的滑动速率、复发周期和构造成因[J].地球物理学报,2008,51(4):166-172.
[3]万天丰.汶川8级地震的形成机理与中国大陆近期地震概况[J].自然杂志,2008,(3):2-6.
[4]江在森,方颖,武艳强,等.汶川8.0级地震前区域地壳运动与变形动态过程[J].地球物理学报,2009,52(2):505-518.
[5]赵祎喆,吴忠良,蒋长胜,等.用地震资料估计的龙门山断裂带深部形变及其对于汶川地震成因的意义[J].地质学报,2008,82(12):1778-1787.
[6]陈章立,李志雄.严重的挫折重要的启示——汶川8.0级地震引发的对地震预测研究的某些科学思考[J].地震,2008,28(1):182-191.
[7]刘杰,郭铁栓,杨立明,等.汶川8.0级地震前地震趋势分析意见的回顾[J].地震,2008,28(1):40-52.
[8]梅世蓉,薛艳,宋治平.汶川8.0级与昆仑山口西8.1级地震前地震活动异常特征与启示[J].地震,2008,28(1):1-21.
[9]张致伟,程万正,阮强,等.汶川8.0级地震前龙门山断裂带的地震活动性和构造应力场特征[J].地震学报,2009,31(2):117-127.
[10]Huang Q.Seismicity changes prior to the MS8.0 Wenchuan earthquake in Sichuan,China[J].Geo-phys Res Lett,2008,35,L23308,doi:10.1029/2008GL 036270.
[11]陈运泰.视应力[A].中国地震局监测预报司.地震参数——数字地震学在地震预测中的应用[C].北京:地震出版社:2003.54.
[12]Frank S,Carl K.Variations of apparent stresses and stress drops prior to the earthquake of 6May1984(mb=5.8)in the Adak seismic zone[J].Bull Seism Soc Am,1984,74(6):2 577-2 592.
[13]程万正,陈学忠,乔慧珍.四川地震辐射能量和视应力研究[J].地球物理学进展,2006,21(3):692-699.
[14]乔慧珍,程万正,陈学忠.安宁河—则木河断裂带地震视应力研究[J].地震研究,2006,29(2):125-130.
[15]刘红桂,刘杰,丁页岭,等.地震视应力在云南地震序列中的前兆特征[J].地震学报,2006,28(5):462-471.
[16]刘红桂,王培玲,杨彩霞,等.地震视应力在地震预测中的应用[J].地震学报,2007,29(4):437-445.
[17]秦嘉政,钱晓东.云南地区地震视应力的时间和空间分布研究[J].地震学报,2006,28(3):221-229.
[18]陈学忠,王小平,王林瑛,等.地震视应力用于震后趋势快速判定的可能性[J].国际地震动态,2003,295(7):1-4.
[19]陈学忠,李艳娥.2006年7月4日河北文安MS5.1地震前震中周围地区小震视应力随时间的变化[J].中国地震,2007,23(4):327-336.
[20]陈学忠,李艳娥,郭祥云.河北文安MS5.1地震前首都圈及邻区震源动力学参数时空变化特征[J].地震,2011,31(4):15-24.
[21]吴晶,顾瑾萍.甘肃景泰MS5.9地震前后小地震视应力计算讨论[J].地震,2004,24(1):171-175.
[22]王琼,陈学忠,王林瑛.岫岩地震序列视应力变化及其预测意义[J].地震,2005,25(2):91-97.
[23]孙燕萍,史勇军.新疆两次强震前后地震视应力变化[J].地震地磁观测于研究,2007,28(4):20-28.
[24]易志刚,宋茉,杨选辉,等.地震视应力在中国大陆西部强震趋势预测中的应用[J].地震,2007,27(4):110-120.
[25]Wyss M.Apparent stresses of earthquakes on ridges compared to apparent stresses of earthquakes intrenches[J].Geophys J R astr Soc,1970,19:479-484.
[26]Archuleta R,Cranswick E,Mueller C,et al.Source parameters of the 1980Mammoth Lakes,Cali-fornia,earthquakes sequence[J].J Geophys Res,1982,87:4 595-4 607.
[2]张培震,徐锡伟,闻学泽,等.2008年汶川8.0级地震发震断裂的滑动速率、复发周期和构造成因[J].地球物理学报,2008,51(4):166-172.
[3]万天丰.汶川8级地震的形成机理与中国大陆近期地震概况[J].自然杂志,2008,(3):2-6.
[4]江在森,方颖,武艳强,等.汶川8.0级地震前区域地壳运动与变形动态过程[J].地球物理学报,2009,52(2):505-518.
[5]赵祎喆,吴忠良,蒋长胜,等.用地震资料估计的龙门山断裂带深部形变及其对于汶川地震成因的意义[J].地质学报,2008,82(12):1778-1787.
[6]陈章立,李志雄.严重的挫折重要的启示——汶川8.0级地震引发的对地震预测研究的某些科学思考[J].地震,2008,28(1):182-191.
[7]刘杰,郭铁栓,杨立明,等.汶川8.0级地震前地震趋势分析意见的回顾[J].地震,2008,28(1):40-52.
[8]梅世蓉,薛艳,宋治平.汶川8.0级与昆仑山口西8.1级地震前地震活动异常特征与启示[J].地震,2008,28(1):1-21.
[9]张致伟,程万正,阮强,等.汶川8.0级地震前龙门山断裂带的地震活动性和构造应力场特征[J].地震学报,2009,31(2):117-127.
[10]Huang Q.Seismicity changes prior to the MS8.0 Wenchuan earthquake in Sichuan,China[J].Geo-phys Res Lett,2008,35,L23308,doi:10.1029/2008GL 036270.
[11]陈运泰.视应力[A].中国地震局监测预报司.地震参数——数字地震学在地震预测中的应用[C].北京:地震出版社:2003.54.
[12]Frank S,Carl K.Variations of apparent stresses and stress drops prior to the earthquake of 6May1984(mb=5.8)in the Adak seismic zone[J].Bull Seism Soc Am,1984,74(6):2 577-2 592.
[13]程万正,陈学忠,乔慧珍.四川地震辐射能量和视应力研究[J].地球物理学进展,2006,21(3):692-699.
[14]乔慧珍,程万正,陈学忠.安宁河—则木河断裂带地震视应力研究[J].地震研究,2006,29(2):125-130.
[15]刘红桂,刘杰,丁页岭,等.地震视应力在云南地震序列中的前兆特征[J].地震学报,2006,28(5):462-471.
[16]刘红桂,王培玲,杨彩霞,等.地震视应力在地震预测中的应用[J].地震学报,2007,29(4):437-445.
[17]秦嘉政,钱晓东.云南地区地震视应力的时间和空间分布研究[J].地震学报,2006,28(3):221-229.
[18]陈学忠,王小平,王林瑛,等.地震视应力用于震后趋势快速判定的可能性[J].国际地震动态,2003,295(7):1-4.
[19]陈学忠,李艳娥.2006年7月4日河北文安MS5.1地震前震中周围地区小震视应力随时间的变化[J].中国地震,2007,23(4):327-336.
[20]陈学忠,李艳娥,郭祥云.河北文安MS5.1地震前首都圈及邻区震源动力学参数时空变化特征[J].地震,2011,31(4):15-24.
[21]吴晶,顾瑾萍.甘肃景泰MS5.9地震前后小地震视应力计算讨论[J].地震,2004,24(1):171-175.
[22]王琼,陈学忠,王林瑛.岫岩地震序列视应力变化及其预测意义[J].地震,2005,25(2):91-97.
[23]孙燕萍,史勇军.新疆两次强震前后地震视应力变化[J].地震地磁观测于研究,2007,28(4):20-28.
[24]易志刚,宋茉,杨选辉,等.地震视应力在中国大陆西部强震趋势预测中的应用[J].地震,2007,27(4):110-120.
[25]Wyss M.Apparent stresses of earthquakes on ridges compared to apparent stresses of earthquakes intrenches[J].Geophys J R astr Soc,1970,19:479-484.
[26]Archuleta R,Cranswick E,Mueller C,et al.Source parameters of the 1980Mammoth Lakes,Cali-fornia,earthquakes sequence[J].J Geophys Res,1982,87:4 595-4 607.
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