地震前兆特征与岩样剪切应变率异常数值模拟
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摘要
利用拉格朗日元法(FLAC)模拟了岩样的宏观力学行为、剪切应变率异常及演化。在峰值强度岩石的本 构模型分别取线弹性模型及应变软化模型的条件下,得到如下结论:1)在弹性阶段之后,应力 时步曲线具有一定的 周期性,与地震复发的周期性类似。在加载过程中,形变场由均匀逐渐向不均匀转变,最终形成交叉的剪切带网 络。被该网络所包围的试样中部可视为背景空区,在空区之外,地震群比较活跃。在应变硬化阶段,可以从未来震 源观测到前兆 剪切应变率异常条带。2)在中期阶段之后,空区内地震活动的开始增强明显要比空区外地震活动增 强晚,地震的迁移是由外向内。3)短期阶段则相反:在硬化阶段,剪切带内外的剪切应变率的差别不很显著,试样 处于相对平静状态。在软化阶段,若采用剪切应变率最大的位置作为震源,可确定震源在试样的中部。源兆和场 兆都集中在老断层上。
Anomaly in shear strain rate (SSR) and its evolution as well as mechanical behavior of rock in biaxial plane strain were modeled by use of FLAC. In elastic stage, the adopted constitutive relation was linear elastic; however, in strain-softening stage, a composite Mohr-Coulomb criterion with tension cuff-off and linear post-peak constitutive relation was used. Beyond the elastic stage, the periodicity in the stress-timestep curve is similar to that in earthquake activities. In the process of loading,deformation field was observed to transit from within specimen uniform to nonuniform and finally network of shear bands (SB) was formed.Part in the middle of specimen which is surrounded by SB, can be seen as a seismic gap. Outside the gap, earthquake swarm is relatively active. In the strain-hardening stage,an effective precursor can be observed from the future earthquake source. Earthquake activities in the gap are obviously later than those in SB. After middle-term stage, migration of earthquake activities is from the SB to the gap, while it is opposite in short-term stage. In strain-hardening stage, no obvious difference in SSR was found inside SB and outside. In strain-softening stage, if zone with highest SSR is considered to be the source, then it lies in the middle of specimen. The field and source precursors appear in old fault belts.
Anomaly in shear strain rate (SSR) and its evolution as well as mechanical behavior of rock in biaxial plane strain were modeled by use of FLAC. In elastic stage, the adopted constitutive relation was linear elastic; however, in strain-softening stage, a composite Mohr-Coulomb criterion with tension cuff-off and linear post-peak constitutive relation was used. Beyond the elastic stage, the periodicity in the stress-timestep curve is similar to that in earthquake activities. In the process of loading,deformation field was observed to transit from within specimen uniform to nonuniform and finally network of shear bands (SB) was formed.Part in the middle of specimen which is surrounded by SB, can be seen as a seismic gap. Outside the gap, earthquake swarm is relatively active. In the strain-hardening stage,an effective precursor can be observed from the future earthquake source. Earthquake activities in the gap are obviously later than those in SB. After middle-term stage, migration of earthquake activities is from the SB to the gap, while it is opposite in short-term stage. In strain-hardening stage, no obvious difference in SSR was found inside SB and outside. In strain-softening stage, if zone with highest SSR is considered to be the source, then it lies in the middle of specimen. The field and source precursors appear in old fault belts.
引文
1 梅世蓉.地震前兆场物理模式与前兆时空分布机制研究(三)──强震孕育时地震活动与地壳形变场异常及机制[J].地震学报,1996,18(2):170～178.
1 MeiShirong.Studyonthephysicalmodelofearthquake precursorfieldsandthemechanismofprecursors'time spacedistribution(Ⅲ)──anomaliesofseismicityand crustaldeformationandtheirmechanismswhenastrong earthquakeisinpreparation[J].ActaSeismologicaSini ca,1996,18(2):170-178.(inChinese)
2 吴云,施顺英.孕震断层的形变模型及其失稳判据[J].地壳形变与地震,1996,16(4):9～14.
2 WuYunandShiShunying.Deformationmodelofseis mogenicfaultanditscriterionofinstability[J].CrustalDeformationandEarthquake,1996,16(4):9-14.(inChinese)
3 吴云,孙建中,乔学军,等.GPS揭示的现今地壳运动与 地震前兆特征[J].大地测量与地球动力学,2003,23(3):14～20.
3 WuYun,SunJianzhong,QiaoXuejunetal.Characteris ticsofcurrentmovementandseismicprecursorsrevealed byGPSsurvey[J].JournalofGeodesyandGeodynam ics,2003,23(3):14-20.(inChinese)
4 王双绪,江在森,陈文胜等.景泰5.9级地震的断层形变异常及中短期预报[J].地震学报,2001,23(2):151～158.
4 WangShuangxu,JiangZaisen,ChenWensheng,etal.Faultdeformationanomalyandmediumandshort term predictionofJingtaiMs5.9earthquake[J].ActaSeis mologicaSinica,2001,23(2):151-158.(inChinese)
5 杨少敏,王琪.昆仑山8.1级地震前中国大陆的构造应变背景[J].大地测量与地球动力学,2003,23(3):61～65.
5 YangShominandWangQi.Tectonicstrainbackground inChinacontinentbeforeKunlunmountainMs8.1earth quake[J].JournalofGeodesyandGeodynamics,2003,23(3):61-65.(inChinese)
6 谭凯,王琪,申重阳.用大地测量数据反演2001年昆仑山地震[J].大地测量与地球动力学,2004,24(3):47～50.
6 TanKai,WangQiandShenChongyang.Usinggeodetic datatoinverseco seismicdislocationof2001Kunlun earthquake[J].JournalofGeodesyandGeodynamics,2004,24(3):47-50.(inChinese)
7 王学滨,赵扬锋,代树红,等.地震块体模型的共轭剪切破裂带数值模拟[J].防灾减灾工程学报,2004,24(2):119～125.
7 WangXuebin,ZhaoYangfeng,DaiShuhong,etal.Nu mericalsimulationofconjugateshearfracturebandsfor seismicblockmodel[J].JournalofDisasterPrevention andMitigationEngineering,2004,24(2):119-125.(inChinese)
8 陈立德.强震中短期前兆异常的共性特征[J].地震,2000,20(2):7～13.
8 ChenLide.Commonfeaturesofmediumandshort term precursoryanomaliesbeforestrongearthquakes[J].Earthquake,2000,20(2):7-13.(inChinese)
9 范燕,车兆宏.华北地区震前断层水平异常活动特征[J].地震,2002,22(2):88～93.
9 FanYanandCheZhaohong.Characteristicsoffaulthori zontalanomalousmovementbeforeearthquakes[J].Earthquake,2002,22(2):88-93.(inChinese)
10 彭美凤,林世敏,林树.台湾海峡7.3级地震及其震后地震趋势研究[J].地震,1997,17(2):184～194.
10 PengMeifeng,LinShiminandLinShu.StudyoftheTaiwanstraitsearthquakeMs7.3andthepost earth quaketendency[J].Earthquake,1997,17(2):184-194.(inChinese)
11 张秋文,张培震,王乘,等.中国大陆若干地震构造带的地震准周期丛复发行为[J].大地测量 与地球动力学,2002,22(1):56～62.
11 ZhangQiuwen,ZhangPerzhen,WangChen,etal.Quasi periodicallyclusteringearthquakerecurrenceinsome seismotectonicbeltsofChinaContinent[J].JournalofGeodesyandGeodynamics,2002,22(1):56-62.(inChinese)
12 任俊杰,陈虹.东昆仑断裂带地震复发周期与发震概率研究[J].大地测量与地球动力学,2004,24(3):51～56.
12 RenJunjieandChenHong.Researchonrecurrencein tervalandprobabilityofmediumandlargeearthquakeat earternKunlunfaultzone[J].JournalofGeodesyandGeodynamics,2004,24(3):51-56.(inChinese)
13 焦明若,张国民.地震中短期前兆某些特征的研究[J].地震,2000,20(3):29～36.
13 JiaoMingruoandZhangGuomin.Researchoncharac teristicsofmedium short termseismicprecursors[J].Earthquake,2000,20(3):29-36.(inChinese)
14 牛安福,张晶,延旭东等.西南地区强震前后地壳变形异常强度场特征研究[J].地震,2002,22(1):61～69.
14 NiuAnfu,ZhangJing,YanXudong,etal.Studyon thecharacteristicsofanomalydeformationfieldaround strongearthquakesinSouthwestChinaarea[J].Earth quake,2002,22(1):61-69.(inChinese)
15 张国民.我国地震监测预报研究的主要科学进展[J].地震,2002,22(1):1～8.
15 ZhangGuomin.Themainscienceadvanceofearthquake monitoringandpredictioninChina[J].Earthquake,2002,22(1):1-8.(inchinese)
16 宋治平,徐平,薛艳.华北地区震群活动的阶段性特征[J].地震,2001,21(1):47～52.
16 SongZhiping,XuePingandXuYan.Stage by stage characteristicsofearthquakeswarmactivityintheNorthChinaregion[J].Earthquake,2001,21(1):47-52.(inChinese)
17 范燕,车兆宏.南北地震带北段及其两侧断层现今活动性[J].地震,2001,21(2):87～93.
17 FanYanandCheZhaohong.Thefaultactivityinrecent timealongnorthernsectionofNorthSouthseismicbelt anditsbothsides[J].Earthquake,2001,21(2):87-93.(inChinese)
18 刘蒲雄,陈永恩,高伟,等.大震前地震活动图像演变及中期向短期过渡的地震活动性标志[J].地震,1997,17(2):113～125.
18 LiuPuxiong,ChenYong’en,GaoWei,etal.Evolu tionofseismicitypatternsbeforestrongearthquakesand short termindicatorofseismicprecursors[J].Earth quake,1997,17(2):113125.(inChinese)
19 张国民,李丽.强震成组孕育、成组发生过程中相互影响的研究[J].地震,1997,17(3):221～231.
19 ZhangGuominandLiLi.Ongroupfeaturesofthe strongearthquakepreparationandoccurrenceandtheir correlation[J].Earthquake,1997,17(3):221-231.(inChinese)
20 高维明,任利生.环渤海地震危险区的初步研究[J].地震,1997,17(3):249～256.
20 GaoWeimingandRenLisheng.Preliminarystudyon theriskareaofearthquakearoundBohaisea[J].Earth quake,1997,17(3):249-256.(inChinese)
1 MeiShirong.Studyonthephysicalmodelofearthquake precursorfieldsandthemechanismofprecursors'time spacedistribution(Ⅲ)──anomaliesofseismicityand crustaldeformationandtheirmechanismswhenastrong earthquakeisinpreparation[J].ActaSeismologicaSini ca,1996,18(2):170-178.(inChinese)
2 吴云,施顺英.孕震断层的形变模型及其失稳判据[J].地壳形变与地震,1996,16(4):9～14.
2 WuYunandShiShunying.Deformationmodelofseis mogenicfaultanditscriterionofinstability[J].CrustalDeformationandEarthquake,1996,16(4):9-14.(inChinese)
3 吴云,孙建中,乔学军,等.GPS揭示的现今地壳运动与 地震前兆特征[J].大地测量与地球动力学,2003,23(3):14～20.
3 WuYun,SunJianzhong,QiaoXuejunetal.Characteris ticsofcurrentmovementandseismicprecursorsrevealed byGPSsurvey[J].JournalofGeodesyandGeodynam ics,2003,23(3):14-20.(inChinese)
4 王双绪,江在森,陈文胜等.景泰5.9级地震的断层形变异常及中短期预报[J].地震学报,2001,23(2):151～158.
4 WangShuangxu,JiangZaisen,ChenWensheng,etal.Faultdeformationanomalyandmediumandshort term predictionofJingtaiMs5.9earthquake[J].ActaSeis mologicaSinica,2001,23(2):151-158.(inChinese)
5 杨少敏,王琪.昆仑山8.1级地震前中国大陆的构造应变背景[J].大地测量与地球动力学,2003,23(3):61～65.
5 YangShominandWangQi.Tectonicstrainbackground inChinacontinentbeforeKunlunmountainMs8.1earth quake[J].JournalofGeodesyandGeodynamics,2003,23(3):61-65.(inChinese)
6 谭凯,王琪,申重阳.用大地测量数据反演2001年昆仑山地震[J].大地测量与地球动力学,2004,24(3):47～50.
6 TanKai,WangQiandShenChongyang.Usinggeodetic datatoinverseco seismicdislocationof2001Kunlun earthquake[J].JournalofGeodesyandGeodynamics,2004,24(3):47-50.(inChinese)
7 王学滨,赵扬锋,代树红,等.地震块体模型的共轭剪切破裂带数值模拟[J].防灾减灾工程学报,2004,24(2):119～125.
7 WangXuebin,ZhaoYangfeng,DaiShuhong,etal.Nu mericalsimulationofconjugateshearfracturebandsfor seismicblockmodel[J].JournalofDisasterPrevention andMitigationEngineering,2004,24(2):119-125.(inChinese)
8 陈立德.强震中短期前兆异常的共性特征[J].地震,2000,20(2):7～13.
8 ChenLide.Commonfeaturesofmediumandshort term precursoryanomaliesbeforestrongearthquakes[J].Earthquake,2000,20(2):7-13.(inChinese)
9 范燕,车兆宏.华北地区震前断层水平异常活动特征[J].地震,2002,22(2):88～93.
9 FanYanandCheZhaohong.Characteristicsoffaulthori zontalanomalousmovementbeforeearthquakes[J].Earthquake,2002,22(2):88-93.(inChinese)
10 彭美凤,林世敏,林树.台湾海峡7.3级地震及其震后地震趋势研究[J].地震,1997,17(2):184～194.
10 PengMeifeng,LinShiminandLinShu.StudyoftheTaiwanstraitsearthquakeMs7.3andthepost earth quaketendency[J].Earthquake,1997,17(2):184-194.(inChinese)
11 张秋文,张培震,王乘,等.中国大陆若干地震构造带的地震准周期丛复发行为[J].大地测量 与地球动力学,2002,22(1):56～62.
11 ZhangQiuwen,ZhangPerzhen,WangChen,etal.Quasi periodicallyclusteringearthquakerecurrenceinsome seismotectonicbeltsofChinaContinent[J].JournalofGeodesyandGeodynamics,2002,22(1):56-62.(inChinese)
12 任俊杰,陈虹.东昆仑断裂带地震复发周期与发震概率研究[J].大地测量与地球动力学,2004,24(3):51～56.
12 RenJunjieandChenHong.Researchonrecurrencein tervalandprobabilityofmediumandlargeearthquakeat earternKunlunfaultzone[J].JournalofGeodesyandGeodynamics,2004,24(3):51-56.(inChinese)
13 焦明若,张国民.地震中短期前兆某些特征的研究[J].地震,2000,20(3):29～36.
13 JiaoMingruoandZhangGuomin.Researchoncharac teristicsofmedium short termseismicprecursors[J].Earthquake,2000,20(3):29-36.(inChinese)
14 牛安福,张晶,延旭东等.西南地区强震前后地壳变形异常强度场特征研究[J].地震,2002,22(1):61～69.
14 NiuAnfu,ZhangJing,YanXudong,etal.Studyon thecharacteristicsofanomalydeformationfieldaround strongearthquakesinSouthwestChinaarea[J].Earth quake,2002,22(1):61-69.(inChinese)
15 张国民.我国地震监测预报研究的主要科学进展[J].地震,2002,22(1):1～8.
15 ZhangGuomin.Themainscienceadvanceofearthquake monitoringandpredictioninChina[J].Earthquake,2002,22(1):1-8.(inchinese)
16 宋治平,徐平,薛艳.华北地区震群活动的阶段性特征[J].地震,2001,21(1):47～52.
16 SongZhiping,XuePingandXuYan.Stage by stage characteristicsofearthquakeswarmactivityintheNorthChinaregion[J].Earthquake,2001,21(1):47-52.(inChinese)
17 范燕,车兆宏.南北地震带北段及其两侧断层现今活动性[J].地震,2001,21(2):87～93.
17 FanYanandCheZhaohong.Thefaultactivityinrecent timealongnorthernsectionofNorthSouthseismicbelt anditsbothsides[J].Earthquake,2001,21(2):87-93.(inChinese)
18 刘蒲雄,陈永恩,高伟,等.大震前地震活动图像演变及中期向短期过渡的地震活动性标志[J].地震,1997,17(2):113～125.
18 LiuPuxiong,ChenYong’en,GaoWei,etal.Evolu tionofseismicitypatternsbeforestrongearthquakesand short termindicatorofseismicprecursors[J].Earth quake,1997,17(2):113125.(inChinese)
19 张国民,李丽.强震成组孕育、成组发生过程中相互影响的研究[J].地震,1997,17(3):221～231.
19 ZhangGuominandLiLi.Ongroupfeaturesofthe strongearthquakepreparationandoccurrenceandtheir correlation[J].Earthquake,1997,17(3):221-231.(inChinese)
20 高维明,任利生.环渤海地震危险区的初步研究[J].地震,1997,17(3):249～256.
20 GaoWeimingandRenLisheng.Preliminarystudyon theriskareaofearthquakearoundBohaisea[J].Earth quake,1997,17(3):249-256.(inChinese)
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