强地震前水汽中长期异常变化特征研究
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摘要
以川西及其邻近地区为例,研究了在强震孕育中长期阶段水汽含量的时空动态特征。通过对2008年汶川8.0级地震、1976年松潘强震群和2010年玉树7.1级地震的分析,发现在川西及其邻近地区的强地震孕育过程中,水汽含量异常频度会出现先下降,然后快速上升的现象。下降开始时间较早,出现在震前10a以上,持续9a以上,属中长期异常信息;而快速上升则发生在震前4a内,属中短期异常表现。地震前水汽含量异常的原因可能是由于岩层中裂隙、孔隙的开合、地下流体的运动和地热能的变化,影响地面温度和潜热交换的分布所致。
The spatial-temporal variations of atmospheric water vapor in western Sichuan Province and its vicinity during the mid-and long-term earthquake preparation process are studied.The MS 8.0 Wenchuan earthquake in 2008,the Songpan-Pingwu earthquake sequence in 1976 and the Yushu MS 7.1 earthquake in 2010 are selected as cases of the study regions.The result shows the frequency of atmospheric water vapor anomalies will decrease at first,then increase quickly during the mid-and long-term process of strong earthquake.The decreasing of the frequency of atmospheric water vapor anomalies begins relatively early,mostly over 10 years before earthquake and will last more than 9 years,which is considered as mid-and long-term precursor.The rapid increase appears 4 years before earthquake,as a kind of mid-and short-term precursor.The frequency of atmospheric water vapor anomalies over epicentral region of Wenchuan earthquake began to decline slowly 18 years before the earthquake and continued for 15 years,then increased rapidly 2 years before the earthquake.The atmospheric water vapor anomalies in the epicenter area changed from lowest frequency to high frequency 1 year before the earthquake,then the event occurred.It continued to increase until 2009 then resumed to normal state.14 years before Songpan-Pingwu earthquake,the frequency of atmospheric water vapor anomalies over the epicenter region began declining and it continued for 9 years,and then increased 4 years before the event.The anomalies in the epicenter region changed from lowest frequency in 1971 to high frequency in 1973,and reached the highest in 1976,and then the main shock happened.After the earthquake,it resumed to normal state.Similarly to the above two cases,there had been atmospheric water vapor anomalies before the MS 7.1 Yushu earthquake in 2010,the frequency of anomalies declined from 1997 to 2008 when the lowest value was reached.It increased quickly in 2009 till the event occurred in 2010.The atmospheric water vapor anomalies over epicentral region may be due to the opening-closing movement of pores and fractures in the rock layer before the earthquake,resulting in the migration of underground fluid and underground heat energy,and then causing the change of the surface temperature and surface latent heat flux.During the mid-and long-term process of earthquake preparation,the rate of latent heat exchange decreases due to the reduction of the hot water vapor from underground caused by the closing of pore and fracture when the crustal rocks undergo compression deformation,so the frequency of atmospheric water vapor anomalies begins to decline.While during the mid-and short-term process of earthquake preparation,the accelerating of the crustal rocks deformation and the expanding of micro fractures will lead to increasing the hot water vapor from underground,accelerating the latent heat exchange,and quickly increasing the frequency of atmospheric water vapor anomalies.Analyses of the above three cases prove preliminarily that this assumption is reasonable.
The spatial-temporal variations of atmospheric water vapor in western Sichuan Province and its vicinity during the mid-and long-term earthquake preparation process are studied.The MS 8.0 Wenchuan earthquake in 2008,the Songpan-Pingwu earthquake sequence in 1976 and the Yushu MS 7.1 earthquake in 2010 are selected as cases of the study regions.The result shows the frequency of atmospheric water vapor anomalies will decrease at first,then increase quickly during the mid-and long-term process of strong earthquake.The decreasing of the frequency of atmospheric water vapor anomalies begins relatively early,mostly over 10 years before earthquake and will last more than 9 years,which is considered as mid-and long-term precursor.The rapid increase appears 4 years before earthquake,as a kind of mid-and short-term precursor.The frequency of atmospheric water vapor anomalies over epicentral region of Wenchuan earthquake began to decline slowly 18 years before the earthquake and continued for 15 years,then increased rapidly 2 years before the earthquake.The atmospheric water vapor anomalies in the epicenter area changed from lowest frequency to high frequency 1 year before the earthquake,then the event occurred.It continued to increase until 2009 then resumed to normal state.14 years before Songpan-Pingwu earthquake,the frequency of atmospheric water vapor anomalies over the epicenter region began declining and it continued for 9 years,and then increased 4 years before the event.The anomalies in the epicenter region changed from lowest frequency in 1971 to high frequency in 1973,and reached the highest in 1976,and then the main shock happened.After the earthquake,it resumed to normal state.Similarly to the above two cases,there had been atmospheric water vapor anomalies before the MS 7.1 Yushu earthquake in 2010,the frequency of anomalies declined from 1997 to 2008 when the lowest value was reached.It increased quickly in 2009 till the event occurred in 2010.The atmospheric water vapor anomalies over epicentral region may be due to the opening-closing movement of pores and fractures in the rock layer before the earthquake,resulting in the migration of underground fluid and underground heat energy,and then causing the change of the surface temperature and surface latent heat flux.During the mid-and long-term process of earthquake preparation,the rate of latent heat exchange decreases due to the reduction of the hot water vapor from underground caused by the closing of pore and fracture when the crustal rocks undergo compression deformation,so the frequency of atmospheric water vapor anomalies begins to decline.While during the mid-and short-term process of earthquake preparation,the accelerating of the crustal rocks deformation and the expanding of micro fractures will lead to increasing the hot water vapor from underground,accelerating the latent heat exchange,and quickly increasing the frequency of atmospheric water vapor anomalies.Analyses of the above three cases prove preliminarily that this assumption is reasonable.
引文
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Kistler R,Kalnay E.2000.The NCEP/NCAR50-year reanalysis[J].Bull Am Met Soc,82:247—267.
Singh R,Simon B,Joshi P C.2001.Estimation of surface latent heat fluxes from IRSP4/MSMR satellite data[J].Proc Indian Acad Sci(Earth Planet Science),110(3):231—238.
陈梅花,邓志辉,王煜,等.2007.2005年九江5.7级地震前后地表热动态初步研究[J].地震地质,29(3):617—626.CHEN Mei-hua,DENG Zhi-hui,WANG Yu,et al.2008.Preliminary study on the dynamic variations of the surface ther-mal flux before and after the MS5.7earthquake of2005in Jiujiang city,Jiangxi Province[J].Earthquake Re-search in China,(22)2:175—184.
邓起东,冉勇康,杨晓平,等.2007.中国活动构造图(1:400万)[Z].北京:地震出版社.DENG Qi-dong,RAN Yong-kang,YANG Xiao-ping,et al.2007.Map of Active Tectonic in China[Z].Seismological Press,Beijing(in Chinese).
郭德勇,韩德馨,冯志亮.1998.围压下构造煤的孔隙度和渗透率特征实验研究[J].煤田地质与勘探,26(4):31—34.GUO De-yong,HAN De-xin,FENG Zhi-liang.1998.Experimental study on the porosity and permeability of disturbed coal under confined pressure[J].Coal Geology&Exploration,26(4):31—34(in Chinese).
郝锦绮,冯锐,周建国,等.2002.岩石破裂过程中电阻率变化机理的探讨[J].地球物理学报,45(3):426—434.HAO Jin-qi,FENG Rui,ZHOU Jian-guo,et al.2002.Study on the mechanism of resistivity changes during rock crack-ing[J].Chinese Journal of Geophysics,45(3):426—434(in Chinese).
杨竹转.2004.地震引起的地下水位变化及其机理初步研究[D]:[学位论文].北京:中国地震局地质研究所.YANG Zhu-zhuan.2004.Water-level changes induced by earthquakes and preliminary study of their mechanism[D].Ph M thesis.Institute of Geology,China Earthquake Administration,Beijing(in Chinese).
岳汉,张竹琪,陈永顺.2008.相邻左旋走滑和逆冲断层之间的相互作用:1976年松潘震群[J].科学通报,53(13):1582—1588.YUE Han.ZHANG Zhu-qi,CHEN Yong-shun.2008.Interaction between adjacent left-lateral strike-slip faults and thrust faults:The1976Songpan earthquake sequence[J].Chinese Science Bulletin,53(16):2520—2526.
严研,邓志辉,陈梅花.2008.基于双温度差分双源模型的遥感方法反演四川汶川地区潜热通量[J].地震地质,30(4):1085—1094.YAN Yan,DENG Zhi-hui,CHEN Mei-hua.2008.Retrieving the latent heat flux of Wenchuan area of Sichuan Province using a dual temperature-difference method[J].Seismology and Geology,30(4):1085—1094(in Chinese).
张培震,徐锡伟,闻学泽,等.2008.2008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,51(4):1066—1073.ZHANG Pei-zhen,XU Xi-wei,WEN Xue-ze,et al.2008.Slip rates and recurrence intervals of the Longmen Shan active fault zone and tectonic implications for the mechanism of the May12Wenchuan earthquake,2008,Sichuan,China[J].Chinese Journal of Geophysics,51(4):1066—1073(in Chinese).
张永双,马寅生,胡道功,等.2010.玉树地震地表破裂调查与灾后重建避让选址研究[J].地质学报,84(5):593—605.ZHANG Yong-shuang,MA Yin-sheng,HU Dao-gong,et al.2010.Investigation and research on the surface rupture of the Yushu earthquake and reconstruction site selection[J].Acta Geologica Sinica,84(5):593—605(in Chinese).
Dey S,Singh R P.2003.Surface latent heat flux as an earthquake precursor[J].Natural Hazards and Earth System Sci-ences,(3):749—755.
Dey S,Sarkar S,Singh R P.2004.Anomalous changes in column water vapor after Gujarat earthquake[J].Advances in Space Research,33:274—278.
Kistler R,Kalnay E.2000.The NCEP/NCAR50-year reanalysis[J].Bull Am Met Soc,82:247—267.
Singh R,Simon B,Joshi P C.2001.Estimation of surface latent heat fluxes from IRSP4/MSMR satellite data[J].Proc Indian Acad Sci(Earth Planet Science),110(3):231—238.
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