2008年新疆于田M_S7.3地震前区域地震活动和应力状态特征初步研究
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摘要
从区域地震活动和中等地震震源机制特征的角度,初步研究了2008年新疆于田7.3级地震前区域地震活动和应力场的应力状态特征.结果表明,于田7.3级地震前区域地震活动存在中短期异常特征.一方面,该地震前1年其震区500km范围内中强震以及西昆仑地震带和阿尔金地震带3.5级以上地震出现了增强活动;另一方面,该地震前出现了4级地震孕震空区和近乎共扼分布的3.5级地震密集条带异常图象.于田7.3级地震前新疆区域应力场和震源区及其附近局部应力场的应力状态发生了一定程度的改变,拉张作用力相对挤压作用力有所加强.这可能是于田7.3级地震前新疆和于田震区及其附近具有正断层性质的中等地震增多的原因.
By analyzing regional seismic activity and focal mechanism solutions of medium earthquakes,we did a preliminarily research on the characteristics of regional seismicity and stress state before the 2008 Yutian MS7.3 earthquake.It is noticed that the regional seismicity showed middle-short term abnormal before the MS7.3 earthquake,i.e.,mid-strong earthquakes within 500 km from the source and MS≥3.5 earthquakes in the western Kunlun and Aerchin seismic belt increased one year before the MS7.3 earthquake.There appeared abnormal pattern of seismic gap of MS≥4.0 earthquakes and nearly conjugate dense belt of MS≥3.5 earthquakes before the MS7.3 earthquake.Both Xinjiang regional stress field and local stress field around the source region were changed to some extent before the Yutian MS7.3 earthquake,with tensional action being strengthened in comparison with the compressional one.This may explain why medium earthquakes of normal-faulting type in Xinjiang and around the Yutian source region increased before the MS7.3 earthquake.
By analyzing regional seismic activity and focal mechanism solutions of medium earthquakes,we did a preliminarily research on the characteristics of regional seismicity and stress state before the 2008 Yutian MS7.3 earthquake.It is noticed that the regional seismicity showed middle-short term abnormal before the MS7.3 earthquake,i.e.,mid-strong earthquakes within 500 km from the source and MS≥3.5 earthquakes in the western Kunlun and Aerchin seismic belt increased one year before the MS7.3 earthquake.There appeared abnormal pattern of seismic gap of MS≥4.0 earthquakes and nearly conjugate dense belt of MS≥3.5 earthquakes before the MS7.3 earthquake.Both Xinjiang regional stress field and local stress field around the source region were changed to some extent before the Yutian MS7.3 earthquake,with tensional action being strengthened in comparison with the compressional one.This may explain why medium earthquakes of normal-faulting type in Xinjiang and around the Yutian source region increased before the MS7.3 earthquake.
引文
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邓起东,张培震,冉勇康,杨晓平,闵伟,陈立春.2003.中国活动构造与地震活动[J].地学前缘,10(特刊):66--73.
高国英,温和平,聂晓红.2005.1991—2002年新疆中强震震源机制解分析[J].地震,25(1):81-87.
陆远忠,沈建文,宋俊高.1982.地震空区与逼近地震[J].地震学报,4(4):327--335.
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:49--65.
万永革,周公威,吴忠良,黄静.2001.中国地震震源机制测定结果的比较[J].地震地磁观测与研究,22(5):1--15.
王盛泽,高国英.1992.新疆及邻近地区现代构造应力场的区域特征[J].地震学报,14(增刊):612--620.
王曰风,刁桂苓,张秀萍,张彦清,朱振兴,马利军.2008.2001年云南永胜6.0级地震余震序列震源机制解与震源区应力场分析.地震研究,31(2):119--123.
许忠淮,汪素云,黄雨蕊,高阿甲.1989.由大量的地震资料推断的我国大陆构造应力场[J].地球物理学报,32(6):636--647.
周仕勇,许忠淮,陈晓非.2001.伽师强震群震源特征及震源机制力学成因分析[J].地球物理学报,44(5):654--662.
朱令人.2002.新疆通志(十一卷,地震志)[M].乌鲁木齐:新疆人民出版社:309--310.
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