硬包体对唐山大地震孕育过程及前兆变化的影响
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摘要
研究了硬包体对唐山大地震孕育过程及前兆变化的影响问题。通过不存在硬包体和包含包体两种情况的计算模拟表明,唐山菱形硬包体的存在是唐山大地震孕育和发生的一个重要因素,它不仅会引起唐山地震孕育的复杂的演化图象,而且会对唐山地震前兆特征发生显著影响,使地震前兆较早地显示,并使前兆变化复杂化。具体表现在: (1)硬包体的存在可能会缩短地震的孕震期,使应力易于向硬包体这个局部地区集中,导致包体内断层的全部破坏。 (2)硬包体的存在,在孕震初期将不利于断层上剪应力和剪应变的增强,但在孕震后期却又有利于包体内部断层的全部破坏的发生,从断层平均剪应力变化上看,硬包体的存在在孕震中期引起了一种先应变软化,后急速强化的变化过程。 (3)硬包体的存在会引起孕震区内出现大面积的非弹性恢复的出现和重新发生非弹性体积膨胀。 (4)硬包体的存在对地震前兆变化会产生显著影响。它不仅会导致波速异常的大面积恢复,也会使地震前兆较早地出现,并且使地震前兆变化复杂化。
Effects of hard inclusion to seismogenic process and precursor changes of Tangshan earthquake have been studied. The numerical simulation on existence and non-existence of hard inclusion shows that the rhombic hard inclusion around Tangshan is an important genesis of Tangshan earthquake. It can not only cause the complicated pattern of seismic evolution, but also cause the significant influence to the characteristics of seismic precursors. For instance the it caused early appearance and the complicated variations of the Tangshan earthquake precursors as follows:1. The existence of hard inclusion may shorten the phases of seismogenic process, cause the concentration of stress to the hard inclusion and the complete failure of the inclusion fault.2. In early period of seismogenic process, the existence of hard inclusion is unfavourable to enhance the shear stress and strain, but in later period, it is favourable to the complete failure of the inclusion fault. From the changes of average stress of fault, we can see that the existence of hard inclusion may cause a variation of strain strengthening shortly after its softening in the middle period.3. The existence of hard inclusion may cause an appearance of non-elastic recovery in large area, and reappearance of non-elastic cubical expansion.4. The existence of hard inclusion may cause a great influence to variations of earthquake precursors. It can not only cause a big recovery of anomalous wave velocity, but also cause the early appearance of seismic precursors and its complicated changes.
Effects of hard inclusion to seismogenic process and precursor changes of Tangshan earthquake have been studied. The numerical simulation on existence and non-existence of hard inclusion shows that the rhombic hard inclusion around Tangshan is an important genesis of Tangshan earthquake. It can not only cause the complicated pattern of seismic evolution, but also cause the significant influence to the characteristics of seismic precursors. For instance the it caused early appearance and the complicated variations of the Tangshan earthquake precursors as follows:1. The existence of hard inclusion may shorten the phases of seismogenic process, cause the concentration of stress to the hard inclusion and the complete failure of the inclusion fault.2. In early period of seismogenic process, the existence of hard inclusion is unfavourable to enhance the shear stress and strain, but in later period, it is favourable to the complete failure of the inclusion fault. From the changes of average stress of fault, we can see that the existence of hard inclusion may cause a variation of strain strengthening shortly after its softening in the middle period.3. The existence of hard inclusion may cause an appearance of non-elastic recovery in large area, and reappearance of non-elastic cubical expansion.4. The existence of hard inclusion may cause a great influence to variations of earthquake precursors. It can not only cause a big recovery of anomalous wave velocity, but also cause the early appearance of seismic precursors and its complicated changes.
引文
牛志仁,陈党民,李炳乾.唐山大地震孕育过程的数值模拟研究.1995．
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[1] 梅世蓉.唐山地震的问题与启示.一九七六年唐山大地震.北京:地震出版社,1982．
[2] 梅世蓉.唐山地震前兆的规则性与复杂性.唐山地震孕育模式研究.北京:地震出版社,1992．
[3] 梅世蓉,张国民,张肇城.唐山地震前后的异常变化与强烈地震的预报问题.地震预报研究,第二辑.北京:地震出版社,1989．
[4] 梅世蓉,梁北援,朱岳清.唐山地震前兆机理的数值模拟.中国地震,1989,5(2) .
[5] 梅世蓉,梁北援.唐山地震孕震过程的数值模拟.中国地震,1989,5(3) .
[6] 梅世蓉,朱岳清,梁北援.唐山地震孕震环境、孕震过程与前兆机理研究.八十年代中国地球物理科学进展.北京:学术期刊出版社,1989．
[7] 朱传镇,傅昌洪,等.唐山7． 8级地震前后微震震源参数.地球物理学报,1977,20(4) .
[8] 林邦慧,李志勇,魏富胜.京津地区Q值及平均应力降的分布.地球物理学报,1982,25(4) .
[9] 陈培善,等.唐山地震前后京津唐张地区的应力场.地球物理学报,1978,21(1) .
[10] 孙若昧,赵燕来,梅世蓉.渤海及其邻区的地震层析成象.地球物理学报,1993,36(1) .
同第24页脚注。
同第24页脚注。
同第24页脚注。
[1] 梅世蓉.唐山地震的问题与启示.一九七六年唐山大地震.北京:地震出版社,1982．
[2] 梅世蓉.唐山地震前兆的规则性与复杂性.唐山地震孕育模式研究.北京:地震出版社,1992．
[3] 梅世蓉,张国民,张肇城.唐山地震前后的异常变化与强烈地震的预报问题.地震预报研究,第二辑.北京:地震出版社,1989．
[4] 梅世蓉,梁北援,朱岳清.唐山地震前兆机理的数值模拟.中国地震,1989,5(2) .
[5] 梅世蓉,梁北援.唐山地震孕震过程的数值模拟.中国地震,1989,5(3) .
[6] 梅世蓉,朱岳清,梁北援.唐山地震孕震环境、孕震过程与前兆机理研究.八十年代中国地球物理科学进展.北京:学术期刊出版社,1989．
[7] 朱传镇,傅昌洪,等.唐山7． 8级地震前后微震震源参数.地球物理学报,1977,20(4) .
[8] 林邦慧,李志勇,魏富胜.京津地区Q值及平均应力降的分布.地球物理学报,1982,25(4) .
[9] 陈培善,等.唐山地震前后京津唐张地区的应力场.地球物理学报,1978,21(1) .
[10] 孙若昧,赵燕来,梅世蓉.渤海及其邻区的地震层析成象.地球物理学报,1993,36(1) .
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