| 雁列式断层组合变形过程中的声发射活动特征 |
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| 引用本文： | 蒋海昆,马胜利,张流,侯海峰,曹文海.雁列式断层组合变形过程中的声发射活动特征[J].地震学报,2002,24(4):385-396. |
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| 作者姓名： | 蒋海昆 马胜利 张流 侯海峰 曹文海 |
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| 作者单位： | 1) 中国济南250014山东省地震局
2) 中国北京100029中国地震局地质研究所，中国地震局构造物理开放实验室 |
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| 基金项目： | “十五”国家科技攻关课题子专题(2001BA601B01-04-01)，地震科学联合基金(102037)资助项目，中国地震局地质研究所构造物理开放实验室部分资助. |
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| 摘 要： | 着重研究拉张或挤压型雁列式断层标本变形过程中声发射(简称AE，下同)的时空演化特征. 结果表明，预置构造对AE空间分布格局具有较强的控制作用，随着差应力的增加，AE首先在两个端点附近丛集，之后向两端点连线附近集中，出现明显的破裂局部化现象，较大事件还通常集中于某一端点附近反复发生. 前期微破裂丛集图象指示后期宏观破裂的扩展方向及扩展范围. 拉张和挤压型雁列区宏观破裂方向分别与轴向应力方向垂直和平行. 雁列式断层标本变形过程中，破裂前的弱化阶段相对较长、弱化过程明显. 微破裂事件累积频次指数增长可能是系统失稳前的典型征兆之一，而雁列区宏观破裂之后，AE数量逐渐减少、应变释放相对减弱. 摩擦滑动过程中，大的粘滑失稳前未见有AE活动前兆性的增强过程.雁列区的b值变化在失稳前显示趋势性降低——快速回升这一典型的变化过程，b值降低一般发生在差应力增强过程之中，并有可能延续至弱化阶段，而快速回升则一般发生在破裂失稳前的短时期内. 对比研究表明，构造差异所导致的b值差异远大于b值随差应力的增加而产生的变化量，而对同一构造标本，力学状态的改变会导致AE序列时序特征的急剧变化，较高的加载速率对应较高的应变能释放及明显的低b值. 先期破碎带由于较低的破坏强度，其对差应力的微小变化具有特殊敏感性，从而成为源、兆分离、窗口或敏感点效应等地震活动性前兆现象的一种可能的原因.
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| 关 键 词： | 声发射& 拉张型雁列式断层& 挤压型雁列式断层& 双轴破裂实验& 差应力 |
| 文章编号： | 0253-3782(2002)04-0385-12 |
| 修稿时间： | 2001年6月4日 |
SPATIO-TEMPORAL CHARACTERISTICS OF ACOUSTIC EMISSION DURING THE DEFORMATION OF ROCK SAMPLES WITH COMPRESSIONAL AND EXTEN-SIONAL EN-ECHELON FAULT PATTERN |
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| Jiang Haikun Ma Shengli Zhang Liu Hou Haifeng Cao Wenhai Seismological Bureau of Shandong Province,Jinan ,China Institute of Geology & Laboratory of Tectonophysics,China Seismological Bureau,Beijing ,China.SPATIO-TEMPORAL CHARACTERISTICS OF ACOUSTIC EMISSION DURING THE DEFORMATION OF ROCK SAMPLES WITH COMPRESSIONAL AND EXTEN-SIONAL EN-ECHELON FAULT PATTERN[J].Acta Seismologica Sinica,2002,24(4):385-396. |
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| Authors: | Jiang Haikun Ma Shengli Zhang Liu Hou Haifeng Cao Wenhai Seismological Bureau of Shandong Province Jinan China Institute of Geology & Laboratory of Tectonophysics China Seismological Bureau Beijing China |
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| Affiliation: | Jiang Haikun1) Ma Shengli2) Zhang Liu2) Hou Haifeng1) Cao Wenhai1) 1) Seismological Bureau of Shandong Province,Jinan 250014,China 2) Institute of Geology & Laboratory of Tectonophysics,China Seismological Bureau,Beijing 100029,China |
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| Abstract: | The spatio-temporal characteristics of acoustic emission (AE) during the deformation of rock samples with compressional and extensional en-echelon faults have been studied. The results show that the pre-existing structure can significantly influence the patterns of AE spatial distribution. With increasing of differential stress, AE events firstly cluster around the two ends of pre-existing faults inside the jog and then along the line joining the two ends. The biggish AE events often occur around one end repeatedly. The image of AE clusters indicates the direction and the area of the fracture propagation. The direction of the macroscopic fracture in extensional and compressional jogs is perpendicular and parallel to the direction of axial stress, respectively. The weakening process before the fracturing of jog area is remarkable, and one of the typical precursors for the instability is that the cumulative frequency of AE events increases exponentially. After the fracturing of the jog the frequency and releasing strain energy of AE events decrease gradually. During the friction period, there is no precursory increasing of AE activity before the big stick-slip events. The change of b value in jog shows a typical change of decreasing tendentiouslyreturning quickly before the instability. The decrease of b value occurs in the process of stress increasing and sometime goes down to the weakening stage, and the quick increase b values appears in a short time just before the instability. The comparative analysis shows that the difference in b value due to the different structures is larger than b value variation caused by increase of the differential stress. For the same sample, the temporal sequence of AE is strongly affected by the mechanical state, and the high loading velocity corresponds to the high release rate of strain energy and low b value. Due to its lower failure strength, the broken area is sensitive to small changes in differential stress. Therefore, it offers a potential explanation for the phenomena of precursory window or sensitive point and separation of seismic source and precursors. |
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| Keywords: | acoustic emission compressional en-echelon fault extensional en-echelon fault biaxial experiment differential stress |
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