| 断层交汇区附近的变形特点与声发射特点的实验研究 |
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| 引用本文： | 马瑾,张渤涛,许秀琴,王宝生.断层交汇区附近的变形特点与声发射特点的实验研究[J].地震学报,1983,5(2):195-206. |
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| 作者姓名： | 马瑾 张渤涛 许秀琴 王宝生 |
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| 作者单位： | 国家地震局地质研究所 |
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| 摘 要： | 把昌平花岗岩切割成20多种含两组断层交汇情况的模型.断层物质用2毫米厚的石膏模拟.模型受单轴应力的作用.实验中得出四种破裂组合情况:1.滑动破裂型 发生在两组断层与主压应力轴1的交角一组大于45,一组小于45的情形下.其中,当断层物质石膏湿度为10——15%时,先在大角度面上产生剪切破裂,后沿小角度面产生最终磨擦滑动.在应力位移曲线上表现为两次应力降.当断层物质石膏湿度小于5%时,则只沿小角度面上产生磨擦滑动.应力位移曲线为单应力降。2.压楔型 发生在两组断层与1夹角均大于45的情况下.其应力位移曲线为阶梯式上升型.断层位移方向反复.3.张楔型 发生在两组断层与1夹角均不大于30时.应力位移曲线为单应力降.4.双滑或双破型 发生在两组断层与1夹角均在30和45之间.应力位移曲线为连续的两次应力降.根据应力位移曲线和应力声发射累积数曲线的相似性,主破裂前的声发射累积数与主破裂时峰值应力的相似性以及断层组合与声发射组合的关系中,看出声发射过程对构造条件是敏感的.文中还对不同断层组合下可能出现的地震前兆进行了讨论.
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MODEL EXPERIMENTAL STUDY ON BEHAVIOR OF DEFORMATION AND ACOUSTIC EMISSION NEAR THE INTERSECTIONS OF FAULTS |
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| Affiliation: | Institute of Geology, State Seismological Bureau |
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| Abstract: | More than 20 kinds of models, each with two intersecting faults are made from the Changping granite. Gypsum used to simulate the fault material is of thickness 2 mm. The models are loaded under uniaxial stress.Four types of fracture combinations are obtained during the experiments:(1). Shearing and slipping In this case, the model contains two faults dipping in opposite directions, one at an angle of more than 45 to 1 and the other at an angle less than 45 to 1. When gypsum in the fault zones has a moisture content of 10-15% the shearing fracture occurred along the fault starts at. larger angles and then a terminal frictional slip along the fault at smaller angles, takes place. There are two stress drops on the stress-displacement curve. When the gypsum in fault zones has a moisture content of less than 5%, a frictional slip occurs only along the surface of the fault at small angles. There is one stress-drop on the stress-displacement curve.(2). Wedge by compression This happens when the two sets of faults make angles larger than 45 with 1. Its stress-displacement curve rises in the form of steps. The direction of fault dislocation may vary repeatedly.(3). Wedge by tension This happens when the sets of faults make angles less than 30 with 1 There is only one stress drop on the stress-displacement curve.(4). Bi-shearing or Bi-slipping This happens when the two sets of faults make angles of 30 to 45 with 1. There appear two succesive stress drops on the stress-displacement curve.Based on the facts of similarity between the stress-displacement curve and the stress-accumulative number of acoustic emission curve and that between the accumulative acoustic emission number before the principal fracture and the peak stress value during it as well as the relation between acoustic emission and faults, it can be seen that the process of acoustic emission is sensitive to structural conditions.Earthquake precursors possibly appear in the case of different combinations of faults have also been discussed in this paper. |
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