基于断层形变协调比的断层形变分析

Analysis of the fault deformation based on the fault deformation coordination ratio

摘要:

基于唐山台跨断层短基线和短水准观测结果，综合应用不同测段的数据组合，分析断层运动状态和测段组合之间的关系，进而计算断层形变协调比参数序列，分析其与区域中等以上地震之间的动力学关系，最后获得两点认识:(1)与断层走向呈不同夹角的测段组合会对认识断层活动特征状态产生影响，因此在台站资料许可的情况下，要尽可能选择不同的组合进行对比分析;同时也表明在建立跨断层观测时，要布置和断层走向呈不同夹角的测段，以便对断层状态做准确的判断。对唐山台的资料而言，据与断层走向夹角较小的两个测段所得结果相对更好，这可能和该断层以走滑为主、该区域应力状态以水平运动为主相关。(2) 4 个序列断层形变协调比的变化幅度虽然有较大差异，但其趋势特征基本一致，与正常背景有显著偏离的变化，且这种变化和唐山区域中等以上(M≥4. 5)地震活动交替出现，且其间隔时间在2000年后逐渐加长。这可能反映了在20 世纪80 ～ 90 年代区域应力场还处于1976 年唐山大地震后的恢复阶段，局部应力场状态在不断地调整和变化之中，而在2000 年之后，区域应力状态逐步稳定。

Abstract:

Based on the short-leveling and short-baseline observation in Tangshan seismic station，the relationship between different combination of segments and the fault movement is discussed． And then the fault deformation coordination ratios are calculated and used to analyze the relation between their sharp deviation and the local med-strong earthquakes． The results show that: ( 1 ) The view on the fault movement would be different because of the different measurement-angle segments with the fault． So it is necessary to calculate and compare the different combinations if the data are suitable． At the same time it is proved that different segments along the same fault are essential to study the fault movement． For the Tangshan seismic station，the combination with two small angle segments data is better than others，which may be the result of the strike-slip fault and horizontal local strain． ( 2 ) The four fault deformation coordination ratio series have similar trends although their amplitudes vary greatly． The sharp deviation to the normal level appeared alternately with the Tangshan med-strong earthquakes (M ≥4． 5)，and the time intervals last longer gradually as time goes after 2000． That may reflect that the local strain in the 1980s ～ 1990s was in their modification period of the great Tangshan earthquake，and after 2000，the regional strain becomes steady．