基于地应力实测数据分析郯庐断裂带中段滑动趋势

郯庐断裂带潜在滑动趋势对于区域地壳稳定性评价具有重要的意义。对郯庐断裂带中段(新沂至渤海段)附近12个钻孔共65条实测地应力数据分析，得出该区段最大和最小水平主应力与垂直应力之比Kmax和Kmin的范围，结果表明郯庐断裂带中段主要表现为逆断层的应力状态，局部地区呈现出有利于走滑断层的特征。研究区内应力比K值由西向东逐渐增大，并在东北部达到最大。通过计算得出断层面上的剪应力与有效正应力比值小于Byerlee准则所定义的摩擦系数，说明目前郯庐断裂带中段处于相对稳定状态；同时发现北西向断裂面上的剪应力与有效正应力比值比北东向断裂的大。区内应力积累指标μm的计算结果和地震的分布特征表明，郯庐断裂带中段北西向断裂上地震活动频繁，应力积累程度低；而北东向断层上应力积累程度高，特别是处于郯庐断裂带中段东北部的北东向断层，在应力集中的区域出现地震空白区，推测为断层的锁固段。最终认为在现今应力场下郯庐断裂带中段更易沿北西向的断裂滑动。

Slip Tendency Analysis of the Mid segment of Tan Lu Fault Belt Based on Stress Measurements

The slip tendency of Tan Lu fault belt is of great importance for regional crustal stability evaluation. The ranges of the ratios of the maximum and minimum horizontal stresses to vertical stresses are obtained by analyzing in situ stress data from 12 boreholes in the vicinity of the mid segment of Tan Lu fault belt(from Xinyi to Bohai). The results show that the stress state of the mid segment of Tan Lu fault belt is predominantly reverse faulting and partly strike slip faulting. The stress ratio K increases gradually from west to east and reaches the maximum value in the northeast of the study area. The calculated ratio of shear stress to effective normal stress on fault planes is smaller than the frictional coefficient defined by the Byerlees law, which indicates that the mid segment of Tan Lu fault belt is in a relatively stable state nowadays. Meanwhile, the ratios of shear stress to effective normal stress of the northwestern striking fault are bigger than those of the northeastern striking fault. The results of stress accumulation index μm in this area and the distribution characteristics of earthquakes reveal that earthquakes are more likely to occur along the northwest striking faults of the mid segment of Tan Lu fault belt, and the degree of stress accumulation near the northwest striking faults is low. On the contrary, the degree of stress accumulation along the northeast striking faults is high, especially along the northeast striking faults in the northeastern part of the mid segment of Tan Lu fault belt, and the seismic gap occurs in this stress accumulating area which is speculated as a deadlocking zone. As a result, it is concluded that the mid segment of Tan Lu fault belt is more likely to slip along the north west direction.