Abstract:

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 μ_m 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.

Key words: in-situ stress, the mid-segment of Tan-Lu fault belt, frictional coefficient, slip tendency