基于地应力实测数据分析郯庐断裂带中段滑动趋势

摘要/Abstract

摘要：

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K_max和K_min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μ_m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。

关键词: 地应力, 郯庐断裂带中段, 摩擦系数, 滑动趋势

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

中图分类号:

刘卓岩, 王成虎, 徐鑫, 慎乃齐, 贾晋. 基于地应力实测数据分析郯庐断裂带中段滑动趋势[J]. 现代地质, 2017, 31(04): 869-876.

LIU Zhuoyan, WANG Chenghu, XU Xin, SHEN Naiqi, JIA Jin. Slip Tendency Analysis of the Mid-segment of Tan-Lu Fault Belt Based on Stress Measurements[J]. Geoscience, 2017, 31(04): 869-876.

图/表 8

图1 研究区地应力测试钻孔位置图(测点处的箭头表示σH方向)

Fig. 1 Borehole locations of crustal stress test in the study area

表1 研究区实测地应力数据

Table 1 Data of measured crustal stress in the study area

图2 应力比K和深度z的关系 (a)1号测点;(b)经1号测点数据拟合后8号测点;(c)研究区内所有测点

Fig.2 Curves showing the relationship between depth and K

表2 8号测点K值的实测值和拟合值对比

Table 2 Measured and calculated values of K in the No.8 point

深度 /m	K_max			K_min
深度 /m	实测值	拟合值	误差/%	实测值	拟合值	误差/%
1 186	1.66	1.37	17	0.81	0.88	9
1 196	1.39	1.37	2	0.90	0.88	3

表3 400 m深处的K值和应力值

Table 3 Values of K and the effective stress in the depth of 400 meters

测点	K_max	K_min	有效正应力/MPa	剪应力/MPa	μ
1	1.74	1.07	13.41	3.01	0.22
2	1.68	1.01	12.50	3.07	0.25
3	1.70	1.01	12.59	3.20	0.25
4	1.33	0.60	8.58	3.23	0.38
5	1.41	0.84	9.75	2.59	0.27
6	1.41	0.90	9.15	2.59	0.28
7	1.65	0.96	12.63	2.79	0.22
8	1.77	1.06	13.53	3.18	0.24
9	1.66	0.97	16.78	4.95	0.30
10	2.18	1.25	18.80	3.19	0.17

图3 研究区400 m深度K值等值线云图

Fig. 3 Contour maps of K in the depth of 400 meters of the study area

图4 郯庐断裂带中段在区域地应力场作用下的滑移趋势分析 (a)郯庐断裂带及周围断层有效应力莫尔圆;(b)郯庐断裂带及周围断层摩擦系数;1.平度崔召路子口村;2.泰安华丰华丰矿;3.新泰孙村矿;4.济宁济北矿区;5.济宁梁山杨营煤矿;6.临沂费县;7.蓬莱姜沟;8.曲阜星村矿;9.新沂市;10.潍坊市

Fig.4 The stress condition of the mid-segment of Tan-Lu fault belt

图5 研究区地震分布图

Fig.5 The distribution of earthquakes in the study area

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