Abstract:

Tan-Lu fault belt is a deep fractured zone in east China, as well as the largest Quaternary active tectonic belt and seismic belt. The recent tectonic stress field obviously controls the motion mode of the fault, the activity intensity, and the seismicity of the fault belt. Therefore, it is of important scientific significance to make further research on the tectonic stress field near the Tan-Lu fault zone and the adjacent region. Based on the previous research results, the paper preliminarily reveals the distribution of the shallow crustal in situ stress, and analyzes the discrepancy of different tectonic positions on the basis of the in-situ stress measuring results at 6 boreholes with the depth of 600-1,000 m near Shandong-Bohai-Liaoning segments of the Tan-Lu fault zone and the vicinities. Then, the recent tectonic stress field in the vicinity of the Tan-Lu fault zone is exhibited combined with other basic stress data, such as focal mechanism solutions, borehole breakouts, stress relief data, and fault slip vector inversion results. Furthermore, the influence of tectonic stress field on the fault active mode is also analyzed. The preliminary results reveal that: (1) In terms of tectonic stress accumulations,the horizontal tectonic stress accumulation in the southern tip of Shandong segment of the Tan-Lu fault zone is the strongest, and that in the Liaodong Peninsula on the eastern and western sides of the Bohai segment takes the second place, and the horizontal tectonic stress accumulation in Benxi region at the northern tip of Liaoning segment is slightly lower than that in the Bohai segment, while it is the lowest in Pingdu region at the northern tip of Shandong segment and Changli of Hebei Province. (2) The stress regimes of the southern and northern tips of Shandong segment of the Tan-Lu fault zone are of thrust and normal faulting states, and are normal faulting and strike-slip faulting in the Bohai and the northeastern tip of Liaoning segments. The stress regime of each segment of the Tan-Lu fault zone can correspond to the active characteristics of the fault belt since the Quaternary. (3) The orientations of principal compressive stress in the tectonic stress field are N70°E, N68°E and N72°E in the vinicinity of Shandong, Bohai and Liaoning segments of the Tan-Lu fault zone, respectively. Under such stress background, the activity of the Tan-Lu fault zone is liable to be right-lateral strike sliping.

Key words: Tan-Lu fault zone, in situ stress, hydraulic fracturing, recent tectonic stress field