Abstract:To investigate the present-day state of tectonic stress and tectonization in a coastal gold mine area near the Laizhou Gulf, North China, overcoring, anelastic strain recovery, and hydraulic fracturing stress measurement campaigns were performed, and a total of 49 groups of stress data were determined. The results indicate that horizontal tectonic stress plays a predominant role in the present-day stress field, which is a typical tectonic stress field. The stress fields are characterized by σ_H>σ_h>σ_v (σ_H, σ_h and σ_v are the maximum horizontal, minimum horizontal and vertical principal stresses, respectively) and σ_H>σ_v>σ_h, which appear to favor thrust and strike-slip faulting, respectively. The stress level is relatively high and is not conducive to the stability of underground excavations. σ_H is oriented in the WNW-ESE or approximately E-W directions, which is in accord with that indicated by focal mechanism solutions and regional geological structure analysis. The contemporary stress field is the result of dynamic action and tectonic movement in various geological periods; the contemporary stress field generally inherited the characteristics of the third stage tectonic stress field (Himalayan movement period) while partially retaining the characteristics of the second stage tectonic stress field (Yanshanian period), and finally evolved into the tectonic stress field characterized by nearly E-W extrusion.

Key words: in situ stress measurement; present-day stress field; tectonization; fault structure; coastal gold mine area