Trans-Bohai passage sea area lacks basic data on measured in-situ stress. Conducting in-situ measurements in this area is challenging and carries significant risks. To obtain firsthand data on the current in-situ stress field characteristics

a comprehensive in-situ stress measurement technology is employed. This technology primarily relies on hydraulic fracturing in-situ stress measurement

supplemented by methods such as hollow inclusion

inelastic strain recovery

differential strain

and acoustic anisotropy. Three-dimensional in-situ stress measurement and research are conducted in the sea area of the study region. A linear regression equation is established

and a regression fitting curve is obtained. The results reveal certain patterns: as the test depth increases in the Bohai strait

the maximum horizontal principal stress

minimum horizontal principal stress

and vertical principal stress all increase linearly with the increase of test depth. In the southern part of the strait

the in-situ stress state follows the relationship

indicating a thrust stress state. The stress field direction is NE

with the maximum horizontal principal stress exceeding the vertical principal stress

suggesting dominance of tectonic forces in the region. In the northern part of the strait

the stress state is

which is conducive to strike-slip fault activity. The stress field direction remains NE

and tectonic forces dominate in the region. Throughout the entire engineering region

there is minimal difference in each component value of the in-situ stress. These values are significantly lower than the lower limit of the active stress value of faults in the area

indicating that the study area is currently in a stable state. These findings align with the general principles of in-situ stress measurement. The testing process adheres to the requirements of in-situ stress testing

and the obtained data can be used to analyze the regional in-situ stress state.