The Recent State of Stress in the Central Qinghai-Tibet Plateau according to In-Situ Stress Measurements

The Qinghai-Tibet plateau is the most active in tectonic activity. In order to learn the recent state of stress, we have carried out stress measurements at different structural positions and depths and in different rocks by using piezomagnetic stress gauge overcoring method in the central Qinghai-Tibet plateau. The results of stress measurements indicate that the direction of the maximum principal stress is generally in NE direction. This agrees with the result of the studies of geology, seismology, and geodesy. The values of the maximum principal stress are 3.6-6.8MPa which are medium or slightly high compared with those obtained elsewhere in China from a viewpoint of regional stress analysis. But the stress measurement site at Amdo is an exception where the direction of the maximum principal stress is NWW and its value is 8.1MPa. This also indicates that the recent state of stress is complex near the plate suture zone. These results of stress measurements can provide important basic data for studies of active faults, geological hazards and engineering stability evaluation in the Qinghai-Tibet railway construction area as well as for research of continental dynamics.