Stress Magnitude Measurements to Mid-Crustal Depth in the KTB Borehole

点击翻译按钮获取中文摘要

Constraining the magnitudes of stresses in the earth's crust if fundamental to a broad range of problems of lithospheric mechanics. The plan to drill and core to 10 km depth by the KTB project of West Germany represents the first opportunity to measure in situ stress magnitudes at seismogenic depth in continental crust. Conventional stress measurement techniques cannot be employed in the KTB main borehole, or most other deep boreholes. Thus, this project is aimed at development of a novel integrated stress measurement strategy for eventual use to 10 km depth in the KTB borehole and other deep holes, such as those that exist in the Soviet Union. There are four main activities associated with developing and implementing the proposed stress measurement strategy: Making detailed observations of breakouts and thermal fractures in the borehole, development of sufficiently comprehensive theories of borehole failure, conducting comprehensive laboratory tests on core and making least principal stress measurements utilizing hydraulic fractures through perforations in the casing. This research is being done in collaboration with Prof. Karl Fuchs of the University of Karlsruhe and Prof. Fritz Rummel of Ruhr University-Bochum. Laboratory strength measurements of core samples will be done in collaboration with Dr. James Byerlee of the U.S. Geological Survey.