This paper mainly focuses on the quality of crustal strain observations. Carry on works in standard, metrology and quality inspection three aspects to establish a quality assurance system ensures crustal strain instruments have corresponding quality assurance measure in production, station construction and routine operation is elaborated. The quality of crustal strain observation will be improved significantly. Accurate and reliable data can be provided for earthquake prediction and seismology research.
Geological mechanics theory created by LI Siguang had successfully guided the development of several major oil fields such as Daqing and promoted the exploit of China's oil and other mineral resources. His theory also demonstrated a clear direction of earthquake prediction research. According to the geological mechanics theory, crustal stress state is one of the most important characteristics of the crust. Accurate determination of crustal stress state and diversification is not only important basis of earth science and its relational subjects but also is scientific basis to discover formation mechanism and prediction of multiple geological disasters, earthquake gestation particularly. Major contradictions of caused earthquake are contradiction of crustal stress and rocks against tension. Li Siguang had Emphasized that crustal stress diversification should be carefully observed on the basis of research of tectonic activity in seismology research. In 2lth century, U.S Government's "Earth- Scope Project: Plate Boundary Observation (PBO)" White Paper indicates that borehole strain instruments are the ideal instruments for continuous observation to reveal crustal deformation in short time (from several seconds to several months) and can play a major role in the observation when or before earthquake and volcanic eruptions.
Borehole strain instruments divided in three types: The first is volumetric borehole strain instruments. According to volume changes of cavity mounted in the instrument, the relative change in rock volume can be obtained.