Abstract: Two level of in-situ calibration of borehole strainmeters is identified. At the first level, in-situ calibration is distinguished from laboratory calibration. It needs to determine the same thing, the transducer's factor. It is referred as relative calibration. At the second level, since local strains cannot be calculated until elastic parameters of surrounding medium are given, in-situ calibration also includes the task for determining these parameters by the known data such as earth tide. This is referred to the absolute calibration. In this paper, a new method for absolute calibration of 4-component strainmeter is put forward with a case study on the observations of Changping station in which good results have been obtained.

Key words: Borehole strain observation, 4-component borehole strainmeters, Calibration