HARMONIC ANALYSIS OF STRAIN TIDAL DATA OBSERVED BY A BOREHOLE STRAINMETER OF CAPACITIVE DISPLACEMENT TYPE AT THE SHESHAN STATION, SHANGHAI CITY

The strain tidal data observed by a YRZ-2 bcrehole strainmeter of capacitive displacement type at the Sheshan Station in Shanghai City wore processed by the method of venedikov harmonic analysis without and with correction of ocean tide loads respectively. Results showed that: 1) the love number l2 of several main semidiurnal tides was close to the result calculated on the basis of the Gutenberg-Bullen earth model A. 2) The love number l2 of several diurnal tides was much smaller, than the one of semidiurnal tides. This was probably caused by the frequency response characteristic of the whole measuring system and the coupling state ibetween the sensor and the rock stratum. 3) In Shanghai the strain effect of ocean tide loads approached the direct effect of tide-generating force, and after correction of ocean tide loads the accuracy of calculation was distinctly improved.