We have collected the data of variometers in period from 1972 through 1984 at Changli and Baijiatuan stations. The results calculated from 19 groups of data show: 1) There are no significant anomalies of A, B at Baijiatuan and that of B at Changli, but there are evident anomalous changes for AM, A~ at Changli station. This result basically agrees to the a, b calculated using the method of measuring magnetograms, which demonstrates that the anomalies limited in the aftershock area and its neighbouring regions. 2) There are some changes of the interstation transfer functions of C., C~., F., F~ before Tangshan earthquake, and the changes of the image parts Cv, F~ are more obvious, which is in agreement with the research results for Hualian earthquake. However, according to the results of Carlisle M = 5.0 earthquake by Beamish (1982), the real parts F., C. change more significantly.Key words: horizontal field inter-station transfer functions underground electric, structure abnormal field normal field *
In this paper, using the variometer data of Changli station and Baijiatuan station from 1972 to 1997, the inter-station transfer functions of horizontal field and the single-station transfer functions of vertical field have been calculated. With analyzing the whole changing process of the transfer functions, we have discovered that only the horizontal field transfer functions arose obvious short-term precursors before Tangshan earthquake. This fact may provide a new method for short-term prediction of earthquake.Key words: horizontal field transfer functions; vertical field transfer functions; short-term precursor of earthquake CLC number: P318.2+1 Document code: A * ACTA SEISMOLOGICA SINICA Vol. 14 functions are more obvious than vertical field transfer functions. We only used the data of variometers during the period from 1972 through 1984 in the 1997 paper and one to two group transfer functions are calculated every year, so the short-term and imminent earthquake precursors are found very difficult. In order to examine whether the short-term precursors exist or not and to test its reliability, we did the following work.
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