PRELIMINARY STUDY OF THE MICROSEISMS IN RELATION TO EARTHQUAKES
ZHU CHUAN-ZHEN FANG MING-SHAN AN ZHEN-WENLUO SHENG-LI (Institute of Geophysics, Academia Sinica)
In order to seek for the earthquake precursors, the characteristic variations of microseisms preceding several larger earthquake occurrences are analysed in brief. It is found that amplitude of microseism decreased abnormally at a station near the epicenter (Δ≈20km) about a few days before the occurrence of the Haicheng (海城) earthquake (M=7.3) on February 4, 1975. Preliminary analysis shows also that the phenomena such as the variation of the direction of approach of microseisms and the correlation between different components of the microseisms before large earthquakes are worthy of note.