Back Ground Noise of Borehole Seismic Data at Hyodongri

효동리 시추공 관측소의 배경잡음 특성

We have installed the borehole seismic recording system at Hyodongri in eastern part of Kyungsan Basin, which has the advantages of reduction in noise by human activities and distorting effects of near-surface rocks. Here we describe briefly the borehole seismic station and recording system. And we analyse the characteistics of back ground the station obtained from borehole sensors. The back ground noise level in time domain is about 50~100$\mu$cm/sec. The average curve of noise spectrum is lower than NHNM(New High Noise Model)of GSN(Global Seismic Network)operated by USGS. The results could be useful prior information for study on earthquake records observed at Hydongri station.