STUDY OF TEMPORAL SEISMIC VELOCITY CHANGES FROM AMBIENT SEISMIC NOISE AND ITS APPLICATION TO CHANGBAISHAN VOLCANO MONITORING

This paper presented the current status of seismic noise interferometry in reconstructing the seismic velocity and discussed the four phases of data processing procedure from single-station data preparation to quality control. Each phase of the processing procedure has been discussed in detail with salient examples using seismic data acquired in Changbaishan volcano region. In the end,we used continuous recordings in Jilin,China to track the temporal changes of seismic velocity with the method introduced in this paper. We filtered the data between the frequency band 0. 02 and 0. 1Hz,where the Rayleigh waves are most sensitive to the shear wave velocities in the crust and uppermost mantle. The long-term seismic variations present strong seasonal influence which may be caused by precipitation. From 2001 to 2007,the amplitude of the relative seismic velocity change increased sharply and the highest variation reached 2%,far beyond the background level. During this time,a turbulence of the magma beneath this volcano occurred. So we conclude that this anomaly of velocity was caused by the turbulence of magma.