利用背景噪声研究地震波速度变化及其在长白山火山监测中的应用

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

介绍了利用背景噪声研究地震波瞬时波速变化的方法,应用长白山火山区的地震监测数据演示并讨论了从单台数据预处理到数据质量控制的4个数据处理步骤。应用文中介绍的方法,使用长白山火山区域地震台网的连续观测数据,研究了长白山火山区地下介质的相对地震波速变化。带通滤波范围是0.02~0.1Hz,这一滤波带的地震波速对应的敏感介质深度位于地壳与上地幔之间。长白山火山区地震波速度的长趋势变化显示出了明显的季节性影响,这可能是由当地降雨量变化引起的。2001—2007年CBS-YNB台站对的地震波速度变化幅度达到2%,高于背景值（1.5%）,因为此间长白山火山地下岩浆发生了一次扰动,可能是岩浆活动导致了地震波速度变化幅度增大。

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 O. 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.