Characteristics of seismic noise in Central Java, Indonesia

The aim of this paper is to discuss the characteristics of recorded seismic noise in central Java by using empirical interstation Green’s function (EGF). We have utilized the data from the MERAMEX project (May – October 2004) to determine the EGF within the study area. We have calculated 6893 cross correlations based Green’s function of vertical-vertical components. In order to study both primary and secondary microseisms, we measured azimuthal dependence of signal-to-noise ratio (SNR) of Green’s function at a period range from 3 to 25 s (or 0.04 – 0.33 Hz). In general, the cross-correlation functions (CCF) of positive and negative axes are not symmetric, which indicate that the dominant source locations are not evenly distributed. Based on period-azimuth maps of SNR the relatively higher SNRs are appeared in the period from 3 to 12 s (0.08 – 0.33 Hz), which can be related to the secondary microseisms. Our result also indicates that the most energetic seismic noise source came from or was generated in the northeastern part or northern part of the study region with range of azimuth form 290° to 360° and from 0° to 25°, which is related to the coupling of the northern coast of central Java and the ocean current of the Java sea.