Seismogram Analysis of Indonesian Earthquakes at DAV Observation Station

The S-wave velocity across the earth structure under Indonesia for Indonesia earthquakes has been investigated through seismogram analysis, simultaneously in the time domain and three Cartesian components. The data were recorded at DAV observational station, the Philippines. The main data set is the seismogram comparison between the measured and synthetic seismogram, instead of travel time data, as commonly used in other seismological research. The synthetic seismogram is calculated using the GEMINI method, which is equivalent to Mode Summation. The above seismogram comparison shows that the global earth mantle of PREMAN gives a deviating synthetic seismogram and has earlier arrival times than those of the measurement. The gradient of βh in the upper mantle layers is altered into a positive, rather than negative slope as stated in the PREMAN model, and negative corrections are imposed to the zero order of the polynomiars coefficients in all earth mantle layers. The excellent fitting, as well as travel time or waveform, is obtained from the surface waves of Love and Rayleigh, surface wave to the S and SS mantle waves as well as the core reflected waves. This result expresses that part of the earth mantle, due to a collision between India and Asia tectonic released zones, has a negative anomaly in S-wave velocity and vertical anisotropy in all of the earth mantle layers.

Seismogram Analysis and Fitting of Three Earthquakes,West Papua,Recorded at Stations ENH and KMI,China

The S wave velocity structure of the earth below Eastern Southeast Asia has been investigated by analyzing the seismogram from surface wave to multiple depth waves in the time domain and three Cartesian components simultaneously.The wave passes across the front area of subduction zone between the Philippine plate and the Asian plate.The main data are waveform comparisons,instead of the arrival times.The synthetic seismogram is calculated using the GEMINI method.The synthetic seismogram constructed by PREMAN global earth model deviates greatly from the measured one.To solve this problem,corrections are needed for the β speed structure.Corrections cover the gradient change of β_h,which turns from negative to positive in upper mantle layers as in the PREMAN,change of earth crust depth and change of zero order coefficients of β velocity function in all earth mantle layers.So,the fitting is obtained,as well as the arrival time or the waveform of Love and Rayleigh surface waves,the S wave and the repetitive depth waves ScS_2 and ScS_3.This result reveals that the Southeast Asia,being stretched due to tectonic release,has a mantle in some parts with negative anomaly of S wave velocity and vertical anisotropy in all earth mantle layers.

The strain seismograms of P- and S-waves of a local event recorded by four-gauge borehole strainmeter

At a sampling rate of 100 samples per second,the YRY-4 four-gauge borehole strainmeters（FGBS） are capable of recording transient strains caused by seismic waves such as P and S waves or strain seismograms. At such a high sampling rate, data from the YRY-4 strainmeters demonstrate fairly satisfactory self-consistency. The strain tensor seismograms demonstrate the senses of motion of P waves, that is, the type of seismic wave travels in the direction of the maximum normal strain change. The observed strain patterns of S waves significantly differ from those of P waves and should contain information about the source mechanism. Spectrum analysis shows that the strain seismograms are consistent with conventional broadband seismograms from the same site.