REAL-TIME SEISMIC WAVE DATA COMPRESSION METHODS

This paper discusses two methods of compressing real-time seismic wave data: Self-Adaptive Sampling (SAS) method and 8-bit Adaptive Differential Pulse Code Modulation (8-bit ADPCM) method. The SAS compresses seismic data with changeable compression ratios for different seismic events that have different frequency properties. The 8-bit ADPCM method is used to compress SAS data with a constand compression factor of 2:1. With the joint application of both methods,high compression ratios and high fidelity are achieved simultaneously,the distortion being negligible. The compression ratios are larger than 12 for Short-Period seismic data,30 for broadband,and 10 for long-period. A high waveform coincidence was achieved not only in the time domain in which waveform cross-correlation coefficients are over 0.997 but also in the frequency domain. Easy in algorithm,those two methods can be applied in highspeed system for seismic data acquisition and transmission. Now,SAS has been used in Basic Seismic Observatory (BSO) developed by the Institute of Geophysics,State Seismological Bureau of China.