A basic program to compute seismic surface-wave group-velocity dispersion curves

Abstract

Abstract In usual exploration seismic surveys, body waves are used to derive information about the subsurface. Seismic surface waves are treated as noise, usually troublesome noise. Because the amplitudes of surface waves are many times greater than those of body waves, they conceal the body waves in seismic records and make it difficult to process and interpret the body-wave data. It may be necessary to conduct a test survey and design, on the basis of test-survey results, an elaborate data acquisition and processing scheme in order to record useful body waves with surface waves suppressed. Generally body-wave data are not usable in some areas in spite of painstaking acquisition and processing efforts. However, the nature of the surface waves that makes them troublesome in exploration surveys may be harnessed to the geophysicist's advantage. Because their amplitudes are several or more times greater than those of body waves, seismic surface waves present far fewer problems in data acquisition and processing. Also, because seismic surface waves sample the near surface of the Earth rather than deep Earth, they are especially suitable to use in surveys for environmental or geotechnical applications. Probably the best way of using seismic surface waves in extracting information on the subsurface is to compute their dispersion relationships and then to apply an inversion scheme to the obtained dispersion curves. This paper presents a computer program written in BASIC to obtain dispersion curves. It is based on an algorithm termed multiple filter analysis.