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| | Abstract | | We have proposed a new idea of conducting multi-channel surface wave survey targeting the near surfaces, and named it hybrid surface wave survey method. The hybrid surface wave survey is characterized as the combination of active and passive surface wave survey sequentially conducted along the same seismic line. Two dispersion curves are combined to form a single dispersion curve for a specific CMP in a survey line. The method enabled us to trace dispersion curves from 2.5 Hz to at a maximum of 100 Hz enough to reconstruct a dense 2D S-wave velocity profile at ultra-shallow depths up to 50 cm. During the field tests, we found a more effective noise source. That is, random walking but along the survey line. We could efficiently obtain wide frequency band dispersion curves emulative to both active and passive survey, only from passive seismic data including noises generated by waking along the survey line. The method is characterized as just a hybrid of active and passive seismic surveys or as quasi-static surveying. The walkaway surface wave measurements are capable to expand the surface wave survey for delineating high-resolution ultra-shallow 2D S-wave velocity structure in large urban areas. |
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