Depth estimation of subsurface heterogeneity through surface waves attributes

Surface waves can carry important information about near surface. For instance if there are some oil pipes beneath the earth and there is a major leakage and a polluted area is made, surface waves can investigate the anomaly and with its interpretation the anomaly can be modeled. Therefore, it is a common practice to apply corrections to the reflection seismic data (known as static corrections) to eliminate the influence of weathering layers or investigate its properties. These corrections are made using estimates of the velocity models near the Earth's surface. Surface-wave methods (SWM) are a seismic approach, which can be used to achieve a velocity model. There are simple effective attributes of SWs that can be used for the location of lateral variations in the subsurface. While their effectiveness in identifying and locating the anomalies has been proven in different studies, their relationship with the depth of these anomalies is still an open scientific question. The autospectrum method can be a way to reveal the energy content of a seismogram. In the present work, we have worked on the relationship between the wavelength and depth of an anomaly near surface with lateral and vertical heterogeneity. For this approach we used the wavelength calculated from dispersion curves and wavelength calculated by wavelength-depth relationships. The different frequencies entered in the dispersion curves are extracted and selected from the autospectrum. Three different types of frequency picking is done to compare the results. The estimated results showed 99% correlation with the real data under specific conditions in a layered model. This study also achieves more than 80% of the R-squared value for the depth of anomaly prediction. The maximum depth investigated in this work is not more than 10 meters.