f COMBINING FREQUENCY-DEPENDENT TRAVELTIME TOMOGRAPHY AND FREQUENCY-DOMAIN WAVEFORM TOMOGRAPHY FOR NEAR-SURFACE SEISMIC REFRACTION DATA

Seismic refraction surveys and tomographic methods are commonly used to characterize the near-surface. The advantage of traveltime tomography is its robustness because it uses only traveltimes. Its disadvantage is that it provides relatively low spatial resolution velocity models. The advantage of waveform tomography is its ability to provide high-resolution models. The disadvantage of waveform tomography is its strong dependence on an accurate starting model since it is a very nonlinear inverse problem. The spatial resolution of traveltimes data is related to the Fresnel zone, which can be very wide, whereas for waveform data it is related to the seismic wavelength, typically a smaller length scale by comparison. A new integrated strategy for deriving velocity models from nearsurface seismic refraction data using two complementary tomographic methods is presented.