Although first-arrival tomography provides an effectiveway to estimate near-surface velocities and static corrections,the undulation of velocity interfaces such as the base of theweathered zone may not be easily determined by this method.The main reason is that first arrivals are insensitive to smallgeometric changes in velocity interfaces because their raypathstend to traverse along those interfaces. To improve thesolution of interface geometry, we developed a deformablelayer tomostatics method that approximates the near-surfacevelocity field as several layers of constant velocity and variablethickness that can be inverted for the geometry of the velocityinterfaces.We use amultiscale model parameterizationin the inversion for interface geometry. Synthetic and fielddata tests showed that the method can determine the interfacegeometry. Constraining the depth range of the basal boundaryof the weathered zone increases the convergence rate ofthe iterative inversion process. Tests on field data showedgreater reflection coherency in a stacked section based onconstrained static corrections than in one from unconstrainedstatic corrections. The method yielded a better match withstatics computed from sand-dune curves than does a matchobtained by using two commercial grid tomographypackages.
展开▼
