High resolution seismic characterization of the shallow subsurface of the Loranca Basin (Spain): high resolution 3D

Abstract

A high-resolution seismic tomography survey was acquired to obtain a full 3-D P-wave seismic velocity image of the Záncara river basin (eastern Spain). The study area consists of lutites and gypsum from a Neogene sedimentary sequence. The project also targeted the geometry of the underground structure with emphasis on defining the lithological contacts but also the presence of cavities and faults or fractures. An extensive drilling campaign provided uniquely tight constraints on the lithology; these included core samples and wireline geophysical measurements. The analysis of the well log data enabled the accurate definition of the lithological boundaries and provided an estimate of the seismic velocity ranges associated with each lithology. The final joint interpreted image reveals a wedge-shaped structure consisting of four different lithological units. The study features the necessary key elements to test the travel time tomographic inversion approach for the high-resolution characterization of the shallow surface. In this methodological validation test, travel-time tomography demonstrated to be a powerful tool with a relatively high capacity for imaging in detail the lithological contrasts of evaporitic sequences located at very shallow depths, when integrated with additional geological and geophysical data.