Abstract. A high-resolution
seismic tomography survey was acquired to obtain a full 3-D P-wave seismic
velocity image in the Záncara river
basin (eastern Spain). The study area consists of lutites and gypsum from a
Neogene sedimentary sequence. A regular and dense grid of 676 shots and 1200
receivers was used to image a 500 m×500 m area of the
shallow subsurface. A 240-channel system and a seismic source, consisting of
an accelerated weight drop, were used in the acquisition. Half a million
travel-time picks were inverted to provide the 3-D seismic velocity
distribution up to 120 m depth. The project also targeted the geometry of
the underground structure with emphasis on defining the lithological contacts
but also the presence of cavities and fault 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. This study
features the necessary key elements to test the travel time tomographic
inversion approach for the high-resolution characterization of the shallow
subsurface. 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.
Examination of the Correlation Between Tectonic Landforms and Shallow Subsurface Structural Datasets for the Estimation of Seismic Source Faults