Abstract
Reliable models of in-situ shear-wave velocities of shallow-water
marine sediments are important for geotechnical applications, lithological
sediment characterization, and seismic exploration studies. We infer
the 2D shear-wave velocity structure of shallow-water marine sediments
from the lateral variation of Scholte-wave dispersion. Scholte waves
are recorded in a common receiver gather generated by an air gun
towed behind a ship away from a single stationary ocean-bottom seismometer.
An offset window moves along the common receiver gather to pick up
a local wavefield. A slant stack produces a slowness-frequency spectrum
of the local wavefield, which contains all modes excited by the air
gun. Amplitude maxima (dispersion curves) in the local spectrum are
picked and inverted for the shear-wave velocity depth profile located
at the center of the window. As the window continuously moves along
the common receiver gather, a 2D shear-wave velocity section is generated.
In a synthetic example the smooth lateral variation of surficial
shear-wave velocity is well reconstructed. The method is applied
to two orthogonal common receiver gathers acquired in the Baltic
Sea (northern Germany). The inverted 2D models show a strong vertical
gradient of shear-wave velocity at the sea floor. Along one profile
significant lateral variation near the sea floor is observed.
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