Constructing a 3-D radially anisotropic crustal velocity model for
Oklahoma using full waveform inversion
Abstract
Over the past decade, the seismicity rate in the state of Oklahoma has
increased significantly, which has been linked to industrial operations,
such as saltwater injection. Taking advantage of induced earthquakes and
recently deployed seismometers, we construct a 3-D radially anisotropic
seismic velocity model for the crust of Oklahoma by using full waveform
inversion. To mitigate the well-known cycle-skipping problem, we use
misfit functions based on phase and waveform differences in several
frequency bands. Relative velocity perturbations in the inverted model
allow us to delineate major geological provinces in Oklahoma, such as
the Anadarko and Arkoma Basins, as well as the Cherokee Platform and
Shelf. In addition, radial anisotropy in the inverted model reflects
deformation within the crust of Oklahoma, which might correlate with
sedimentary layers, micro-cracks/fractures, as well as the dominant
orientation of anisotropic minerals. The crystalline basement beneath
Oklahoma can be inferred from the new velocity model, which enables us
to classify induced seismicity in current earthquake catalogs better.
Furthermore, synthetic experiments suggest that the new velocity model
enables us to better constrain earthquake location in Oklahoma,
especially for determining their depths, which are important for
investigating induced seismicity.