Full-waveform joint inversion of ambient noise data and teleseismic P
waves: methodology and applications to central California
Abstract
Adjoint tomography (i.e., full-waveform inversion) has been recently
applied to ambient seismic noise and teleseismic P waves separately to
unveil fine-scale lithospheric structures beyond the resolving ability
of traditional ray-based traveltime tomography. In this study, we
propose a joint inversion scheme that alternates between
frequency-dependent traveltime inversions of ambient noise surface waves
and waveform inversions of teleseismic P waves to take advantage of
their complementary sensitivities to the Earth’s structure. We apply our
method to ambient noise empirical Green’s functions from 60 virtual
sources, direct P and scattered waves from 11 teleseismic events
recorded by a dense linear array (~ 7 km station spacing) and other
regional stations (~ 40 km average station spacing) in central
California. To evaluate the performance of the method, we compare
tomographic results from ambient noise adjoint tomography, full-waveform
inversion of teleseismic P waves, and the joint inversion of the two
data sets. Both applications to practical field data sets and synthetic
checkerboard tests demonstrate the advantage of the joint inversion over
individual inversions as it combines the complementary sensitivities of
the two independent data sets towards a more unified model. The 3D model
from our joint inversion not only shows major features of velocity
anomalies and discontinuities in agreement with previous studies. but
also reveals small-scale heterogeneities which provide new constraints
on the geometry of the Isabella Anomaly and mantle dynamic processes in
central California. The proposed joint inversion scheme can be applied
to other regions with similar array deployments for high-resolution
lithospheric imaging.