Ambient noise surface wave tomography
The method is based on the extraction of surface-wave Green functions from cross-correlating sequences of ambient or background seismic noise that from the random seismic wavefield. Dispersion measurements based on ambient noise have distinct advantage over traditional earthquake-based measurements, including extension to the band of measurements to shorter periods, generating information between any arbitrary station pairs, and shrinking lateral sensitivity kernels. The consequence is that surface wave tomography based on the cross-correlation of ambient noise promises significantly lateral and vertical resolution relative to traditional methods of surface wave tomography.
Finite-frequency surface wave tomography
Evaluate 2-D sensitivity kernel validity in predicting surface wave filed
variation when propagating over a heterogeneous structure using numerical
simulation. Develop a regional surface wave tomography method based on 2-D
sensitivity kernels. Using normal mode Rayleigh wave data filtered and windowed
from seismograms recorded at the TriNet network in southern California, I invert
for phase velocities at periods from 25 to 143 s. The phase velocities are
further inverted for shear wave velocity structure at depth range from surface
to 250 km.
Oceanic earthquake location using T-phase
a method to locate small oceanic earthquakes and estimate their earthquake
magnitude using T-phases recorded in an array of ocean-bottom seismometers. The
method can locate small oceanic events with Ms magnitude as low as 2.0 with
epicentral distance about 500 km from the ocean-bottom seismometers. We find
there is a relatively uniform liner relationship between the surface wave
magnitude and T-phase maximum amplitude.
T-phase excitation mechanism
a multiple-reverberation seafloor-scattering model, I model T-phase envelopes
excited by a relatively shallow earthquake beneath a flat seafloor. The
numerical method can accurately predict the character of T-phase shape, rapid
growth followed by gradual decay.
Numerical simulation of seismic waves
a pseudo-spectral method, I model surface wave and body wave propagation over a
3-D heterogeneous medium. The synthesized seismograms can be used to investigate
a number of seismic problems, such as the tradeoff between the azimuthal
anisotropy and heterogeneities that I am working on now.