|SOUTHERN CALIFORNIA WAVEFIELD RECONSTRUCTION|
High density network
data is now making it possible to visualize seismic wavefields as time-varying
two-dimensional fields at the surface of the earth. This project uses
the Southern California Seismic Network with station contributions from
AMOES, USGS, and TERRASCOPE. The study area incorporates stations from
37.5 degrees latitude to 32.5 degrees latitude and from -114 degrees longitude
to -120 degrees longitude. There are many benefits of analyzing data in
2D instead of 1D, such as ease in visualization of wave propagation in
areas of high complexity and the ability to see the spatial extent of
seismic disturbances directly.
Initially we used
a 2D direct B-spline method to approximate the wavefield. This method
failed primarily due to insufficient network density for the frequencies
of interest. For this method the minimum wavelength that can be reasonably
recovered is 100-150 kilometers; however P-waves require resolution of
wavelengths between 50-60 kilometers even for filtered long period signals(
period of 10 seconds ). This method had to be modified to the present
method which uses the azimuth of arriving wavepackets, its apparent velocity,
and approximate waveform from the same data to create a reference wavefield.
This reference wavefield fits the data reasonably well and the misfit
can be fitted using cubic B-splines. This method works due to the fact
that the misfit consists mostly of long period wavelengths. At the moment
this method works for telesiesmic events and not yet for local events.
|Please be patient with this site; movie downloads take between five and ten minutes. If you have any questions or comments please contact Toshiro Tanimoto at email@example.com. Note: all earthquake mpegs displacement scales are in micrometers.|
Check out the station map for coverage details. Notice the large resonating peak in the vicinity of the LA Basin.
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