[CIG-SEISMO] Unbounded response when inputting a point source with ormsby wavelet source function

[Jose A. Abell M.]

Dear developers,

I'm using SW4 to model a simple layered velocity structure with a single
double-couple point source representing a simple 45-degree dip-slip reverse
fault. I'm trying to use an ormsby wavelet as a source time function. The
Ormsby wavelet was defined to have a frequency bandwidth of 10Hz (content
from about 0.1Hz to 10 Hz), and and a peak at t0 = 2s. The wavelet is
further windowed with a cosine taper so that we avoid the initial
transient.

The idea is to provide an input with a specific simple frequency content
and then see what the spectrum looks like at receiver stations. With a
Vs_min of 500m/s at the top layer and a grid spacing of 15m, I expect that
not all this wavelet will be resolvable by the model. This is another issue
that I want to explore.

I'm getting unbounded results at the receiver stations. That is, response
oscillates with ever increasing amplitude.

I've attached my model file, input source time function (ormsby.txt), the
SLURM script I'm using to run this file, the outputs I'm getting with my
run, and a plot at one of the stations.

Could you please help me understand what I might be doing wrong?

Best regards,

--

José Abell
*PhD Candidate*
Computational Geomechanics Group
Dept. of Civil and Environmental Engineering
UC Davis
www.joseabell.com
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