question on TauP

Hi Everyone,
I am trying to calculate predicted P and S travel times using the TauP implementation on Obspy using spherical 1D velocity models. For some particular cases, I don’t get any arrivals. For example,

from obspy.taup import TauPyModel
model0=TauPyModel(model=“ak135”)
arrivals=model0.get_travel_times(source_depth_in_km=139.6,distance_in_degree=6.2989,phase_list=[“P”,“S”])
print(arrivals)
0 arrivals

For a different distance, I get arrivals.

arrivals=model0.get_travel_times(source_depth_in_km=139.6,distance_in_degree=11.244,phase_list=[“P”,“S”])
print(arrivals)
2 arrivals
P phase arrival at 156.531 seconds
S phase arrival at 280.654 seconds

Any thoughts on what I am doing wrong and how to fix this ? I will appreciate your help.
Thanks.
Regards,
Avinash

Hi Avinash

taup denotes the phases according to (see ):

P compressional wave, upgoing or downgoing, in the crust or mantle
p strictly upgoing P wave in the crust or mantle
S shear wave, upgoing or downgoing, in the crust or mantle
s strictly upgoing S wave in the crust or mantle
K compressional wave in the outer core
I compressional wave in the inner core
J shear wave in the inner core

Thus try:

from obspy.taup import TauPyModel
model0=TauPyModel(model=“ak135”)
print model0.get_travel_times(source_depth_in_km=139.6,distance_in_degree=6.2989,phase_list=[“p”,“P”,“s”,“S”])
2 arrivals
p phase arrival at 90.571 seconds
s phase arrival at 161.350 seconds

print model0.get_travel_times(source_depth_in_km=139.6,distance_in_degree=11.244,phase_list=[“P”,“S”])
2 arrivals
P phase arrival at 156.531 seconds
S phase arrival at 280.654 seconds

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Generally speaking, different travel paths (p or s phases) are associated with distance. So the phases you specified may not show up at closer or further distances. You probably should specify later reflective phases or diffracted phases. I believe that they provide a list of all the phases taup can list for you. You can also refer to IASP95 travel time curve charts to identify the p and s phases you may be interested in.

Andrea

Professors Schmidt and van Wijk, thanks very much for your help. Using lower case ‘p’ and ‘s’ solved my problem.

Regards,

Avinash