Travel Time Curves for Specific Distance Samples
When MKTTCURVES computes travel times, it scans the take off angle of each phase
with a constant angular increment. This translates into an uneven sampling of
epicentral distance. But in many cases one would like to have travel times for
a set of specific predefined epicentral distances.
A loop which calls MKTTIME many times could be used to produce travel time curves
in such cases, but it would waste a lot of CPU time to do so, since each call of
MKTTIME invokes MKFINDP to determine the necessary ray parameter.
It is far better to use MKTTQUICK with a list of ray parameters that correspoond to
the desired epicentral distances:
- Call [p,a,d]=mkfindp(phase,delta,h,model); with input parameters
- phase
- The seismic phase for which you would like to have travel times
- delta
- A list of epicentral distances, in degrees
- h
- Source depth in kilometers. This has to be a single value!
- model
- a MODEL structure containing the velocity model
- Call ttcurves=mkttquick(model,h,p,a,phase); with input
parameters
- model
- a MODEL structure containing the velocity model
- h
- Source depth in kilometers. This still has to be a single value!
- p
- Output parameter p from MKFINDP. This is a list of ray parameters
which corresponds to the list of epicentral distances used in
the call of MKFINDP
- a
- Output parameter a from MKFINDP. Thuis is a list of take off
angles, corresponding to the ray parameters at source depths.
These angles are necesary to distinguish upgoing from downgoing
rays, when a non-surface source is used.
- phase
- The seismic phase for which you would like to have travel times.
This has to be the same as in the call of MKFINDP.
- ttcurves is now a TTCURVES structure as returned by MKTTCUVRES,
but sampled at the distances you initially defined when calling MKFINDP.
eof.