SUMMARY

Computes traveltime of selected phases for pre-defined velocity models Description and examples assume the calls are made from within SSS. To see the help file for the non-SSS version, go to TRAVELTIME.

SYNTAX

TRAVELTIME {MODEL string} {PICKS number} {PHASE phase list}  {VERBOSE | QUIET} {M |KM}

INPUT

MODEL:	IASP91 [default], AK135
Picks:	If the number is n (0<=n<=9), the first phase will be at Tn in the header. If PICKS is not included among the command-line options, VERBOSE will be turned on and the phase arrival times will be displayed but will not be put in the header.
PHASE:	List of phases for which times are picked and displayed. If PICKS n is among the options, the phase arrivala times and their labels will be added to the header starting at Tn.
VERBOSE | QUIET:
	If VERBOSE is among the options in the TRAVELTIME command line, phase arrival times are displayed relative to both the origin time (O) and to the first-point time (B). If QUIET is among the options in the TRAVELTIME command line, VERBOSE is turned off (if it was on) and nothing is displayed on the screen. If neither has been displayed, the depth used by TRAVELTIME is displayed.
M | KM:	If M is among the options in the command line, SAC interprets EVDP as being in meters. If KM is displayed, EVDP is interpreted as being in kilometers.
DEFAULT VALUES:	MODEL iasp91 KM PHASE P S Pn Pg Sn Sg

DESCRIPTION

All waeforms in memory must have event and station locations defined as well as the origin time.

This command calculates traveltimes using the iaspei-tau procedures developed for models IASP91 or AK135. For more information on this package, go to the iaspei-tau link at URL <http://www.iris.edu/software/downloads/processing/>. The phase picks are stored in the SAC header for all files in memory in header variables Tn, where n is in the range 0 to 9. The times are calculated relative to the origin time (O) but the Tn times are relative to the first-point time (B). The resulting traveltime curves can be plotted on top of a record section plot using the PLOTRECORDSECTION command. If n and the number of phases are such that the phase list runs about T9, those extra phases are not plotted or recorded in the header, but curves will be displayed with the PLOTRECORDSECTION command if the TTIME option is turned on.

The traveltime tables used to calculate the stored degree-distance measure (GCARC). (GCARC is calculated from the event and station latitude and longitudes using spherical-triangle geometry after converting geographic latitudes to geocentric.)

For historical reason, the units for EVDP were meters, and SAC waveforms proudced by RDSEED have EVDP in meters. In v101.5, the default for EVDP is kilometers, but as many waveforms have EVDP in meters, we introduced the command option M which if set to ON means the input EVDP for all files in memory have EVDP inmeters. vIn the next example, the SAC files had been extracted from a SEED vlume using RDSEED, so EVDEP is in meters.

EXAMPLES

A regional event using the default phases:

SAC> fg seismo
SAC> SSS
Signal Stacking Subprocess.
SAC/SSS>  traveltime
traveltime: depth: 15.000000
traveltime: error finding phase P
traveltime: error finding phase S
traveltime: setting phase Pn       at 10.464321 s [ t = 51.894321 s ]
traveltime: setting phase Pg       at 22.904724 s [ t = 64.334724 s ]
traveltime: setting phase Sn       at 50.047722 s [ t = 91.477722 s ]
traveltime: setting phase Sg       at 66.414337 s [ t = 107.844337 s ]
SAC/SSS>

For regional events the first arrivals are Pn or Pg, so by the convention used here there is no "P" arival. For the above example, no picks are added to the header.:

SAC> fg seismo
SAC> SSS
Signal Stacking Subprocess.
SAC/SSS> traveltime picks 0 phase Pn Pg Sn Sg
traveltime: depth: 15.000000
SAC/SSS> lh AMARKER T0MARKER T1MARKER T2MARKER T3MARKER
AMARKER = 10.464                        T0MARKER = 10.464           (Pn)
T1MARKER = 22.905           (Pg)        T2MARKER = 50.048           (Sn)
T3MARKER = 66.414           (Sg)
SAC/SSS> qs
SAC> write seismo-picks.z
SAC>

We see that the already defined A is at Pn. The file written to seismo-picks.z will have T0 through T3 in the header, and a call to PLOT1 will show labeled vertical lines at the calculated times.

Note that even though VERBOSE was not turned on, the depth (in km) used is printed out. This is a safeguard to assure that one has made the correct assumption about the EVDP units. The printing of traveltime depth can be suppressed by entering QUIET on the command line.

The header for the waveform in the following example was produced by RDSEED (V5.0) and EVDP is in meters:

SAC> r 2008.052.14.16.03.0000.XC.OR075.00.LHZ.M.SAC
SAC> lh evdp
evdp = 6.700000e+03
SAC> SSS
Signal Stacking Subprocess.
SAC/SSS> traveltime M picks 0
traveltime: depth: 6.700000 km
SAC/SSS> qs
SAC> lh t0marker t1marker t2marker t3marker
t0marker = 61.48            (Pn)        t1marker = 76.413           (Pg)
t2marker = 109.66           (Sn)        t3marker = 132.11           (Sg)
SAC> ch evdp (0.001 * &1,evdp&)
SAC> setbb station &1,KSTNM&
SAC> write %station%.z
SAC>

The saved file, OR075.z, will have evdp in kilometers and annotated picks at the times for Pn, Pg, Sn, and Sg. (One could have done the chnhdr command before calling TRAVELTME and then not entered M on the command line.)

Phase names are case sensitive. See the iaspei-tau documentation.

See Commands

PLOTRECORDSECTION

LATEST REVISION

August, 2011 (Version 101.5)