SUMMARY

Computes traveltimes of selected phases for pre-defined velocity models. This routine has the same source code as SSS/TRAVELTIME. If one is in SSS, one can use different plotting routines. For an exampole, see SSSTRAVELTIME.

SYNTAX

TRAVELTIME {MODEL string} {ONLINE} {VERBOSE | QUIET} {PICKS number}
    {PHASE phase list}  {CLEAR} {ONRECORD ON|OFF} {M | KM}

INPUT

MODEL: iasp91 [default], ak135. Traveltimes are calculated using the iaspei-tau procedures and traveltime tables. (For further informati, see documentation referenced below.)

ONLINE: Retrieve traveltimes from the IRIS Traveltime Web Service. This uses Crotwell's TauP Toolkit internally. In addition to iasp91 and ak135, it includes model prem. Also, it includes additional phases, and some phase groupings are not the same as for the iaspei-tau tables used by SAC. (For further informati, see documentation referenced below.)

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 the first-point time (B). If instead, QUIET is among the options, nothing is displayed. VERBOSE is the default.

PICKS: There are 10 time picks in the SAC header: t0 to t9. If the number is n (0<=n<=9), the first phase will be at Tn. The default is n=0. If PICKS is included among the command-line options and if phases are within the taime range of and seismogram in memory, the picks will be included in the header for that seismogram and will be displayed in subsequent plots such as PLOT1 and PLOTPK. The default is not to have PICKS on, but if PICKS is turned on, it will remain on for subsequent runs with the same data set. Traveltimes are calculated relative to the origin (O) but the displayed and stored Tn times are relative to (B).

PHASE: List of phases for which times are displayed (unless QUIET is turned on). Phase names are generally case sensitive. As of SAC v102.0, verbose ... phase displays phases in chronological order, and the sorting is done before comparison with PICKS list If PICKS n is among the command-line options, the phase arrival times and their times and labels will be added to the header starting at Tn. If n is 0, one can have up to 10 phases put in the header and available for subsequent plots. If n is 8, one can have at most 2 new phases added to the header.

ONRECORD ON|OFF:

If the command line has ONRECORD ON, phases are displayed (VERBOSE) and/or included as a PICK if the arrival time is between (B) and (E) for each station. ONRECORD OFF is the Default

CLEAR: Clears the phase list from previous runs. An empty phase list will be populated with the DEFAULT phases (see below) or values taken from the environment variable SAC_TRAVELTIME_PHASES. (See below.) In the command line, CLEAN must come before PHASE

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. M was the default in SAC until 2005. For all runs of TRAVELTIME VERBOSE, the depth is printed to the screen so it is obvious whether meters or kilometers were used

DEFAULT VALUES: MODEL iasp91 ONRECORD OFF KM PHASE P S Pn Pg Sn Sg

MODEL:	iasp91 [default], ak135. Traveltimes are calculated using the iaspei-tau procedures and traveltime tables. (For further informati, see documentation referenced below.)
ONLINE:	Retrieve traveltimes from the IRIS Traveltime Web Service. This uses Crotwell's TauP Toolkit internally. In addition to iasp91 and ak135, it includes model prem. Also, it includes additional phases, and some phase groupings are not the same as for the iaspei-tau tables used by SAC. (For further informati, see documentation referenced below.)
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 the first-point time (B). If instead, QUIET is among the options, nothing is displayed. VERBOSE is the default.
PICKS:	There are 10 time picks in the SAC header: t0 to t9. If the number is n (0<=n<=9), the first phase will be at Tn. The default is n=0. If PICKS is included among the command-line options and if phases are within the taime range of and seismogram in memory, the picks will be included in the header for that seismogram and will be displayed in subsequent plots such as PLOT1 and PLOTPK. The default is not to have PICKS on, but if PICKS is turned on, it will remain on for subsequent runs with the same data set. Traveltimes are calculated relative to the origin (O) but the displayed and stored Tn times are relative to (B).
PHASE:	List of phases for which times are displayed (unless QUIET is turned on). Phase names are generally case sensitive. As of SAC v102.0, verbose ... phase displays phases in chronological order, and the sorting is done before comparison with PICKS list If PICKS n is among the command-line options, the phase arrival times and their times and labels will be added to the header starting at Tn. If n is 0, one can have up to 10 phases put in the header and available for subsequent plots. If n is 8, one can have at most 2 new phases added to the header.
ONRECORD ON\|OFF:
	If the command line has ONRECORD ON, phases are displayed (VERBOSE) and/or included as a PICK if the arrival time is between (B) and (E) for each station. ONRECORD OFF is the Default
CLEAR:	Clears the phase list from previous runs. An empty phase list will be populated with the DEFAULT phases (see below) or values taken from the environment variable SAC_TRAVELTIME_PHASES. (See below.) In the command line, CLEAN must come before PHASE
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. M was the default in SAC until 2005. For all runs of TRAVELTIME VERBOSE, the depth is printed to the screen so it is obvious whether meters or kilometers were used
DEFAULT VALUES:	MODEL iasp91 ONRECORD OFF KM PHASE P S Pn Pg Sn Sg

DESCRIPTION

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

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

A quick way to find out all the possible phases that could be be visible on a seismogram according to TRAVELTIME, use phase all. Eg..:
SAC> read my-seismogram
SAC> traveltime verbose phase all
SAC> traveltime verbose onrecord on clear phase all
The second traveltime command displays only arrivals that are between (B) and (E) for my-seismogram. The clear option removes phase data from memory for the previous call .

As discussed in DATAGEN, seismograms from a deep-focus event have been added: ${SACHOME}/aux/datagen/deep/. Arrivals are sharp, and several converted phases can be seen. We use that event to demonstrate how to use TRAVELTIME:
SAC> datagen sub deep bla.r
SAC> lh b e o gcarc evdp
   b = 5.911000e+02                        e = 1.499100e+03
   o = 0.000000e+00                    gcarc = 8.627435e+01
   evdp = 6.110000e+02
SAC> traveltime verbose picks 0 onrecord on phase all
   traveltime: depth: 611.000 km
   ...
   traveltime: setting phase SKSac    at 1265.9326 s [ t = 1265.9326 s ] t9
   ...
SAC> traveltime picks 9 clear phase SKS
   traveltime: depth: 611.000 km
   traveltime: error finding phase SKSdf
   traveltime: setting phase SKSac    at 1265.9326 s [ t = 1265.9326 s ] t9
In the traveltime call, arrival SKSac was the 10th arrival so would be the last stored pick. If clear had not been included in the second command, the VERBOSE output would have been incorrect. (Try it.) Prior to SAC v102.0, phase SKS would have returned error finding phase SKS.

Next are the commands and an output plot for a run using the radial component for four stations and six phases. Because plot command PLOT1 plots traces from top-to-bottom in the order read in, we manually re-ordered the files so that distance increases from first to last. Phase sPP is not in the isasp-tau tables but is in the ONLINE tau-p tables. (A nice feature for SAC TRAVELTIME is the ability to combine phases from multiple traveltime table in a single plot:
SAC> datagen sub deep  kev.r kip.r pas.r bla.r
SAC> rtr
SAC> traveltime quiet online picks 0 phase sPP
SAC> traveltime  picks 1 phase P pP sP S sS SKS
SAC> FILEID LOCATION UL TYPE LIST KSTCMP
SAC> TITLE 'Sakhalin Island Event: &1,KZDATE&, Depth is &1,EVDP& KM'
SAC> p1
SAC> save sakhalin-picks_p1.pdf
In SSSTRAVELTIME a plot is created for the same seismograms and phases using PLOTRECORDSECTION.

DEFAULT PHASES

The default phases for TRAVELTIME are set as local crustal phases: "P S Pn Pg Sn Sg". If a different set of default phases is desired the environment variable SAC_TRAVELTIME_PHASES can be set to override the default. The variable is comma or space delimited. For teleseismic data, one might use "P pP sS S pS sS PP SS". An alternative is to use "all" to capture as many phases as possible.

Note:Environmental variables must be set outside of SAC. In the sh shell, for all, enter export SAC_TRAVELTIME_PHASES-"all". For shell csh: setenv SAC_TRAVELTIME_PHASES "all".

REFERENCES

Iaspei-tau: https://seiscode.iris.washington.edu/projects/iaspei-tau/

TauP Toolkit: http://www.seis.sc.edu/downloads/TauP/taup.pdf Section 4: Phase naming in TauP

IRIS DMC IRISWS traveltime Web Service Documentation https://service.iris.edu/irisws/traveltime/1/

LATEST REVISION

Version 2.0