Misc. Reference Manual Pages BW_RELP(3.1) NAME bw_relp - Broadband Waveform Regional Earthquake Location Program SYNOPSIS bw_relp -i ipar_file -v vmod_file -a amod_file -p pta_file DESCRIPTION bw_relp is an earthquake location algorithm designed specif- ically for locating earthquakes at local and regional dis- tances using phase onset times and onset azimuths recorded by relatively sparse network of three-component broadband stations. An adaptive, migrating grid search algorithm is used to locate the hypocenter. The grid migrates and the mesh size shrinks as it homes in on the global minimum in the L**n misfit parameter space. The value of "n" in L**n is the norm (n = 2 is standard least-squares, for example) and n can be any positive real number (0 < n < Inf). bw_relp only requires forward model calculations, thus it differs from most commonly used earthquake location algo- rithms in that NO derivatives are required. This greatly simplifies the required computations, particularly for com- plex 2-D and 3-D velocity and azimuthal models. The current implementation of bw_relp uses a linear gradient over a halfspace velocity model and a halfspace azimuth model. bw_relp is designed so that the user can easily supply the appropriate subroutines for calculating phase onset times and azimuths using more complex models. OPTIONS The following arguments must all be specified as the four files provide bw_relp with the algorithmic parameters, velo- city model, azimuth model, and observed onset times and azimuths. -i par_file Algorithmic parameter file which sets all the parame- ters required to implement the adaptive grid search. -v vmod_file Velocity model file which contains the velocity model for each phase. -a amod_file Azimuthal model file which contains the azimuthal model for each phase. -p pta_file Observed phase onset times and onset azimuths file. BDSN Last change: 28 December 1999 1 Misc. Reference Manual Pages BW_RELP(3.1) ALGORITHMIC PARAMETERS The following parameters are specified in the par_file. The input are free format and the file contains 6 lines: Line 1 -> g_alpha g_beta g_gamma g_epsilon g_grid g_vrb Where: g_alpha specifies the relative weight of onset time and onset azimuth data. The range of g_alpha is 0.0 to 1.0: 0.0 -> only onset times used in solution 0.5 -> equal weight 1.0 -> only onset azimuths used in solution g_beta Grid reduction ratio which determines how much the grid step size is reduced for each successive iteration. g_gamma Number of grid elements in the migrating grid. The number of nodes, in each dimension over which the grid search is performed, is two times g_gamma plus one. It is recommended that g_gamma be no less than 3. g_epsilon Solution convergence criteria. The successive itera- tions stop when the grid mesh size is smaller than g_epsilon. g_grid Enables writing a bw_relp.gd file containing location and norm parameter for each node. Set to 1.0 to enable and 0.0 to disable. g_vrb Enables writing of verbose output. Set to 1.0 to enable and 0.0 to disable. Line 2 -> d_metric g_ln g_tplat g_tplon g_uncfac Where: d_metric Metric for comparing time and azimuth data. It should be set to the average propagation velocity in km/sec. g_ln Order of the calculated norm. Set to 2.0 for classical least-squares norm. g_tplat Tangent plane latitude (deg +north). BDSN Last change: 28 December 1999 2 Misc. Reference Manual Pages BW_RELP(3.1) g_tplon Tangent plane longitude. The grid search uses a local cartesian coordinate frame defined by a plane tangent to the sphere at g_tplat and g_tplon. g_uncfac Uncertainty scaling factor. Set to 1.0 for standard error and 2.0 for 95 percent confidence interval, for example. Line 3 -> g_lat0 g_lat1 g_dlat Where: g_lat0 Southern boundary of the initial grid (deg, +north). g_lat1 Northern boundry of the initial grid (deg, +east). g_dlat Initial grid latitude step size (deg). The maximum mesh dimension is 99 in any direction due to the way the grid search is indexed. .B bw_relp will abort with an appropriate error message if the maximum mesh dimen- sion is exceeded. Line 4 -> g_lon0 g_lon1 g_dlon Where: g_lon0 Western boundry of the initial grid (deg, +east). g_lon1 Eastern boundry of the initial grid (deg, +east). g_dlon Initial grid longitude step size (deg). Line 5 -> g_t0hr g_t0mn g_t0sc g_t0tic g_t1hr g_t1mn g_t1sc g_t1tic g_dt Where: g_t0hr Initial grid minimum time hour. g_t0mn Initial grid minimum time minute. g_t0sc BDSN Last change: 28 December 1999 3 Misc. Reference Manual Pages BW_RELP(3.1) Initial grid minimum time second. g_t0tic Initial grid minimum time tics (1 tic = 0.1 msec). g_t1hr Initial grid maximum time hour. g_t1mn Initial grid maximum time minute. g_t1sc Initial grid maximum time second. g_t1tic Initial grid maximum time tics (1 tic = 0.1 msec). g_dt Initial grid time step (sec). Line 6 -> g_d0 g_d1 g_dd Where: g_d0 Minimum depth of initial grid (km). g_d1 Maximum depth of initial grid (km). g_dd Initial grid depth step size (km). EXAMPLE PHASE FILE - par_file 0.0 0.20 5.0 0.0001 1.0 0.0 6.0 2.00 37.876 -122.267 1. 37.8 38.0 0.025 -122.4 -122.1 0.025 19 15 05 0000 19 15 08 0000 0.1 7.0 9.0 0.25 VELOCITY MODEL PARAMETERS The following parameters specify the velocity model for each phase. Currently the models are limited to a linear gra- dient layer over a halfspace. The parameters are: where the following data are repeated for each phase: v_ph Phase id (limited to 2 characters (a2)). v_a Layer surface velocity (km/sec). v_b Layer velocity gradient ((km/sec)/km). v_c Halfspace velocity (km/sec). BDSN Last change: 28 December 1999 4 Misc. Reference Manual Pages BW_RELP(3.1) v_d Layer thickness (km). EXAMPLE VELOCITY MODEL FILE - vmod_file P 5.24 0.068 7.98 25.0 S 3.03 0.039 4.61 25.0 AZIMUTH MODEL PARAMETERS The following parameters specify the azimuth model for each phase. Currently the only option available is use to use a halfspace for the calculation of azimuths. The parameter is: a_nam Azimuth model. Must be set to 1 in current implementa- tion of algorithm to use a halfspace for calculating azimuths. EXAMPLE ANGLE MODEL FILE - amod_file 1 PHASE PARAMETERS The following parameters specify the phase onset time and onset azimuth data and all related information (repeated for each station/phase): s_code s_net s_lat s_lon s_elv s_str s_ph s_yr s_doy s_hr s_mn s_sc s_tic s_tcp s_seot s_az s_seaz s_aoi s_seaoi s_tdel s_dur s_lpfc s_otad s_oazad s_oaiad Where: s_code Station code (a4). s_net Network code (a2). s_lat Station latitude (deg, +north). s_lon Station longitude (deg, +east). s_elv Station elevation (m). s_str Data stream (a3) (use SEED conventions). s_ph Phase identifier (a2). BDSN Last change: 28 December 1999 5 Misc. Reference Manual Pages BW_RELP(3.1) s_yr Onset time year (i4) (include century). s_doy Onset time day of year (i). s_hr Onset time hour (i). s_mn Onset time minute (i). s_sc Onset time second (i). s_tic Onset time tics (i) (fractions of a second). s_tcp Onset time tic precision (i1) (number of decimal places required to represent s_tic) (eg: 4 for 0.1 msec reso- lution and 6 for 1 microsecond resolution) s_seot Uncertainty of onset time (sec). Set to a negative value if the phase onset time is not to be used in solution. s_az Phase onset azimuth (deg CW from north). Set to nega- tive value if azimuth is not to be used in solution. s_seaz Uncertainty in phase onset azimuth (deg). s_aoi Phase onset apparent angle of incidence (aaoi) (deg). Set to a negative value if azimuth is not to be used in solution. s_seaoi Uncertainty in phase onset apparent angle of incidence (deg). s_tdel Time delay (sec) between above phase time information and the start of time window used to determine s_az and aoi. s_dur Time interval (sec) used to determine s_az and s_aoi. s_lpfc Low-pass filter corner frequency (Hz). Typically set to the frequency of the anti-aliasing filter. s_otad BDSN Last change: 28 December 1999 6 Misc. Reference Manual Pages BW_RELP(3.1) Station phase onset time adjustment (sec). s_oazad Station phase onset azimuth adjustment (deg). s_oaia Station phase onset aaoi adjustment (deg). EXAMPLE PHASE FILE - pta_file BKS BK 37.877 -122.235 276. HHE S 1996 313 19 15 09 7174 4 -0.02 -1.0 0.0 -1.0 0.0 0.0 0.0 8.0 0.000 0.0 0.0 BKS BK 37.877 -122.235 276. HHZ P 1996 313 19 15 08 1674 4 0.02 -1.0 0.0 -1.0 0.0 0.0 0.0 8.0 0.000 0.0 0.0 BRIB BK 37.9189 -122.1506 0. BHZ P 1996 313 19 15 09 5283 4 0.02 -1.0 0.0 -1.0 0.0 0.0 0.0 8.0 0.000 0.0 0.0 BRIB BK 37.9189 -122.1506 0. DP3 S 1996 313 19 15 11 1877 4 0.02 -1.0 0.0 -1.0 0.0 0.0 0.0 8.0 0.000 0.0 0.0 BRK BK 37.873 -122.260 81. BHZ P 1996 313 19 15 08 1674 4 0.02 -1.0 0.0 -1.0 0.0 0.0 0.0 8.0 0.000 0.0 0.0 BRK BK 37.873 -122.260 81. DP3 S 1996 313 19 15 09 2420 4 0.02 -1.0 0.0 -1.0 0.0 0.0 0.0 8.0 0.000 0.0 0.0 CMSB BK 37.8720 -122.2506 0. CL1 P 1996 313 19 15 08 0837 4 0.02 -1.0 0.0 -1.0 0.0 0.0 0.0 8.0 0.000 0.0 0.0 CMSB BK 37.8720 -122.2506 0. CL2 S 1996 313 19 15 09 2817 4 0.02 -1.0 0.0 -1.0 0.0 0.0 0.0 8.0 0.000 0.0 0.0 RFSB BK 37.9162 -122.3350 0. HL1 P 1996 313 19 15 08 6834 4 0.02 -1.0 0.0 -1.0 0.0 0.0 0.0 8.0 0.000 0.0 0.0 RFSB BK 37.9162 -122.3350 0. HL2 S 1996 313 19 15 10 3234 4 0.02 -1.0 0.0 -1.0 0.0 0.0 0.0 8.0 0.000 0.0 0.0 YBIB BK 37.8143 -122.3581 4. HL1 P 1996 313 19 15 09 1856 4 0.02 -1.0 0.0 -1.0 0.0 0.0 0.0 8.0 0.000 0.0 0.0 YBIB BK 37.8143 -122.3581 4. HL2 S 1996 313 19 15 11 1296 4 0.02 -1.0 0.0 -1.0 0.0 0.0 0.0 8.0 0.000 0.0 0.0 OUTPUT Besides what is printed to the screen, bw_relp outputs two files, an event file and a solution file bw_relp.el which gives the event location and its uncertainties. For exam- ple, envoking bw_relp with the above example input files produces the following: EXAMPLE EVENT LOCATION FILE - bw_relp.el 1996.313 19:15:06.8848 37.87523 -122.26545 7.398 ( 0.0367) ( 0.432) ( 0.285) ( 0.199) Where the numbers in parenthesis are the uncertainty in sec for time and km for latitude, longitude, and depth. bw_relp.sl gives the event solution with the residuals for each observation. For example, envoking bw_relp with the above example input files produces the following: EXAMPLE EVENT SOLUTION FILE - bw_relp.sl Date -> 1996.313 Origin Time -> 19:15:06.8848 ( 0.0367) Latitude -> 37.87523 ( 0.432) Longitude -> -122.26545 ( 0.285) Depth -> 7.398 ( 0.199) Std Error -> 0.122 Threshold -> 5.8138E-01 BDSN Last change: 28 December 1999 7 Misc. Reference Manual Pages BW_RELP(3.1) STN NW STR PH YEAR DOY HR MN SC TICS DELTA Tobs Tse Tcalc Tres AZobs AZse AZcalc AZres BKS BK HHZ P 1996.313,19:15:08.1674 2.69 1.283 0.020 1.434 -0.152 BRIB BK BHZ P 1996.313,19:15:09.5283 11.21 2.644 0.020 2.445 0.199 BRIB BK DP3 S 1996.313,19:15:11.1877 11.21 4.303 0.020 4.230 0.073 BRK BK BHZ P 1996.313,19:15:08.1674 0.54 1.283 0.020 1.352 -0.069 BRK BK DP3 S 1996.313,19:15:09.2420 0.54 2.357 0.020 2.338 0.019 CMSB BK CL1 P 1996.313,19:15:08.0837 1.35 1.199 0.020 1.370 -0.172 CMSB BK CL2 S 1996.313,19:15:09.2817 1.35 2.397 0.020 2.371 0.026 RFSB BK HL1 P 1996.313,19:15:08.6834 7.62 1.799 0.020 1.935 -0.136 RFSB BK HL2 S 1996.313,19:15:10.3234 7.62 3.439 0.020 3.348 0.091 YBIB BK HL1 P 1996.313,19:15:09.1856 10.60 2.301 0.020 2.353 -0.052 YBIB BK HL2 S 1996.313,19:15:11.1296 10.60 4.245 0.020 4.071 0.174 In addition to the above two files, bw_relp also outputs a bw_relp.gds file if g_grid is enabled. This file contains a latitude, longitude, norm parameter triplet for each point on the grid which is searched. In order to make the con- tents of bw_relp.gds easy to interpret, set g_tt and g_dd equal to 0.0 so that the grid search is confined to latitude and longitude. AUTHOR Bob Uhrhammer, UC Berkeley Seismological Laboratory bob@seismo.berkeley.edu BUGS Report any bugs, problems or suggestions to the author.