MLOC stn File

~.stn File

A ~.stn file is created every time mloc runs. It is written by routines in a number of modules, including:

  • mloc.f90
  • mlocset.f90
  • mlocio_mnf.f90
  • mloclib_stations.f90
  • mlocout_gmt.f90

The information carried in a ~.stn file is of many types and the exact contents of a ~.stn file vary according to specifics of the arrival time dataset and the relocation strategy. Some of it is included for archival purposes but the most important function is to provide information about station codes and their coordinates that is helpful in diagnosing problems.

If supplemental station files have been used in a relocation analysis the first section of the ~.stn file deals with them:

Supplemental station files: 
SSTN-1 salmas2/makhin_stn_bhrc.dat
SSTN-2 salmas2/makhin_stn_dda.dat
SSTN-3 salmas2/makhin_stn_neic.dat

salmas2/makhin_stn_bhrc.dat
3 BHRC stations for Makhin
    1 stations read

salmas2/makhin_stn_dda.dat
3
    7 stations read

salmas2/makhin_stn_neic.dat
5 Supplemental station file from NEIC Metadata
   13 stations read

Note that the number in column 1 of the first line of each supplemental station file, which is printed after the file name, is not the number of station codes in the file, but rather an index specifying the format of the file. The number of stations read is printed on the next line.

The next section deals with reading the master station file. While it is read, cases of duplication between the master station file (annotated as “IR” for International Registry) and one or more of the supplemental station files are compiled:

tables/stn/master_stn.dat
0 MLOC master station list
22113 stations read

22134 total stations read
ALKP                   -29.9418             22.2467     1.065 SSTN-3  
ALKP                   -29.9423             22.2480     1.066 IR      
                         0.0005             -0.0013    -0.001 significant difference in coordinates  

SKN                     61.9800           -151.5317     0.581 SSTN-3  
SKN                     42.9915            -76.4672     0.226 IR      
                        18.9885            -75.0645     0.355 conflicting station codes              

KHWEE                  -21.9464             25.4469     1.080 SSTN-3  
KHWEE                  -21.9463             25.4468     1.083 IR      
                        -0.0001              0.0001    -0.003 minor difference in coordinates        

HSNB                    47.2769            -66.0601     0.337 SSTN-3  
HSNB                    47.2769            -66.0601     0.337 IR      
                         0.0000              0.0000     0.000 pure duplicate                         

POIN                    72.7012            -77.9620     0.021 SSTN-3  
POIN                    72.7012            -77.9620     0.021 IR      
                         0.0000              0.0000     0.000 pure duplicate                         

EDA                      3.7789             10.1534     0.140 SSTN-3  
EDA                      3.7791             10.1533     0.000 IR      
                        -0.0002              0.0001     0.140 significant difference in coordinates  

ACRG                     5.6415             -0.2072     0.075 SSTN-3  
ACRG                     5.6415             -0.2072     0.075 IR      
                         0.0000              0.0000     0.000 pure duplicate                         


Duplicate stations:
    3 pure duplicates
    1 with minor differences
    2 with significant differences
    1 station conflicts
    7 total

Each case is characterized, depending on how different the coordinates are; the difference in each parameter (latitude, longitude, elevation) is shown. Pure duplicates can be ignored (the coordinates from the first occurrence will be used by mloc), or the instance of that station can be deleted from the corresponding supplemental station file to simplify things. Likewise, minor differences in coordinates can be ignored, or resolved by deleting the one from the supplemental station file, unless that station is being used for direct calibration. In that case it is advisable to investigate further.

Significant differences in coordinates also require investigation; in many cases they are caused by discrepancies in the elevation (see station EDA, above). An entry with zero elevation (like the master station file for EDA) is probably in error. The solution could be to let mloc use the entry from the supplemental station, or to check the elevation with Google Earth and correct it in the master station file.

Conflicting station codes may represent a problem or the solution to a problem, depending on whether or not the arrival time dataset contains readings from a station that has the same station code as one in the master station file but different coordinates. If it does then it is necessary to introduce the correct coordinates in a supplemental station file, which will lead to the report of a conflict. If it does not, however, the conflicting station code should be removed from the supplemental station file. This often happens when a supplemental station file is for an entire network, of which only a few are actually needed for the arrival time dataset.

The next section reports on any cases where the date of an arrival in the dataset falls outside the operational epoch specified for that station in whichever station file was used for its coordinates; usually it is the master station file:

   stafind: failed date_range:   11 527 MAG    1976329 1952001 1975259                                                                 
   stafind: failed date_range:   11 528 MAG    1976329 1952001 1975259                                                                 
   stafind: failed date_range:   11 529 MAG    1976329 1952001 1975259                                                                 
   stafind: failed date_range:   19 461 MAG    1977146 1952001 1975259                                                                 
   stafind: failed date_range:   19 462 MAG    1977146 1952001 1975259                                                                 
   stafind: failed date_range:   66 572 DMT    2011296 1979213 1998001                                                                 
mlocset:    6 readings failed the station file date range

The first entry is interpreted as : “For the reading of MAG on line 527 of event 11 the observed date (day 329 of 1976) is outside the operational epoch (day 1 of 1952 to day 259 of 1975) currently specified for this station”. As discussed elsewhere the normal solution is to edit the operational epoch information in the station file.

This is followed by a report on missing stations:

Stations in the dataset that are missing from the station files:
TDG                    2 instances
MAG                    5 instances
AHLTE                  1 instances

Note that the 5 instances of MAG missing are caused by the failed date range condition. Cases where there is a single instance can usually be ignored, since such a reading will not contribute to the cluster vectors. If it would contribute to a direct calibration, however, it would be important to resolve the problem.

The next section is helpful in cases where one or more large supplemental files have been referenced to obtain coordinates for only a few stations:

Stations from supplemental station files that are present in the dataset, generic format:
3 Supplemental station file for salmas2.2
QOT1                  38.4800   44.4000  1946                       SSTN-1
3001                  37.5744   43.7877  1732                       SSTN-2
3604                  40.3313   42.5899  2098                       SSTN-2
4702                  37.4171   41.3574   933                       SSTN-2
4904                  38.7356   41.7742  1300                       SSTN-2
6506                  39.0196   43.3380  1681                       SSTN-2
6508                  38.6573   43.9767  1994                       SSTN-2
OLTU                  40.5460   41.9734  1350                       SSTN-2
ALKP                 -29.9418   22.2467  1065                       SSTN-3
KHWEE                -21.9464   25.4469  1080                       SSTN-3
BLKN                  64.3185  -96.0024    40                       SSTN-3
HSNB                  47.2769  -66.0601   337                       SSTN-3
POIN                  72.7012  -77.9620    21                       SSTN-3
YKAW3                 62.5616 -114.6099   196                       SSTN-3
EDA                    3.7789   10.1534   140                       SSTN-3
ACRG                   5.6415   -0.2072    75                       SSTN-3
SHAA                  37.5620   68.1228   868                       SSTN-3

The text provided here could be copied and pasted into a new cluster-specific supplemental station file, eliminating the need for the original supplemental station files and greatly reducing the chance of inadvertent station conflicts. The next section is also helpful in trimming unnecessary entries from supplemental station files:

Stations from supplemental station files that are not present in the dataset:
SKN                   61.9800 -151.5317   581                       SSTN-3
ZAA0B                 53.9481   84.8188   229                       SSTN-3
DHK1                  36.8606   42.8665    16                       SSTN-3
E28B                  46.5748 -100.6934   704                       SSTN-3

The next section is quite long, so only the first few entries are shown below. This is a section of the ~.stn file that is mainly included for archival and/or forensic purposes:

  3762 stations in the arrival time dataset for which coordinates were found:
BAK                   40.3720   49.8180    83       1903001         IR
KSA                   33.8233   35.8900   920               2001365 IR
FEO                   45.0190   35.3900    40       1927001         IR
YAL                   44.4875   34.1547    23       1928001         IR
SEV                   44.5450   33.6680    42       1928001         IR
HLW                   29.8583   31.3417   135       1899244         IR
SAM                   39.6733   66.9900   704       1913001         ERE
KUC                   55.7500   37.9667   155                       IR

The cases shown have all taken the coordinates from the master station file (including one case where coordinates from Bob Engdahl “ERE” are preferred). In the full listing there will be some entries referencing the supplemental station files (e.g., “SSTN-1”, “SSTN-2”, etc). For any cases that showed up in the station conflicts section of the ~.stn file, the nature of the conflict will be added for annotation.

For a direct calibration relocation the last section of the ~.stn file lists the stations used for the hypocentroid, breaking out any S-P data separately:

Seismic stations used for direct calibration.
ERE                   40.1700   44.4700   998
TAB                   38.0675   46.3267  1430
GRS                   39.5000   46.3333  1399
NAK                   39.2050   45.4150   887
KDR                   39.1500   46.1000  2155
ISHB                  38.2833   45.6192  2300
VANT                  38.4210   43.2653  1750
ITBZ                  38.2348   46.1498  1600
IMRD                  38.7132   45.7022  2100
VANB                  38.5090   43.4058  1227
TVAN                  38.5286   43.4061  2008
HKR                   37.5780   43.7408  1750
IAZR                  37.6775   45.9837  2300
MAKU                  39.3549   44.6834  1234
HAKT                  37.5579   43.7071  2153
CUKT                  37.2474   43.6076  1298
CLDR                  39.1431   43.9170  2087
DYDN                  39.5436   43.6889  2010
GEVA                  38.3122   43.0586  1672
TUTA                  39.4019   42.8137  2154
AGRB                  39.5755   42.9920  1820
NAX                   39.1740   45.4950   927
VMUR                  38.9894   43.5716  1717
BASK                  38.0523   44.0040  1931
EKAR                  39.2559   42.0640  2129
ERCV                  39.0198   43.3380  1681
ADCV                  38.8080   42.7245  1774
TATV                  38.5080   42.2672  1831
OZAP                  38.6614   43.9928  2058
YOVA                  37.5871   44.2896  1946
3001                  37.5744   43.7877  1732
6508                  38.6573   43.9767  1994
6506                  39.0196   43.3380  1681
AKDM                  38.3285   42.9800  1662
MLAZ                  39.1410   42.5495  1581
GURO                  38.5509   42.0322  1388
QOT1                  38.4800   44.4000  1946

S-P stations used for direct calibration.
GEVA                  38.3122   43.0586  1672

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