~.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