5.3.4 High accuracy in SEISAN

SEISAN can use higher accuracy than the default. The goal is to have an accuracy of 1 ms in time and 1 m in location.

In order to write out the high accuracy numbers, a new parameter has been added to SEISAN.DEF. The parameter is HIGH_ACCURACY. Setting it to 1.0 enables high accuracy operation. This parameter affects the programs MULPLT, FK, HYP and UPDATE.

Station locations: The station file looks like before except that in order to get higher accuracy of station locations, the minutes of latitude and longitude are specified without the point. E.g. the minutes 22.122 can now be written as 22122 in the same columns as before while if the point is given, only 2 decimals can be used as 22.12. This changes do not affect any old station coordinates. Programs reading station coordinates, will use high accuracy input if available.

EPIMAP will always read in high accuracy mode, if any high accuracy data is present, whether station locations or hypocenters.

FK will always read high accuracy station coordinates, if available and FK can therefore now be used with very small arrays.

Programs with output affected by high accuracy mode:

MULPLT will write the phase readings as f6.3 instead of f5.2 like e.g. 11.234 instead of 11.23. For normal use, this is not needed and the files look better if high accuracy mode is not used. In new Nordic format, Nordic2, seconds are always written with 3 decimals.

HYP and UPDATE writes an extra high accuracy hypocenter line which has been given type H. An example is

 1996  6 3 2006 35.5 D  46.787 153.722 33.0  TES 15 1.9 3.4STES 5.8BTES 5.6BPDE1
 1996  6 3 2006 35.511  46.78711  153.72245   33.011  1.923                    H
The format is
1 -15      As type 1 line
16         Free
17         Seconds, f6.3
23         Free
24-32      Latitude, f9.5
33         Free
34-44      Longitude, f10.5
44         Free
45-52      Depth, f8.3
53         Free
54-59      RMS, f6.3
60-79      Free
80         H