wiki:HowTo/IaspeiFilters

New filter sets following IASPEI recommendations

Beginning with version 2012a Seismic Handler includes with new filter sets for the following simulated instruments:

  • Wood-Anderson (WOODAND)
  • WWSSN-SP
  • WWSSN-LP

The complete recommendation text by the IASPEI working group is available as PDF.

Important note: Please be aware that all magnitude values determined differ slightly between these two filter sets. If you do statistics for several years, you should think very carefully about this issue! At the German Seismological Observatory we found a mean difference of 0.033 magnitude units for mb by analyzing more than 10.000 events. This seems quite small, but individual events show higher differences.

The next three plots show IASPEI (red) versus classic (blue) transfer functions (click to zoom).

Wood-Anderson transfer function WWSSN-SP transfer function WWSSN-LP transfer function

What has been changed?

  1. Wood-Anderson: changed static magnification from 2800 to 2080 ( Urhammer & Collins (1990))
  2. WWSSN-SP and WWSSN-LP: adapted poles and zeros from IASPEI recommendation.

New installations

During installation you'll be asked which filter set should be used: classic or iaspei (default). You should make sure that anyone at your institute/workplace uses the same filter set to prevent confusion.

Upgrading existing installations

There are two choices if you decide to upgrade your current installation:

  1. Simply download the IASPEI filter set and overwrite existing files in $SH_FILTER. This method is recommended for users who have not created own filter set. The easiest way is a checkout from subversion, e.g.
    svn co https://www.seismic-handler.org/svn/SH_SHM/tags/2012a/filter/iaspei /tmp/iaspei
    mv /tmp/iaspei/* $SH_FILTER
    
    Alternatively download  all files manually. Backup $SH_FILTER first!
  2. If you created a lot of own filter sets please use the replacement script. This will try to create new simulation filters for any seismometer transfer function found in $SH_FILTER. It's strongly advised to use the review option (enabled by default). This will display the transfer functions of simulated instrument, current seismometer, resulting simulation filter and former simulation filter. Afterwards it's possible to apply one additional filter in order to closely reproduce the simulated instrument. This is a quite complex work, please make sure that you have a working backup of $SH_FILTER!

If you want to keep your existing filter sets, but use the IASPEI simulation filters for newly created filter sets (using $SH_UTIL/prep_simfilters.csh), simply replace the following files in $SH_FILTER:

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