Play back archived waveforms

Aims:

  • Use previously recorded waveform files to re-run the analysis of an old event using SeisComP. This is known as a waveform playback.

  • Insert results into your current SeisComP database for later processing.

  • Review the results from playbacks.

Pre-requisites for this tutorial:

  • Have SeisComP installed and configured

  • Have access to miniSEED waveforms

Afterwards/Results/Outcomes:

Time range estimate:

  • 60 minutes

Related tutorial(s):


Playbacks are an important way of testing module and whole-system configurations, operator trainings, system demonstrations and validations and tuning of the SeisComP modules used for detecting and locating events, e.g. involving

Playbacks rely on miniSEED data which are obtained from the SDS archive or other sources. The miniSEED data records in the data files must be sorted by end time!

There are two types of playbacks:

Data preparation

First extract the data. Make sure the miniSEED records are sorted by end time. The data extraction depends on the data source.

Examples:

  • SDS archive: Extract the data from your own SDS archive using scart and save it in a new miniSEED file [your miniSEED file], sorted by end time of the records.

    Examples:

    scart -dsE -l [list file] $SEISCOMP_ROOT/var/lib/archive > [your miniSEED file]
    
  • FDSNWS: Get the miniSEED data from an external FDSNWS server. The obtained data are initially sorted by station and must therefore be sorted by end time using scmssort. Use the resulting file [your miniSEED file] for your playback.

    Example for one hour of data from the GE network from FDSNWS at GEOFON:

    wget -O data.mseed "http://geofon.gfz-potsdam.de/fdsnws/dataselect/1/query?net=GE&cha=BH*&starttime=2021-04-01T06:00:00Z&endtime=2021-04-01T07:00:00Z"
    scmssort -u -E data.mseed > [your miniSEED file]
    
  • CAPS server: Extract the data from gempa’s CAPS server :cite:p:`caps` using :cite:t:`capstool`:

    capstool -H [host]:[port] [request file] > data.mseed
    

    or scart with the caps recordstream:

    scart -I caps://[host]:[port] -l [list file] --stdout > data.mseed
    

    Eventually, sort the downloaded data by end time with scmssort creating a new file, [your miniSEED file]:

    scmssort -u -E data.mseed > [your miniSEED file]
    

Use the resulting file [your miniSEED file] for your playback.

Playbacks

Real-time playbacks

In a real-time playback data are injected into the seedlink buffer from a file using the command-line tool msrtsimul. Therefore, seedlink requires a configuration.

  1. Prepare seedlink to except data from msrtsimul:

    • In the module configuration of seedlink set

      msrtsimul = true
      
    • Save the configuration, update the configuration and restart seedlink:

      seiscomp update-config
      seiscomp restart seedlink
      

      Open :scrttv: to verify the success of this re-configuration. No new data must arrive.

  2. Restart all automatic data processing modules you wish to involve. Additionally start slarchive to archive the miniSEED data in the SDS archive for post-processing.

    seiscomp restart scmaster scautopick scautoloc scamp scmag scevent slarchive
    
  3. Start all desired GUI modules to observe the data acquisition and processing and the event results, e.g.:

    scrttv & scmv & scesv & scolv
    
  4. Start the playback using msrtsimul:

    msrtsimul -v [your miniSEED file]
    

    This will play back the data as if they where perfectly recorded and received now. To preserve the time of the records use msrtsimul with the historic mode:

    msrtsimul -v -m historic [your miniSEED file]
    

    Note

    Using msrtsimul with the historic mode requires to reset the seedlink buffer and the buffer of other processing modules by removing the buffer files and restarting the modules. This mode may therefore be exclusively used by experienced users.

Revert the seedlink configuration after the playback to return to the original real-time data acquisition.

Warning

Be careful with executing real-time playbacks on production SeisComP systems:

  • You potentially disrupt the real-time data acquisition

  • You potentially add data at wrong times to seedlink and your SDS waveform archive

  • You modify the history of the created events

  • You potentially add events at wrong origin times to your database.

Better use separate test systems for real-time playbacks.

Non-real-time playbacks

In non-real-time playbacks, also referred to as offline playbacks, data are processed by each module as fast as possible. The results can be communicated by

  • Messages: message-based playback

  • XML files in SCML format: XML playback. They require the processing modules to provide the - -ep option.

Warning

In non-real-time playbacks scheduling and the creation history are not representative of real-time situations.

Reviewing results

Use scolv or other GUIs to review the results:

  • Event parameters are in the default database. Configure RecordStream if the waveforms are in the seedlink or in the SDS archive:

    scolv -d mysql://sysop:sysop@localhost/seiscomp
    
  • Event parameters are in the default database but the waveforms are read from the miniSEED file:

    scolv -d mysql://sysop:sysop@localhost/seiscomp -I file://[your file]
    

    Note

    Reading from the original file will only work if the actual times of the data are preserved during the playback. This is not the case when starting msrtsimul without the historic mode.

  • Event parameters are available in one XML file and the waveforms are read from the miniSEED file:

    scolv --offline -d mysql://sysop:sysop@localhost/seiscomp -I file://[your miniSEED file]
    

    To open the XML file click on the File menu of scolv. When results are available in several XML files, the files can be merged beforehand using scxmlmerge.

Note

Adjust the arguments to match your configuration. Use your own values for arguments enclosed by brackets, e.g. [your file]