Southern California Earthquake Data Center

Earthquake Catalogs

SCSN Catalog Change History

These pages describe any changes in Southern California Seismic Network real time processing, post processing, or in Southern California Earthquake Data Center catalog archival that might be of interest to users of the earthquake catalog. Catalog users may also want to review our SCEDC Archive Information page. Since August 18, 2012, daily versions of SCSN and SCEDC format catalog files are stored on GitHub. Thank you for your interest in southern California seismicity!

 

2013

June 13, 2013 Changes in Real Time Processing Parameters

The Southern California Seismic Network (SCSN) made changes to its real time event detection software which should improve its accuracy in detecting events as well as determining accurate locations and magnitude. The change was to add the no_S_on_Z parameter to binder.

 

April 23, 2013 Update to Data Processing Protocol

Due to a recent confluence of moderately high seismicity, more stations to process, and level staffing, we have been forced to make some changes in the earthquake catalog processing. These changes went into effect at the time of the March 2013 Anza sequence. Prior to April 2013, we made every reasonable effort to place every impulsive pick at the correct time, and some emergent picks as well. This procedure improved the locations, but also caused long delays in getting large sequences processed.

  • Each earthquake must still be reviewed by an analyst, to make sure that the location and magnitude are within reasonable accuracy (which depends on the geographic location), and quarry blasts are appropriately marked.
  • More reliance on an automatic picker that is tailored to the post-processing environment.
  • Nearest 5 to 10 stations are accurately timed.
  • Since more stations means denser coverage, most picks beyond 100 km distance not included (again, this depends on the geographic area).
  • Earthquakes with 2.5 or larger magnitude get the same attention as before.
  • Because the automatic picker may not choose the correct wave, there may be a degradation in the focal mechanisms for small quakes. New software probably offsets this problem, by also incorporating S amplitudes into the solution.
  • If an earthquake passes through this process, it has an “I” or “intermediate” processing state, which flags the event for further review at a later time. If activity is low, or there is some reason it is efficient or necessary to completely time an earthquake, it moves to an “F” or “finalized” processing state. This means analysis has been completed for this event.

    As we have time, we may be able to go back and finalize most of the earthquakes in question.

    We also continue to work on finalizing the unfinished El Mayor Cucupah earthquakes in April and May 2010.

     

    April 17, 2013 Changes in real time processing parameters

    The Southern California Seismic Network (SCSN) made changes to its real time event detection software which should improve its accuracy in detecting events as well as determining accurate locations and magnitude. A detailed list is as follows:
  • new binder_ew binary Version <1.0.11 2013.03.22>
  • binder_ew, eqproc and eqassemble using PICK_RING (instead of FILTERPICK_RING)
  • changed the grid weight from 0,0 to 2,1 for picks with quality 2 and 3
  • no_P_on_Horiz
  • Channel number Maps:
    • ChannelNumberMapByNet NEZ PB
    • ChannelNumberMapByNet ZNE CI
    • ChannelNumberMapByNet ZNE CE
    • ChannelNumberMap ZNE
  • rstack 60.0
  • new trimag binary - VERSION: TriMag2 v0.2.8, 2011-05-06
  • parameters for trimag:
    • MinCutoffDist 20.0
    • MaxCutoffDist 200.0
    • StepCutoffDist 20.0
    • DefaultCutoffDist 150.0
    • UseCITwindows 0
    • PostSMult 1.0
    • PostBuffer 1.0
  •  

     

    2012

    August 18, 2012 SCSN and SCEDC catalog files daily versioned at GitHub

    In response to the user community, we are now putting our catalog files, both SCSN and SCEDC format in version control at GitHub. The repository is https://github.com/SCEDC/SCEDC-catalogs

     

     

    2008

    January 1, 2008 Recalibration of the Southern California Earthquake Catalog

    On January 1, 2008, the Southern California Seismic Network began using an updated method of measuring local magnitude (Ml). To ensure consistency in the Southern California Earthquake Catalog, we will begin recalibrating the Ml magnitudes for events between January 1, 1992 to January 1 2008 using this same method. The processing will be starting with events in December 2007, and going back one month at a time. These recalibrated magnitudes will be seen in the catalog search page. Processing begins May 1, 2009. If you wish to view historical data with the legacy magnitudes, text files of the catalogs can be found here: http://www.data.scec.org/ftp/catalogs/SCSN_pre2008/ Information on the revised Ml calculation is given the publication: R. A. Uhrhammer, M. Hellweg, K. Hutton, P. Lombard, A. W. Walters, E. Hauksson and D. Oppenheimer; California Integrated Seismic Network (CISN) Local Magnitude Determination in California (to be submitted) to BSSA, 2009

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