Quick Epicenter Determinations

              EXPLANATION OF ABBREVIATIONS AND SYMBOLS APPEARING IN THE QED

Abbreviations in Heading:

UTC TIME - Origin time in Coordinated Universal Time. 
 HRMNSEC - Hour, minute, second.
     LAT - Geographic latitude in degrees.
    LONG - Geographic longitude in degrees.
     DEP - Depth in kilometers.
 GS MAGS - Magnitudes computed by USGS/NEIS.
      MB - Body wave magnitude.
     Msz - Vertical surface wave magnitude.
      SD - Standard Deviation from the arithmetic mean of residuals.
STA USED - Number of stations reporting P or PKP phases used in computation.

Symbols Following Origin Time:

 &  Indicates that parameters of the hypocenter were supplied or determined by a computational 
    procedure not normally used by NEIS.  The source or nature of the determination is indicated
    by a 2 to 5 letter code enclosed by angle brackets and appearing in the first line of 
    comments.  A "-P" appended to the code indicates that the computation is preliminary.  These
    codes are included in the list of abbreviations below.

 %  Indicates a single network solution.  A non-furnished hypocenter has been computed using 
    data reported by a single network of stations for which the date and/or origin time cannot 
    be confirmed from seismograms available to a NEIS analyst.  The geometric mean of the 
    semi-major and semi-minor axes of the horizontal 90% confidence ellipse is less than or 
    equal to 16.0 km.

 *  Indicates a less reliable solution.  In general, the geometric mean of the semi-major and 
    semi-minor axes of the horizontal 90% confidence ellipse is greater than 8.5 km and less 
    than or equal to 16.0 km.

 ?  Indiates a poor solution, published for completeness of the catalogue.  In general, the 
    geometric mean of the semi-major and semi-minor axes of the horizontal 90% confidence 
    ellipse is greater than 16.0 km.  This includes a poor solution computed using data 
    reported by a single network.

 Q  Indicates a preliminary solution obtained from the NEIC Earthquake Early Alerting Service 
    program "Quick-quake." 

    The lack of any symbol indicates that the geometric mean of the semi-major and semi-minor 
    axes of the horizontal 90% confidence ellipse is less than or equal to 8.5 km.

Symbols Following Depth:

N  Indicates depth was restrained at 33 km for earthquakes whose character on seismograms 
   indicate a shallow focus but whose depth is not satisfactorily determined by the data.

D  Indicates depth was restrained by the computer program based on 2 or more compatible pP 
   phases and/or unidentified secondary arrivals used as pP.

G  Indicates the depth was restrained by a geophysicist.

*  Indicates a less well-constrained free depth.  The 90% marginal confidence interval on 
   depth is greater than 8.5 km and less than or equal to 16.0 km.

?  Indicates a poorly-constrained free depth.  The 90% marginal confidence interval on depth
   is greater than 16.0 km.

   The lack of any symbol indicates that the 90% marginal confidence interval on depth is 
   less than or equal to 8.5 km, or that a contributed hypocenter was computed with a free
   depth, regardless of the size of the confidence interval. 




Symbols and Abbreviations Used in Comments


Roman     Used to indicate intensity (when not followed by RF or JMA they refer to the Modified
Numerals  Mercalli Scale or any 12-point intensity scale closely related to it).

      -P  Supplied hypocenter is a preliminary computation.

          Any additional 3 to 5 letter codes enclosed in parentheses or angle brackets refer to
          individual station codes.  These codes may be found in Geological Survey Open File 
          Report 85-714, "Seismograph Station Codes and Coordinates" (1985) or its addenda.


For an explanation of other topics such as magnitude formulas, travel time tables or intensity 
scales, please refer to the latest January or July issue of the publication "Preliminary 
Determination of Epicenters, Monthly Listing."