Subject: HDF File Format

The HDF files are generated from the same procedures that produce the 
weekly PDE and Monthly listings.  The HDF is a machine readable version 
of the PDE/Monthly and contains exactly the same events as the equivalent 
PDE or Monthly. Therefore the monthly HDF file is more complete (ie. has 
more events, most of which have been computed using more data) than the 
weekly HDF file, just as the Monthly Listing is more complete than the 
weekly PDE.  The monthly HDF file contains identical hypocenter data to 
the Monthly Listing and ALSO identical hypocenter data to the EDR. 
In addition, the EDR contains the phase data.

Attached below is the format of the HDF file.

Best regards,
  Bruce Presgrave

                          FORMAT OF USGS/NEIC HDF FILE


Char. Pos.      Description
 1-2            "GS"
 3-4            blank
 5-12           EVENT DATE in YYYYMMDD format
13-19           ORIGIN TIME in HHMMSST format
20-25           LATITUDE
        20-24           geographic latitude value in f5.3 format (DDTHT)
        25              N or S
26-32           LONGITUDE
        26-31           geographic longitude value in f6.3 format (DDDTHT)
        32              E or W
33-35           DEPTH in kilometers in i3 format (NNN)
36-38           GS AVERAGE MB
39-40           characters "MB"
41-50           FLAGS
        41-43           Isoseismal map or fault plane solution
                            FPS = fault plane solution
                            BOT = fault plane solution and isoseismal map
                            USE = isoseismal map in U.S. earthquakes
                            PDE = isoseismal map in PDE or Monthly Listing
        44              maximum intensity (a1 format - 1-9, X, E or T)
        45              diastrophic phenomena (U = uplift/subsidence or 
                            F = faulting)
        46              tsunami (T or ?)
        47              seiche (S or ?)
        48              volcanism (V)
        49              non-tectonic source 
                            E = known or suspected explosion
                            I = collapse
                            C = coal bump or rockburst in coal mine
                            R = rockburst
                            G = geyser activity
                            M = meteoritic source
                            L = lights or other visual phenomena
                            O = odors
        50              guided waves in atmosphere/ocean (T = t wave, 
                            A = acoustic wave, G = gravity wave, B = both
                            acoustic and gravity waves)
51-53           FLINN-ENGDAHL GEOGRAPHIC REGION NUMBER (in i3 format)
54-55           GS AVERAGE MS in f2.1 format (NT)
56-58           characters "MSZ"
59              CULTURAL EFFECTS FLAG
                        (H = heard, F = felt, D = damage, C = casualties)
60              blank
61-66           CONTRIBUTED MAGNITUDE 
        61-63           magnitude value in f3.2 format (NTH - with H usually 0)
        64-66           contributor (a3 format - blank if source is NEIS)
67              IDE EVENT FLAG (X)
68              DEPTH CONTROL/QUALITY INDICATOR (N, G, D, * or ?)
69-72           HYPOCENTER QUALITY INDICATORS
        69-71           number of P or PKP arrivals used in solution (i3 format)
        72              authority/quality indicator (&, *, % or ?)
73-80           CONTRIBUTED LOCAL MAGNITUDE
        73-75           magnitude value in f3.2 format (NTH - with H usually 0)
        76-77           type (ML, LG, RG, MD, CL or MG)
        78-80           contributor (a3 format - blank if source is NEIS)
81-87           HYPOCENTER CONTRIBUTOR
        81              "<"
        82-86           contributor (left justified, "-P" means preliminary)
        87              ">"




PDE symbol      QED letter      meaning
   &                f           furnished (contributed) hypocenter
   %                n           single network solution
   *                s           starred (less reliable) solution
   ?                p           poor solution

For a more detailed description of these symbols, refer to page 33 of the
Preliminary Determination of Epicenters Monthly Listing for January 1990.

Note that s and p also replace * and ?, respectively in the column following
the depth. Depth symbols N, G and D on the QED are the same as the PDE. See
page 32 of the January 1990 Monthly Listing for more details about these
symbols.