MLOC dcal File

~.dcal File

When a relocation analysis in mloc is done with direct calibration (command dcal), it means that the hypocentroid will be estimated with arrival time data over a restricted epicentral distance in order to minimize the biasing effects of unknown Earth structure. Usually the cutoff in epicentral distance is in the range 0.5-1.5° so that only (or mainly) direct-arriving crustal phases are used. This would also normally be done with a carefully developed local crustal model (command lmod).

Therefore a direct calibration analysis looks very much like an uncalibrated relocation analysis as far as output files go, and there is no need for an extensive supplemental estimation process as there is for indirect calibration. Therefore, although there is a special output file (~.dcal) for direct calibration, it is much simpler than the ~.cal file produced in an indirect calibration. The first few lines of a ~.dcal file are shown as an example:

Cumulative uncertainty of direct-calibrated events
iev     alpha        xl        yl      area       eqr      ddep       dot
  1   -77.265     2.748     4.769    41.162     3.620     0.000     0.267
  2   -78.380     3.303     5.400    56.028     4.223     0.000     0.296
  3   -64.416     2.785     3.297    28.850     3.030     0.000     0.256
  4   -76.395     3.728     5.288    61.939     4.440     0.000     0.382
  5    68.269     2.442     3.454    26.497     2.904     0.000     0.310
  6   -19.484     2.706    12.653   107.575     5.852     0.000     0.651
  7     5.891     4.157     4.939    64.507     4.531     0.000     0.346
  8   -68.576     2.483     2.933    22.876     2.698     0.000     0.201
  9   -79.697     5.652     7.650   135.825     6.575     0.000     0.516
 10    80.105     3.866     4.266    51.811     4.061     0.000     0.259

After the event number the 90% confidence ellipse for cumulative uncertainty (cluster vector plus hypocentroid) is given by three values, the azimuth of the semi-minor axis, and the lengths of the two semi-axes, the area of the ellipse, the radius of a circle with the same area, and uncertainties in depth and origin time. All these values except equivalent circular radius are also given in the ~.hdf_dcal file.

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