NAME
mdcalc - computes duration magnitude
SYNOPSIS
mdcalc [-p pfile] database orid [size]
SUPPORT
Contributed code: NO BRTT support.
THIS PIECE OF SOFTWARE WAS CONTRIBUTED BY THE ANTELOPE USER COMMUNITY. BRTT DISCLAIMS ALL OWNERSHIP, LIABILITY, AND SUPPORT FOR THIS PIECE OF SOFTWARE.
FOR HELP WITH THIS PIECE OF SOFTWARE, PLEASE CONTACT THE CONTRIBUTING AUTHOR.
DESCRIPTION
This program emulates the computation of coda-duration magnitude MD by the
PICKEM program at UNR Seismological Laboratory. PICKEM was run interactively,
and the analyst got immediate feedback on coda-length calculation at each
station and could change the coda-start pick according to the result. This
has been automated in the current program due to lack of a communication
method with dbpick. Thus, this program is a post-processor.
The algorithm basically fits an exponential function to the coda, starting
at the point picked by the analyst. The correlation coefficient of the fit
is computed, with r > 0.90 being acceptable, according to PICKEM practice.
The magnitude is computed from all the individual coda lengths according to
md = 2.65*log10[Sum(ti)/n]-1.70
Due to the fact that interactive processing is eliminated, the program will
do a search around the time of the "C1" phase to get a coda estimate with
a correlation coef. > 0.90. The search is performed forwards by increments
which depend on event size. Event size must be given on the command line if
other than small -- S, M, L are the 3 allowable inputs. For larger events,
this increases the coda length to be fit. This option is for compatibility
with PICKEM and anything other than S, the default, is not expected to be
used but rarely. For any event large enough to do M or L, a standard ML
magnitude should be available.
A "C2" pick by the analyst specifies the end of the coda. The coda length is
then merely the C2 time minus the P time. No computations are involved.
This program will compute MD for events in the Antelope origin table using
available data as indicated by arrival picks in the arrival table.
Only sta-chan's specified in the parameter file (default = mdcalc.pf) are used
in the calculation even though "C" picks can be made on any component.
Former practice with PICKEM at UNRSL was to use only vertical components.
OPTIONS
-
-p pfile
specify the parameter file name [optional, "mdcalc" is default]
-
database
database name
-
orid
orid of event to be processed
-
[size]
earthquake size ("S"|"M"|"L", with default = "S" if not given)
EXAMPLE
% mdcalc -p mdcalc_anza anza 97114 M
PF FILE
The parameter file for mdcalc contains a list of stations and channels for
which duration magnitudes may be computed. A sample file is
stachans &Tbl{
ADH EHZ
GMN EHZ
QSM EHZ
VIP EHZ
}
DIAGNOSTICS
mdcalc will complain about various data problems as appropriate.
SEE ALSO
N/A
BUGS AND CAVEATS
None.
AUTHOR
David von Seggern
Antelope User Group Contributed Software