• Antelope Release 5.5 Mac OS X 10.8.5 2015-04-21

 

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

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
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