2) Probabalistic Power Spectral Density analysis using tools from Antelope (

is a perl script that utilizes Antelope database functionality to compute power spectral density estimates and then determine probability of these spectral estimates similar to the original work by USGS (see ref)Extended reading can be found here (ref).  The IRIS/DMC also makes use of this analysis - see link

A quick link to these plots for AK network stations can be found here.

Below is a comparison between the IRIS/DMC product and the output of dbpsdpdf for station AK_CCB for the month of 12/2011.  The daily PSD bin files were retrieved from IRIS/DMC ( and plotted using the sequence of surface commands from the included Matlab script.  (A) PSDs calculated by IRIS/DMC (B) PSDs calculated by dbwfmeas and processed with dbpsdpdf, plotted using the same surface commands from Matlab (C) Overlay of data from IRIS and that from dbwfmeas/dbpsdpdf.


Some further plots were made from the ensemble analysis for a month of data.  Here the IRIS/DMC figures were downloaded from the web, rather than retrieving the raw PSD bin files.  dbpsdpdf figures were created with GMT surface routine.



Additionally, Bob Herrman created PSD software to analyze SAC files (  sacpsd computes PSD, but does not perform the binning of PSD to determine probability.  Comparison of results from sacpsd and dbwfmeas/dbpsdpdf is shown below for TA_121A_BHZ.  A one-hour segment during night time hours (07:00 GMT) was selected from four different months in 2009.  The comparison is shown below.  The blue line is the smoothed and resampled PSD from sacpsd,  the black line is the raw PSD as computed by dbwfmeas.


dbpsdpdf uses dbwfmeas to calculate the PSD for a given time range.  The time windowing for dbwfmeas is not straight forward or exactly the same as the IRIS/DMC product.  An example dbwfmeas parameter file is below:

global_defaults &Arr{
remove_mean yes
use_det_filter yes
latency 20.0
timeout 120.0
ptype single
calib_from_calibration yes
measurements &Tbl{
        type spec
        channels &Tbl{
        .* .*
        rsptype A
        offset 614.4
        tdur 3600
        twin 819.2
           taper gaussian