Pick_FP is an alternative to classic Earthworm picker (pick_ew). It implements the FilterPicker algorithm (Lomax et al., 2011), a general purpose, broad-band, phase detector and picker which is applicable to real-time seismic monitoring and earthquake early-warning.
Pick_FP gets real-time data in the form of demultiplexed Earthworm waveform messages (TYPE_TRACEBUF2 messages). The program picks each channel independently, and produces pick messages, which are sent to an Earthworm transport ring.
In its present implementation, pick_FP does not measure the lenght of
the waveform coda.
People who need this feature (e.g. for computing a coda magnitude
through eqproc), can use the modules
coda_aav or
coda_dur.
Since the program does not need to wait for a coda measurement,
picks are released immediately.
If the data has time gaps, pick_FP can be set up, using configuration parameters, to either interpolate through the gaps or restart itself. For time gaps up to several samples long, it is probably best to interpolate. For longer gaps, it is better to restart. The drawback to interpolating is that the data is somewhat corrupted. The drawback to restarting is that the picker will not start picking again for about one second after a restart.
Pick_FP can be run in standalone mode on a tracebuf data file. In standalone mode, picks are written to the standard output. This allows to quickly test picking parameters without having to run a full Earthworm/tankplayer stack.
Picks times are calculated using FilterPicker (Lomax et al., 2011),
an efficient algorithm which operates stably on continuous, real-time,
broadband signals, avoids excessive picking during large events, and
produces onset timing, realistic timing uncertainty, onset polarity and
amplitude information.
In practice, it operates on a pre-defined number of frequency bands by
generating a set of band-passed time-series with different center
frequencies. Characteristic functions are determined for each frequency
band and a pick is declared if and when, within a window of predefined
time width, the integral of the maximum of the characteristic functions
exceeds a pre-defined threshold.
For more information on FilterPicker, see
this page.
Lomax, A., C. Satriano and M. Vassallo (2012), Automatic picker developments and optimization: FilterPicker - a robust, broadband picker for real-time seismic monitoring and earthquake early-warning, Seism. Res. Lett. , 83, 531-540, doi: 10.1785/gssrl.83.3.531.
In addition, M. Vassallo et al. (2012) discussed a strategy for optimizing automatic picking parameters, with applications to pick_FP and pick_ew.
Vassallo, M., C. Satriano and A. Lomax, (2012), Automatic picker developments and optimization: A strategy for improving the performances of automatic phase pickers, Seism. Res. Lett. , 83, 541-554, doi: 10.1785/gssrl.83.3.541.