Seis_Pick

Seis_pick provides an interactive environment for picking seismic waveforms. It has been developed with the principal purpose of processing downhole microseismic data, although is suitable for all seismic data. Seis_Pick displays seismic traces, allowing the user to pick P-wave and S-wave phases.

Seis_Pick can take Matlab workspace variables as input arguments. Alternatively, Seis_Pick can read SAC files directly. When SAC files have been read, Seis_Pick can save picks back into the SAC file headers.

When phases have been picked, the user can enter spectral analysis to view the frequency content of each phase, as well as pre-event noise. The user can also enter hodogram analysis to view the polarization of phases. This is particularly useful to check that picked P-wave and S-wave phases are polarized orthogonally, as well as to compute the back-azimuth of the detected event (using P-wave polarization). Seis_Pick also provides a number of other signal-processing facilities, including a band-pass filter, or predictive filter that uses pre-event noise to create a notch filter.

Seis_Pick has been developed as part of BUMPS (Bristol University Microseismicity ProjectS).

Seis_Pick Action Buttons:

p :- Pick P-wave start
s :- Pick S-wave start
o :- Pick P-wave end
a :- Pick S-wave end
P :- Delete P-wave start pick
S :- Delete S-wave start pick
O :- Delete P-wave end pick
A :- Delete S-wave end pick
w :- Wipe picks on one trace
W :- Wipe picks on all traces

f :- Predictive filter - The predictive filter inverts the frequency spectrum of the pre-event noise to create a notch filter. To define the pre-event noise, the predictive filter requires that the P-wave start be picked. If it is not, no filtering will occur.

b :- Bandpass filter - Once bandpass has been selected, the user must enter a length 2 vector defining the low and high pass corner frequencies.

F :- Remove filtering - When filtering, the unfiltered traces are stored in a dummy trace. If selected, SEIS_PICK returns to the original unfiltered trace. The filtered traces are not saved.

h :- Enter hodogram analysis (individual station)
q :- Enter spectral analysis (individual station)
H :- Perform hodogram analysis on all stations - Performs hodogram analysis on P-wave windows only to compute event azimuth.

c :- Cut traces - Effectively, this tool controls Matlab’s xlim property, to view a subset of the full trace. This is only an xlim operation, the trace itself is not cut. When using ‘c’, the user must press ‘c’ once to define the start of the new time window, and ‘c’ again to define the end of the window.

z :- Zoom to selected traces - Effectively, this tool controls Matlab’s ylim property, to view one (or more) of the geophones only. As per the ‘cut’ option, press ‘z’ once to select the topmost trace to view, and ‘z’ again to select the lowermost trace to view.

C :- Undo cut to view full trace - Resets Matlab’s xlim property to default settings.

Z :- Undo zoom to view all traces - Resets Matlab’s ylim property to default settings.

E :- Save plot of traces to .eps - On selecting this option, the user must input the file-name to which the plot of traces is saved.

L :- Load pre-existing pickmatrix - If an ascii file of picks already exists, ‘L’ loads them. See ‘Pickmatrix format’ section for details on the format of a pick matrix file. On selecting this option, the user is prompted for the file-name of the picks file.

M :- Save picks to ascii file - Saves the picks to an ascii format pick matrix file. On selecting this option, the user is prompted for the file-name of the picks file.

m:- Save picks to SAC headers. Picks are saved to SAC headers t0 - t3 as following: t0= P-wave start, t1= S-wave start, t2= P-wave end, t3= S-wave end.

J :- Toggle help panel - Removes/displays a helpful reminder of all SEIS_PICK options.

X :- Exit SEIS_PICK