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Abstract
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From the seismologists’ point of view, it
is extremely important to accurately detect the first
P wave arrival time. The P wave arrivals have considerable
information about events such as location,
magnitude, mechanism, and source parameters. In the
classic methods, P wave pickings have been accomplished
manually in a visual way. But in the era of
information and communication technology, it can
be done by computer programs. Seismologists have
developed many methods for the picking of the first
arrival time of P wave. The wavelet transform is one
of the methods to analyze the arrival times and useful
for picking up the singularities of any function.
Decomposing signals by wavelet transform is a master
key to the study of time-frequency varying signals
such as earthquake seismograms. This paper presents
P phase picking without any prior information using
undecimated wavelet transform. For undertaking this
study, a simple envelope characteristic function is used
for P phase picking. The proposed method is tested on
5 earthquakes recorded by the Fnet network in Japan
that have varying signal-to-noise ratio levels for calibrating.
Then the method is applied on 50 earthquakes.
The observed results are compared with manual phase
picking and standard STA/LTA method. The wavelet
base method shows the higher accuracy of phase picking
in event detection and time picking, respect to the
standard STA/LTA method, when compared to manual
picking.
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