SC3-RAV™ 2011 - Baziw Consulting Engineers Ltd.

BCE SC3­RAV 2011 Seismic Data Analysis Software
3.1.1.1.2 Manual Filtering
The Manual Filtering option is a more detailed analysis of the in-situ seismic traces. In this
option, a start time is specified if desired, the inputted waves are then analyzed for frequency
content, after which the filtered and unfiltered traces are displayed in order to decide whether the
correct seismic waves were isolated. Finally the crosscorrelation function is displayed followed
by the velocity, accuracy and time shift estimates.
In the Manual Filtering option the seismic traces are more thoroughly analyzed with interactive
graphics. These graphics facilitate choosing the proper frequency filters to be used in the
Automatic Filtering and Batch Processing options. For illustrative purposes, an example of data
processed with SC1-RAV using the Manual Filtering option will be presented.
In this example data files Ds4.aci and Ds7.aci are analyzed, and the relevant parameters
describing these digital seismic traces are as follows:
Ds4.aci:
Sampling rate: 0.1 ms
Depth: 2.7 m
X offset: 2.1 m
Y offset: 0.0 m
Ds7.aci:
Sampling rate: 0.1 ms
Depth: 3.7 m
X offset: 2.1 m
Y offset: 0.0 m
Figure 11 shows the Ds4 seismic trace and its corresponding frequency spectrum. The cross-hair
displayed in the frequency spectrum and time series is moved around by the mouse, with the
corresponding frequency and time displayed above the charts. The frequency spectrum and time
series can be zoomed into a desired range by pressing the left mouse button and moving the
mouse left to right. The traces are shifted left to right by pressing the right mouse button and
moving the mouse. The user can zoom out again by pressing the left mouse button and moving
the mouse right to left.
The user has the capability to apply a time window on the seismic wave so that the frequency
bandpass parameters can be better selected. The time window is specified by moving the crosshair
in the time domain window and selecting the times (ie., pressing the mouse middle button or
+ right or left mouse buttons) which incorporate the desired wavelet (note : T1 < T2).
The user then selects the button so that the specified time window’s frequency spectrum is
displayed. The selected time window can be cleared by double clicking on the left mouse button.
Figure 11 illustrates the zoomed in frequency spectrum (i.e., 0 to 143 Hz) of the specified time
window (ie., T1 and T2). The user can enable a bandpass filter by enabling check box Bandpass
Filter. The frequency bandpass is selected by pressing the middle mouse button or +
right or left mouse button for each frequency in the bandpass (ie., F1 < F2). Figure 11 illustrates
the frequencies selected by the characters F1 and F2. The Notch, Low Pass and High Pass
Filters are enabled by checking the appropriate check boxes and specifying the notch, low pass
and high pass frequencies, respectively.
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