SC1-RAV® / 7.2
BCE Ltd. is pleased to announce the release of SC1-RAV®/7.2!
SC1-RAV® is a
comprehensive uniaxial downhole seismic testing (DST) data reduction, analysis and display
software package. The user is provided with an extensive set of mathematical
tools and patented (U.S. Patent #5,177,709 / Canadian Patent # 2,077,387)
algorithms in deriving DST interval velocities and quantifying vertical seismic profiling. In addition, SC1-RAV®
has functionality for reviewing frequency spectrums, comparing unfiltered and
digitally filtered traces and plotting interval velocity profiles. SC1-RAV® also provides extensive chart editing, plotting, and exporting
functionality. SC1-RAV® includes the following features:
- Configurable for either geophones or accelerometers.
- Extensive frequency spectrum analysis. Bandpass, high pass, low pass, and
notch digital filters.
- Patented (i.e. U.S. Patent #5,177,709) P-Wave and S-wave velocity
estimation algorithm.
- Batch job processing.
- Source wave arrival time estimation.
- Linear least squares regression interval
velocity estimation.
- Reverse Polarity Technique.
- Forward Modeling Downhill Simplex Method in estimating interval
velocities.
- Display of seismic depth profile with trend line specification.
- Display of peak particle accelerations, velocities, and displacements.
- Calculation of interval Gmax values.
- The ability to carry out data interpolation to increase the time series
resolution.
- Post data stacking.
- Display of calculated interval velocities.
Download SC1-RAV® User's Manual
SEISMIC ANALYSIS
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The Seismic Analysis menu option allows the user to process acquired
seismic traces so that important Geotechnical design parameters are obtained.
The Seismic Analysis option contains the submenus of Interval
Velocities, Depth Profile,
Data Interpolation, Data Stack, Signal Decay and Data
Interpolation.
INTERVAL VELOCITIES
The Crosscorrelation Technique implements a patented (U.S.
Patent #5,177,709 / Canadian Patent # 2,077,387) mathematical algorithm in
deriving DST interval velocity profiles . This technique derives
DST interval velocities based upon crosscorrelating the waves recorded at
consecutive depth increments (Baziw 1993). The value of the time shift at the
maximum crosscorrelation value is assumed to be the relative travel time
difference for the wavelet to travel the depth increment. This technique has the
following advantages over the standard Reverse Polarity Technique
- Minimizes the human bias associated with visually selecting a crossover
point in deriving interval times which is required by the reverse polarity
technique.
- Utilizes the full waveform in deriving interval travel times as opposed to
a single point.
- The correlation coefficient between the two wavelets can be used as a
velocity accuracy estimate. This parameter gives the investigator an
indication of the similarity between the two wavelets being correlated and the
subsequent accuracy of the velocity estimate.
- Obtains two independent velocity estimate for each depth increment by
comparing source wavelets generated on both the right and left side of the
seismic probe.
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The Batch Job Analysis option facilitates the user to process many
seismic traces with similar filter parameters in a batch mode. In addition,
Batch Job Analysis allows for the estimation of the arrival times for each
depth increment and the implementation of linear least squares regression (LLSR)
in deriving interval velocities. The LLSR technique facilitates in the
minimization of the variability of the interval velocities. The LLSR utilizes
three adjacent crosscorrelation relative arrival times, the corresponding time
series depths of acquisition and a reference arrival time and depth to determine
the slope of the best fitting line through the three points. The slope of the
best fit line is defined to be the interval velocity.
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ITERATIVE FORWARD MODELING
The Forward Modeling / Downhill Simplex Method (FMDSM) utilizes
seismic ray tracing and optimal estimation techniques in deriving DST
interval velocities. The standard techniques implemented in deriving DST
interval velocities rely upon obtaining reference P and S wave arrival times as
the probe is advanced into the soil profile. By assuming a straight ray travel
path from source to seismic receiver and calculating relative reference
arrival time differences, interval DST velocities are obtained.
The FMDSM offers distinct advantages over conventional DST velocity
profile estimation methods. Some of the advantages over conventional techniques
provided by the FMDSM are outlined as follows:
- Utilization of Snell’s Law at layer boundaries for ray path refraction.
- Optimization of a non-linear cost function which takes into account more
detail of the SCPT testing environment and subsequent seismic data recorded
compared to standard techniques.
- Allowance for measurement weights to be specified, the possibility to
incorporate unlimited input data (e.g., crossover point arrival times, maximum
cross-correlation time shifts, angles of incidence, and P-wave / S-wave time
separations) into the interval velocity estimation algorithm.
- The ability to accurately interpolate interval velocities when measurement
data is not available.
- Provides meaningful error residuals which indicate the accuracy of the
estimated interval velocity.
In the FMDSM the user is provided with
user friendly interfaces for specifying seismic wave arrival times and
crosscorrelation time shifts information (derived from Depth Profile and Crosscorrelation Technqiue) with corresponding weights within a Windows compatible database.
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The FMDSM derived interval velocities
are also stored in the previously described database so that they can
be utilized in other applications, report generation or for future
reference.
DEPTH PROFILE
SC1-RAV® 's Depth Profiling software allows the
user to filter and plot the captured uniaxial seismic traces on a depth vs time
plot, specify or automate trend lines for preliminary velocity estimation and
display peak particle accelerations, velocities or displacements.
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DATA STACK
The Data Stack option allows the user to post-stack acquired seismic
time series data.
DATA INTERPOLATION
This analysis feature allows the investigator to increase the resolution of
the captured seismic data for post processing purposes. This facilitates greater
data resolution when carrying out analyses such as obtaining relative time
shifts utilizing the cross-correlation function, reverse polarity analysis and specifying trend lines in
depth profiling. In addition, SC1-RAV® ’s Data Interpolation software
feature allows the investigator to synchronize seismic time series data captured
with differing sampling rates (i.e., set data to same sampling rate).
POLARITY CHANGE
The Polarity Change option facilitates the investigator in selecting a set of
seismic data files and subsequently changing the polarity of the time series.
SIGNAL DECAY
The Signal Decay option allows the investigator to minimize the effect of
possible source wavelet multiples on the first arriving source wavelet. The
technique implemented relies upon the application of an exponential decay
applied to the selected time series data after a user specified time.
VIEW
The View menu option consists of the sub-menus Interval Velocities
and Seismic Data. These software features allow the user to display
derived seismic interval velocities (ie., Interval Velocities) and
analyze seismic data on a trace by trace basis (Seismic Data).
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UTILITIES
The Utilities menu option consists of sub-menus Default GUI
Settings, Sensor Type, Enable Time Delay and Shear Modulus
Calculation. These software features
allow the user to specify general interface settings, the type of seismic data
recorded (i.e., accelerometer or geophone), enable the ability to implement time
delay corrections within Depth Profiling and calculate and store Gmax
values.
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