VIBIST-20* - Surface
The VIBSIST-20 is based on the
Swept Impact Seismic Technique (SIST) which is a
combination of the Vibroseis swept-frequency and the
Mini-Sosie multi-impact ideas. The seismic signals are
produced as a series of pulses, according to a specific
pre-programmed sequence which makes the system similar
to a smaller Vibroseis.
The use of the monotonous variation
of the impact rate controls effectively the
non-repeatability of the impact intervals and achieves a
wide bandwidth even when the coupling to the rock or
ground is relatively poor.
Using standard construction
equipment allows the VIBSIST-20 to become a safe,
non-destructive and environmentally friendly high
resolution seismic source. It also makes this seismic
method reliable and highly cost effective.
The VIBSIST-20 can be used in a
wide range of applications, they include:
depth to bedrock
ground water exploration
location of fractured zones
shear and surface wave studies
static correction surveys
research and education
EXCELLENT SOURCE FOR HIGH
RESOLUTION SEISMIC SURVEYS
The VIBSIST-20 is an excellent
reflection/refraction source because it obtains
equivalent depth or better than would small caps
explosive or single pulse sources while maintaining a
higher resolution and an increased productivity.
The high S/N Ratio is achieved by a
signal energy of 10 kJ over a period of 25 seconds or
the equivalent of 22 impacts per second. It is the
accumulation of these low energy impacts which leads to
significant depth penetration.
Significant productivity gains are
obtained because the VIBSIST-20 hand-held
electromechanical hammer is not dependent on the energy
of the operator using a sledgehammer or on the lengthy
preparation needed to use explosives, such as drilling
holes, filling them in, setting up the wires, etc.
For refraction applications, the VIBSIST technique is at
least 10 times faster than using a sledgehammer and for
reflection more than 10 to 20 times faster than using
explosives, depending on the operator.
With the VIBSIST-20, you can finish
the job quite sooner than with alternate methods.
HIGHER DATA QUALITY
The VIBSIST-20 produces high
frequency content (up to 2500 Hz) while achieving
significant depth penetration as shown on Figure 1. The
high frequency content of the signal emitted by a
seismic source tends to decrease when the power of the
source increases, which makes higher resolution and wide
investigation range difficult to achieve simultaneously.
The investigation range can however be increased with
little or no expense of resolution if the signal energy
is built over time, rather than being emitted as a short
Figure 1: Axial component receiver gathers obtained
at GTS Grimsel Tunnel site, Switzerland from a single
pulse source (PH-62 on the left) and the VIBSIST-20 (on
MODULAR AND PORTABLE
The reduced number of modules make
the VIBSIST-20 portable and highly mobile. It allows
jobs to be done faster and in difficult field conditions
that would otherwise have been almost inaccessible such
as mountainous regions, underground mines, confined
The VIBSIST-20 is an
environmentally friendly seismic source. It is a
non-destructive alternative that does not create
environmental pollution such as chemicals, sound, etc.
Legal risks frequently associated with using explosives
The VIBSIST-20 incorporates and
upgrades standard rock breaker equipment commonly used
in the construction industry. The many thousands of
impacts per day used by the Swept Impact Technique
require a rugged electromechanical hammer that is
already well proven and that also meets established
environmental (sound) standards.
COMPATIBLE WITH MANY
The VIBSIST can be used with many
seismographs. A correlator is required as well a large
enough memory per channel.
INTEGRATED WITH TUNNEL TO HOLE
AND VSP SURVEYS
The VIBSIST-20 is ideal for tunnel
to hole and VSP high resolution surveys. It generates
enough energy to be used with borehole seismic systems
at depth of 400 meters or less.
SURFACE WAVE CAPABILITY
The VIBSIST-20 can be used to
produce and measure surface waves, which can be
processed and analyzed.
The VIBSIST-20 includes the
The controller transfers
to the impact hammer the sweep control sequence
provided by the computer
The impact hammer is
modified to operate in accordance with the sweep
control sequence. A power source such as a motor
generator is needed to operate the hammer
The ground impact assembly
includes an impact rod and a ground coupling plate
(two versions are available depending on the ground
conditions, either hard or soft).
A laptop is required but
not provided with the VIBSIST-20.
Ground Impact Assembly
Field Control Unit
The system also includes the
necessary cables between the controller, the hammer and
Four software modules are included
as part of the VIBSIST-20 system, they are:
Controller, used to program the
sweep control sequence
Signal Decoder, deconvolves the
long sweeps. It may also be used for On Line
monitoring or Off Line processing.
Signal Conditioning, includes a
collection of filtering programs used for processing
of the records before or after deconvolution
Signal Display Interface allows
the operator to visualize the data.
Power supply: 115 V / 60
Hz or 230 V / 50 Hz
programmable between 15 to 32 impacts per second
Impact energy: approximately 20 J / impact for a typical hand-held
Impact frequency band:
approximately 50 to 2500 Hz
characteristics: computer controlled (any shape)
or preset (linear) sweep .
Impact rate ratio: minimum 1.5 / 1.
Sweep time adjustment:
2.5 to 30 seconds (this is restricted by the number
of samples available per channel).
Length: 571.5 mm.
Weight: 22.5 kg
Length: 300 mm
Weight: 3.0 kg
Ground Coupling Plate