www.sgc.com.auwww.sgc.com.au
PASSIVE SEISMIC (HVSR)
SARA Electronic InstrumentsSouthern Geoscience Consultants is
the agent in Australia and Canada of SARA Electronic Instruments.
SARA manufactures instrumentation for passive and active
seismological, geophysical, engineering, and vibration studies,
providing cost-effective solutions for earthquake monitoring,
exploration, soil investigations, and risk assessment. SARA’s
offerings include the full range of seismological equipment,
including mono-,bi-, and triaxial broadband seismometers, the
Digital Array modular real-time network, the DoReMi digital
telemetry system for near-surface and engineering applications, and
borehole sensors. Additionally, SARA offers a range of custom
software solutions for survey planning and data processing and
visualisation.
GeoBox makes the differenceFor data acquisition, SGC uses the
versatile and lightweight SARA GeoBox. The GeoBox contains a
high-accuracy three component seismometer and all electronics
required to sample, digitize, and transmit the data. The GeoBox’
performance is excellent and results compare positively with those
obtained with other equipment; resonance frequencies are defined in
great detail and the noise floor is demonstrably low. The GeoBox
has the most user-friendly interface on the market: the raw data
and a preliminary HVSR plot are visualized in real time on a field
tablet allowing for quality control and survey optimisation during
acquisition. In combination with SGC’s proprietary software, which
is designed for efficient processing and visualisation of large
datasets, the GeoBox is the ideal tool for HVSR passive seismic
surveys.
The Passive Seismic method uses ambient noise as a seismic
source and is a rapid and completely non-disturbing method for the
exploration, hydrogeological, environmental and construction
industries. Utilizing the horizontal-to-
vertical spectral ratio, it can be used for measuring depth to
bedrock and other stratigraphic boundaries, paleochannel mapping,
site response analysis, and geotechnical material property
assessment amongst other applications.
Southern Geoscience Consultants - HEAD OFFICE39 Richardson
Street, West Perth, WA 6005 AustraliaT: +61 (8) 6254 5000 E:
[email protected]
Southern Geoscience Consultants - AMERICASSuite 401, 15 Toronto
Street, Toronto, Ontario, M5C 2E3, CanadaT: +1 (416) 407 6355 E:
[email protected]
www.sgc.com.auwww.sgc.com.au
GEOBOX SPECIFICATIONSPower supply: embedded batteryBattery life:
up to 10 hoursNumber of channels: 3 24bitOperating temperature: -20
to +75°CSensor availability: 4.5, 2.0, 1.0, 0.5, 0.2HzOptional: GPS
for time synchronization
Solutions, instruments and software for seismology,
geophysics and vibrometry
APPLICATIONSDepth to bedrock mappingGeoBox passive seismic data
is frequently used to estimate the thickness of overburden. For
strong contrasts in acoustic impedance, the horizontal-to-vertical
spectral ratio (HVSR) of the ground motion displays a resonance
peak, the frequency of which depends on the depth to the contrast
and the shear wave velocity of the overburden. Where paleochannels
are incised in bedrock, the HVSR method is an efficient way for
targeting drilling locations.
Geotechnical engineering propertiesFor structures sensitive to
liquefaction or other forms of deformation and collapse, it is
critical to understand material strength. The joint inversion of
HVSR and MASW dispersion curves are a rapid and reliable way to
obtain Vs profiles across a site. HVSR Vs data also provide
valuable complimentary information to CPT(u) and shear-wave seismic
data.
Site response micro-zonationDetermination of a soil’s resonance
frequency and amplification factor can save lives, as was
tragically proven in 1985. Amplitude amplification of acoustic
energy (originating from an earthquake at distance) in the soft
soils below Mexico City caused enormous damage. Passive seismic
surveys are now routinely employed in tectonically active areas to
prepare cities by highlighting vulnerable areas.
Modal analysisModal analysis is signal processing aimed at
identifying the vibrational modes of a structure. It provides
experimental evidence on the mechanical properties of the structure
and can identify potential design problems. Using modal analysis
the dynamic properties of a structure, including the natural
vibrations and torsional motion induced by human activities or
natural excitation phenomena like wind, are measured.
When employed on different levels of a building or structure,
modal frequencies can be derived and compared with soil resonance
frequencies.
MORE FROM SARACritical infrastructure monitoringThe S.S.E.
system is a turnkey solution for monitoring complex structures like
dams or high-rises. It puts in action an automatic process for
evaluating (within seconds) if a seismic event impacted the
structure. As soon as an event is detected, the ESCAP software
module performs corrections and calculates seismological indices
and a response spectrum relevant for assessing structure
vulnerabilities. If necessary, alert messages are sent. Operators
can monitor the real-time evolution of the seismic sequence,
analyse velocity, acceleration and displacement, and evaluate
structural impacts through 3D particle motion and force vector
visualisation.VelBoxThe VelBox is a tri-axial seismometer with
similar functionality as the GeoBox but with menu-based operation
and internal storage, making it a fully stand-alone solution for
passive seismic surveys.DoReMi seismographThe DoReMi is a fully
modular seismograph with a very high quality/price ratio and
state-of-the-art features, including digital telemetry, embedded
batteries, and digitization along the cables to reduce EM noise and
cross talk. The DoReMi can be used for all active (MASW,
Refraction, Reflection, Downhole) and passive seismic (ReMi,
ESAC/SPAC) and for HVSR and structural surveys.
For more information On the products on offer or a price list
contact us at [email protected]