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Geophysical Tools

The LLO uses a wide variety of geophysical tools in its studies of lake floor morphology and sedimentary processes. These acoustic tools allow LLO researchers to produce high resolution images of the lake floor and the underlying sediments.

Geophysical Tools

High resolution bathymetric surveys (see examples) can be collected with LLO's multibeam bathymetric system, which may be used on the RV Blue Heron or vessels of opportunity. The system consists of a 240 kHz Reson SeaBat 8101 multibeam coupled to an Applanix POS-MV 320 motion and positioning system. The combined system is capable of producing high-quality hydrographic-survey-grade data in freshwater lacustrine systems up to 400 meters deep. The data are recorded in the industry standard XTF format using a Triton Imaging ISIS acquisition system. Survey design and management functions are provided by a Coastal Oceanographic Hypack system. Post-acquisition processing is conducted using CARIS HIPS/SIPS. In addition to depth information, the LLO's Reson 8101 provides sidescan sonar imagery for creation of mosaics and lakefloor substrate classification.

The RV Blue Heron is equipped with an EdgeTech dual frequency (100/400 kHz) Full Spectrum CHIRP sidescan sonar system. The system is depth rated to 300 m and includes an electric-hydraulic winch equipped with 1000m of armored tow cable. Post-acquisition processing of the sidescan-sonar data with CARIS SIPS software is used to produce mosaics from the data. The towfish also includes an EdgeTech Full Spectrum 512 CHIRP sub-bottom profiler with a 0.5-12 kHz frequency range.

In addition to the EdgeTech CHIRP sub-bottom profiler in the sidescan-sonar towfish, seismic-reflection systems available on the RV Blue Heron include: a 28 kHz Knudsen Model 320B Echo Sounder; a Geopulse Boomer, and Bolt airguns that may be equipped with chambers of varying sizes. The RV Blue Heron is equipped with a dedicated Bauer high pressure compressor for seismic surveying with airgun sources. Data acquired with the boomer and airgun sources use a 24-element Benthos AQ-4 hydrophone streamer. The data are digitally recorded in the industry standard SEGY format using a Triton Imaging SB-Logger system.

Limnology studentsPortable electrical generators and a high pressure air compressor are available for seismic surveys on remote lakes. A small, hand-deployable EdgeTech 424 CHIRP sub-bottom profiler is available for seismic-reflection studies either from the Blue Heron, or from small vessels on small, remote lakes.

The Geophysical Laboratory at LLO has several computers (SGI Unix workstations and PC workstations) equipped with software for processing and interpreting seismic, multibeam sonar and sidescan sonar data (Parallel Geoscience SPW and SU seismic processing packages, SeismicMicro Technology Kingdom interpretation Suite, CARIS HIPS/SIPS hydrographic packages, Quester Tangent QTC bottom classification packages). Supporting equipment includes: large format inkjet plotters, scanners and tape backup units for archiving data.

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Last modified on 02/07/14 12:46 PM
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