Methods - Lacustrine Seismic
One of the major differences between marine and lacustrine seismic is the dimension of both the area in question and the equipment used. In polar and sub-polar regions, lakes are often remote and transport of equipment is complicated, vessels are small (if present at all) and electric power is not always easily accessible.
Based upon success in Swiss alpine lakes in the late seventies/early eighties using a very small system, the AWI lacustrine seismic group developed a small portable seismic system:
- a portable aluminum platform of 3x4 m (‘RV Helga’, the smallest ‘research vessel’ of the AWI)
- a small Mini-G gun (SODERA)
- diving compressors (Bauer)
- single hydrophones that can be combined to a streamer of up to 300 m length and up to 14 channels for multi-channel seismics
- a 20-element single channel hydrophone for single-channel seismics (GeoAcoustics)
- sonobuoys (AWI Bremerhaven)
- 3.5 kHz sediment echosounder (ORE)
- a chirp system (GeoAcoustics, UK model Geochirp I)
- fishfinder for water depth and GPS for navigation
Figures:
Figure 1: Single hydrophones are transportable in ZARGES boxes and can be combined to a streamer.
Figure 2: ‘RV Helga’ fully equipped on Lake El’gygytgyn in 2000.