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Figures
Fig. 2.1
Fig. 2.2
Fig. 2.3
Fig. 2.4
Fig. 2.5
Fig. 3.1
The selected shot point at about 57°7'N, 0045'V. The
position of shallow boreholes is taken from Thomson & Eden
(1977), the deepest penetrates to 81 m. The AMOCO VeIl
27/3-1 penetrates to about 2 km. HBF: Highland Boundary
Fault. SUF: Southern Upland Fault. The coarse dashed
line represents probable offshore extension of the HBF and
the SUF, and significant offshore faulting. The fine
dashed line represents the 50 m isobath.
Plan of the experiment. The ragged star shows the 2 ton
shot point, about 80 km east of Aberdeen. Recording
packages were placed at the locations 1-4, BGS, 5 and 6
along the great circle from the shot point to Tentsmuir, in
Fife. The triangles on-shore show the positions of
vertical component seismometer sites, squares show
three-component seismometer sites, associated with LOYNET
and additional "soft" rock coastal seismic installations.
Cross-section of the experiment. The ragged star shows the
2 ton shot point in 75 m water depth. 1-6 represent the
positions of Pull-up sea bottom seismometers (PUSSes), each
of which contains one three-component geophone and a
hydrophone. Each PUSS is ship independent. BGS represents
the position of the BGS Sea Bottom Package, which contained
one three-component accelerometer and one hydrophone,
cabled to the Salmaster. BGS also represents the position
of the vertical hydrophone string (VHS), consisting of 10
hydrophones at 5 m intervals from the sea-bed, and of other
hydrophones; all of which are cabled to the Salmaster.
Tentsmuir is the position of a three- component seismometer
in a "soft" rock site onshore but near to the coast.
Charge configuration and shot point moorings. The shackle
ring is the shot point identifier at sea; it is the
mid-point of the cable held under tension between the two
Class 5 mooring buoys. It was intended to detonate the
2 ton charge at 5 m above the sea-bed using floats to
create positive buoyancy for the charge anchored to the
sea-bed. Sponge shaped floats give buoyancy to the
detonation cable which should be slack or strain relieved
to avoid snapping. The stand-off distance Goosander to
shot point is of order 500 m.
Local magnitude, ML, versus charge size for underwater
explosions (adapted from Jacob and Neilson 1977).
Enveloping curves and mean trend (dashed line) are eyeball
fits.
Shot timing system configurations.
Fig. 3.2 Three-dimensional impression of the configuration of the 78
equipment deployed at sea by BGS, i.e. BGS Sea Bottom
Package, Vertical Hydrophone String, Pull Up Shallow-water
Seismometer.
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