1 Concept scheme: SeaDataNet Device Thesaurus

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Concepts

1.1 Seismic source instrument

Categories used in the SeaDataNet project to classify energy sources used in seismic surveys.
Alternate labels: SeaDataNet seismic source types, seismic sources,
Concept URI: http://vocab.nerc.ac.uk/collection/L21/current/ICAT07

Child of: ICAT07
Marine seismic sources that send sound pulses into the sub-sea floor sediments. The sound pulses bounce off the sea floor and subsequent buried sediment layers according to differences in their acoustic impedance (hardness) and in turn, their density. Pingers are linear, single channel, high frequency systems that typically operate at frequencies greater than 2 kHz and penetrate to several tens of metres.
Concept URI: http://vocab.nerc.ac.uk/collection/L05/current/394

Child of: ICAT07
Marine seismic sources that send sound pulses into the sub-sea floor sediments. The sound pulses bounce off the sea floor and subsequent buried sediment layers according to differences in their acoustic impedance (hardness) and in turn, their density. Parametric sub-bottom profilers are non-linear systems that transmit two different higher frequencies that interact during sound propagation to generate a resultant lower operating frequency with narrow bandwidth. They typically operate at frequencies greater than 2 kHz and penerate to several hundreds of metres.
Concept URI: http://vocab.nerc.ac.uk/collection/L05/current/396

Child of: ICAT07
A marine seismic source where a propane-oxygen mixture is exploded inside a steel cylinder.
Concept URI: http://vocab.nerc.ac.uk/collection/L05/current/AQPL

Child of: ICAT07
A marine seismic source where multiple airguns of different sizes are tuned so that a broader frequency spectrum will be generated.
Concept URI: http://vocab.nerc.ac.uk/collection/L05/current/ARAG

Child of: ICAT07
A marine seismic energy source in which capacitors are charged to high voltage and then discharged through a transducer in the water. The transducer consists of a flat coil with a spring-loaded aluminium plate. Eddy currents force the plates to separate sharply, producing a low pressure region between the plates into which the water rushes generating a pressure wave by implosion.
Concept URI: http://vocab.nerc.ac.uk/collection/L05/current/BOMR

Child of: ICAT07
Chirp systems emit a ‘swept-frequency signal’, meaning that the transmitted signal is emitted over a period of time and over a set range of frequencies. This repeatable (transmitted) waveform can be varied in terms of pulse length, frequency bandwidth, and phase/amplitude. A matched filter, or correlation process, collapses the swept frequency modulated (FM) received signal into a pulse of short duration, maximizing the signal-to-noise-ratio. The reflected signal is received by a tuned transducer array that generates the outgoing acoustic energy. Chirps operate within a range of 400Hz - 24 kHz and are used for the first 20-30 metres of unconsolidated sediments.
Concept URI: http://vocab.nerc.ac.uk/collection/L05/current/CHRP

Child of: NATS ICAT07
A sudden release of stress in the Earth’s crust that creates energy in the form of seimic waves.
Concept URI: http://vocab.nerc.ac.uk/collection/L05/current/ERTQ

Child of: ICAT07
An implosive energy source for marine shooting. Two plates are separated by compressed air until they lock into position. The air between them is then pumped out creating a vacuum. On the signal the plates are unlocked and the water pressure forces them together creating a shock wave in the water.
Concept URI: http://vocab.nerc.ac.uk/collection/L05/current/FLXS

Child of: ICAT07
A seismic method for marine shooting whereby small charges are propelled through a rubber hose by water under pressure into a steel cage where they are detonated. Holes in the cage allow the water repelled by the explosion to flow out and in thus dissipating some of the energy in the bubble effect.
Concept URI: http://vocab.nerc.ac.uk/collection/L05/current/FLXT

Child of: ICAT07
A marine seismic source where a pair of conventional airguns (one, the generator, fires in the conventional manner; the second, known as the injector) fires some milliseconds later to prevent bubble from collapsing. Could be used in true GI mode (volume of injector twice of volume of generator), harmonic mode (same volume of generator and injector) or true airgun (no delay between generator and injector).
Concept URI: http://vocab.nerc.ac.uk/collection/L05/current/GIAG

Child of: ICAT07
A marine seismic source generating sweeps of controlled varying frequency (from a few Hz to hundreds of Hz) and duration.
Concept URI: http://vocab.nerc.ac.uk/collection/L05/current/MVBR

Child of: ICAT07
Any kind of natural source of acoustic waves, that can be used in passive seismics.
Concept URI: http://vocab.nerc.ac.uk/collection/L05/current/NATS

Child of: NATS ICAT07
A sudden release of stress in the Earth’s crust that creates energy in the form of seimic waves.
Concept URI: http://vocab.nerc.ac.uk/collection/L05/current/ERTQ

Child of: ICAT07
Array of air gun tuned in order to obtain the necessary energy wile reducing the size of the air guns.
Concept URI: http://vocab.nerc.ac.uk/collection/L05/current/SBAG

Child of: ICAT07
A marine seismic source which injects a bubble of highly compressed air into the water. Oscillations of the bubble as it alternatively expands and contracts generate a sonic wave whose frequency depends on the amount of air in the bubble, its pressure, and the water depth.
Concept URI: http://vocab.nerc.ac.uk/collection/L05/current/SNAG

Child of: ICAT07
A marine seismic energy source divided into two chambers, the firing chamber, which contains compressed air, and the other chamber, which is filled with water. When the gun is fired, the compressed air forces the shuttle downward and this expels the water from the lower chamber. The shot of water leaving the gun creates a void behind it and the collapse of water into this void creates an acoustic wave.
Concept URI: http://vocab.nerc.ac.uk/collection/L05/current/SNWG

Child of: ICAT07
A seismic source in which an electrical discharge in water is the energy source.
Concept URI: http://vocab.nerc.ac.uk/collection/L05/current/SPRK

Child of: ICAT07
A marine seismic energy source in which a quantity of superheated steam under high pressure is iniected into water. Subsequent condensation of the steam attenuates bubble oscillation.
Concept URI: http://vocab.nerc.ac.uk/collection/L05/current/VSHC