SPARKER source

A sparker is a high-resolution seismic source which can be deployed on various vessels of the French Oceanographic Fleet. In particular, it is deployed on coastal vessels (Thalia and L'Europe) in order to acquire seismic data close to the shore.

Sparkers function as follows: A high-voltage bank of capacitors, charged to several thousand volts and connected to a spark-gap system, is periodically discharged across several submerged electrodes in a conductive liquid (saltwater). The spark vaporizes the surrounding water and creates a plasma bubble which, on collapsing, provokes the emission of an acoustic signal. The frequency of the emitted signal depends on the chosen configuration (type of electrode, energy), generally between 250 Hz and 2000 Hz.

The resulting sound wave propagates through the water and into the subsurface. At the interface between two successive geological layers, some of the energy of the incident wave is reflected back to the surface. Such signals are then picked up by a set of pressure sensors (hydrophones) spread along a cable towed by the vessel (streamer).

Characteristics of the Fleet’s sparker:

  • Supplier: SIG
  • Model:
    • Sparker source of 2000 Joules (ref. 0609J2000E21) with an extension of 3000 Joules.
    • Electrodes: SIG multi-tip with 50 (ref. ELC050), 100 (ref. ELC820), 200 (ref. EDL1020) and 360 tips (ref. SIG360).
    • SIG streamer comprising 8 hydrophones (ref. SIG16, omnidirectional hydrophones). The first five hydrophones are spaced 30 cm apart, the following three are spaced 1 m apart (see diagram below). Two configurations are possible:
      • Configuration 1: hydrophones H1, 2, 3 and 4 in parallel.
      • Configuration 2: all the hydrophones in parallel.

Data is acquired using the SUBOP software, the latter also used for acquiring the data generated by the sub-bottom profilers

During acquisition, the electrode and the streamer are towed approximately 50 m behind the vessel, and close to the surface.

The equipment fits into a 10’ container and can be deployed on all the vessels of the Fleet.