Abstract: A method of providing a marine seismic signal comprising the steps of: arranging a plurality of seismic sources into a seismic array having at least two seismic subarrays with each subarray having a plurality of seismic sources, towing the seismic array behind a vessel and operating the plurality of seismic sources such that the seismic array satisfies a predetermined relation which is a function of the operating pressure, gun volume and towing depth of the respective seismic sources in the respective subarrays.

Abstract: Apparatus for measuring the force actually exerted by the base plate of a seismic vibrator on the earth surface is provided. This apparatus consists of a plurality of individual sensor elements, which are arranged on the side of the base plate which is directed towards the earth surface. The sensor elements couple the energy from the base plate to the earth surface.

Abstract: A method for marine seismic exploration, comprising the steps of first discharging simultaneously a set number of seismic sources having a known volume V.sub.1, resulting in several seismic waves with substantially identical form which after reflection by a same series of reflection points are detected by hydrophones as a sum signal of the individual emitted source waves having a frequency range f.sub.1. The sum signal is subsequently filtered by means of a suitable filter operation having a frequency range f.sub.1, resulting in a sum signal having substantially equal phase of the individual components in the frequency range f.sub.1, next discharging simultaneously a set number of seismic sources having a known volume V.sub.2, different from volume V.sub.1, resulting in several seismic waves with substantially identical form which after reflection are detected by hydrophones as a sum signal of the individual emitted source waves having a frequency range f.sub.2.

Abstract: A method and apparatus for controlling the firing of a seismic source, wherein the firing circuit is coupled to the source by a two-conductor cable whose impedence is changed upon firing of the source. The change in cable impedence is detected and the time delay between the firing command signal and the detected change is used to control the firing command signal in order that a plurality of sources may be fired in a desired sequence.

Abstract: A method for controlling the firing times of a plurality of marine seismic sources which are towed as a seismic array behind a towing vessel is provided. The marine seismic sources are adapted to create seismic pulses after having been fired. The method measures and determines physical quantities representing the instantaneous operating depths of the individual seismic sources of the array and transmits the values of said quantities to a controling means for the seismic sources which compares the depth values thus obtained with predetermined depth values, and, if the measured depths are different from a preset depth, adjusts the firing times of the seismic sources of the seismic array in relation to the measured instantaneous depth values.Apparatus for carrying out the method is also provided.