APPLICATION OF THE SINGLE-BUBBLE AIRGUN TECHNIQUE FOR OBS-DATA ACQUISITION ACROSS THE JAN-MAYEN RIDGE, NORTH-ATLANTIC

A 140 km long wide-angle seismic profile has been acquired by use of 6 Ocean Bottom Seismographs across the Jan Mayen Ridge, North Atlantic. The profile was acquired twice; once with a traditionally tuned stand ard source and secondly with a somewhat smaller source tuned on the fi rst bubble pulse. Analysis of the frequency content of the data reveal s that the single-bubble source within the 10-15 Hz frequency range ge nerates a signal with a level about 5 db above that of the standard so urce. These differences can partly be related to differences in airgun depth. The higher output level for these frequencies enables the sing le-bubble source to resolve intra-crustal structures with a higher deg ree of certainty, when compared to the data acquired by use of the sta ndard source array. The standard source seems to generate slightly mor e energy for frequencies around 6 Hz, probably due to the use of a lar ge 1200 in(3) gun in this array. These low frequencies are of importan ce for mapping of lower crustal and upper mantle structures? and it is recommended that this is taken into account when seismic sources for mapping of deep crustal and upper mantle structures are designed.