Abstract: Described herein is a method for performing a long offset refraction seismic survey of a subsurface area of interest using a fiber-optic cable (170) positioned on or under the earth's surface and extending between a first cable end (172) closer to the area of interest and a second cable end further from the area of interest, the method comprising: connecting an interrogator to an end of the fiber-optic cable, wherein the interrogator is configured to emit light into the cable through the end and detect reflected light from the cable; simultaneously steering and activating a low frequency seismic source and operating the interrogator to collect seismic refraction data; wherein steering the source comprises directing the source along a travel path that extends between a first source position closer to the area of interest and a second source position further from the area of interest, wherein the second source position is horizontally offset at least 9 km from the first cable end, and the cable and source trave

Abstract: Seismic airgun arrangement for attenuating unwanted oscillations in the emitted signal. The airgun has one or more outlet ports (9) for exhausting air in a generally radial direction from a central axis of the airgun (10), and a perforated screen (20) of plate material is provided around the airgun for the attenuation mentioned. The volume generally delimited within the screen (20) is significantly smaller than the maximum bubble size which is normally generated by the airgun (10). The screen (20) has an open side or end (20A) at a part of the screen that is adapted to face at least partially downward in the normal operative position of the airgun (10). At least edge portions of the screen along the open side or end (20A) are located substantially directed opposite the outlet port or ports (9).