Geostuff Land Streamers
A land streamer is an array of geophones designed to be towed along the ground. The name originates from marine streamers which are strings of hydrophones towed behind boats for marine seismic surveys. Land geophysicists have long envied the high productivity achieved in marine surveys. Now it appears that highly-productive reflection, refraction, and surface-wave surveys can be achieved on land.
Land streamers have been developed by individuals using a variety of innovative methods. A survey of such systems was described in the March 2003 issue of Geoprofiles, Geometrics' periodic newsletter with articles of interest to geophysicists. Additional references can be found on the web by searching for "land streamer", including papers comparing data quality and productivity between towed array and conventional surveys. As a general rule, geophones planted in the ground set the standard for data quality, but land streamers record excellent data in many applications while making the survey economically feasible. A "good" affordable survey often will be a better choice than a "great" survey that can't be done due to its cost.
Geostuff has introduced a commercial land-streamer system which we believe will provide better data, be less expensive, more reliable, and easier to use than individually constructed units. To satisfy the needs of individual applications and users, systems will be available with a wide variety of geophones in single or multi-component and fixed or gimbaled versions.
The basic LS-1 system consists of a base plate, tow webbing, top plate and wing. It is designed to be used with your existing geophones and cables to quickly convert them to a low-cost land streamer.
The top plate is drilled and tapped for standard 5/16 and 3/8-inch male threaded geophone cases from Sensor, Mark Products, Geospace and others, or a 3/8-inch flat head screw can be inserted for female-studded geophone cases, such as the 3-component Geospace GS-3C case shown here.
The base plate is cast of a special Cr-Mn-Mo alloy steel developed for the hard-rock mining industry. Heat treated, it is highly abrasion-resistant for long use. The tripod support provides stability, even if the ground surface has loose material, so the sensor will respond properly to ground vibrations. The legs will tend to plow into soft ground for better coupling.
The 5-cm wide webbing is reinforced with Kevlar® for tensile strength and anti-stretch properties. Loops are woven in the top surface at short intervals so that the geophone cables can be secured to the top surface with nylon cable ties, thus protecting the cables from dragging on the ground. The Kevlar® strap is firmly clamped between the top and bottom plates without perforating or damaging the webbing. This maintains the 2200 Kg tensile strength of the webbing and also allows the placement (and re-placement) of the geophones at any interval chosen by the user. Choose Metric, English or even non-linear geophone intervals as allowed by your spread cables. When used with longer group intervals on rough ground, stations can tip over. In that case, just install the Anti-rotation wing (pictured) provided with the system.
The land streamer will work with Mueller clips or split-ring takeouts, but for systems assembled from scratch for land streamer use, Kooter type takeouts (pictured here) are recommended because they keep the wires close in to avoid catching on passing obstructions.
References (downloadable, in Adobe Acrobat format):
Land Streamer Data Sheet (includes examples of MASW data gathered with the Geostuff Land Streamer and processed on SurfSeis)
Survey of Land Streamers, Article by Geometrics;
Design and application of a towed land-streamer system for cost-effective 2-D and pseudo–3-D shallow seismic data acquisition, by M. van der Veen, R. Spitzer, A. G. Green, and P. Wild
For purchase information, e-mail firstname.lastname@example.org or, telephone 1-530-274-4445, fax 1-530-274-4446.
Land Streamers are available for rental from Geomatrix Earth Science Ltd in Europe and Exploration Instruments in the U.S.A.
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