GEOSPHERE INC -- Seismic Methods: Field Procedures

View of the 9048 Seismograph (bottom center) and
Roll Switch (left center)

seismic source. Geophones are also selected according to the needs of the survey: higher-frequency phones for high-resolution work, lower-frequency for deeper targets. Our Bison Instruments 9048 seismograph offers 48-channel recording capability, with internal data storage to enhance field productivity. The 9048 floating-point system is one of the best engineering seismographs available today, with recording specifications better than many petroleum exploration systems.

Seismic field acquisition involves three basic elements:

a source of acoustic energy
seismic receivers, or geophones
a seismograph, or recorder, to collect and store the data

The arrangement of source and geophones depends on the nature of the survey. Typically, the geophones are placed along a line at equal intervals (1 to 5 feet for high-resolution, 10 to 20 feet for deeper work). For seismic reflection, the relative source and geophone positions are usually held constant with the entire 48-geophone array being moved along with the shot. (The logistical difficulties of this are eased by using a "roll switch", which

Seismic Refraction: Midspread Setup with Seismograph, EWG III, and Geophones in view

$3-D color plot of bedrock topography interpolated from seismic refraction data$

The choice of seismic source depends on the needs of the particular survey. For deeper work, a powerful source, such as one of our Elastic Wave Generators (EWG), trailer-mounted accelerated weight drops, would be used. Shallow, high-resolution work, not requiring the power of an EWG, can be done by striking a steel plate with a sledgehammer or using the "Betsy"

selects 48 geophones from an overall spread of 96.) Refraction work requires shots at opposite ends of the spread, with additional shot locations depending on the particular needs of the job.