Equipment Overview
Compared to the equipment used for gravity
and magnetic and even
resistivity surveying, the amount
and complexity of the equipment used in seismic surveying can be staggering.
Due to the complexity of the equipment (which stems from the complexity of the
field surveys we would like to employ), seismic surveying can become logistically
very intensive.
Typical seismic acquisition systems consist of the following components.
- Seismic Source - This is nothing more than an apparatus for delivering
seismic energy into the ground. Sources can vary greatly in their size and
complexity. All, however, share the following characteristics:
- They must be repeatable. That is, the nature of the energy delivered into
the ground (its amount and the time duration over which it is delivered)
should not change as the source is used in different locations and
- Time of delivery must be controllable. We must be able to tell exactly when
the source delivered its energy into the ground. In some cases, we can
control the time of delivery. In others, we simply note the time the source
delivered its energy.
- Geophones - These are devices capable of measuring ground motion
generated by the seismic source. As we will describe
later, these typically convert the ground motion into electrical signals
(voltages) that are recorded by a separate device.
- Recording System - This actually consists of a number of components.
In essence, this entire system does nothing more than store the ground
motion detected by a number of geophones. This number could be quite large.
Today, it is not unusual for oil exploration surveys to record ground motion
detected by 1000's of seismometers at a time. In addition to recording
ground motion, this system must also control the synchronization of
the source. It consists of not only a "black box" to store information but
also numerous electrical connections to the geophones and the source and
usually a device to select subsets of the installed geophones to record.
