Question: How do you conduct a seismic survey?

James Verdon answered on 29 Jun 2012:

Hi lucky,

A seismic survey is a lot like a giant version of an ultrasound that you might see in a hospital.

Firstly, you put out an array of maybe 20 to 1000 seismometers around the area of interest. Then you need a source, to create seismic waves that will travel through the ground. The most common thing to use is what is called a vibroseis truck – basically a big truck with a hydraulically activated plate underneath. The hydraulics can push this plate down at speed, smacking it into the ground. It’s like a giant foot stamping on the ground.

This creates the seismic waves that travel down into the ground. Whenever there is a change in the type of rock, some of the seismic waves are reflected back upwards towards the surface. These reflected waves are picked up by the seismometers that we’ve put out, and we can use the signals we record to build up a picture of the layers of rock below our feet.

Seismic surveys are most commonly used by the oil and gas industries to look for the layers of rock that might contain oil. But in the ‘My Typical Day’ section of my profile you can see an example of us doing a small survey in a volcanic crater (3rd picture down) to try to see the structure of the rocks underneath.

Rather than a truck, we have a sledgehammer to create the seismic waves. You can see my boss in the middle holding it. You can then see the seismometers layed out in front, attached to the cables that send the signals back to the recording computer.