A seismic survey is a method of determining the structure of the subsurface geology. The basic theory is that a vibration (wave of energy) is initiated at the earth's surface which will travel throught the earth. Every time the density of a rock formation changes, a reflection of the energy is sent back to the surface where it is monitored by an array of geophones (listening devices, if you will). By correlating the time between the initial vibration and receiving the signal reflection, it is possible for geophysicists to determine the depth of the rock formation that reflected the energy. This allows them to map rock formations of interest and assist in the exploration for oil and gas.
There are two methods of initiating the energy signal at the surface. The first method is by drilling shallow holes and placing a small explosive charge in them (this is generally strictly regulated by the state and you should be able to find the regulations on your state oil and gas website). The second method of initiating the energy signal is with a large seismic truck. This truck has a large pad or "foot" that is lowered; the truck then "shakes" itself thus sending an energy signal to the ground.
A seismic company needs to have the surface owner's permission before conducting a survey. It might be worth calling the seismic company to inquire about the survey. Ask if they will be using charges or a seismic truck, how many holes they need to drill on your property, when they will be filled back in, how soon any surface damages will be repaired, etc.