In the beginning, some of the initial assessment activities might not be noticeable to residents. It is common to spot a team of geologists taking pictures and making field observations. Seismic tests, on the other hand, are likely to draw attention. If using thumper or vibrator trucks, the survey team may employ as many as 5–6 trucks 1 accompanied by personal vehicles. Depending on the size of the sample area, the testing takes place over a period of days to months. A seismic survey team can cover several miles a day on average, and the surveys typically cover 50–100 square miles or more. 2
If the survey company plans to conduct seismic tests on private property, the company will contact landowners to notify them when it will take place and/or request their permission. Company personnel will first survey the property to stake out the exploration area and to mark areas for the survey team to avoid. Depending on the type of survey, they might temporarily place geophones (a receiver for the sound waves generated by the testing), data boxes, or cables on the property. The company might cut narrow lanes through forested areas or brush for the survey equipment. If using explosive charges, the company drills small diameter shot holes that can be up to 150 feet deep (although they not usually more than 80 feet deep). 3
During seismic testing, approximately 40 members of the survey team will set up the seismic recording equipment, generate the sound waves—either by moving a thumper or vibrator truck through the area or detonating the charges—and record the data. After testing is complete, the company should remove all the equipment and materials and plug any shot holes. Depending on the type of test, the equipment might be present on the property for a few days to 3–4 weeks.
Will seismic exploration activities cause any damage? If so, who will cover repairs?
Due to their weight, seismic survey trucks can damage roads and bridges or cause surface disturbance if the infrastructure is not well-maintained or cannot accommodate heavy loads (even DOT-permitted ones). Such disturbance could possibly lead to erosion and sedimentation of surface waters. 4
If the surveyor uses underground dynamite charges instead of trucks, the detonations take place far enough underground that they do not impact the surface. The shot holes drilled for such testing might disturb the water table, however, affecting the flow of water to wells or allowing contaminants to migrate into the groundwater. 5 Company ATVs and other vehicles can also cause surface disturbance or leave track marks.
Companies must comply with state regulations covering exploration activities, which often include requirements to post a bond for any damages and to plug shot holes, among other provisions. Companies are required to compensate public or private property owners for any damages or the impacts of “non-normal” use that takes place during seismic surveying. 6 If landowners sign a permit to access their property, there may be provisions pertaining to any damages sustained. For information on the regulations in your state, contact the state oil and gas regulatory agency (see Table 2).
Could seismic testing cause earthquakes?
Seismic testing has long been a feature of traditional oil and gas exploration, preceding the recent boom in shale development, and this aspect of the process has not been linked to earthquakes. The amount of explosives used in seismic surveying (approximately 10–20 pounds), is much less than would be needed to generate seismic waves similar to a 1.5 earthquake on the Richter scale (320 pounds). 7 Vibrator trucks generate even less energy than explosives. 8 For more on the topic of seismicity, see the safety section in Stage 4.
- Rigzone, “Training: How Does Land Seismic Work?”, accessed September 20, 2015. ↩
- John B. McFarland, “How Do Seismic Surveys Work?” Oil and Gas Lawyer Blog (April 15, 2009). ↩
- Mark R. Milligan, “What Are Seismic Surveys and How Much ‘Shaking’ Do They Create?” Utah Geological Survey website (July 3, 2004). ↩
- Earthworks, Oil and Gas at Your Door? pp. 6–13. ↩
- Earthworks, Oil and Gas at Your Door? pp. I-7. ↩
- “Can You Conduct a Seismic Survey without a Landowner’s Permission?” Courthousedirect.com (August 14, 2013). ↩
- Mark R. Milligan, “What Are Seismic Surveys and How Much ‘Shaking’ Do They Create?” Utah Geological Survey website (July 3, 2004). Earthquakes of magnitude 1.5 to 2 on the Richter scale are rarely felt. ↩
- Mark R. Milligan, “What Are Seismic Surveys?” ↩