[8.10.2024] During October, seismic survey began in the area around Litoměřice, with the aim to determine the response of the geological bedrock to artificially generated seismic waves. The way the bedrock reflects the vibrations will detect the interfaces of the geological layers, their direction and possible tectonic faults that could affect the planning of drilling operations. Seismic survey is carried out both horizontally, on four lines drawn around Litoměřice, and vertically in the 2 km deep test borehole PVGT-LT1, located on the site of the Jiří z Poděbrad barracks in Litoměřice.
Implementation of field survey
The receivers or Geophones - small plastic boxes 10x10 cm with a short spike - are placed at 10 m intervals on predefined lines of approximately 10 km. A truck-sized vehicle with vibrating plates underneath will drive along them. The vehicle will create seismic waves at intervals of 20 meters, which will be recorded by the geophones. The waves themselves are so weak that there is no risk of damage to the property. The only problem may be the passage of a heavy vehicle through the farmland. Therefore, prior to the event, consent with the passage is negotiated with all affected landowners and compensation for crop damage is guaranteed. The truck passage is timed with the end of the harvest, to minimize the damage.
Vertical survey
"In the PVGT-LT1 borehole, with a depth of over 2 km, geophones are placed at certain intervals - with deployable "packs" that clamp the geophones against the borehole wall. The vibrotrucks create seismic waves first in the close vicinity of the borehole, then at a distance of about a kilometer." explains seismologist Josef Vlček from the Faculty of Science at Charles University. It is necessary that the borehole is empty before the actual survey. That is why a seismic probe was pulled out of the borehole in early September. It was used to monitor the natural seismicity and tremors caused by traffic or industrial activity. This monitoring has been ongoing for 3 years and is particularly important to ensure the safety of future drilling of deep wells, planned by the SYNERGYS project.
