Seismic structure of the Cheb Basin from high resolution surveying – traveltime tomography results

In our study we investigate the subsurface velocity structure of the Cheb Basin (Czech Republic) based on shallow high-resolution 2D seismic data collected in the years 2014-2020. The Cheb Basin is a small intracontinental basin, located in the north-west part of the Bohemian Massif and at the western end of the Cenozoic Eger Rift. The basin and underlying crustal structure are the subject of the ongoing International Continental Scientific Drilling Program (ICDP) “Drilling the Eger Rift''. Our surveys aim to investigate the up to 350-m-thick Miocene and Quaternary sediments and the bedrock, made of Paleozoic Variscan units and post-Variscan granites.

Four datasets were collected, each with a 480-m-long split-spread of single geophones at 2 m spacing. The 2014 dataset was acquired with a 10 m source interval, mainly with a weight-drop source and partly with a SISSY source, resulting in an almost 3 km long profile. The 2017, 2020 line 1 and 2020 line 2 datasets were shot with a buffalo gun at a 20 m source interval. Their lengths are 2 km, 0.8 km and 1 km respectively.

We present the traveltime tomography output for all 4 profiles, which brings important information about the subsurface. The results give us insight into the velocities of the sediments, which in this area mainly range from 600 m/s to 2500 m/s. The bedrock is observed with velocities up to 4500 m/s and is present at a depth of around 250 m below the surface. This velocity information is complimented by the preliminary results of the ongoing reflection processing.