Air shower simulation for background estimation in muon tomography of volcanoes

One of the main sources of background for the radiography of volcanoes with atmospheric muons comes from the accidental coincidences produced in the muon telescopes by the air showers. In order to quantify this background, Monte-Carlo simulations of the showers and of the detector are developed by the Tomuvol collaboration. As a first step, the atmospheric showers were simulated and investigated using two Monte-Carlo packages, CORSIKA and GEANT4. We compared the results provided by the two programs for the muonic component of vertical proton-induced showers at three energies: 1, 10 and 100 TeV. We found that the spatial distribution and energy spectrum of the muons were in good agreement for the two codes, while significant differences were observed for the arrival time of the muons.