Peak ground acceleration produced by local earthquakes in volcanic areas of Campi Flegrei and Mt. Vesuvius

Abstract

The scaling law of the seismic spectrum experimentally calculated at Mt. Vesuvius and Campi Flegrei is used to constrain the estimate of the maximum expected peak acceleration of ground motion. The scaling law was calculated for earthquakes recorded at BKE and OVO stations in the period 1997-2000 for Mt. Vesuvius and for earthquakes occurred during the 1983-1984 bradyseismic crises at Campi Flegrei. For Mt. Vesuvius the scaling law clearly deviates from a constant stress drop relation in the whole range of magnitude (0.4 < MD < 3.6) whilst constant stress-drop is found for Campi Flegrei data (0.7 < M D < 3.4). These results are used to give a first estimate of the maximum ground motion corresponding to the largest magnitude (Mmax.) inferred in the two investigated areas by the Gutenberg-Richter formula. The values of the seismic moment M O and the characteristic source radius corresponding to Mmax are used to evaluate the peak ground acceleration PGA. This parameter is determined by stochastic simulation of ground motion. Two different methods (Random Vibration Theory (RVT) (Boore, 2003) and ground motion generated from a Gaussian distribution with σ = a rms (GMG)) give slightly different values of PGA. The values of PGA were 0.10 g (RVT), 0.14 g (GMG) for Mt. Vesuvius and 0.04 g (RVT and GMG) for Campi Flegrei.