Numerical modelling of the barometric pressure-induced noise in horizontal components for the observatories Moxa and Schiltach

Barometric pressure-induced noise in records of broadband seismometers is one of the major limiting factors in analysing the data to study the Earth's interior. Horizontal components of seismometers and also strainmeters are strongly affected. Studies to identify the main physical transfer mechanisms and to develop reliable reduction methods are carried out for the observatories Moxa (MOX) and Schiltach (BFO), Germany. For this purpose three-dimensional Finite Element (FE) models of both observatories and their vicinity have been developed. In the computation an elastic rheology is used and the models are modified with regard to structural geological features. By applying typical atmospheric pressure situations dominant effects can be detected. It can be shown that all situations produce significant effects at the instruments' sites even in a depth of 170 m. Due to cavity effects, clefts have also an influence on the instruments' sites. The results obtained are generally in good agreement with the observed data, improve the understanding of observed phenomena related to barometric pressure, and are an important prerequisite for the development of reliable correction algorithms for barometric pressure-induced noise in horizontal components.