DOI: 10.5281/zenodo.8056416
title: Supplementary Material: Numerical Simulations of Seismoacoustic Nuisance Patterns from an Induced M 1.8 Earthquake in the Helsinki, Southern Finland, Metropolitan Area

description: Seismic waves can couple with the atmosphere and generate sound waves. The influence of faulting mechanisms on earthquake sound patterns provides opportunities for earthquake source characterization. Sound radiated from earthquakes can be perceived as disturbing, even at low ground-shaking levels, which can negatively impact the social acceptance of geoengineering applications. Motivated by consistent reports of felt and heard disturbances associated with the weeks-long stimulation of a 6-km-deep geothermal system in 2018 below the Otaniemi district of Espoo, Helsinki, we conduct fully coupled 3D numerical simulations of wave propagation in the solid Earth and the atmosphere. We assess the sensitivity of the ground shaking and audible noise distributions to the source geometry of the induced earthquakes based on the properties of the largest local magnitude ML 1.8 event. Utilizing recent computational advances and the open-source software SeisSol, we model seismoacoustic frequencies up to 25 Hz, thereby reaching the lower limit of the audible sound frequency range. We present synthetic distributions of shaking and audible sounds at the 50–100 m scale across a 12 km × 12 km area and discuss implications for better under- standing seismic nuisances in metropolitan regions. In five 3D coupled elastic–acoustic scenario simulations that include data on topography and subsurface structure, we analyze the ground velocity and pressure levels of earthquake-generated seismic and acoustic waves. We show that S waves generate the strongest sound disturbance with sound pressure levels ≤ 0.04 Pa. We use statistical analysis to compare our noise distributions with commonly used empirical relationships. We find that our 3D synthetic amplitudes are generally smaller than the empirical predictions and that the interaction of the source mechanism-specific radiation pattern and topography can lead to significant nonlinear effects. Our study highlights the complexity and information content of spatially variable audible effects associated with small induced earthquakes on local scales.
description: Acknowledgements: The authors thank Editor L. Martire and reviewers J. Assink and J. W. Bishop for the comments that helped to improve the article. The authors thank P. Mäntyniemi for curating the macroseismic reports and O. D. Lamb and the St1 team for sharing the acoustic microphone data. G. H. appreciates discussions with P. Mäntyniemi, P. Bäcklund, and V. Bernelius on factors relevant to citizen participation. This work is supported by an Academy of Finland grant, Decision Number 337913. The 2018 temporary deployments were supported by the Geophysical Instrument Pool Potsdam under Grant Number 201802. L. K., S. W., A. A. G., and M. B. acknowledge funding provided (as part of the EuroHPC Joint Undertaking) for the ChEESE-2P cluster of excellence by Horizon Europe (Grant Agreement Number 1010930) and by the German Ministry of Research and Education. S. W. and M. B. acknowledge funding from the Competence Network for Scientific High-Performance Computing in Bavaria (KONWIHR). A. A. G. acknowledges funding from the European Union's Horizon 2020 research and innovation program (TEAR, Grant Agreement Number 852992) and Horizon Europe (DT-Geo, Grant Agreement Number 101058129 and Geo-Inquire, Grant Agreement Number 101058518), as well as the National Science Foundation under NSF EAR-2121666 and the National Aeronautics and Space Administration under 80NSSC20K0495. The CSC IT Center for Science, Finland, grand challenge Project Number 2003841 provided access to the CSC Mahti computational infrastructure. The authors acknowledge resources provided by the Gauss Centre for Supercomput- ing e.V. available at www.gauss-centre.eu on SuperMUC-NG at the 9 Leibniz Supercomputing Centre available at www.lrz.de, project pr83no. The authors use the Python library contextily for the back- ground maps. The background map tiles were obtained from OpenStreet maps, Stamen Design, and CARTO. The Stamen map tiles are licensed under CC BY 3.0. Data by OpenStreetMap, under ODbL. Refer to openstreetmap.org/copyright for more details.