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The Hellenic Arc is an active seismogenic zone in the Mediterranean Sea that hosted at least two historical M≥8 earthquakes, which both caused destructive tsunamis. The low-angle geometry of its subduction interface could promote shallow slip amplification, enhancing seafloor displacement. Long-term seismic-probabilistic tsunami hazard assessment (S-PTHA, e.g., Scala et al., 2020) and early warning systems typically rely on kinematic models and Okada's analytical solution to compute static seafloor displacements. The static displacement is then used to source tsunami models. However, the complex interaction of earthquake dynamics and tsunami-genesis may not be fully captured.We recently demonstrated mechanically consistent dynamic rupture models in generic megathrust settings informed from long-term geodynamic modeling that can provide building blocks toward integrating physics-based dynamic rupture modeling in Probabilistic Tsunami Hazard Analysis (Wirp et al., 21). We here present a range of 3D multi-physics, high-resolution dynamic rupture subduction earthquake scenarios accounting for the complex slab geometry of the Hellenic Arc. We vary hypocenter locations, which leads to a wide range of rupture speeds, extent of shallow fault slip, and moment magnitudes. Our dynamic rupture models include highly resolved bathymetry and topography data and detailed knowledge of the tectonic structure of the Hellenic Arc (seismic velocity structure, stresses, and strengths). We use the slab geometry from the European Database of Seismogenic Faults (EDSF, Basili et al., 2013) to create a 3D dynamic rupture scenario that covers great parts of the Mediterranean Sea. The initial conditions in our models are constrained on the subduction zone scale (Ulrich et al., 2021) and specified for the Hellenic Arc region.Only part of the Hellenic Arc is fully seismically coupled (e.g., Laigle et al., 2004) and most of the convergence is assumed to occur as aseismic creep. We follow Ramos et al. (2021) and apply different friction parameters accounting for high or low coupling of the plate interface.Our modeling suggests that margin-wide rupture would yield an Mw 9.3 earthquake. More reasonable smaller magnitude earthquakes are obtained by increasing the along-arc complexity of the reference model. Different hypocenter locations result in remarkable differences in shallow fault slip penetrating into velocity-strengthening regions, which translate into strong variations of the final seafloor displacement across scenarios. In additional models with partially consolidated and totally unconsolidated sediments (Ulrich et al., 2021) we show that off-fault plastic yielding, which limits shallow fault slip, may drastically increase the seafloor uplift. Finally, we explore a novel 3D fully coupled earthquake-tsunami modeling approach (Lotto and Dunham, 2018; Krenz et al., 2021) by adding a water layer to the modeling domain. This enables simulating earthquake dynamics, acoustic waves, and the resulting tsunami simultaneously. The fully coupled model will capture the dynamics of the entire tsunami-genesis in a single simulation, overcoming typical approximations for standard earthquake-tsunami coupling workflows. We envision that mechanically consistent dynamic rupture models can provide building blocks toward combined, self-consistent, and physics-based Seismic and Tsunami Hazard Analysis.

With this contribution, we expand the discussion of effects that earthquakes induced by geo-energy projects can have on local communities, and that should probably be considered in future legislation or permitting processes. Inspired 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 numerical simulations of wave propagation in the solid earth and the atmosphere to assess the sensitivity of the ground shaking and audible noise patterns to various parameters. We explore the effects of three different local velocity models, realistic topography, variations of the source mechanism, and earthquake size on the loudness of the synthetic waves at frequencies up to 20 Hz, therefore reaching the lower limit of human sound sensitivity. We discuss the results of 18 elastic-acoustic coupled scenario simulations conducted on the Mahti high-performance computing infrastructure of the Finnish IT Center for Science CSC using the SeisSol wavefield solver. The computationally challenging simulations target the Otaniemi case study, i.e., we discretize a 12 km x 12 km x 15 km domain with a 2 km thick air layer over the solid earth domain. The earthquake point source is located at the 6.5 km deep location of the largest M1.8 event induced by the stimulation. In the target central area, we use a mesh with element lengths of about 14 m in the air and 97 m in the solid earth. Inside each element, we approximate the solution by a fifth-degree polynomial, by which we achieve a resolution of roughly 2.3 m in the air and 16 m in the earth. We develop an interactive visualization to facilitate instant access to the results governed by the different parameter combinations, where the synthetics are shown on top of a map of the Helsinki metropolitan region. This tool facilitates “what-if” analyses by quickly comparing the effects of fault orientation, source mechanism, and the velocity model. This supports effective communication of physics-based nuisance analysis to decision-makers and stakeholders, not only in environments such as the case study where there is little experience with natural earthquake phenomena. Together, these results resolve for the first time synthetic nuisance sound patterns at the 50 – 100 m scale in a densely populated capital region. The study highlights the mostly disregarded spatially variable audible effects that can negatively impact the public attitude towards geothermal stimulations, even if the ground shaking limits are safe, and it provides first estimates of the resources needed for comprehensive scenarios for future stimulation projects.