Prof. Dr. Michael Bader
Chair of Scientific Computing in Computer Science
Technische Universität München
“Induced seismicity” are earthquakes caused by human activities, such as by operating enhanced geothermal systems (EGS) for geothermal energy or oil/gas reservoirs or carbon capturing. Induced earthquakes are potentially hazardous as they typically happen in shallow depth and close to urban environments. While such events are mostly of small size, several exceptions (e.g., the 2017 M5.5 Pohang earthquake) have shown that induced earthquakes can also lead to substantial damage and economic loss. In addition, even smaller events can affect the acceptance by the general public by causing damage to buildings (even though mostly minor) or just by exciting irritating tremors or noises.
Areas of geothermal power production often have low seismic activity which translates into a lack of observational data to inform reliable hazard mitigation measures. Physics-based simulation of earthquake rupture processes and of the associated seismic and acoustic wave fields are thus essential to better understand ground motions and the physical processes associated with induced events. However, modeling of induced seismicity poses research questions on the physical mechanisms of induced earthquakes and on the complexity of the multi-physics feedback mechanisms between evolving fault and fracture networks and the reservoir stimulation. More advanced material models than a simple elastic medium are required to model the response of the solid Earth in geo-reservoirs: To correctly capture ground shaking and seismic wave propagation, we need to consider a porous medium, where the pores of rocks or sediments are filled by a fluid phase. In addition, the interplay of earthquake nucleation, propagation and arrest and poroelastic wave effects is also not properly studied. To investigate sound disturbances, we have to couple seismic wave propagation in the solid Earth to acoustic waves in the atmosphere.
In the proposed project, we will improve and optimise the earthquake simulation software SeisSol for extreme-scale simulations of two demonstrator scenarios that take up recent research by two collaborating groups: The group of Alice-Agnes Gabriel (LMU) investigates (in collaboration with Martin Mai, KAUST) the earthquake mechanisms and ground shaking of the Pohang 2017 event. We will extend the current studies, which are based on elastic material models, to take poroelastic materials, specifically sediments, into account. The research of GregorHillers (University of Helsinki, UH) focuses on seismic monitoring and analysis of induced wavefields in the context of enhanced geothermal reservoirs. Our respective scenario will simulate the 2018 Otaniemi/Espoostimulation experiment, for which sound patterns have been recorded. Respective models will build on the elastic-acoustic coupling currently developed in SeisSol to simulate submarine earthquakes and tsunami generation. Extending this work to study sounds generated by earthquakes leads to grand challenge scenarios, as we need to resolve frequencies up to the audible spectral range (>>20 Hz).
Key contribution of the project will be to optimise SeisSol in terms of node performance, scalability and overall time to solution for the required advanced seismic wave propagation models (esp. poroelastic media and coupling to acoustic media). This will include algorithmic improvements and optimisation of the required novel numerical scheme for poroelasticity.
From an HPC point of view, a further major goal of the proposed project will be to ensure performance portability of the implementation on future HPC architectures. We will therefore evaluate and optimise the models not only on SuperMUC-NG, but also on the exascale architectures offered on LRZ’s BEAST cluster.