In the earthquake seismology group we focus on earthquakes, fault zone structure, modes of deformation along fault zones, and earthquake and fault zone interaction and triggering mechanisms on a local and regional scale. We analyze seismic waves emanated from earthquakes, but extract also information from the ambient seismic wave field or noise. The research depends on the application and development of analysis techniques for estimating earthquake source parameters, for structural imaging and for the monitoring of time dependent changes in crustal and fault zone materials on time scales ranging from seconds to years. Our work is based on processing large seismic data sets (big data at its very best) and has thus multiple connections to physics and atmospheric sciences (wave propagation), mathematics and medical imaging (inverse problems), and computer science (code development).
Seismic imaging constitutes a fundamental building block of Earth Science research that is practiced by a large community and applied across many scales. The analogy between ultrasonic medical sensors and spatially dense seismic arrays opens up an alternative way for seismic imaging that differs from tomographic methods. We research to what extend the near-field phenomenon referred to as “focal spot” in acoustics can provide simultaneous estimates of the local seismic velocity structure, azimuthal anisotropy, and proxies for intrinsic attenuation without solving an inverse problem.
Modern societies critically depend on sustainable natural resource production and renewable energy sources. Geothermal energy is in many ways an advantageous energy source for local heat and electricity production in densely populated areas. The low environmental impact compared to non-renewables, and the independence on atmospheric, climatic or weather patterns that severely constrain wind and solar technologies have led to a growing interest and use of geothermal energy production. The development of deep geothermal energy projects is, however, not without risks. Our group is dedicated to contribute to a sustainable and safe use of deep geothermal energy. We have been collecting an outstanding data set during the stimulation of the St1 Enhanced Geothermal System between 5 and 6 km depth below Otaniemi, Espoo, in summer 2018. The analysis of the induced earthquakes, and of the altered rock properties will help to mature the application of geothermal energy use in Finland. We target a comprehensive understanding of the rock types and their seismic response, their permeability and geochemical properties, and the location of faults; of the local temperature profile, the stress regime and stress orientations; and of the hydrological situation.
Leader: Gregor Hillers, Associate Professor