Anne Schulz (Jena), Katrin Huhn (Bremen), Ingo Stotz (München), Peter Bunge (München), Moritz Ziegler (Potsdam), Nina Kukowski (Jena)
Numerical and physical models are indispensable tools for an efficient and process-oriented data interpretation. They allow us to identify key data-sets that are sensitive to the processes in question, while data in turn allows us to improve model parametrisation, including boundary conditions, physical properties and rheological behaviour. Geophysics has a long history of model-data integration, for instance in tectonics and geodynamics or geo-hazard related research. Both fields address different geo-settings in terms of spatial scale and time, reaching from near surface sedimentary processes, sedimentary basins, crustal structure to whole Earth models. In particular when regarding uncertainties, an intelligent approach is required in order to keep CPU-time at a reasonable level. Even then, some simulations require HPC computing, such as also does joint inversion of data sets. Model-data integration will become even stronger in the upcoming era of exa-scale computing. The arrival of vast computing resources enables simulations with a more streamlined representation of key processes, and allows models to resolve a much broader range of spatial and temporal scales, necessitating even more to place observational constraints into the center of model formulation. To this end, growing modelling capabilities are going along with an equally impressive growth in publicly available datasets and observational capabilities, enabled through satellite remote sensing, new sensor technology and the digitalization of legacy data sets. We invite contributions to this focus theme from all areas in geophysics, both, marine and onshore, where model-data integration plays a key role to better understand complex geophysical processes and represent the subsurface in a model.
Plenary Talk by Ylona van Dinther (Utrecht)
Valentin Kasburg (Jena), Roman Leonhardt (Wien), Stephan Großwig (Jena), Nina Kukowski (Jena)
In the various layers of the Earth system, processes occur at very different rates. These can be both continuous and episodic. Several processes change their course if thresholds (tipping points) are exceeded. To identify and determine the amplitudes of such processes, such as mass redistributions (gravity changes), hydrological events, tectonic processes, magnetic field changes, weather, and climate phenomena, often at least decades of observations are required. This is, for example, an important task of geophysical and geodynamic observatories located in very different geological settings. As an example, the Geodynamic Observatory Moxa of Friedrich Schiller University Jena, established 60 years ago, can be mentioned here. On the other hand, individual events often last only a very short time. This requires registrations with very high sampling rates. In the recorded time series, the effects of long-term processes overlap with those of short events. It is often necessary to analyze several time series together in order to identify processes and events and assign them to different sources. To analyze and process these ever-increasing volumes of data, AI-supported methods are increasingly being used alongside traditional methods. In the context of this focus session, processes and events from the various layers of the Earth system, as well as advances in sensor technology and methodology, will be discussed. We invite contributions on sensory and methodological work for the acquisition, processing, and analysis of time series.
Under this focus topic, we therefore invite scientists from research and industry, not only from geophysics but also from the many associated fields of geosciences, physics, and technology, to report on possible techniques and application areas, and to formulate the needs of future developments.
Plenary Talk by: Bruno Meurers
Torsten Dahm (Potsdam), Sabrina Keil (München), Marcel van Laaten (Jena), Ulrich Wegler (Jena)
Crustal fluids are recognized as playing a major role in many geophysical processes including earthquakes and volcanism. Fluids not only influence geochemical and magmatic processes such as the fracture healing, or rock melting, but can also affect the mechanical properties of faults and change the pore pressure in the rock. The pressure and friction changes can trigger shear ruptures if the faults are under stress. Strong overpressure can also lead to the formation of opening fractures, accompanied by earthquake swarms, which can cause the fluids or melts to migrate upwards in intrusions. Similar processes lead to the formation of deep low-frequency earthquakes. Geotechnical applications such as geothermal heat production or hydraulic fracturing may also influence pore pressure and trigger earthquakes and may change the seismic hazard of a region. Some models also emphasize the role of fluids in the formation of natural aftershocks, foreshocks or remotely triggered earthquakes in hydrothermal regions. Changes in water levels in wells document the dynamic changes in pore pressure and permeability due to seismic waves.
For this special session, contributions and case studies are sought on naturally and anthropogenically induced and triggered seismicity, as well as on earthquakes associated with magmatic processes or changes in the hydrological system. Physical and numerical modelling on the interaction of fluids with the rock and existing fracture networks, and how these influence earthquakes, are welcome. We also invite contributions on geophysical imaging of fluids in the Earth's crust and upper mantle as well as presentations on seismic hazard caused by anthropogenic and natural fluid-induced seismicity.
Plenary Talk by: Nicolai Shapiro (Grenoble)
Celine Hadziioannou (Hamburg), Ulrich Wegler (Jena)
Seismic noise is a continuous signal recorded by seismometers when there is no earthquake. The origin of this signal is a complex superposition of a large number of randomly distributed sources. Recently, seismic noise caused by wind turbines has interfered with the detection of earthquakes signals. Ambient vibrations are also one of the limiting factors for detecting gravitational waves in newly developed gravitational-wave observatories such as the planned third generation Einstein Telescope. On the other hand, in the last decade ambient seismic noise has established itself as a new useful signal. Ambient seismic noise cross-correlations are used to study the structure of the Earth based on the principle of seismic interferometry. Changes in the phase information of ambient noise cross-correlation functions have been used to monitor minute changes in the Earth’s structure The application of these methods requires detailed knowledge of the anthropogenic and natural sources as well as characteristics of ambient seismic noise. Multiply scattered seismic coda waves are a related random seismic wave field which shares many characteristics with seismic noise. Coda waves carry information about small heterogeneities in the Earth and have been used to estimate the spatial distribution and the frequency dependence of the strength of seismic scattering attenuation and intrinsic absorption.
We would like to invite contributions on observations and modelling of seismic noise sources of anthropogenic and natural origin as well as presentations on the theory and application of seismic interferometry to the imaging and monitoring Earth’s heterogeneous structure. We are also seeking contributions on theoretical and observational studies of coda waves, seismic attenuation and scattering.
Plenary Talk by: Katharina Isleif (Hamburg)