Geophysics

Mountain belts are one of the major features on the Earth's surface and have a profound influence on its inhabitants and their ways of living, amongst others by affecting climate and weather and providing attractive and unique habitats. At the same time, mountain belts are prone to natural disasters like earthquakes, landslides and floods. Mountain belts, or their remains, tell us also about how planet Earth developed under much of its long history. To research their distribution over time and the processes that act under their development is a multidisciplinary endeavour.

Research on mountain building at Uppsala University deals with Scandinavian and Arctic mountain belts as old as 2 billion years, but presently with a strong focus on the c. 400-million-year-old and deeply eroded Scandinavian Caledonides. Applied geophysical methods like reflection seismics, magnetotellurics and potential field measurements allow us to explore and model the subsurface, the latter in close collaboration with geological and rock physics research on the character of the rocks at the surface.

The flagship project is the Collisional Orogeny in the Scandinavian Caledonides (COSC) scientific drilling project, supported by the International Continental Scientific Drilling Program (ICDP). In this project, an international science team performs mountain building research on two fully cored boreholes of about 2.5 km depth (drilled in 2014 and 2020, respectively) that together sample a key-section through a major, "Himalaya-sized" Paleozoic mountain belt.

For more information on COSC, please refer to:

• International Continental Scientific Drilling Program(ICDP): COSC-1 and COSC-2
• COSC på Facebook

Earthquake seismology at Uppsala University has a long history which goes back to the installation of the first Nordic seismograph in 1904. Professor Markus Båth built a national seismic network and developed earthquake analysis to a world leading position. Today, the Department of Earth Sciences maintains the Swedish National Seismic Network (SNSN) used to analyse earthquakes in Sweden and worldwide with 67 state-of-the-art seismographs. Earthquake research at the Geophysics programme is to a large extent data driven and focuses on methodological development and specific geological targets. We have developed the data acquisition and analysis systems used in the Swedish and Icelandic seismic networks (the SIL-system), which very successfully detects and analyses microearthquakes to below magnitude 0. The locations, focal mechanisms and underlying stress states are analysed to understand why the earthquakes occur where they do. We investigate structures in the crust and mantle using various methods developed within areas of seismic tomography and surface-wave analysis, among other, in order to understand processes such as mountain building and volcano development. In Sweden, our earthquake research focuses on understanding the mechanism of large end-glacial earthquakes (see photo) that occurred in northern Fennoscandia at the end of the last Ice Age, investigating mechanisms of current intra-plate seismicity and structure of the crust and upper mantle of the Fennoscandian Shield to understand its evolution through the past billions of years. In Iceland we participate in research on understanding and monitoring volcanoes, analysing earthquakes which occur in geothermal systems and understanding the triggering of earthquakes during geothermal energy extraction.

The Geophysics programme at Uppsala University has a long history and strong current research focus within lithosphere geophysics. The lithosphere forms the plates that “float” and move on top of the deeper, more viscous convecting mantle driven by plate tectonics. The lithosphere is made up of two main, chemically different layers, which are chemically different, the crust at the top and the mantle lithosphere at the bottom and exhibits a long-lasting archive of past geodynamic history.

Chemical, structural and thermal changes within the lithosphere affect the physical properties of rocks, such as density, magnetic properties, and the speed of seismic waves passing through the medium. We use various geophysical methods to detect, model and image these variations in physical properties – the lithospheric structure. From these studies, we can make implications on composition, thermal state and past and current geodynamic processes [link to geodynamics] of Earth. At Uppsala we have a clear focus on seismological and electromagnetic techniques [link to EM], but we also use gravity and magnetic techniques as supporting tools.

We currently have projects across the globe, with many applications including studies in Scandinavia, the Alps, Central-and Eastern Europe, the Arctic, Greenland, Iceland, Brazil, the middle East, China and others.

Geophysical methods are fundamental in the monitoring of volcanoes and can provide important insights into how a volcano works. This is partly to know if an eruption is imminent, but also what character an eruption may take so that warnings can be issued in time and reasonable measures be taken depending on distance from the volcano. This is possible because a volcanic eruption usually, but not always, is preceded by “unusual” activity prior to an eruption. The volcano may, e.g., "inflate" because the amount of magma or gas increases in the system underneath the volcano (e.g. in a shallow magma chamber), or seismic activity (earthquakes or continuous tremor) may increase when magma intrudes into it. If the precision of earthquake or tremor locations is high enough, one may follow magma movements, and thus know where in the volcanic system an eruption is likely to occur. Various geophysical methods can also be used to image volcano interiors. Here, at the geophysics program, we work primarily with seismological methods, but also electromagnetic ones, in order to image the volcano's interior. Interpretation of our images is done in close collaboration with geologists and volcanologists, both here and at other universities, to enhance our understanding of volcanic processes and provide context for the interpretation of activity. We also work with and develop systems for registering and locating earthquakes in near real time.

Contact persons: Ari Tryggvason, Olafur Gudmundsson, Björn Lund

Applied Geophysics covers a broad range of applications and methods related to exploration, site characterization, cavity detection, environmental problems and much more. Exploration can be for petroleum, minerals, groundwater and other resources of economic value. The scale of the target that the experiments are conducted over may vary from tens of kilometers to determine crustal thickness to a few meters to find a buried pipe. All types of geophysical techniques are employed, including seismic, magnetic, gravimetric, electrical, electromagnetic (EM) and radiometric ones.

Examples of ongoing research in applied geophysics at the Geophysics Program include improving hard rock seismic processing methods, characterization and monitoring of carbon dioxide storage sites, development of EM instrumentation and interpretation methods, borehole logging for rock properties, and development of new seismic acquisition methods. This work is generally of societal importance, but there are also many components of basic research within the activities. One example of this is using geophysics to better understand the geological history of the Scandinavian mountain belt by "looking" into its structure down to depths of tens of kilometers.

The geomagnetic field is a persistent feature throughout much of Earth’s past. Its presence enables habitability of the planet, deflecting harmful Solar energetic particles and limiting erosion of the atmosphere. Humans have used the magnetic field for navigation for more than two thousand years. Some animals and bacteria also use the magnetic field for navigation purposes, a trait that has an evolutionary origin. To large extent the field appears as a magnetic dipole, similar to that of a regular permanent magnet. The magnetic field originates from convective and turbulent flow of metallic liquid in the outer core, which is known as the geodynamo. The magnetic properties of sediments and rocks can provide quantitative information on the inclination, declination and intensity of the past geomagnetic field. This information can be used to study the past movement of tectonic plates, a discipline which is part of paleogeography. Measurements of these properties also provide the possibility to study the development of the magnetic field.

The Geophysics research program co-leads the Uppsala paleomagnetic laboratory together with the research Natural Resources and Sustainable Development (NRHU), which hosts instruments to carry out measurements of magnetic susceptibility and remanence. The research undertaken in the laboratory focuses on paleomagnetism and plate tectonic reconstruction, development of the past geomagnetic field in time and space and the fundamental magnetic properties of minerals, sediments and rocks. Studies range from Proterozoic rocks in continental interiors, to sediments of the Baltic Sea, to loess deposits (wind-blown sediments) in central Asia. Fundamental magnetic properties of iron-oxides and iron-sulphides, as well as rare-earth bearing minerals, form a focus of the geophysics and NRHU programs. The research is founded upon strong interdisciplinary collaboration, both nationally and internationally, across Earth sciences, chemistry, physics and materials science.