Seismology
Research in the seismology group focuses on studying the information contained in seismic signals recorded in seismically calm times in the absence of earthquakes. Typically, these signals, which account for over 90% of seismic recordings worldwide, are discarded as "noise." It turns out, however, that this noise is made up of seismic waves that carry the imprint of the sources that produced them and the material they passed through.
The recording of seismic noise can therefore be used for many different purposes: signals obtained from the noise are used to illuminate the Earth's interior and evaluate how its structure changes over time. Applications range from the deep mantle and crust to the near surface to buildings. The noise itself can tell us how the solid earth interacts with the ocean and the atmosphere, which in turn provides information about weather conditions and climate.
In the seismology group, we "listen" to the seismic background noise to find out how the ocean produces it. We also use the seismic noise that surrounds us to monitor soil changes and damage to buildings. Finally, we are working on a number of projects using new sensor technologies (ring lasers, dense arrays and DAS/fiber optic cables) or developing new applications for established sensors (ocean bottom seismometers).
Are there Marsquakes? Mars lander "InSight" and its seismic signals
Contact: Christoph Schröer, Lorenz Marten or David Essing
On November 26, 2018, a seismometer was placed on Mars as part of the InSight mission. In preparation for the evaluation of the data, a blind test with synthetic data was carried out, in which, among others, our working group participated. The challenge: How to localize earthquakes on another planet with just one station and what additional information can be found in the data?
How to use urban noise to monitor the groundwater level?
R. Steinmann (2019)
For some years now, not only more earthquakes are interesting for seismologists, but also the unpopular background noise of the earth. With some tricks you can observe some interesting processes in the earth's interior from the noise. I am concerned with whether Hamburg's urban noise can also be used to monitor superficial processes such as groundwater changes, rain events or temperature fluctuations.
Waves in the North Sea and the North Atlantic - What can we learn from seismological observations on Helgoland?
Wave movements in the sea stimulate elastic waves in the solid earth, which can be recorded with the help of seismometers. Since the period as well as the amplitude of the waves in the sea is very variable in time as well as in space, seismological recordings can be used to find out something about the waves. For example, the data recorded on Helgoland can be used to determine at what times there were distinct waves in the North Sea, while in large areas of the coastal regions of the North Atlantic it was quite calm.
Monitoring Groundwater in Hamburg using Seismic Interferometry
The water content in soil plays a crucial role for humans, especially in urban areas. While the installation of soil sensors is an expensive and time-consuming process, there are numerous seismic stations available globally. This study aims to utilize seismic stations for the additional purpose of monitoring groundwater content using seismic interferometry. To achieve this, temperature and water content measurements in Billwerder, Hamburg are combined with seismic velocity changes to understand the interaction between these quantities.
Unsupervised Learning to find Seismic Sources on Urban DAS Data
Antonia Kiel (collaboration with Machine Learning Group by Conny Hammer)
An optical fibre installed at DESY is used to measure seismic movements using distributed acoustic sensing technology. The objective is to identify the variety of seismic sources, which are mostly unknown. To achieve this, different unsupervised learning methods are compared. The resulting universal guide for seismologists will assist in selecting the optimal clustering algorithm. This will facilitate the integration of machine learning into seismological research.
Project ET-EMR: Ambient Seismic Noise at the possible Einstein telescope site in the Maas-Rhein-Region
Dirk Becker, Céline Hadziioannou
The successful operation of detectors in the planned gravity wave telescope (Einstein telescope) depends on a precise knowledge of the seismic ground motion in the vicinity of the installation. Such knowledge allows an optimized positioning of detector chambers before construction and a monitoring of the incoming seismic wavefield in real time for active compensation of detector positions during operation. In addition, the influence of density changes in the material due to passing seismic waves can be estimated.
Predictive modeling of seismic wave fields
Jana Klinge, Sven Schippkus, Céline Hadziioannou
Enhancing our understanding of seismic activity means we can, for example, try to predict wave events at stations that are no longer operational. To achieve this, we use advanced deep learning techniques to learn and predict time series data from nearby seismic stations, focusing on approximating the transfer function between them. This approach allows us to reconstruct data from offline or missing stations, and improves our ability to study seismic events and noise, especially in areas with limited station coverage. We validate our method using field data from regions with infrastructure like roads, wind turbines, and oil pump jacks.
Hybrid numerical simulations of tele-seismic earthquakes
Aida Hejazi Nooghabi, Anjali Dhabu, Céline Hadziioannou
Within the ErUm-WAVE project, we are working on hybrid numerical simulation of earthquakes which works on the basis of injecting a simulated wavefield from a tele-seismic earthquake into a regional higher resolution model. Our goal is to find the subsurface model for the Hamburg area and validate the results with DAS data. Knowledge of the subsurface structure of the Hamburg area will not only be useful for the seismic community, but is also essential for understanding the coupling mechanisms of the incoming seismic waves with sensitive structures such as the ones at the DESY campus.