@phdthesis{Budweg2002,
  author    = {Budweg, Martin},
  title     = {Der obere Mantel in der Eifel-Region untersucht mit der Receiver Function Methode},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-0000704},
  school      = {Universit{\"a}t Potsdam},
  year      = {2002},
  abstract  = {Die Eifel ist eines der j{\"u}ngsten vulkanischen Gebiete Mitteleuropas. Die letzte Eruption ereignete sich vor ungef{\"a}hr 11000 Jahren. Bisher ist relativ wenig bekannt {\"u}ber die tieferen Mechanismen, die f{\"u}r den Vulkanismus in der Eifel verantwortlich sind. Erdbebenaktivit{\"a}t deutet ebenso darauf hin, dass die Eifel eines der geodynamisch aktivsten Gebiete Mitteleuropas ist. In dieser Arbeit wird die Receiver Function Methode verwendet, um die Strukturen des oberen Mantels zu untersuchen. 96 teleseismische Beben (mb > 5.2) wurden ausgewertet, welche von permanenten und mobilen breitbandigen und kurzperiodischen Stationen aufgezeichnet wurden. Das tempor{\"a}re Netzwerk registrierte von November 1997 bis Juni 1998 und {\"u}berdeckte eine Fl{\"a}che von ungef{\"a}hr 400x250 km². Das Zentrum des Netzwerkes befand sich in der Vulkaneifel. Die Auswertung der Receiver Function Analyse ergab klare Konversionen von der Moho und den beiden Manteldiskontinuit{\"a}ten in 410 km und 660 km Tiefe, sowie Hinweise auf einen Mantel-Plume in der Region der Eifel. Die Moho wurde bei ungef{\"a}hr 30 km Tiefe beobachtet und zeigt nur geringe Variationen im Bereich des Netzwerkes. Die beobachteten Variationen der konvertierten Phasen der Moho k{\"o}nnen mit lateralen Schwankungen in der Kruste zu tun haben, die mit den Receiver Functions nicht aufgel{\"o}st werden k{\"o}nnen. Die Ergebnisse der Receiver Function Methode deuten auf eine Niedriggeschwindigkeitszone zwischen 60 km bis 90 km in der westlichen Eifel hin. In etwa 200 km Tiefe werden im Bereich der Eifel amplitudenstarke positive Phasen von Konversionen beobachtet. Als Ursache hierf{\"u}r wird eine Hochgeschwindigkeitszone vorgeschlagen, welche durch m{\"o}gliches aufsteigendes, dehydrierendes Mantel-Material verursacht wird. Die P zu S Konversionen an der 410 km Diskontinuit{\"a}t zeigen einen sp{\"a}teren Einsatz als nach dem IASP91-Modell erwartet wird. Die migrierten Daten weisen eine Absenkung der 410 km Diskontinuit{\"a}t um bis zu 20 km Tiefe auf, was einer Erh{\"o}hung der Temperatur von bis zu etwa 140° Celsius entspricht. Die 660 km Diskontinuit{\"a}t weist keine Aufw{\"o}lbung auf. Dies deutet darauf hin, dass kein Mantelmaterial direkt von unterhalb der 660 km Diskontinuit{\"a}t in der Eifel-Region aufsteigt oder, dass der Ursprung des Eifel-Plumes innerhalb der {\"U}bergangszone liegt.},
  language  = {de}
}
@phdthesis{Lilienkamp2024,
  author    = {Lilienkamp, Henning},
  title     = {Enhanced computational approaches for data-driven characterization of earthquake ground motion and rapid earthquake impact assessment},
  doi       = {10.25932/publishup-63195},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-631954},
  school      = {Universit{\"a}t Potsdam},
  pages     = {x, 145},
  year      = {2024},
  abstract  = {Rapidly growing seismic and macroseismic databases and simplified access to advanced machine learning methods have in recent years opened up vast opportunities to address challenges in engineering and strong motion seismology from novel, datacentric perspectives. In this thesis, I explore the opportunities of such perspectives for the tasks of ground motion modeling and rapid earthquake impact assessment, tasks with major implications for long-term earthquake disaster mitigation. In my first study, I utilize the rich strong motion database from the Kanto basin, Japan, and apply the U-Net artificial neural network architecture to develop a deep learning based ground motion model. The operational prototype provides statistical estimates of expected ground shaking, given descriptions of a specific earthquake source, wave propagation paths, and geophysical site conditions. The U-Net interprets ground motion data in its spatial context, potentially taking into account, for example, the geological properties in the vicinity of observation sites. Predictions of ground motion intensity are thereby calibrated to individual observation sites and earthquake locations. The second study addresses the explicit incorporation of rupture forward directivity into ground motion modeling. Incorporation of this phenomenon, causing strong, pulse like ground shaking in the vicinity of earthquake sources, is usually associated with an intolerable increase in computational demand during probabilistic seismic hazard analysis (PSHA) calculations. I suggest an approach in which I utilize an artificial neural network to efficiently approximate the average, directivity-related adjustment to ground motion predictions for earthquake ruptures from the 2022 New Zealand National Seismic Hazard Model. The practical implementation in an actual PSHA calculation demonstrates the efficiency and operational readiness of my model. In a follow-up study, I present a proof of concept for an alternative strategy in which I target the generalizing applicability to ruptures other than those from the New Zealand National Seismic Hazard Model. In the third study, I address the usability of pseudo-intensity reports obtained from macroseismic observations by non-expert citizens for rapid impact assessment. I demonstrate that the statistical properties of pseudo-intensity collections describing the intensity of shaking are correlated with the societal impact of earthquakes. In a second step, I develop a probabilistic model that, within minutes of an event, quantifies the probability of an earthquake to cause considerable societal impact. Under certain conditions, such a quick and preliminary method might be useful to support decision makers in their efforts to organize auxiliary measures for earthquake disaster response while results from more elaborate impact assessment frameworks are not yet available. The application of machine learning methods to datasets that only partially reveal characteristics of Big Data, qualify the majority of results obtained in this thesis as explorative insights rather than ready-to-use solutions to real world problems. The practical usefulness of this work will be better assessed in the future by applying the approaches developed to growing and increasingly complex data sets.},
  language  = {en}
}
@phdthesis{Schellbach2021,
  author    = {Schellbach, Konrad},
  title     = {Erdbeben in der Geschichtsschreibung des Fr{\"u}h- und Hochmittelalters},
  series = {Historical catastrophe studies},
  journal   = {Historical catastrophe studies},
  publisher = {de Gruyter},
  address   = {Berlin},
  isbn      = {978-3-11-061998-0},
  issn      = {2699-7231},
  doi       = {10.1515/9783110620771},
  pages     = {XII, 354},
  year      = {2021},
  abstract  = {"Terrae motus factus est magnus". In diesen und {\"a}hnlichen Worten erinnern mittelalterliche Geschichtsschreiber stets an das versp{\"u}rte Eintreten von Erdbeben. F{\"u}r die ereignisgeschichtliche Rekonstruktion der historischen Seismizit{\"a}t besitzt das Verst{\"a}ndnis, dieser seit dem Fr{\"u}hmittelalter zunehmend standardisiert gebrauchten Narrativen, einen hohen Wert. Daher ist es wichtig, mit den bislang nahezu unerkannt geblieben Intentionen, Vorstellungsstrukturen und Argumentationsstrategien fr{\"u}h- und hochmittelalterlicher Geschichtsschreiber bekannt zu werden. Ausgehend von den antiken Urspr{\"u}ngen ermittelt diese Arbeit die Bandbreite einer auf "terrae motus" aufbauenden, spezifisch mittelalterlichen Traditionsbildung und setzt sie in den Kontext zum Wissens- und Erfahrungshorizont fr{\"u}h- und hochmittelalterlicher Gelehrter. Erdbeben besaßen ein außerordentliches hermeneutisches Potential f{\"u}r das mittelalterliche Weltverst{\"a}ndnis. Somit sind mittelalterliche Erdbebenbeschreibungen hinsichtlich ihrer deskriptiven Qualit{\"a}t und argumentativen Wertigkeit verschieden. Die Historiographie- und Ideengeschichte sowie die seismologische Parametrisierung von mittelalterlichen Erdbeben wird von diesem Wissen gleichermaßen profitieren.},
  subject      = {Deutschland},
  language  = {de}
}
@phdthesis{Metz2023,
  author    = {Metz, Malte},
  title     = {Finite fault earthquake source inversions},
  doi       = {10.25932/publishup-61974},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-619745},
  school      = {Universit{\"a}t Potsdam},
  pages     = {143},
  year      = {2023},
  abstract  = {Earthquake modeling is the key to a profound understanding of a rupture. Its kinematics or dynamics are derived from advanced rupture models that allow, for example, to reconstruct the direction and velocity of the rupture front or the evolving slip distribution behind the rupture front. Such models are often parameterized by a lattice of interacting sub-faults with many degrees of freedom, where, for example, the time history of the slip and rake on each sub-fault are inverted. To avoid overfitting or other numerical instabilities during a finite-fault estimation, most models are stabilized by geometric rather than physical constraints such as smoothing. As a basis for the inversion approach of this study, we build on a new pseudo-dynamic rupture model (PDR) with only a few free parameters and a simple geometry as a physics-based solution of an earthquake rupture. The PDR derives the instantaneous slip from a given stress drop on the fault plane, with boundary conditions on the developing crack surface guaranteed at all times via a boundary element approach. As a side product, the source time function on each point on the rupture plane is not constraint and develops by itself without additional parametrization. The code was made publicly available as part of the Pyrocko and Grond Python packages. The approach was compared with conventional modeling for different earthquakes. For example, for the Mw 7.1 2016 Kumamoto, Japan, earthquake, the effects of geometric changes in the rupture surface on the slip and slip rate distributions could be reproduced by simply projecting stress vectors. For the Mw 7.5 2018 Palu, Indonesia, strike-slip earthquake, we also modelled rupture propagation using the 2D Eikonal equation and assuming a linear relationship between rupture and shear wave velocity. This allowed us to give a deeper and faster propagating rupture front and the resulting upward refraction as a new possible explanation for the apparent supershear observed at the Earth's surface. The thesis investigates three aspects of earthquake inversion using PDR: (1) to test whether implementing a simplified rupture model with few parameters into a probabilistic Bayesian scheme without constraining geometric parameters is feasible, and whether this leads to fast and robust results that can be used for subsequent fast information systems (e.g., ground motion predictions). (2) To investigate whether combining broadband and strong-motion seismic records together with near-field ground deformation data improves the reliability of estimated rupture models in a Bayesian inversion. (3) To investigate whether a complex rupture can be represented by the inversion of multiple PDR sources and for what type of earthquakes this is recommended. I developed the PDR inversion approach and applied the joint data inversions to two seismic sequences in different tectonic settings. Using multiple frequency bands and a multiple source inversion approach, I captured the multi-modal behaviour of the Mw 8.2 2021 South Sandwich subduction earthquake with a large, curved and slow rupturing shallow earthquake bounded by two faster and deeper smaller events. I could cross-validate the results with other methods, i.e., P-wave energy back-projection, a clustering analysis of aftershocks and a simple tsunami forward model. The joint analysis of ground deformation and seismic data within a multiple source inversion also shed light on an earthquake triplet, which occurred in July 2022 in SE Iran. From the inversion and aftershock relocalization, I found indications for a vertical separation between the shallower mainshocks within the sedimentary cover and deeper aftershocks at the sediment-basement interface. The vertical offset could be caused by the ductile response of the evident salt layer to stress perturbations from the mainshocks. The applications highlight the versatility of the simple PDR in probabilistic seismic source inversion capturing features of rather different, complex earthquakes. Limitations, as the evident focus on the major slip patches of the rupture are discussed as well as differences to other finite fault modeling methods.},
  language  = {en}
}
@phdthesis{Sharma2024,
  author    = {Sharma, Shubham},
  title     = {Integrated approaches to earthquake forecasting},
  doi       = {10.25932/publishup-63612},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-636125},
  school      = {Universit{\"a}t Potsdam},
  pages     = {xvi, 76},
  year      = {2024},
  abstract  = {A comprehensive study on seismic hazard and earthquake triggering is crucial for effective mitigation of earthquake risks. The destructive nature of earthquakes motivates researchers to work on forecasting despite the apparent randomness of the earthquake occurrences. Understanding their underlying mechanisms and patterns is vital, given their potential for widespread devastation and loss of life. This thesis combines methodologies, including Coulomb stress calculations and aftershock analysis, to shed light on earthquake complexities, ultimately enhancing seismic hazard assessment. The Coulomb failure stress (CFS) criterion is widely used to predict the spatial distributions of aftershocks following large earthquakes. However, uncertainties associated with CFS calculations arise from non-unique slip inversions and unknown fault networks, particularly due to the choice of the assumed aftershocks (receiver) mechanisms. Recent studies have proposed alternative stress quantities and deep neural network approaches as superior to CFS with predefined receiver mechanisms. To challenge these propositions, I utilized 289 slip inversions from the SRCMOD database to calculate more realistic CFS values for a layered-half space and variable receiver mechanisms. The analysis also investigates the impact of magnitude cutoff, grid size variation, and aftershock duration on the ranking of stress metrics using receiver operating characteristic (ROC) analysis. Results reveal the performance of stress metrics significantly improves after accounting for receiver variability and for larger aftershocks and shorter time periods, without altering the relative ranking of the different stress metrics. To corroborate Coulomb stress calculations with the findings of earthquake source studies in more detail, I studied the source properties of the 2005 Kashmir earthquake and its aftershocks, aiming to unravel the seismotectonics of the NW Himalayan syntaxis. I simultaneously relocated the mainshock and its largest aftershocks using phase data, followed by a comprehensive analysis of Coulomb stress changes on the aftershock planes. By computing the Coulomb failure stress changes on the aftershock faults, I found that all large aftershocks lie in regions of positive stress change, indicating triggering by either co-seismic or post-seismic slip on the mainshock fault. Finally, I investigated the relationship between mainshock-induced stress changes and associated seismicity parameters, in particular those of the frequency-magnitude (Gutenberg-Richter) distribution and the temporal aftershock decay (Omori-Utsu law). For that purpose, I used my global data set of 127 mainshock-aftershock sequences with the calculated Coulomb Stress (ΔCFS) and the alternative receiver-independent stress metrics in the vicinity of the mainshocks and analyzed the aftershocks properties depend on the stress values. Surprisingly, the results show a clear positive correlation between the Gutenberg-Richter b-value and induced stress, contrary to expectations from laboratory experiments. This observation highlights the significance of structural heterogeneity and strength variations in seismicity patterns. Furthermore, the study demonstrates that aftershock productivity increases nonlinearly with stress, while the Omori-Utsu parameters c and p systematically decrease with increasing stress changes. These partly unexpected findings have significant implications for future estimations of aftershock hazard. The findings in this thesis provides valuable insights into earthquake triggering mechanisms by examining the relationship between stress changes and aftershock occurrence. The results contribute to improved understanding of earthquake behavior and can aid in the development of more accurate probabilistic-seismic hazard forecasts and risk reduction strategies.},
  language  = {en}
}
@phdthesis{Sen2014,
  author    = {Sen, Ali Tolga},
  title     = {Inversion of seismic source parameters for weak mining-induced and natural earthquakes},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-71914},
  school      = {Universit{\"a}t Potsdam},
  year      = {2014},
  abstract  = {The purpose of this thesis is to develop an automated inversion scheme to derive point and finite source parameters for weak earthquakes, here intended with the unusual meaning of earthquakes with magnitudes at the limit or below the bottom magnitude threshold of standard source inversion routines. The adopted inversion approaches entirely rely on existing inversion software, the methodological work mostly targeting the development and tuning of optimized inversion flows. The resulting inversion scheme is tested for very different datasets, and thus allows the discussion on the source inversion problem at different scales. In the first application, dealing with mining induced seismicity, the source parameters determination is addressed at a local scale, with source-sensor distance of less than 3 km. In this context, weak seismicity corresponds to event below magnitude MW 2.0, which are rarely target of automated source inversion routines. The second application considers a regional dataset, namely the aftershock sequence of the 2010 Maule earthquake (Chile), using broadband stations at regional distances, below 300 km. In this case, the magnitude range of the target aftershocks range down to MW 4.0. This dataset is here considered as a weak seismicity case, since the analysis of such moderate seismicity is generally investigated only by moment tensor inversion routines, with no attempt to resolve source duration or finite source parameters. In this work, automated multi-step inversion schemes are applied to both datasets with the aim of resolving point source parameters, both using double couple (DC) and full moment tensor (MT) models, source duration and finite source parameters. A major result of the analysis of weaker events is the increased size of resulting moment tensor catalogues, which interpretation may become not trivial. For this reason, a novel focal mechanism clustering approach is used to automatically classify focal mechanisms, allowing the investigation of the most relevant and repetitive rupture features. The inversion of the mining induced seismicity dataset reveals the repetitive occurrence of similar rupture processes, where the source geometry is controlled by the shape of the mined panel. Moreover, moment tensor solutions indicate a significant contribution of tensile processes. Also the second application highlights some characteristic geometrical features of the fault planes, which show a general consistency with the orientation of the slab. The additional inversion for source duration allowed to verify the empirical correlation for moment normalized earthquakes in subduction zones among a decreasing rupture duration with increasing source depth, which was so far only observed for larger events.},
  language  = {en}
}
@phdthesis{Metzger2023,
  author    = {Metzger, Sabrina},
  title     = {Neotectonic deformation over space and time as observed by space-based geodesy},
  doi       = {10.25932/publishup-59922},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-599225},
  school      = {Universit{\"a}t Potsdam},
  pages     = {V, 217},
  year      = {2023},
  abstract  = {Alfred Wegeners ideas on continental drift were doubted for several decades until the discovery of polarization changes at the Atlantic seafloor and the seismic catalogs imaging oceanic subduction underneath the continental crust (Wadati-Benioff Zone). It took another 20 years until plate motion could be directly observed and quantified by using space geodesy. Since then, it is unthinkable to do neotectonic research without the use of satellite-based methods. Thanks to a tremendeous increase of instrumental observations in space and time over the last decades we significantly increased our knowledge on the complexity of the seismic cycle, that is, the interplay of tectonic stress build up and release. Our classical assumption, earthquakes were the only significant phenomena of strain release previously accumulated in a linear fashion, is outdated. We now know that this concept is actually decorated with a wide range of slow and fast processes such as triggered slip, afterslip, post-seismic and visco-elastic relaxation of the lower crust, dynamic pore-pressure changes in the elastic crust, aseismic creep, slow slip events and seismic swarms. On the basis of eleven peer-reviewed papers studies I here present the diversity of crustal deformation processes. Based on time-series analyses of radar imagery and satellited-based positioning data I quantify tectonic surface deformation and use numerical and analytical models and independent geologic and seismologic data to better understand the underlying crustal processes. The main part of my work focuses on the deformation observed in the Pamir, the Hindu Kush and the Tian Shan that together build the highly active continental collision zone between Northwest-India and Eurasia. Centered around the Sarez earthquake that ruptured the center of the Pamir in 2015 I present diverse examples of crustal deformation phenomena. Driver of the deformation is the Indian indenter, bulldozing into the Pamir, compressing the orogen that then collapses westward into the Tajik depression. A second natural observatory of mine to study tectonic deformation is the oceanic subduction zone in Chile that repeatedly hosts large earthquakes of magnitude 8 and more. These are best to study post-seismic relaxation processes and coupling of large earthquake. My findings nicely illustrate how complex fashion and how much the different deformation phenomena are coupled in space and time. My publications contribute to the awareness that the classical concept of the seismic cycle needs to be revised, which, in turn, has a large influence in the classical, probabilistic seismic hazard assessment that primarily relies on statistically solid recurrence times.},
  language  = {en}
}
@masterthesis{Lehmann2017,
  type      = {Bachelor Thesis},
  author    = {Lehmann, Lukas},
  title     = {Performance Test von Phasenpickern},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-401993},
  school      = {Universit{\"a}t Potsdam},
  pages     = {I, 40, XXXIX},
  year      = {2017},
  abstract  = {Die genauen Einsatzzeiten seismischer P-Phasen von Erdbeben werden in SeisComP3 und anderen Auswerteprogrammen standardm{\"a}ßig und in Echtzeit automatisch bestimmt. S-Phasen stellen dagegen eine weit gr{\"o}ßere Herausforderung dar. Nur mit genauen Picks der P- bzw. S-Phasen k{\"o}nnen die Erdbebenlokationen korrekt und stabil bestimmt werden. Darum besteht erhebliches Interesse, diese mit hoher Genauigkeit zu bestimmen. Das Ziel der vorliegenden Bachelorarbeit war es, vier verschiedene, bereits vorhandene S-Phasenpicker auf ausgew{\"a}hlte Parameter optimal zu konfigurieren, auf Testdaten anzuwenden und deren Leistungsf{\"a}higkeit objektiv zu bewerten. Dazu wurden ein S-Picker (S-L2) aus dem OpenSource SeisComp3-Programmpaket, zwei S-Picker (S-AIC, S-AIC-V) als kommerzielles Modul der Firma gempa GmbH f{\"u}r SeisComP3 und ein S-Picker (Frequenzband) aus dem OpenSource PhasePaPy-Paket ausgew{\"a}hlt. Die Bewertung erfolgte durch Vergleich automatischer Picks mit manuell bestimmten Einsatzzeiten. Alle vier Picker wurden separat konfiguriert und auf drei verschiedene Datens{\"a}tze von Erdbeben in N-Chile und im Vogtland, Deutschland, angewandt. Dazu wurden regional bzw. lokal typische Erdbeben zuf{\"a}llig ausgew{\"a}hlt und die P- und S-Phasen manuell bestimmt. Mit den zu testenden S-Pickeralgorithmen wurden dieselben Daten durchsucht und die Picks automatisch bestimmt. Die Konfigurationen der Picker wurden gleichzeitig automatisch und objektiv durch iterative Anpassung optimiert. Ein neu erstelltes Bewertungssystem vergleicht die manuellen und die automatisch gefundenen S-Picks anhand von definierten Qualit{\"a}tsfaktoren. Die Qualit{\"a}tsfaktoren sind: der Mittelwert und die Standardabweichung der zeitlichen Differenzen zwischen den S-Picks, die Anzahl an {\"u}bereinstimmenden S-Picks, die Prozentangaben {\"u}ber m{\"o}gliche S-Picks und die ben{\"o}tigt Rechenzeit. Die objektive Bewertung erfolgte anhand eines Scores. Der Scorewert ergibt sich aus der gewichteten Summe folgender normierter Qualit{\"a}tsfaktoren: Standardabweichung (20\%), Mittelwert (20\%) und Prozentangabe {\"u}ber m{\"o}gliche S-Picks (60\%). Konfigurationen mit hohem Score werden bevorzugt. Die bevorzugten Konfigurationen der verschiedenen Picker wurden miteinander verglichen, um den am besten geeigneten S-Pickeralgorithmus zu bestimmen. Allgemein zeigt sich, dass der S-AIC Picker f{\"u}r jeden der drei Datens{\"a}tze die h{\"o}chsten Scores und damit die besten Ergebnisse liefert. Dabei wurde f{\"u}r jeden Datensatz ein andere Konfiguration der Parameter des S-AIC Pickers als die am besten geeignete bezeichnet. Daher ist f{\"u}r jede Erdbebenregion eine andere Konfigurationen erforderlich, um optimale Ergebnisse mit diesem S-Picker zu bekommen.},
  language  = {de}
}
@phdthesis{Koehler2009,
  author    = {K{\"o}hler, Andreas},
  title     = {Recognition and investigation of temporal patterns in seismic wavefields using unsupervised learning techniques},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-29702},
  school      = {Universit{\"a}t Potsdam},
  year      = {2009},
  abstract  = {Modern acquisition of seismic data on receiver networks worldwide produces an increasing amount of continuous wavefield recordings. Hence, in addition to manual data inspection, seismogram interpretation requires new processing utilities for event detection, signal classification and data visualization. Various machine learning algorithms, which can be adapted to seismological problems, have been suggested in the field of pattern recognition. This can be done either by means of supervised learning using manually defined training data or by unsupervised clustering and visualization. The latter allows the recognition of wavefield patterns, such as short-term transients and long-term variations, with a minimum of domain knowledge. Besides classical earthquake seismology, investigations of temporal patterns in seismic data also concern novel approaches such as noise cross-correlation or ambient seismic vibration analysis in general, which have moved into focus within the last decade. In order to find records suitable for the respective approach or simply for quality control, unsupervised preprocessing becomes important and valuable for large data sets. Machine learning techniques require the parametrization of the data using feature vectors. Applied to seismic recordings, wavefield properties have to be computed from the raw seismograms. For an unsupervised approach, all potential wavefield features have to be considered to reduce subjectivity to a minimum. Furthermore, automatic dimensionality reduction, i.e. feature selection, is required in order to decrease computational cost, enhance interpretability and improve discriminative power. This study presents an unsupervised feature selection and learning approach for the discovery, imaging and interpretation of significant temporal patterns in seismic single-station or network recordings. In particular, techniques permitting an intuitive, quickly interpretable and concise overview of available records are suggested. For this purpose, the data is parametrized by real-valued feature vectors for short time windows using standard seismic analysis tools as feature generation methods, such as frequency-wavenumber, polarization, and spectral analysis. The choice of the time window length is dependent on the expected durations of patterns to be recognized or discriminated. We use Self-Organizing Maps (SOMs) for a data-driven feature selection, visualization and clustering procedure, which is particularly suitable for high-dimensional data sets. Using synthetics composed of Rayleigh and Love waves and three different types of real-world data sets, we show the robustness and reliability of our unsupervised learning approach with respect to the effect of algorithm parameters and data set properties. Furthermore, we approve the capability of the clustering and imaging techniques. For all data, we find improved discriminative power of our feature selection procedure compared to feature subsets manually selected from individual wavefield parametrization methods. In particular, enhanced performance is observed compared to the most favorable individual feature generation method, which is found to be the frequency spectrum. The method is applied to regional earthquake records at the European Broadband Network with the aim to define suitable features for earthquake detection and seismic phase classification. For the latter, we find that a combination of spectral and polarization features favor S wave detection at a single receiver. However, SOM-based visualization of phase discrimination shows that clustering applied to the records of two stations only allows onset or P wave detection, respectively. In order to improve the discrimination of S waves on receiver networks, we recommend to consider additionally the temporal context of feature vectors. The application to continuous recordings of seismicity close to an active volcano (Mount Merapi, Java, Indonesia) shows that two typical volcano-seismic events (VTB and Guguran) can be detected and distinguished by clustering. In contrast, so-called MP events cannot be discriminated. Comparable results are obtained for selected features and recognition rates regarding a previously implemented supervised classification system. Finally, we test the reliability of wavefield clustering to improve common ambient vibration analysis methods such as estimation of dispersion curves and horizontal to vertical spectral ratios. It is found, that in general, the identified short- and long-term patterns have no significant impact on those estimates. However, for individual sites, effects of local sources can be identified. Leaving out the corresponding clusters, yields reduced uncertainties or allows for improving estimation of dispersion curves.},
  language  = {en}
}
@phdthesis{Roessler2006,
  author    = {R{\"o}ßler, Dirk},
  title     = {Retrieval of earthquake source parameters in inhomogeneous anisotropic mediawith application to swarm events in West Bohemia in 2000},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-7758},
  school      = {Universit{\"a}t Potsdam},
  year      = {2006},
  abstract  = {Earthquakes form by sudden brittle failure of rock mostly as shear ruptures along a rupture plane. Beside this, mechanisms other than pure shearing have been observed for some earthquakes mainly in volcanic areas. Possible explanations include complex rupture geometries and tensile earthquakes. Tensile earthquakes occur by opening or closure of cracks during rupturing. They are likely to be often connected with fluids that cause pressure changes in the pore space of rocks leading to earthquake triggering. Tensile components have been reported for swarm earthquakes in West Bohemia in 2000. The aim and subject of this work is an assessment and the accurate determination of such tensile components for earthquakes in anisotropic media. Currently used standard techniques for the retrieval of earthquake source mechanisms assume isotropic rock properties. By means of moment tensors, equivalent forces acting at the source are used to explain the radiated wavefield. Conversely, seismic anisotropy, i.e. directional dependence of elastic properties, has been observed in the earth's crust and mantle such as in West Bohemia. In comparison to isotropy, anisotropy causes modifications in wave amplitudes and shear-wave splitting. In this work, effects of seismic anisotropy on true or apparent tensile source components of earthquakes are investigated. In addition, earthquake source parameters are determined considering anisotropy. It is shown that moment tensors and radiation patterns due to shear sources in anisotropic media may be similar to those of tensile sources in isotropic media. In contrast, similarities between tensile earthquakes in anisotropic rocks and shear sources in isotropic media may exist. As a consequence, the interpretation of tensile source components is ambiguous. The effects that are due to anisotropy depend on the orientation of the earthquake source and the degree of anisotropy. The moment of an earthquake is also influenced by anisotropy. The orientation of fault planes can be reliably determined even if isotropy instead of anisotropy is assumed and if the spectra of the compressional waves are used. Greater difficulties may arise when the spectra of split shear waves are additionally included. Retrieved moment tensors show systematic artefacts. Observed tensile source components determined for events in West Bohemia in 1997 can only partly be attributed to the effects of moderate anisotropy. Furthermore, moment tensors determined earlier for earthquakes induced at the German Continental Deep Drilling Program (KTB), Bavaria, were reinterpreted under assumptions of anisotropic rock properties near the borehole. The events can be consistently identified as shear sources, although their moment tensors comprise tensile components that are considered to be apparent. These results emphasise the necessity to consider anisotropy to uniquely determine tensile source parameters. Therefore, a new inversion algorithm has been developed, tested, and successfully applied to 112 earthquakes that occurred during the most recent intense swarm episode in West Bohemia in 2000 at the German-Czech border. Their source mechanisms have been retrieved using isotropic and anisotropic velocity models. Determined local magnitudes are in the range between 1.6 and 3.2. Fault-plane solutions are similar to each other and characterised by left-lateral faulting on steeply dipping, roughly North-South oriented rupture planes. Their dip angles decrease above a depth of about 8.4km. Tensile source components indicating positive volume changes are found for more than 60\% of the considered earthquakes. Their size depends on source time and location. They are significant at the beginning of the swarm and at depths below 8.4km but they decrease in importance later in the course of the swarm. Determined principle stress axes include P axes striking Northeast and Taxes striking Southeast. They resemble those found earlier in Central Europe. However, depth-dependence in plunge is observed. Plunge angles of the P axes decrease gradually from 50° towards shallow angles with increasing depth. In contrast, the plunge angles of the T axes change rapidly from about 8° above a depth of 8.4km to 21° below this depth. By this thesis, spatial and temporal variations in tensile source components and stress conditions have been reported for the first time for swarm earthquakes in West Bohemia in 2000. They also persist, when anisotropy is assumed and can be explained by intrusion of fluids into the opened cracks during tensile faulting.},
  subject      = {Seismologie},
  language  = {en}
}
@misc{KruegerOhrnbergerRoessler2008,
  author    = {Kr{\"u}ger, Frank and Ohrnberger, Matthias and R{\"o}ßler, Dirk},
  title     = {Rupture imaging of large earthquakes with a poststack isochrone migration method},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18395},
  year      = {2008},
  abstract  = {Rapid and robust characterization of large earthquakes in terms of their spatial extent and temporal duration is of high importance for disaster mitigation and early warning applications. Backtracking of seismic P-waves was successfully used by several authors to image the rupture process of the great Sumatra earthquake (26.12.2004) using short period and broadband arrays. We follow here an approach of Walker et al. to backtrack and stack broadband waveforms from global network stations using traveltimes for a global Earth model to obtain the overall spatio-temporal development of the energy radiation of large earthquakes in a quick and robust way. We present results for selected events with well studied source processes (Kokoxili 14.11.2001, Tokachi-Oki 25.09.2003, Nias 28.03.2005). Further, we apply the technique in a semi-real time fashion to broadband data of earthquakes with a broadband magnitude >= 7 (roughly corresponding to Mw 6.5). Processing is based on first automatic detection messages from the GEOFON extended virtual network (GEVN).},
  language  = {en}
}
@misc{RoesslerKruegerOhrnberger2007,
  author    = {R{\"o}ßler, Dirk and Kr{\"u}ger, Frank and Ohrnberger, Matthias},
  title     = {Rupture propagation of recent large TsE off-coast Sumatra and Java},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-13039},
  year      = {2007},
  abstract  = {The spatio-temporal evolution of the three recent tsunamogenic earthquakes (TsE) off-coast N-Sumatra (Mw9.3), 28/03/2005 (Mw8.5) off-coast Nias, on 17/07/2006 (Mw7.7) off-coast Java. Start time, duration, and propagation of the rupture are retrieved. All parameters can be obtained rapidly after recording of the first-arrival phases in near-real time processing. We exploit semblance analysis, backpropagation and broad-band seismograms within 30°-95° distance. Image enhancement is reached by stacking the semblance of arrays within different directions. For the three events, the rupture extends over about 1150, 150, and 200km, respectively. The events in 2004, 2005, and 2006 had source durations of at least 480s, 120s, and 180s, respectively. We observe unilateral rupture propagation for all events except for the rupture onset and the Nias event, where there is evidence for a bilateral start of the rupture. Whereas average rupture speed of the events in 2004 and 2005 is in the order of the S-wave speed (≈2.5-3km/s), unusually slow rupturing (≈1.5 km/s) is indicated for the July 2006 event. For the July 2006 event we find rupturing of a 200 x 100 km wide area in at least 2 phases with propagation from NW to SE. The event has some characteristics of a circular rupture followed by unilateral faulting with change in slip rate. Fault area and aftershock distribution coincide. Spatial and temporal resolution are frequency dependent. Studies of a Mw6.0 earthquake on 2006/09/21 and one synthetic source show a ≈1° limit in resolution. Retrieved source area, source duration as well as peak values for semblance and beam power generally increase with the size of the earthquake making possible an automatic detection and classification of large and small earthquakes.},
  language  = {en}
}
@article{RoesslerKruegerOhrnberger2007,
  author    = {R{\"o}ßler, Dirk and Kr{\"u}ger, Frank and Ohrnberger, Matthias},
  title     = {Rupture propagation of the TsE (Mw7.7) on 17 July 2006 off-coast Java},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-12964},
  year      = {2007},
  abstract  = {The Mw=7.7 tsunamogenic earthquake (TsE) on 17 July 2006, 08:19:28 shock the Indian Ocean at about 15 km depth off-coast Java, Indonesia. It caused a local tsunami with wave heights exceeding 2 m. The death toll reached several hundred. Thousands of people were displaced. By means of standard array methods, we have investigated the propagation and the extent of the rupture front of the causative earthquake. Waveform similarity is expressed by means of the semblance. We back-propagate the semblance for first-arrival phases recorded at broad-band stations within teleseismic distances (30°-95°). Image enhancement is realised by stacking the semblance of 8 arrays within different epicentral and azimuthal directions. From teleseismic observations we find rupturing of a 200 x 100 km wide area in at least 2 phases with propagation from NW to SE and source duration >125 s. The event has some characteristics of a circular rupture followed by unilateral faulting with change in slip rate. Unusually slow rupturing (≈1.5 km/s) is indicated. Fault area and aftershock distribution coincide. Spatial and temporal resolution are frequency dependent. Studies of a Mw6.0 earthquake on 2006/09/21 and one synthetic source show a ≈1° limit in resolution. Retrieved source area, source duration as well as peak values for semblance and beam power increase with the size of the earthquake making possible an automatic detection and classification of large and small earthquakes.},
  language  = {en}
}
@phdthesis{Zeckra2020,
  author    = {Zeckra, Martin},
  title     = {Seismological and seismotectonic analysis of the northwestern Argentine Central Andean foreland},
  doi       = {10.25932/publishup-47324},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-473240},
  school      = {Universit{\"a}t Potsdam},
  pages     = {vii, 120},
  year      = {2020},
  abstract  = {After a severe M W 5.7 earthquake on October 17, 2015 in El Galp{\´o}n in the province of Salta NW Argentina, I installed a local seismological network around the estimated epicenter. The network covered an area characterized by inherited Cretaceous normal faults and neotectonic faults with unknown recurrence intervals, some of which may have been reactivated normal faults. The 13 three-component seismic stations recorded data continuously for 15 months. The 2015 earthquake took place in the Santa B{\´a}rbara System of the Andean foreland, at about 17km depth. This region is the easternmost morphostructural region of the central Andes. As a part of the broken foreland, it is bounded to the north by the Subandes fold-and-thrust belt and the Sierras Pampeanas to the south; to the east lies the Chaco-Paran{\´a} basin. A multi-stage morphotectonic evolution with thick-skinned basement uplift and coeval thin-skinned deformation in the intermontane basins is suggested for the study area. The release of stresses associated with the foreland deformation can result in strong earthquakes, as the study area is known for recurrent and historical, destructive earthquakes. The available continuous record reaches back in time, when the strongest event in 1692 (magnitude 7 or intensity IX) destroyed the city of Esteco. Destructive earthquakes and surface deformation are thus a hallmark of this part of the Andean foreland. With state-of-the-art Python packages (e.g. pyrocko, ObsPy), a semi-automatic approach is followed to analyze the collected continuous data of the seismological network. The resulting 1435 hypocenter locations consist of three different groups: 1.) local crustal earthquakes (nearly half of the events belong to this group), 2.) interplate activity, of regional distance in the slab of the Nazca-plate, and 3.) very deep earthquakes at about 600km depth. My major interest focused on the first event class. Those crustal events are partly aftershock events of the El Galp{\´o}n earthquake and a second earthquake, in the south of the same fault. Further events can be considered as background seismicity of other faults within the study area. Strikingly, the seismogenic zone encompass the whole crust and propagates brittle deformation down, close to the Moho. From the collected seismological data, a local seismic velocity model is estimated, using VELEST. After the execution of various stability tests, the robust minimum 1D-velocity model implies guiding values for the composition of the local, subsurface structure of the crust. Afterwards, performing a hypocenter relocation enables the assignment of individual earthquakes to aftershock clusters or extended seismotectonic structures. This allows the mapping of previously unknown seismogenic faults. Finally, focal mechanisms are modeled for events with acurately located hypocenters, using the newly derived local velocity model. A compressive regime is attested by the majority of focal mechanisms, while the strike direction of the individual seismogenic structures is in agreement with the overall north - south orientation of the Central Andes, its mountain front, and individual mountain ranges in the southern Santa-B{\´a}rbara-System.},
  language  = {en}
}
@misc{Petersen2017,
  type      = {Master Thesis},
  author    = {Petersen, Gesa Maria},
  title     = {Source array and receiver array analysis of Vogtland/ West Bohemia earthquake clusters},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-406671},
  school      = {Universit{\"a}t Potsdam},
  pages     = {107},
  year      = {2017},
  abstract  = {Die Region Vogtland/ West B{\"o}hmen im Grenzgebiet zwischen Deutschland und Tschechien ist bekannt f{\"u}r ihre geologische Aktivit{\"a}t. Holoz{\"a}ner Vulkanismus, Gasaustritte an Mofetten und Quellen und wiederkehrende Erdbebenschw{\"a}rme sind Ausdruck geodynamischer Prozesse im Untergrund. W{\"a}hrend des Erdbebenschwarms 2008/2009 in Nov{\´y} Kostel installierte die Universit{\"a}t Potsdam ein tempor{\"a}res Array in Rohrbach, in einer Epizentraldistanz von etwa 10 km und mit einer Aperatur von etwa 0.75 km. 22 Erdbeben wurden f{\"u}r Quellarray- beam forming ausgew{\"a}hlt. Quellarrays sind {\"o}rtliche Cluster von Erdbeben, die von einer Empf{\"a}ngerstation aufgezeichnet werden. Wegen der Reziprozit{\"a}t der Green'schen Funktionen k{\"o}nnen diese in {\"a}hnlicher Weise genutzt werden wie Empf{\"a}ngerarrays, bei denen mehrere Stationen ein einzelnes Beben aufzeichnen. Die Kreuzkorrelationskoeffizienten aller Beben des Quellarrays, aufgezeichnet an einer einzelnen Station, sind in der Regel h{\"o}her als f{\"u}r einzelne Ereignisse, die an allen Stationen des Empf{\"a}ngerarrays aufgezeichnet wurden. Dies deutet hinsichtlich der aufgel{\"o}sten Frequenzen auf einen heterogenen Untergrund unter den Array-Stationen und ein vergleichsweise homogenes Quellarray-Volumen hin. Beam forming wurde mit den horizontalen und vertikalen Spuren aller Quellarray-Beben, aufgezeichnet auf allen 11 Stationen des Empf{\"a}ngerarrays, durchgef{\"u}hrt. Die Ergebnisse wurden im Hinblick auf Konversionen und reflektierte Phasen analysiert. W{\"a}hrend die theoretische Richtung der direkten P-Welle im Falle der Quellarray-Aufzeichnungen gut {\"u}bereinstimmt, wird eine Empf{\"a}ngerarray-Missweisung von 15° bis 25° beobachtet. Eine PS Phase, die der direkten P Phase folgt und eine m{\"o}gliche SP Phase, die kurz vor der direkten S-Phase ankommt, wurden auf den summierten Spuren mehrerer Stationen interpretiert. Aus der Betrachtung der Laufzeiten resultiert eine Konversionstiefe von 0.6-0.9 km Tiefe. Ein zweites Quellarray, bestehend aus 12 tieferen Beben wurde zus{\"a}tzlich analysiert, um eine nach ca. 0.85 s ausschließlich auf den Aufzeichnungen tieferer Beben auftretende Strukturphase zu deuten. Zus{\"a}tzlich zum beam forming wurden zwei Lokalisierungsmethoden von Reflexionen und Konversionen f{\"u}r einfach reflektierte/konvertierte Phasen entwickelt und zur Auswertung verwendet. W{\"a}hrend die erste, analytische Methode eine homogene Geschwindigkeit entlang des Laufwegs annimmt, wird in der zweiten Methode eine 3-D-Rastersuche ausgef{\"u}hrt, in der ein 1-D-Geschwindigkeitsmodell verwendet wird. Auf Grund der eindeutigen beam forming Ergebnisse und der hohen {\"A}hnlichkeit der Wellenformen der Erdbeben, die f{\"u}r das Quellarray genutzt wurden, bieten Quellarrays bestehend aus Mikrobeben aus dem untersuchten Gebiet gute M{\"o}glichkeiten zur Untersuchung von Krustenstrukturen.},
  language  = {en}
}
@phdthesis{Kulikova2015,
  author    = {Kulikova, Galina},
  title     = {Source parameters of the major historical earthquakes in the Tien-Shan region from the late 19th to the early 20th century},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-88370},
  school      = {Universit{\"a}t Potsdam},
  pages     = {xiv, 164},
  year      = {2015},
  abstract  = {The Tien-Shan and the neighboring Pamir region are two of the largest mountain belts in the world. Their deformation is dominated by intermontane basins bounded by active thrust and reverse faulting. The Tien-Shan mountain belt is characterized by a very high rate of seismicity along its margins as well as within the Tien-Shan interior. The study area of the here presented thesis, the western part of the Tien-Shan region, is currently seismically active with small and moderate sized earthquakes. However, at the end of the 19th beginning of the 20th century, this region was struck by a remarkable series of large magnitude (M>7) earthquakes, two of them reached magnitude 8. Those large earthquakes occurred prior to the installation of the global digital seismic network and therefore were recorded only by analog seismic instruments. The processing of the analog data brings several difficulties, for example, not always the true parameters of the recording system are known. Another complicated task is the digitization of those records - a very time-consuming and delicate part. Therefore a special set of techniques is developed and modern methods are adapted for the digitized instrumental data analysis. The main goal of the presented thesis is to evaluate the impact of large magnitude M≥7.0 earthquakes, which occurred at the turn of 19th to 20th century in the Tien-Shan region, on the overall regional tectonics. A further objective is to investigate the accuracy of previously estimated source parameters for those earthquakes, which were mainly based on macroseismic observations, and re-estimate them based on the instrumental data. An additional aim of this study is to develop the tools and methods for faster and more productive usage of analog seismic data in modern seismology. In this thesis, the ten strongest and most interesting historical earthquakes in Tien-Shan region are analyzed. The methods and tool for digitizing and processing the analog seismic data are presented. The source parameters of the two major M≥8.0 earthquakes in the Northern Tien-Shan are re-estimated in individual case studies. Those studies are published as peer-reviewed scientific articles in reputed journals. Additionally, the Sarez-Pamir earthquake and its connection with one of the largest landslides in the world, Usoy landslide, is investigated by seismic modeling. These results are also published as a research paper. With the developed techniques, the source parameters of seven more major earthquakes in the region are determined and their impact on the regional tectonics was investigated. The large magnitudes of those earthquakes are confirmed by instrumental data. The focal mechanism of these earthquakes were determined providing evidence for responsible faults or fault systems.},
  language  = {en}
}
@misc{LipkeKruegerRoessler2008,
  author    = {Lipke, Katrin and Kr{\"u}ger, Frank and R{\"o}ßler, Dirk},
  title     = {Subduction zone structure along Sumatra from receiver functions},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18260},
  year      = {2008},
  abstract  = {Receiver functions are a good tool to investigate the seismotectonic structure beneath the a seismic station. In this study we apply the method to stations situated on or near Sumatra to find constraints on a more detailed velocity model which should improve earthquake localisation. We estimate shallow Moho-depths (~ 21 km) close to the trench and depths of ~30 km at greater distances. First evidences for the dip direction of the slab of ~60° are provided. Receiver functions were calculated for 20 stations for altogether 110 earthquakes in the distance range between 30° and 95° from the receiver. However the number of receiver functions per station is strongly variable as it depends on the installation date, the signal-to-noise-ratio of the station and the reliability of the acquisition.},
  language  = {en}
}
@article{RoesslerKruegerRuempkeretal.2006,
  author    = {R{\"o}ßler, Dirk and Kr{\"u}ger, Frank and R{\"u}mpker, Georg and Psencik, Ivan},
  title     = {Tensile source components of swarm events in West Bohemia in 2000 by considering seismic anisotropy},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-12975},
  year      = {2006},
  abstract  = {Earthquake swarms occur frequently in West Bohemia, Central Europe. Their occurrence is correlated with and propably triggered by fluids that escape on the earth's surface near the epicentres. These fluids raise up periodically from a seemingbly deep-seated source in the upper mantle. Moment tensors for swarm events in 1997 indicate tensile faulting. However, they were determined under assumption of seismic isotropy although anisotropy can be observed. Anisotropy may obscure moment tensors and their interpretation. In 2000, more than 10,000 swarm earthquakes occurred near Novy Kostel, West Bohemia. Event triggering by fluid injection is likely. Activity lasted from 28/08 until 31/12/00 (9 phases) with maximum ML=3.2. High quality P-wave seismograms were used to retrieve the source mechanisms for 112 events between 28/08/00 and 30/10/00 using > 20 stations. We determine the source geometry using a new algorithm and different velocity models including anisotropy. From inversions of P waves we observe ML<3.2, strike-slip events on steep N-S oriented faults with additional normal or reverse components. Tensile components seem to be evident for more than 60\% of the processed swarm events in West Bohemia during the phases 1-7. Being most significant at great depths and at phases 1-4 during the swarm they are time and location dependent. Although tensile components are reduced when anisotropy is assumed they persist and seem to be important. They can be explained by pore-pressure changes due to the injection of fluids that raise up. Our findings agree with other observations e.g. correlation of fluid transport and seismicity, variations in b-value, forcing rate, and in pore pressure diffusion. Tests of our results show their significance.},
  language  = {en}
}
@misc{Gassner2012,
  type      = {Master Thesis},
  author    = {Gassner, Alexandra Carina},
  title     = {The character of the core-mantle boundary : a systematic study using PcP},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-63590},
  school      = {Universit{\"a}t Potsdam},
  year      = {2012},
  abstract  = {Assuming that liquid iron alloy from the outer core interacts with the solid silicate-rich lower mantle the influence on the core-mantle reflected phase PcP is studied. If the core-mantle boundary is not a sharp discontinuity, this becomes apparent in the waveform and amplitude of PcP. Iron-silicate mixing would lead to regions of partial melting with higher density which in turn reduces the velocity of seismic waves. On the basis of the calculation and interpretation of short-period synthetic seismograms, using the reflectivity and Gauss Beam method, a model space is evaluated for these ultra-low velocity zones (ULVZs). The aim of this thesis is to analyse the behaviour of PcP between 10° and 40° source distance for such models using different velocity and density configurations. Furthermore, the resolution limits of seismic data are discussed. The influence of the assumed layer thickness, dominant source frequency and ULVZ topography are analysed. The Gr{\"a}fenberg and NORSAR arrays are then used to investigate PcP from deep earthquakes and nuclear explosions. The seismic resolution of an ULVZ is limited both for velocity and density contrasts and layer thicknesses. Even a very thin global core-mantle transition zone (CMTZ), rather than a discrete boundary and also with strong impedance contrasts, seems possible: If no precursor is observable but the PcP_model /PcP_smooth amplitude reduction amounts to more than 10\%, a very thin ULVZ of 5 km with a first-order discontinuity may exist. Otherwise, if amplitude reductions of less than 10\% are obtained, this could indicate either a moderate, thin ULVZ or a gradient mantle-side CMTZ. Synthetic computations reveal notable amplitude variations as function of the distance and the impedance contrasts. Thereby a primary density effect in the very steep-angle range and a pronounced velocity dependency in the wide-angle region can be predicted. In view of the modelled findings, there is evidence for a 10 to 13.5 km thick ULVZ 600 km south-eastern of Moscow with a NW-SE extension of about 450 km. Here a single specific assumption about the velocity and density anomaly is not possible. This is in agreement with the synthetic results in which several models create similar amplitude-waveform characteristics. For example, a ULVZ model with contrasts of -5\% VP , -15\% VS and +5\% density explain the measured PcP amplitudes. Moreover, below SW Finland and NNW of the Caspian Sea a CMB topography can be assumed. The amplitude measurements indicate a wavelength of 200 km and a height of 1 km topography, previously also shown in the study by Kampfmann and M{\"u}ller (1989). Better constraints might be provided by a joined analysis of seismological data, mineralogical experiments and geodynamic modelling.},
  language  = {en}
}
@phdthesis{Illien2023,
  author    = {Illien, Luc},
  title     = {Time-dependent properties of the shallow subsurface},
  doi       = {10.25932/publishup-59936},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-599367},
  school      = {Universit{\"a}t Potsdam},
  pages     = {xviii, 133},
  year      = {2023},
  abstract  = {The shallow Earth's layers are at the interplay of many physical processes: some being driven by atmospheric forcing (precipitation, temperature...) whereas others take their origins at depth, for instance ground shaking due to seismic activity. These forcings cause the subsurface to continuously change its mechanical properties, therefore modulating the strength of the surface geomaterials and hydrological fluxes. Because our societies settle and rely on the layers hosting these time-dependent properties, constraining the hydro-mechanical dynamics of the shallow subsurface is crucial for our future geographical development. One way to investigate the ever-changing physical changes occurring under our feet is through the inference of seismic velocity changes from ambient noise, a technique called seismic interferometry. In this dissertation, I use this method to monitor the evolution of groundwater storage and damage induced by earthquakes. Two research lines are investigated that comprise the key controls of groundwater recharge in steep landscapes and the predictability and duration of the transient physical properties due to earthquake ground shaking. These two types of dynamics modulate each other and influence the velocity changes in ways that are challenging to disentangle. A part of my doctoral research also addresses this interaction. Seismic data from a range of field settings spanning several climatic conditions (wet to arid climate) in various seismic-prone areas are considered. I constrain the obtained seismic velocity time-series using simple physical models, independent dataset, geophysical tools and nonlinear analysis. Additionally, a methodological development is proposed to improve the time-resolution of passive seismic monitoring.},
  language  = {en}
}
@article{LipkeZitzmannAmbergeretal.2007,
  author    = {Lipke, Katrin and Zitzmann, Max and Amberger, Manuel and Ehlert, Carsten and R{\"o}ßler, Dirk and Kr{\"u}ger, Frank and Ohrnberger, Matthias},
  title     = {Traveltime residuals at regional and teleseismic distances for SE-Asia},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-14117},
  year      = {2007},
  abstract  = {Traveltime residuals for worldwide seismic stations are calculated. We use P and S waves from earthquakes in SE-Asia at teleseismic and regional distances. The obtained station residuals help to enhance earthquake localisation. Furthermore we calculated regional source dependent station residuals. They show a systematic dependence of the locality of the source. These source dependent residuals reflect heterogenities along the path and can be used for a refinement of earthquake localisation.},
  language  = {en}
}