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  • 1
    Online Resource
    Online Resource
    Oxford :Oxford University Press, Incorporated,
    Keywords: Seismology--Mathematics. ; Electronic books.
    Description / Table of Contents: This book is an introductory text to a range of numerical methods used today to simulate time-dependent processes in Earth science, physics, engineering, and many other fields. It looks under the hood of current simulation technology and provides guidelines on what to look out for when carrying out sophisticated simulation tasks.
    Type of Medium: Online Resource
    Pages: 1 online resource (340 pages)
    Edition: 1st ed.
    ISBN: 9780191026850
    DDC: 551.220151
    Language: English
    Note: Cover -- Computational Seismology: A Practical Introduction -- Copyright -- Dedication -- Preface -- Acknowledgements -- Contents -- 1 About Computational Seismology -- 1.1 What is computational seismology? -- 1.2 What is computational seismology good for? -- 1.3 Target audience and level -- 1.4 How to read this volume -- 1.5 Code snippets -- Further reading -- Part I Elastic Waves in the Earth -- 2 Seismic Waves and Sources -- 2.1 Elastic wave equations -- 2.2 Analytical solutions: scalar wave equation -- 2.3 Rheologies -- 2.3.1 Viscoelasticity and attenuation -- 2.3.2 Seismic anisotropy -- 2.3.3 Poroelasticity -- 2.4 Boundary and initial conditions -- 2.4.1 Initial conditions -- 2.4.2 Free surface and Lamb's problem -- 2.4.3 Internal boundaries -- 2.4.4 Absorbing boundary conditions -- 2.5 Fundamental solutions -- 2.5.1 Body waves -- 2.5.2 Gradient, divergence, curl -- 2.5.3 Surface waves -- 2.6 Seismic sources -- 2.6.1 Forces and moments -- 2.6.2 Seismic wavefield of a double-couple point source -- 2.6.3 Superposition principle, finite sources -- 2.6.4 Reciprocity, time reversal -- 2.7 Scattering -- 2.8 Seismic wave problems as linear systems -- 2.9 Some final thoughts -- Chapter summary -- Further reading -- Exercises -- 3 Waves in a Discrete World -- 3.1 Classification of partial differential equations -- 3.2 Strategies for computational wave propagation -- 3.3 Physical domains and computational meshes -- 3.3.1 Dimensionality: 1D, 2D, 2.5D, 3D -- 3.3.2 Computational meshes -- 3.3.3 Structured (regular) grids -- 3.3.4 Unstructured (irregular) grids -- 3.3.5 Other meshing concepts -- 3.4 The curse of mesh generation -- 3.5 Parallel computing -- 3.5.1 Physics and parallelism -- 3.5.2 Domain decomposition, partitioning -- 3.5.3 Hardware and software for parallel algorithms -- 3.5.4 Basic hardware architectures -- 3.5.5 Parallel programming. , 3.5.6 Parallel I/O, data formats, provenance -- 3.6 The impact of parallel computing on Earth Sciences -- Chapter summary -- Further reading -- Exercises -- Part II Numerical Methods -- 4 The Finite-Difference Method -- 4.1 History -- 4.2 The finite-difference method in a nutshell -- 4.3 Finite differences and Taylor series -- 4.3.1 Higher derivatives -- 4.3.2 High-order operators -- 4.4 Acoustic wave propagation in 1D -- 4.4.1 Stability -- 4.4.2 Numerical dispersion -- 4.4.3 Convergence -- 4.5 Acoustic wave propagation in 2D -- 4.5.1 Numerical anisotropy -- 4.5.2 Choosing the right simulation parameters -- 4.6 Elastic wave propagation in 1D -- 4.6.1 Displacement formulation -- 4.6.2 Velocity-stress formulation -- 4.6.3 Velocity-stress algorithm: example -- 4.6.4 Velocity-stress: dispersion -- 4.7 Elastic wave propagation in 2D -- 4.7.1 Grid staggering -- 4.7.2 Free-surface boundary condition -- 4.8 The road to 3D -- 4.8.1 High-order extrapolation schemes -- 4.8.2 Heterogeneous Earth models -- 4.8.3 Optimizing operators -- 4.8.4 Minimal, triangular, unstructured grids -- 4.8.5 Other coordinate systems -- 4.8.6 Concluding remarks -- Chapter summary -- Further reading -- Exercises -- 5 The Pseudospectral Method -- 5.1 History -- 5.2 The pseudospectral method in a nutshell -- 5.3 Ingredients -- 5.3.1 Orthogonal functions, interpolation, derivative -- 5.3.2 Fourier series and transforms -- 5.4 The Fourier pseudospectral method -- 5.4.1 Acoustic waves in 1D -- 5.4.2 Stability, convergence, dispersion -- 5.4.3 Acoustic waves in 2D -- 5.4.4 Numerical anisotropy -- 5.4.5 Elastic waves in 1D -- 5.5 Infinite order finite differences -- 5.6 The Chebyshev pseudospectral method -- 5.6.1 Chebyshev polynomials -- 5.6.2 Chebyshev derivatives, differentiation matrices -- 5.6.3 Elastic waves in 1D -- 5.7 The road to 3D -- Chapter summary -- Further reading. , Exercises -- 6 The Finite-Element Method -- 6.1 History -- 6.2 Finite elements in a nutshell -- 6.3 Static elasticity -- 6.3.1 Boundary conditions -- 6.3.2 Reference element, mapping, stiffness matrix -- 6.3.3 Simulation example -- 6.4 1D elastic wave equation -- 6.4.1 The system matrices -- 6.4.2 Simulation example -- 6.5 Shape functions in 1D -- 6.6 Shape functions in 2D -- 6.7 The road to 3D -- Chapter summary -- Further reading -- Exercises -- 7 The Spectral-Element Method -- 7.1 History -- 7.2 Spectral elements in a nutshell -- 7.3 Weak form of the elastic equation -- 7.4 Getting down to the element level -- 7.4.1 Interpolation with Lagrange polynomials -- 7.4.2 Numerical integration -- 7.4.3 Derivatives of Lagrange polynomials -- 7.5 Global assembly and solution -- 7.6 Source input -- 7.7 The spectral-element method in action -- 7.7.1 Homogeneous example -- 7.7.2 Heterogeneous example -- 7.8 The road to 3D -- Chapter summary -- Further reading -- Exercises -- 8 The Finite-Volume Method -- 8.1 History -- 8.2 Finite volumes in a nutshell -- 8.3 The finite-volume method via conservation laws -- 8.4 Scalar advection in 1D -- 8.5 Elastic waves in 1D -- 8.5.1 Homogeneous case -- 8.5.2 Heterogeneous case -- 8.5.3 The Riemann problem: heterogeneous case -- 8.6 Derivation via Gauss's theorem -- 8.7 The road to 3D -- Chapter summary -- Further reading -- Exercises -- 9 The Discontinuous Galerkin Method -- 9.1 History -- 9.2 The discontinuous Galerkin method in a nutshell -- 9.3 Scalar advection equation -- 9.3.1 Weak formulation -- 9.3.2 Elemental mass and stiffness matrices -- 9.3.3 The flux scheme -- 9.3.4 Scalar advection in action -- 9.4 Elastic waves in 1D -- 9.4.1 Fluxes in the elastic case -- 9.4.2 Simulation examples -- 9.5 The road to 3D -- Chapter summary -- Further reading -- Exercises -- Part III Applications. , 10 Applications in Earth Sciences -- 10.1 Geophysical exploration -- 10.2 Regional wave propagation -- 10.3 Global and planetary seismology -- 10.4 Strong ground motion and dynamic rupture -- 10.5 Seismic tomography-waveform inversion -- 10.6 Volcanology -- 10.7 Simulation of ambient noise -- 10.8 Elastic waves in random media -- Chapter summary -- Exercises -- 11 Current Challenges in Computational Seismology -- 11.1 Community solutions -- 11.2 Structured vs. unstructured: homogenization -- 11.3 Meshing -- 11.4 Nonlinear inversion, uncertainties -- Appendix A Community Software and Platforms in Seismology -- A.1 Wave propagation and inversion -- A.2 Data processing, visualization, services -- A.3 Benchmarking -- A.4 Jupyter Notebooks -- A.5 Supplementary material -- References -- Index.
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  • 2
    Keywords: Forschungsbericht
    Type of Medium: Online Resource
    Pages: Online-Ressource (11 S., 15,7 MB) , Ill., graph. Darst.
    Language: German
    Note: Förderkennzeichen BMBF 03F0325A. - Verb.-Nr.:01020264. - Literaturverz , Unterschiede zwischen dem gedruckten Dokument und der elektronischen Ressource können nicht ausgeschlossen werden , Auch als gedr. Ausg. vorhanden , Systemvoraussetzungen: Acrobat reader.
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  • 3
    Publication Date: 2023-06-05
    Description: A 6 degrees-of-freedom (6DoF) sensor, measuring three components of translational acceleration and three components of rotation rate, provides the full history of motion it is exposed to. In Earth sciences 6DoF sensors have shown great potential in exploring the interior of our planet and its seismic sources. In space sciences, apart from navigation, 6DoF sensors are, up to now, only rarely used to answer scientific questions. As a first step of establishing 6DoF motion sensing deeper into space sciences, this article describes novel scientific approaches based on 6DoF motion sensing with substantial potential for constraining the interior structure of planetary objects and asteroids. Therefore we estimate 6DoF-signal levels that originate from lander–surface interactions during landing and touchdown, from a body’s rotational dynamics as well as from seismic ground motions. We discuss these signals for an exemplary set of target bodies including Dimorphos, Phobos, Europa, the Earth’s Moon and Mars and compare those to self-noise levels of state-of-the-art sensors.
    Description: Horizon 2020 http://dx.doi.org/10.13039/501100007601
    Description: Projekt DEAL
    Keywords: ddc:523 ; Planetary exploration ; Planetary seismology ; Librations ; Tides ; 6DoF sensors
    Language: English
    Type: doc-type:article
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  • 4
    Publication Date: 2023-06-09
    Description: Microzonation is one of the essential tools in seismology to mitigate earthquake damage by estimating the near-surface velocity structure and developing land usage plans and intelligent building design. The number of microzonation studies increased in the last few years as induced seismicity becomes more relevant, even in low-risk areas. While of vital importance, especially in densely populated cities, most of the traditional techniques suffer from different shortcomings. The microzonation technique presented here tries to reduce the existing ambiguity of the inversion results by the combination of single-station six-component (6C) measurements, including three translational and three rotational motions, and more traditional H/V techniques. By applying this new technique to a microzonation study in the downtown area of Munich (Germany) using an iXblue blueSeis-3A rotational motion sensor together with a Nanometrics Trillium Compact seismometer, we were able to estimate Love and Rayleigh wave dispersion curves. These curves together with H/V spectral ratios are then inverted to obtain P- and S-wave velocity profiles of the upper 100 m. In addition, there is a good correlation between the estimated velocity models and borehole-derived lithology, indicating the potential of this single-station microzonation approach.
    Description: European Research Council https://doi.org/10.13039/501100000781
    Description: Bundesministerium für Wirtschaft und Energie https://doi.org/10.13039/501100006360
    Keywords: ddc:551.22 ; Microzonation ; Rotational seismology ; Ambient noise
    Language: English
    Type: doc-type:article
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Geophysical prospecting 49 (2001), S. 0 
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: We present a numerical method of simulating seismic wave propagation on unstructured 2D grids. The algorithm is based on the velocity–stress formulation of the elastic wave equation and therefore uses a staggered grid approach. Unlike finite-element or spectral-element methods, which can also handle flexible unstructured grids, we use explicit differential operators for the calculation of spatial derivatives in each time step. As shown in previous work, three types of these operators are used, and their particular performance is analysed and compared with standard explicit finite-difference operators on regular quadratic and hexagonal grids. Our investigations are especially focused on the influence of grid irregularity, sampling rate (i.e. gridpoints per wavelength) and numerical anisotropy on the accuracy of numerical seismograms. The results obtained from the various methods are therefore compared with analytical solutions. The algorithm is then applied to a number of models that are difficult to handle using (quasi-)regular grid methods. Such alternative techniques may be useful in modelling the full wavefield of bodies with complex geometries (e.g. cylindrical bore-hole samples, 2D earth models) and, because of their local character, they are well suited for parallelization.
    Type of Medium: Electronic Resource
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  • 6
    Publication Date: 2020-02-05
    Description: Recently, due to observations of rotational ground motions, a promising new field of research in seismology and engineering has developed. However, exploration of rotation’s potential has been hampered by the lack of a portable, reliable, and highly sensitive broadband rotational ground‐motion sensor. In this work, we present laboratory tests of the BlueSeis3A, the first commercially available fiber‐optic gyroscope specifically designed for applications in broadband seismology. Here, we estimate the sensor’s self‐noise level by means of power spectral density, operating range diagrams, and Allan deviation. Scale factor linearity is measured up to the largest likely rotation rates in seismology (⁠∼900  mrads−1⁠). Tests of the sensor’s susceptibility to changes in ambient conditions, such as temperature or magnetic field, demonstrate the BlueSeis3A’s reliability in field installations. Estimation of the orthogonality of the three sensor components completes our tests. We conclude that the BlueSeis3A is fit for a wide range of field applications in seismology, volcanology, ocean‐bottom observations, and earthquake engineering.
    Type: Article , PeerReviewed
    Format: text
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  • 7
    Publication Date: 2024-02-07
    Description: Six-degree-of-freedom (6DoF) sensors measure translation along three axes and rotation around three axes. These collocated measurements make it possible to fully describe building motion without the need for an external reference point. This is an advantage for building health monitoring, which uses interstory drift and building eigenfrequencies to monitor stability. In this paper, IMU50 6DoF sensors are characterized to determine their suitability for building health monitoring. The sensors are calibrated using step table methods and by comparison with earth’s rotation and gravity. These methods are found to be comparable. The sensor’s self-noise is examined through the power spectral density and the Allan deviation of data recorded in a quiet environment. The effect of temperature variation is tested between 14 and 50 ∘C. It appears that the self-noise of the rotation components increases while the self-noise of the acceleration components decreases with temperature. The comparison of the sensor self-noise with ambient building signal and higher amplitude shaking shows that these sensors are in general not sensitive enough for ambient signal building health monitoring in the frequency domain, but could be useful for monitoring interstory drift and building motion during, for example, strong earthquake shaking in buildings similar to those examined here.
    Type: Article , PeerReviewed
    Format: text
    Format: archive
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  • 8
    Publication Date: 2021-07-13
    Description: The VERCE project has pioneered an e-Infrastructure to support researchers using established simulation codes on high-performance computers in conjunction with multiple sources of observational data. This is accessed and organised via the VERCE science gateway that makes it convenient for seismologists to use these resources from any location via the Internet. Their data handling is made flexible and scalable by two Python libraries, ObsPy and dispel4py and by data services delivered by ORFEUS and EUDAT. Provenance driven tools enable rapid exploration of results and of the relationships between data, which accelerates understanding and method improvement. These powerful facilities are integrated and draw on many other e-Infrastructures. This paper presents the motivation for building such systems, it reviews how solid-Earth scientists can make significant research progress using them and explains the architecture and mechanisms that make their construction and operation achievable. We conclude with a summary of the achievements to date and identify the crucial steps needed to extend the capabilities for seismologists, for solid-Earth scientists and for similar disciplines.
    Description: Published
    Description: UK
    Description: 1SR. TERREMOTI - Servizi e ricerca per la Società
    Keywords: Computer Science - Distributed; Parallel; and Cluster Computing ; Computer Science - Distributed; Parallel; and Cluster Computing
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: Conference paper
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  • 9
    Publication Date: 2019-07-16
    Description: Petroleum systems located at passive continental margins received increasing attention in the last decade mainly because of deep- and ultra‐deep-water hydrocarbon exploration and production. The high risks associated with these settings originate mainly from the poor understanding of inherent geodynamic processes. The new priority program SAMPLE (South Atlantic Margin Processes and Links with onshore Evolution), established by the German Science Foundation in 2009 for a total duration of 6 years, addresses a number of open questions related to continental breakup and post‐breakup evolution of passive continental margins. 27 sub‐projects take advantage of the exceptional conditions of the South Atlantic as a prime “Geo‐archive.” The regional focus is set on the conjugate margins located east of Brazil and Argentina on one side and west of Angola, Namibia and South Africa on the other (Figure 1) as well as on the Walvis Ridge and the present‐day hotspot of Tristan da Cunha. The economic relevance of the program is demonstrated by support from several petroleum companies, but the main goal is research on fundamental processes behind the evolution of passive continental margins.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Book , peerRev
    Format: application/pdf
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  • 10
    Publication Date: 2020-06-03
    Description: The additional observation of three components of rotational ground motions has benefitsfor tilt-seismometer coupling (e.g., ocean-bottom seismometry and volcano seismology),local site characterization, wavefield separation, source inversion, glacial and planetaryseismology, as well as the monitoring of structural health. Field applications have beenmostly hampered by the lack of portable sensors with appropriate broadband operationrange and weak-motion sensitivity. Here, we present field observations of the firstcommercial portable broadband rotation sensor specifically designed for seismology.The sensor is a three-component fiber-optic gyro strictly sensitive to ground rotation only.The sensor field performance and records are validated by comparing it with both arrayderivedrotation measurements and a navigation-type gyro. We present observations ofthe 2018 Mw 5.4 Hualien earthquake and the 2016 central Italy earthquake sequence.Processing collocated rotation and classical translation records shows the potential inretrieving wave propagation direction and local structural velocity from point measurementscomparable to small-scale arrays of seismic stations. We consider the availabilityof a portable, broadband, high sensitivity, and low self-noise rotation sensor to be a milestonein seismic instrumentation. Complete and accurate ground-motion observations(assuming a rigid base plate) are possible in the near, local, or regional field, openingup a wide range of seismological applications.
    Description: Published
    Description: 953-969
    Description: 8T. Sismologia in tempo reale
    Description: JCR Journal
    Keywords: Rotational Seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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