Article
Astronomy & Astrophysics
Johannes V. Roth, Dominik Schweitzer, Leon J. Sieke, Lorenz von Smekal
Summary: This study develops and compares different real-time methods for calculating spectral functions, including classical-statistical simulations, the Gaussian state approximation, and functional renormalization group methods. Results show that at high temperatures, the different methods yield consistent results, but at low temperatures, the real-time FRG method qualitatively approaches the exact solution.
Article
Geochemistry & Geophysics
Jack B. Muir, Zachary E. Ross
Summary: The spatio-temporal properties of seismicity provide valuable insights into the stress state evolution and fault structures of the Earth's crust. Empirical models based on self-exciting point processes, such as the epidemic-type aftershock sequence (ETAS) model, continue to be important tools for analyzing seismicity, especially given the uncertainties associated with physical models. However, the traditional ETAS model has limitations in capturing complex seismicity patterns in seismic swarms dominated by aseismic processes. To address this, a deep Gaussian process (GP) formulation for the background rate is introduced as an extension to ETAS, allowing for robust modeling of time-varying seismicity rates. This deep-GP-ETAS model is demonstrated to successfully capture multiscale temporal behavior in synthetic examples and real-data catalogues.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2023)
Article
Geochemistry & Geophysics
Jun Su, Christine Houser, John W. Hernlund, Frederic Deschamps
Summary: Seismic tomography models provide information on the distribution and magnitude of P- and S-wave velocity variations in the Earth's mantle. The presence of large low shear velocity provinces (LLSVPs) beneath the Pacific and Africa has important implications for their origin. However, the absence of these features in P-wave velocity models may be due to lower resolution compared to S-wave velocity models. By applying tomographic filters and analyzing thermochemical mantle convection models, it is revealed that distinct phase and/or composition can be differentiated from cases where only temperature varies. A new proxy called 'large uncorrelated modulus provinces' (LUMPs) is developed to explore uncorrelated P- and S-wave velocity anomalies.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2023)
Article
Geochemistry & Geophysics
I Firsov, D. Jault, N. Gillet, J. Aubert, M. Mandea
Summary: The relationship between the Earth's magnetic field and mantle electrical conductivity is studied in this paper. It is found that there is a linear relationship between surface shear and surface velocity, and a method to calculate surface shear using synthetic data is validated. The results suggest that mantle electrical conductivity may have an impact on surface flow shear at the Earth's core.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2023)
Article
Geochemistry & Geophysics
T. Schwaiger, D. Jault, N. Gillet, N. Schaeffer, M. Mandea
Summary: Inference of fluid motion below the core-mantle boundary from geomagnetic observations is a highly non-unique inverse problem. A new method is proposed that provides a unique local estimate of the velocity field by assuming quasi-geostrophic flow and neglecting magnetic diffusion. The method overcomes the underdetermination by inverting the flow at each point of a spherical grid representing the core surface and mitigates the unreliable reconstruction of small-scale flows by smoothing the velocity field using Gaussian process regression.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2023)
Article
Geochemistry & Geophysics
Yunus Levent Ekinci, Caglayan Balkaya, Gokhan Gokturkler, Hanbing Ai
Summary: This study presents a gravity inversion procedure using the success-history-based adaptive differential evolution (SHADE) algorithm to reconstruct the 3-D basement relief geometry in sedimentary basins. The method involves exponential population size reduction and self-adaptive control parameters to solve the highly nonlinear inverse problem. The results demonstrate the power and reliability of the SHADE with EPSR strategy as an alternative inversion tool for highly nonlinear geophysical problems.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2023)
Article
Geochemistry & Geophysics
Yunus Levent Ekinci, Caglayan Balkaya, Gokhan Gokturkler, Senol Ozyalin
Summary: The study focused on the Aegean Graben System in western Turkey, using differential evolution algorithm (DEA) to invert the depths of sediment cover-metamorphic basement. Parameterization was done through discretizing the basins into vertical blocks, and mathematical nature of the inverse problem was explored. Both synthetic and field data inversions showed that the maximum depths to the metamorphic basement reliefs in the grabens are shallower than previous findings, with the sediment thicknesses resolvable.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2021)
Article
Multidisciplinary Sciences
Yiannis Contoyiannis, Pericles Papadopoulos, Niki-Lina Matiadou, Stelios M. Potirakis
Summary: Video surveillance is crucial for public safety in smart cities, with Person Re-Identification being a key task. Existing methods often neglect unlabeled gallery images, while Manifold Embedding (ME) is limited by its scalability. A novel approach incorporating graph weight construction and manifold regularization shows promising results in Person Re-ID tasks.
Article
Geochemistry & Geophysics
Nils Olsen
Summary: The sensitivity of magnetic measurements taken by satellites in elliptical orbits to the lithospheric magnetic field is studied. The variances of the lithospheric Gauss coefficients for different satellite orbital constellations are compared and analytical expressions for the variances are presented. It is found that low-altitude magnetic data collected by satellites in low-perigee elliptical orbits enable improved global lithospheric field modelling at spatial wavelengths beyond what is currently possible with data from satellites in circular orbits.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2023)
Article
Mathematics, Applied
L. Baratchart, C. Gerhards, A. Kegeles, P. Menzel
Summary: Inverse problems in (geo)magnetism are typically ill-posed and exhibit non-uniqueness, but there exist nontrivial model spaces where the problem is uniquely solvable. This paper discusses the characteristics of subspaces that lead to non-uniqueness in the magnetization problem and identifies a subspace where the inversion becomes unique. The space of piecewise constant vector fields is too large to ensure uniqueness, but a dense subspace in L (2) is identified where the problem becomes uniquely solvable.
Article
Geochemistry & Geophysics
R. Rotondi, G. Bressan, E. Varini
Summary: In recent years, there has been growing interest in using statistical physics to describe seismic activity. This study analyzes a descriptor of seismic activity as a measure of the system's criticality and finds significant changes in this descriptor and the system's entropy before and after earthquakes. These results suggest that these indicators can serve as indicators of energy concentration and system activation state.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2022)
Article
Geochemistry & Geophysics
Muzammil Hussain Rammay, Sergey Alyaev, Ahmed H. Elsheikh
Summary: This paper explores the challenges of real-time inversion using Bayesian algorithms in the presence of uncertain model parameters, and investigates the effects of the approximate nature and model errors of deep learning models on the inversion results. By utilizing deep neural networks for model evaluation and the flexible iterative ensemble smoother to reduce model bias, the quality of the inversion results for geosteering can be improved. The paper also describes a method for identifying inversion multimodality and proposes possible solutions to alleviate it in real-time.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2022)
Article
Water Resources
Frsat Abdullah Ababakr, Kaywan Othman Ahmed, Ata Amini, Mehdi Karami Moghadam, Hueseyin Goekcekus
Summary: A groundwater quality map was created and evaluated to assess the quality and changes in groundwater in Erbil, Iraq. The water quality index (WQI) was calculated based on 13 parameters, showing a decrease in water quality in 2017 compared to previous years. Untreated domestic and industrial wastewater were identified as the main cause of groundwater pollution in the city.
APPLIED WATER SCIENCE
(2023)
Article
Multidisciplinary Sciences
Joseph Vovrosh, Johannes Knolle
Summary: The study demonstrates that state-of-the-art quantum computers are capable of simulating confinement physics in spin chains, observing confinement signatures of the TFIM and the slowdown of entanglement spreading induced by confinement.
SCIENTIFIC REPORTS
(2021)
Article
Astronomy & Astrophysics
V. V. Pipin
Summary: Through non-linear mean-field dynamo models, we investigate the magnetic cycle parameters of solar analogues with different rotation periods, finding a non-linear relationship between rotation rate and dynamo period, as well as saturation of magnetic activity parameters accompanied by a decrease in differential rotation.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)