Preprints
Filtering by Subject: Geophysics and Seismology
Mechanical Response of Shallow Crust to Groundwater Storage Variations: Inferences from Deformation and Seismic Observations in the Eastern Southern Alps, Italy
Published: 2020-06-06
Subjects: Earth Sciences, Geophysics and Seismology, Hydrology, Physical Sciences and Mathematics
Changes in continental water storage generate vertical surface deformation, induce crustal stress perturbations and modulate seismicity rates. However, the degree to which regional changes in terrestrial water content influence crustal stresses and the occurrence of earthquakes remains an open problem. We show how changes in groundwater storage, computed for a ~1000 km^2 basin, focus deformation [...]
Breakup Without Borders: How Continents Speed Up and Slow Down During Rifting
Published: 2020-05-30
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics, Tectonics and Structure
Relative plate motions during continental rifting result from the interplay of local with far-field forces. Here, we study the dynamics of rifting and breakup using large-scale numerical simulations of mantle convection with self-consistent evolution of plate boundaries. We show that continental separation follows a characteristic evolution with four distinctive phases: (1) An initial slow [...]
Where does subduction initiate and cease? A global scale perspective
Published: 2020-05-29
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics, Tectonics and Structure
The thermo-mechanical evolution of the Earths mantle is largely controlled by the dynamics of subduction zones, which connect the surface tectonic plates with the interior. However, little is known about the systematics of where subduction initiates and ceases within the framework of global plate motions and evolving continental configurations. Here, we investigate where new subduction zones [...]
Oceanic high-frequency global seismic wave propagation with realistic bathymetry
Published: 2020-05-28
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
We present a new approach to simulate high-frequency seismic wave propagation in and under the oceans. Based upon AxiSEM3D (Leng et al. 2019), this method sup- ports a fluid ocean layer, with associated water-depth phases and seafloor topography (bathymetry). The computational efficiency and flexibility of this formulation means that high-frequency calculations may be carried out with relatively [...]
Kilometer-scale sound speed structure that affects GNSS-A observation: Case study off the Kii channel
Published: 2020-05-28
Subjects: Earth Sciences, Geophysics and Seismology, Oceanography, Oceanography and Atmospheric Sciences and Meteorology, Physical Sciences and Mathematics
The Global Navigation Satellite System-Acoustic ranging combination technique (GNSS-A) is a recently developed technology to precisely detect seafloor crustal deformation. This method can also estimate km-scale underwater sound speed structure (SSS) as a by-product of monitoring seafloor crustal deformation. This paper evaluates the validity of the spatial gradient and its temporal variation of [...]
Hotspots and mantle plumes revisited: Towards reconciling the mantle heat transfer discrepancy
Published: 2020-05-27
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Mantle convection is the principal mechanism by which heat is transferred from the deep Earth to the surface. Cold subducting slabs sink into the mantle and steadily warm, whilst upwelling plumes carry heat to the base of lithospheric plates where it can subsequently escape by conduction. Accurate estimation of the total heat carried by these plumes is important for understanding geodynamic [...]
Including Earth-structure uncertainties in nonlinear moment-tensor estimations
Published: 2020-05-27
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Earthquake-source parameters can be estimated from seismic waveforms. Since these data indirectly observe the deformation process, parameters of a physical model that quantifies the deformation process are inferred through the inverse problem; which is under-determined. This requires several assumptions to be made about Earth structure and other aspects that affect the source parameter [...]
Optimal processing for seismic noise correlations
Published: 2020-05-27
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
A wide spectrum of processing schemes is commonly applied during the calculation of seismic noise correlations. This is intended to suppress large-amplitude transient and monochromatic signals, to accelerate convergence of the correlation process, or to modify raw correlations into more plausible approximations of inter-station Greens functions. Many processing schemes, such as one-bit [...]
Stress Recovery for the Particle-in-cell Finite Element Method
Published: 2020-05-26
Subjects: Applied Mathematics, Computer Sciences, Earth Sciences, Geophysics and Seismology, Mathematics, Numerical Analysis and Computation, Numerical Analysis and Scientific Computing, Physical Sciences and Mathematics, Tectonics and Structure
The interelement stress in the Finite Element Method is not continuous in nature, and stress projections from quadrature points to mesh nodes often causes oscillations. The widely used particle-in-cell method cannot avoid this issue and produces worse results when there are mixing materials of large strength (e.g., viscosity in Stokes problems) contrast in one element. The post-processing methods [...]
60 YEARS OF AIRBORNE AFMAG METHOD EVOLUTION
Published: 2020-05-25
Subjects: Civil and Environmental Engineering, Earth Sciences, Engineering, Geophysics and Seismology, Geotechnical Engineering, Physical Sciences and Mathematics
Development and following commercial use of the airborne electromagnetic method based on natural fields in the audio-frequency band (AFMAG) started in late 50s of the last century. After several decades of the development downtime, limitations inherent to the method were resolved in 80s by adapting the tensor analysis, remote reference noise bias removal techniques and computation of the tippers. [...]
Automated Seismic Source Characterisation Using Deep Graph Neural Networks
Published: 2020-05-25
Subjects: Artificial Intelligence and Robotics, Computer Sciences, Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Most seismological analysis methods require knowledge of the geographic location of the stations comprising a seismic network. However, common machine learning tools used in seismology do not account for this spatial information, and so there is an underutilised potential for improving the performance of machine learning models. In this work, we propose a Graph Neural Network (GNN) approach that [...]
Deep ductile shear localization facilitates near-orthogonal strike-slip faulting in a thin brittle lithosphere
Published: 2020-05-25
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics, Tectonics and Structure
Some active fault systems comprise near-orthogonal conjugate strike-slip faults, as highlighted by the 2019 Ridgecrest and the 2012 Indian Ocean earthquake sequences. In conventional failure theory, orthogonal faulting requires a pressure-insensitive rock strength, which is unlikely in the brittle lithosphere. Here, we conduct 3D numerical simulations to test the hypothesis that near-orthogonal [...]
The influence of spreading rate and permeability on melt focusing beneath mid-ocean ridges
Published: 2020-05-25
Subjects: Earth Sciences, Geophysics and Seismology, Other Earth Sciences, Physical Sciences and Mathematics
At mid-ocean ridges, oceanic crust is emplaced in a narrow neovolcanic region on the seafloor, whereas basaltic melt that forms this oceanic crust is generated in a wide region beneath as suggested by a few geophysical surveys. The combined observations suggest that melt generated in a wide region at depths has to be transported horizontally to a small region at the surface. We present results [...]
On the thermo-poro-mechanics of chemically active faults
Published: 2020-05-21
Subjects: Civil and Environmental Engineering, Earth Sciences, Engineering, Geophysics and Seismology, Geotechnical Engineering, Physical Sciences and Mathematics
Shear zones in outcrops and core drillings on active faults commonly reveal two scales of localization, with centimeter to tens of meters thick deformation zones embedding much narrower zones of mm- to cm-scale. The narrow zones are often attributed to some form of fast instability such as earthquakes or slow slip events. Surprisingly, the double localisation phenomenon seem to be independent of [...]
Multi-task learning based P/S wave separation and reverse time migration for VSP
Published: 2020-05-14
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
P/S wave mode separation is an essential tool for single-mode analysis from multi-component seismic data. Wave separation methods in recorded data require expert knowledge to choose parameters in different shots of data. To make this process automatic, we propose a machine learning-based method to separate P/S waves. This method employs a multi-task neural network that extracts P- and S-potential [...]