Preprints

Filtering by Subject: Geophysics and Seismology

Influence of ductile substrates and layer thickness on the spacing and topology of layer bound fault systems

Mark Ireland, Chris K Morley, Richard Davies

Published: 2020-11-02
Subjects: Earth Sciences, Geology, Geophysics and Seismology, Sedimentology, Tectonics and Structure

Polygonal fault systems are extraordinary features of many fine grained sedimentary succession and have been described from a significant number of deepwater sedimentary basins over the last two decades. Their formation represents an important mechanism by which fine grained sediments compact often resulting in a variety of complex patterns for which several controlling factors have been [...]

Rayleigh wave H/V amplitude ratio measurement using multicomponent ambient noise cross-correlations, and its relationship to Vp/Vs

Ajay Malkoti, Arjun Datta, Shravan M. Hanasoge

Published: 2020-10-30
Subjects: Earth Sciences, Geophysics and Seismology

The promise of passive seismology has increasingly been realized in recent years. Given the expense in installing and maintaining these seismic networks, it is important to extract as much information from the measurements as possible. In this context, the ellipticity or H/V amplitude ratio of Rayleigh waves can prove to be a valuable observable in ambient noise seismology due to its potential [...]

High-frequency global wavefields for local 3D structures by wavefield injection and extrapolation

Marta Pienkowska, Vadim Monteiller, Tarje Nissen-Meyer

Published: 2020-10-28
Subjects: Geophysics and Seismology

Earth structure is multiscale, and seismology remains the primary means of deciphering signatures from small structures over large distances. To enable this at the highest resolution, we present a flexible injection and extrapolation type hybrid framework that couples wavefields from a precomputed global database of accurate Green’s functions with a local three dimensional (3-D) method of choice [...]

Mapping and classifying large deformation from digital imagery: application to analogue models of lithosphere deformation

Taco Broerse, Nemanja Krstekanic, Cor Kasbergen, Ernst Willingshofer

Published: 2020-10-24
Subjects: Geophysics and Seismology, Tectonics and Structure

Particle Image Velocimetry (PIV), an image cross-correlation technique, is widely used for obtaining velocity fields from series of images of deforming objects. Rather than instantaneous velocities, we are interested in reconstructing cumulative deformation, and use PIV-derived incremental displacements for this purpose. Our focus is on analogue models of tectonic processes, which can accumulate [...]

Characterizing seismic scattering in 3D heterogeneous Earth by a single parameter

Jagdish Chandra Vyas, Martin Galis, Paul Martin Mai

Published: 2020-10-24
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics

We derive a theoretical parameter for three seismic scattering regimes where seismic wavelengths are either much shorter, similar, or much longer than the correlation length of small-scale Earth heterogeneities. We focus our analysis on the power spectral density of the von Karman autocorrelation function, used to characterize the spatial heterogeneity of small-scale variations of elastic rock [...]

DeepPhasePick: A method for Detecting and Picking Seismic Phases from Local Earthquakes based on highly optimized Convolutional and Recurrent Deep Neural Networks

Hugo Soto, Bernd Schurr

Published: 2020-10-22
Subjects: Geophysics and Seismology

Seismic phase detection, identification and first-onset picking are basic but essential routines to analyse earthquake data. As both the number of seismic stations, globally and regionally, and the number of experiments greatly increase due to ever greater availability of instrumentation, automated data processing becomes more and more essential. E.g., for modern seismic experiments involving [...]

Linking elastic and electrical properties of rocks using cross-property DEM

Phillip Andrew Cilli, Mark Chapman

Published: 2020-10-22
Subjects: Earth Sciences, Engineering Science and Materials, Geophysics and Seismology, Materials Science and Engineering, Physical Sciences and Mathematics

Joint electrical-elastic rock physics modelling can be instrumental in lowering uncertainty in subsurface reservoir characterisation. Typical electrical-elastic cross-property models, however, are empirical or require an intermediate step of porosity estimation to link a rock's electrical and elastic moduli, which can be error-prone away from well controls. Another outstanding issue in [...]

Seismic energy radiation and along-strike heterogeneities of shallow tectonic tremors at the Nankai Trough and Japan Trench

Suguru Yabe, Satoru Baba, Takashi Tonegawa, Masaru Nakano, Shunsuke Takemura

Published: 2020-10-21
Subjects: Geophysics and Seismology

Shallow slow earthquakes have been documented along shallow plate interfaces near trenches. Recent geophysical observation networks located offshore of Japan enable us to analyze shallow tremors in the Nankai Trough and the Japan Trench. Onshore seismic stations are also important for detecting shallow very low frequency earthquakes (VLFEs) and for evaluating their seismicity prior to the [...]

High-Pressure Deformation of Iron–Nickel–Silicon Alloys and Implications for Earth’s Inner Core

Matthew C Brennan, Rebecca A Fischer, Samantha Couper, Lowell Miyagi, Daniele Antonangeli, Guillaume Morard

Published: 2020-10-21
Subjects: Earth Sciences, Geophysics and Seismology, Mineral Physics, Physical Sciences and Mathematics

Earth’s inner core exhibits strong seismic anisotropy, often attributed to the alignment of hexagonal close-packed iron (hcp-Fe) alloy crystallites with the Earth’s poles. How this alignment developed depends on material properties of the alloy and is important to our understanding of the core’s crystallization history and active geodynamical forcing. Previous studies suggested that hcp-Fe is [...]

Dynamics of core-mantle separation: influence of viscosity contrast and metal/silicate partition coefficients on the chemical equilibrium

Vincent Clesi, Julien Monteux, Baraa Qaddah, Michael Le Bars, Jean-Baptiste Wacheul, Mohamed Ali Bouhifd

Published: 2020-10-21
Subjects: Earth Sciences, Geochemistry, Geophysics and Seismology, Physical Sciences and Mathematics

The composition of the Earth's core and mantle is set by the chemical equilibrium between metals and silicates during core/mantle segregation. The metallic core separated from the mantle by gravitational descent in the form of diapirs in a magma ocean, and therefore the dynamics of the diapir's downward movement has an influence on the chemical equilibrium. In this study, we characterize the [...]

GARPOS: analysis software for the GNSS-A seafloor positioning with simultaneous estimation of sound speed structure

Shun-ichi Watanabe, Tadashi Ishikawa, Yusuke Yokota, Yuto Nakamura

Published: 2020-08-21
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics

Global Navigation Satellite System – Acoustic ranging combined seafloor geodetic technique (GNSS-A) has extended the geodetic observation network into the ocean. The key issue for analyzing the GNSS-A data is how to correct the effect of sound speed variation in the seawater. We constructed a generalized observation equation and developed a method to directly extract the gradient sound speed [...]

The Ediacaran Grenville dykes (SE Canada) reveal the weakest sustained palaeomagnetic field on record.

Daniele Thallner, Andrew Biggin, Henry Halls

Published: 2020-08-20
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics

Long-term variations of the geomagnetic field, observed in the palaeomagnetic record, have the potential to shed much light on the evolution of Earth’s deep interior. With a geomagnetic field characterised by anomalous directions and ultra-low intensities, the Ediacaran period (635-541 Ma) is a time of special interest. Steep and shallow directions, leading to virtual geomagnetic poles (VGPs), [...]

Structure of the North Anatolian Fault Zone imaged via teleseismic scattering tomography

Sebastian Rost, Greg Houseman, Andrew Frederiksen, David G. Cornwell, Metin Kahraman, Sleda Altuncy Poyraz, Ugur Teoman, David A. Thompson, Niyazi Türkelli, Levent Gülen

Published: 2020-08-20
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics

Information on fault zone structure is essential for our understanding of earthquake mechanics, continental deformation and our understanding of seismic hazard. We use the scattered seismic wavefield to study the subsurface structure of the North-Anatolian Fault Zone (NAFZ) in the region of the 1999 {\.I}zmit and D\"uzce rupture using data from an 18-month dense deployment of seismometers with a [...]

Quantitative estimates of average geomagnetic axial dipole dominance in deep geological time

Andrew Biggin, Richard Bono, Domenico Giovanni Meduri, Courtney Sprain, Christopher J. Davies, Richard Holme, Pavel Doubrovine

Published: 2020-08-20
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics

A defining characteristic of the recent geomagnetic field is its dominant axial dipole which provides its navigational utility and dictates the shape of the magnetosphere. Going back through time, much less is known about the degree of axial dipole dominance. Here we use a substantial and diverse set of 3D numerical dynamo simulations and recent observation-based field models to derive a power [...]

Resolving the Kinematics and Moment Release of Early Afterslip within the First Hours following the 2016 Mw 7.1 Kumamoto Earthquake: Implications for the Shallow Slip Deficit and Frictional Behavior of Aseismic Creep

Chris Milliner, Roland Bürgmann, Asaf Inbal, Teng Wang, Cunren Liang

Published: 2020-08-17
Subjects: Earth Sciences, Environmental Sciences, Geophysics and Seismology, Physical Sciences and Mathematics

Continuous measurements of postseismic surface deformation provide insight into variations of the frictional strength of faults and the rheology of the lower crust and upper mantle as stresses following rupture are dissipated. However, due to the difficulty of capturing the earliest phase of afterslip, most analyses have focused on understanding postseismic processes over timescales of [...]

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