Preprints

Filtering by Subject: Geophysics and Seismology

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 [...]

Multiple Small Scale Landslides Triggered by Typhoon Talas 2011

Ryo Okuwaki, Wenyuan Fan, Masumi Yamada, Hikaru Osawa, Tim J. Wright

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

Devastating landslides can cause significant damage. In particular, typhoon-triggered landslides pose a chain of natural hazards. However, such events are difficult to detect due to their remote locations, leaving the physical processes poorly understood. Here we apply a novel surface-wave detector using intermediate-period surface waves to detect and locate landslides during the transit of [...]

Three-Station Interferometry and Tomography: Coda vs. Direct Waves

Shane Zhang, Lili Feng, Michael H. Ritzwoller

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

Traditional two-station ambient noise interferometry estimates the Greens function between a pair of synchronously deployed seismic stations. Three-station interferometry considers records observed three stations at a time, where two of the stations are considered receiver-stations and the third is a source-station. Cross-correlations between records at the source-station with each of the [...]

On the Evolution of Thermally Stratified Layers at the top of Earth’s Core

Sam Greenwood, Jonathan Mound, Christopher J. Davies

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

Stable stratification at the top of the Earth’s outer core has been suggested based upon seismic and geomagnetic observations, however, the origin of the layer is still unknown. In this paper we focus on a thermal origin for the layer and conduct a systematic study on the thermal evolution of the core. We develop a new numerical code to model the growth of thermally stable layers beneath the CMB, [...]

Rapid finite-frequency microseismic noise source inversion at regional to global scales

Jonas Karl Hans Igel, Laura Ermert, Andreas Fichtner

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

Ambient noise cross-correlations can be used as self-consistent observables, opening novel possibilities for investigating ambient noise sources. To optimise the forward- modelling of global ambient cross-correlations for any given noise distribution of noise sources in the microseismic frequency range up to 0.2 Hz, we implement (i) pre-computed wavefields and (ii) spatially variable grids. This [...]

Bridging the gap between geophysics and geology with Generative Adversarial Networks (GANs)

Suihong Song, Tapan Mukerji, Jiagen Hou

Published: 2020-08-17
Subjects: Artificial Intelligence and Robotics, Computer Sciences, Databases and Information Systems, Earth Sciences, Environmental Monitoring, Environmental Sciences, Geology, Geomorphology, Geophysics and Seismology, Natural Resource Economics, Oil, Gas, and Energy, Other Earth Sciences, Physical Sciences and Mathematics, Sedimentology, Water Resource Management

Inverse mapping from geophysics to geology is a difficult problem due to the inherent uncertainty of geophysical data and the spatially heterogeneous patterns (structure) in geology. We describe GANSim, a type of generative adversarial networks (GANs) that discovers the mapping between remotely-sensed geophysical information and geology with realistic patterns, with a specially designed loss [...]

Stress, rigidity and sediment strength control megathrust earthquake and tsunami dynamics

Thomas Ulrich, Alice-Agnes Gabriel, Elizabeth Madden

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

Megathrust faults host the largest earthquakes on Earth which can trigger cascading hazards such as devastating tsunamis. Determining characteristics that control subduction zone earthquake and tsunami dynamics is critical to mitigate megathrust hazards, but is impeded by structural complexity, large spatio-temporal scales, and scarce or asymmetric instrumental coverage. Here we show that [...]

A Source Clustering Approach for Efficient Inundation Modeling and Regional Scale PTHA

Amy Williamson, Donsub Rim, Loyce Adams, Randall J LeVeque, Diego Melgar, Frank Gonzalez

Published: 2020-08-14
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics

For coastal regions on the margin of a subduction zone, near-field megathrust earthquakes are the source of the most extreme tsunami hazards, and are important to handle properly as one aspect of any Probabilistic Tsunami Hazard Assessment (PTHA). Typically, great variability in inundation depth at any point is possible due to the extreme variation in extent and pattern of slip over the fault [...]

Isotropic and Azimuthally Anisotropic Rayleigh Wave Dispersion Across the Juan de Fuca and Gorda Plates and U.S. Cascadia from Earthquake Data and Ambient Noise Two- and Three-Station Interferometry

Shane Zhang, Hongda Wang, Mengyu Wu, Michael H. Ritzwoller

Published: 2020-08-09
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics, Physics

We use data from the Cascadia Initiative (CI) amphibious array and the USArray Transportable Array to construct and compare Rayleigh wave isotropic and azimuthally anisotropic phase speed maps across the Juan de Fuca and Gorda Plates extending onto the continental northwestern U.S. Results from both earthquakes (28--80~s) as well as ambient noise two- and three-station interferometry (10--40~s) [...]

Principal component analysis of seismic facies

Thilo Wrona, Indranil Pan, Rebecca E. Bell, Haakon Fossen, Robert Gawthorpe

Published: 2020-08-05
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics

Seismic facies analyses are fundamental to the study of sedimentary, tectonic and magmatic systems using seismic reflection data. These analyses generally assume that seismic facies are: (1) well defined, (2) distinct and (3) prevalent patterns in the data. Here, we examine these assumptions critically. First, we demonstrate how to extract the main seismic facies from conventional industry [...]

Seismic diffraction imaging to better characterise mass-transport complexes: examples from the Gulf of Cadiz, south west Iberian Margin

Jonathan Ford, Roger Urgeles, Angelo Camerlenghi, Eulàlia Gràcia

Published: 2020-08-04
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics

Mass-transport complexes are characterised by complex, laterally discontinuous internal structure, such as pressure ridges, local shear zones and intact translated blocks. Their internal structure is often poorly imaged by seismic reflection techniques, which are fundamentally limited in lateral resolution by the bandwidth of the seismic source. Diffraction imaging, instead, directly images [...]

Notes on Seismic Source Models in Elastostatics

Deyu Ming

Published: 2020-07-31
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics

Seismic source models in elastostatics lay the foundations for the popular earthquake deformation formula derived in Okada (1992), which forms key components for many studies in earthquake displacement simulations, earthquake source inversions and ground-motion predictions. However,despite of their importance, we found that the assumptions and proofs of some important theorems about the topic are [...]

Inferring Interseismic Coupling along the Lesser Antilles Arc: a Bayesian Approach

Elenora van Rijsingen, Eric Calais, Romain Jolivet, Jean Bernard de Chabalier, Jorge Jara, Steeve Symithe, Richard Robertson, Graham A. Ryan

Published: 2020-07-31
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics

The Lesser Antilles subduction zone is a challenging region when it comes to unraveling its seismogenic behavior. Over the last century, the subduction megathrust has been seismically quiet, with no large thrust event recorded, which raises the question whether this subduction zone is able to produce large interplate earthquakes or not. However, two historical earthquakes in the 19th century, a M [...]

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