Preprints
Filtering by Subject: Geophysics and Seismology
A Stability Analysis of Neural Networks and Its Application to Tsunami Early Warning
Published: 2023-05-14
Subjects: Geophysics and Seismology, Hydrology, Numerical Analysis and Computation
Neural networks (NNs) enable precise modeling of complicated geophysical phenomena but are sensitive to small input changes. In this work, we present a new method for analyzing this instability in NNs. We focus our analysis on adversarial examples, test-time inputs with carefully-crafted human-imperceptible perturbations that expose the worst-case instability in a model's predictions. Our [...]
Slip-stuck kinematics of fault surfaces in laboratory experiments: implications for heterogeneous slip distributions during earthquake events
Published: 2023-05-05
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics, Tectonics and Structure
Combining field observations with analogue laboratory experiments, this study aims to use surface-roughness characteristics as an indicator of the heterogeneous slip partitioning along shear surfaces. We investigated the roughness of shear surfaces in sheared quartzite of the Singhbhum Shear Zone, eastern India, and identified two distinct kinematic domains: slip zone and stuck zone, marked by [...]
Lateral Heterogeneity Analysis Using Multiwell ZVSP Unsupervised Machine Learning Classification
Published: 2023-05-03
Subjects: Geophysics and Seismology
In 3D and 2D surface seismic interpretation, seismic waveform shapes and attributes can identify facies and reservoir parameters laterally with more details than traditional amplitude mapping. Herein, a method on 1D zero offset VSP (ZVSP) data was adapted, giving a unique perspective of lateral heterogeneity analysis using VSP seismic waveform shapes and attributes. The downgoing wavefield of VSP [...]
Active Learning with Deep Autoencoders for Seismic Facies Interpretation
Published: 2023-04-26
Subjects: Geophysics and Seismology
Machine learning-assisted seismic interpretation tasks require large quantities of labeled data annotated by expert interpreters, which is a costly and time-consuming process. Where existing works to minimize dependence on labeled data assume the data annotation process to already be completed, active learning---a field of machine learning---works by selecting the most important training samples [...]
A comparative study of transfer learning methodologies and causality for seismic inversion with temporal convolutional networks
Published: 2023-04-25
Subjects: Geophysics and Seismology
Machine learning-based seismic inversion methods suffer from high labeled data requirement in the absence of which they may fail to generalize. Recent data-driven inversion methodologies based on temporal convolutional networks use 2-D sequence models and transfer learning to unburden the algorithm from high training data requirements. Such methods are restricted in that they only model seismic [...]
In-situ frictional behavior of subducting sediment in the shallow Nankai Trough
Published: 2023-04-22
Subjects: Geology, Geophysics and Seismology, Sedimentology, Tectonics and Structure
The transition from smectite to illite at around the depth with temperature of ~150 °C has long been hypothesized as one of controlling factors of the updip limit depth of the seismogenic zone of subduction zones. Although illite has a higher friction coefficient than smectite, previous friction experiments have little reported that the smectite-illite transition accompanies the transition from [...]
Locating tectonic tremors with uncertainty estimates: Time- and amplitude-difference optimization, wave propagation-based quality control, and Bayesian inversion
Published: 2023-04-11
Subjects: Geophysics and Seismology
The accurate location of tectonic tremors helps improve understanding of their underlying physical processes. However, current location methods often do not statistically evaluate uncertainties to a satisfactory degree and do not account for potential biases due to subsurface structures not included in the model. To address these issues, we propose a novel three-step process for locating tectonic [...]
Consolidated Geothermal Database UK (CGD-UK): A digital open license database for temperature and thermal conductivity in the UK.
Published: 2023-04-08
Subjects: Earth Sciences, Geology, Geophysics and Seismology, Natural Resource Economics, Oil, Gas, and Energy, Other Earth Sciences, Tectonics and Structure
Variations in subsurface heat flow within the upper crust control the distribution of geothermal resources. Development of a robust understanding of these variations requires reliable measurements of temperature and thermal conductivity. To date, measurements of temperature and conductivity onshore the UK have been unavailable in an accessible, clearly structured digital format. Here, we rectify [...]
Examining the power supplied to Earth's dynamo by magnesium precipitation and radiogenic heat production
Published: 2023-04-05
Subjects: Earth Sciences, Geophysics and Seismology, Mineral Physics, Physical Sciences and Mathematics, Planetary Sciences
We examine magnesium and potassium solubility in liquid Fe mixtures, representative of Earth’s core composition, in equilibrium with liquid silicate mixtures representative of an early magma ocean. Our study is based on the calculation of the chemical potentials of MgO and K2O in both phases, using density functional theory. For MgO, we also study stability against precipitation of the solid [...]
Compressibility of ferropericlase at high-temperature: evidence for the iron spin crossover in seismic tomography
Published: 2023-04-05
Subjects: Earth Sciences, Geophysics and Seismology, Mineral Physics
The iron spin crossover in ferropericlase, the second most abundant mineral in Earth’s lower mantle, causes changes in a range of physical properties, including seismic wave velocities. Understanding the effect of temperature on the spin crossover is essential to detect its signature in seismic observations and constrain its occurrence in the mantle. Here, we report the first experimental results [...]
The Spectrum of Fault Slip in Elastoplastic Fault Zones
Published: 2023-03-31
Subjects: Civil and Environmental Engineering, Geophysics and Seismology, Mechanical Engineering
Natural faults are typically surrounded by damage zones that exhibit inelastic material response. This study investigates the role of fault zone strength in modulating the spectrum of fault slip across different spatio-temporal scales. We carry out long-term simulations of seismic and aseismic slip for an elastoplastic spring slider model with rate-and-state friction as well as a continuum model [...]
Bayesian estimation of nonlinear centroid moment tensors using multiple seismic data sets
Published: 2023-03-27
Subjects: Earth Sciences, Geophysics and Seismology
Centroid moment tensor (CMT) parameters of earthquakes are routinely estimated to gain information on structures and regional tectonics. However, for small earthquakes (M<4), it is still challenging to determine CMTs due to the lack of high-quality waveform data. In this study, we propose to improve solutions for small earthquakes by incorporating multiple seismic data types in Bayesian joint [...]
Linking the core heat content to Earth's accretion history
Published: 2023-03-26
Subjects: Earth Sciences, Geochemistry, Geophysics and Seismology, Planetary Geochemistry, Planetary Geophysics and Seismology
In this study we use a parameterized model of differentiation in a magma ocean setting, in which the magma ocean depth evolves during accretion, to predict the composition of the primordial core. We couple this chemical model to a thermal evolution model of the accreting metal to estimate the Earth's core heat content at the end of its formation. We find geochemically consistent models. All these [...]
Can homogeneous nucleation resolve the inner core nucleation paradox?
Published: 2023-03-24
Subjects: Condensed Matter Physics, Earth Sciences, Geophysics and Seismology, Mineral Physics, Planetary Geophysics and Seismology, Planetary Mineral Physics
Continuous isolated noise sources induce repeating waves in the coda of ambient noise correlations
Published: 2023-03-17
Subjects: Geophysics and Seismology, Other Physics
Continuous excitation of isolated noise sources leads to repeating wave arrivals in cross correlations of ambient seismic noise, including throughout their coda. These waves propagate from the isolated sources. We observe this effect on correlation wavefields computed from two years of field data recorded at the Gräfenberg array in Germany and two master stations in Europe. Beamforming the [...]