Preprints
Filtering by Subject: Geophysics and Seismology
Urban Near-surface Seismic Monitoring using Distributed Acoustic Sensing
Published: 2019-11-26
Subjects: Civil and Environmental Engineering, Civil Engineering, Earth Sciences, Engineering, Geophysics and Seismology, Physical Sciences and Mathematics
Urban subsurface monitoring requires high temporal-spatial resolution, low maintenance cost, and minimal intrusion to nearby life. Distributed acoustic sensing (DAS), in contrast to conventional station-based sensing technology, has the potential to provide a passive seismic solution to urban monitoring requirements. Based on data recorded by the Stanford Fiber Optic Seismic Observatory, we [...]
A grid for multidimensional and multivariate spatial representation and data processing.
Published: 2019-11-22
Subjects: Computer Sciences, Earth Sciences, Geophysics and Seismology, Numerical Analysis and Scientific Computing, Physical Sciences and Mathematics
Researchers use 2D and 3D spatial models of multivariate data of differing resolutions and formats. It can be challenging to work with multiple datasets, and it is time consuming to set up a robust, performant, grid to handle such spatial models. We share a Python module that provides a framework for containing multidi- mensional data and functionality to work with those data. The module provides [...]
Centroid moment tensor inversions of offshore earthquakes using a three-dimensional velocity structure model: Slip distributions on the plate boundary along the Nankai Trough
Published: 2019-11-20
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics, Planetary Sciences
Due to complex three-dimensional (3D) heterogeneous structures, conventional one-dimensional (1D) analysis techniques using onshore seismograms can yield incorrect estimation of earthquake source parameters, especially dip angles and centroid depths of offshore earthquakes. Combining long-term onshore seismic observations and numerical simulations of seismic wave propagation in a 3D model, we [...]
Logarithmic growth of dikes from a depressurizing magma chamber
Published: 2019-11-13
Subjects: Earth Sciences, Geology, Geophysics and Seismology, Physical Sciences and Mathematics, Volcanology
Dike propagation is an intrinsically multiphase problem, where deformation and fluid flow are intricately coupled in a fracture process. Here we perform the first fully-coupled simulations of dike propagation in two dimensions, accounting for depressurization of a circular magma chamber, dynamic fluid flow, fracture formation, and elastic deformation. Despite the complexity of the governing [...]
Directionality of ambient noise in the Mississippi embayment
Published: 2019-11-12
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Cross-correlations of ambient seismic noise from 277 broadband stations within the Mississippi embayment (ME) with at least 1-month of recording time between 1990 and 2018 are used to estimate source locations of primary and secondary microseisms. We investigate source locations by analyzing the azimuthal distribution of the signal-to- noise ratio (SNR) and positive/negative amplitude [...]
Ancient subducted oceans controlling the positioning of deep mantle plumes
Published: 2019-11-08
Subjects: Earth Sciences, Geochemistry, Geophysics and Seismology, Physical Sciences and Mathematics, Tectonics and Structure
Seismic imaging of the Earths interior reveals plumes originating from relatively hot regions of the lower mantle, surrounded by cooler material thought to be remnants of ancient subducted oceans. Based largely on geophysical data, two opposing hypotheses dominate the discussion on dynamics at the base of mantle: the large hot anomalies are thermo-chemical in nature; or, alternatively, they are [...]
On the statistical significance of foreshock sequences in Southern California
Published: 2019-11-05
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Earthquake foreshocks may provide information that is critical to short-term earthquake forecasting. However, foreshocks are far from ubiquitously observed, which makes the interpretation of ongoing seismic sequences problematic. Based on a statistical analysis, Trugman & Ross (2019) suggested that as much as 72% of all mainshocks in Southern California is preceded by foreshock sequences. In [...]
The variation and visualisation of elastic anisotropy in rock-forming minerals
Published: 2019-10-31
Subjects: Earth Sciences, Geochemistry, Geology, Geophysics and Seismology, Mineral Physics, Physical Sciences and Mathematics, Tectonics and Structure
All minerals behave elastically, a rheological property that controls their ability to support stress, strain and pressure, the nature of acoustic wave propagation and influences subsequent plastic (i.e. permanent, non-reversible) deformation. All minerals are intrinsically anisotropic in their elastic properties – that is, they have directional variations that are related to the configuration [...]
The Earthquake Arrest Zone
Published: 2019-10-31
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Earthquake ruptures are generally considered to be cracks that propagate as fracture or frictional slip on preexisting faults. Crack models have been used to describe the spatial distribution of fault offset and the associated static stress changes along a fault, and have implications for friction evolution and the underlying physics of rupture processes. However, field measurements that could [...]
Deep Unsupervised 4D Seismic 3D Time-Shift Estimation with Convolutional Neural Networks
Published: 2019-10-30
Subjects: Applied Statistics, Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics, Statistics and Probability
We present a novel 3D warping technique for the estimation of 4D seismic time-shift. This unsupervised method provides a diffeomorphic 3D time shift field that includes uncertainties, therefore it does not need prior time-shift data to be trained. This results in a widely applicable method in time-lapse seismic data analysis. We explore the generalization of the method to unseen data both in the [...]
Did deglaciation of the Greenland ice sheet cause a large earthquake and tsunami around 10,600 years ago?
Published: 2019-10-30
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Due to their large mass, ice sheets induce significant stresses in the Earth’s crust. Stress release during deglaciation can trigger large-magnitude earthquakes, as indicated by surface faults in northern Europe. Although glacially-induced stresses have been analyzed in northern Europe, they have not yet been analyzed for Greenland. We know that the Greenland Ice Sheet experienced a large melting [...]
Crustal structure of Sri Lanka derived from joint inversion of surface wave dispersion and receiver functions using a Bayesian approach
Published: 2019-10-30
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
We study the crustal structure of Sri Lanka by analyzing data from a temporary seismic network deployed in 2016--2017 to shed light on the amalgamation process from a geophysical perspective. Rayleigh wave phase dispersion curves from ambient noise cross-correlation and receiver functions were jointly inverted using a transdimensional Bayesian approach. The Moho depths in Sri Lanka range between [...]
Another look at the treatment of data uncertainty in Markov chain Monte Carlo inversion and other probabilistic methods
Published: 2019-10-25
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
In probabilistic Bayesian inversions, data uncertainty is a crucial parameter for quantifying the uncertainties and correlations of the resulting model parameters or, in transdimensional approaches, even the complexity of the model. However, in many geophysical inference problems it is poorly known. Therefore, it is common practice to allow the data uncertainty itself to be a parameter to be [...]
Intermittent fluid connectivity during two-phase flow in a heterogeneous carbonate rock
Published: 2019-10-24
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Subsurface fluid flow is ubiquitous in nature, and understanding the interaction of multiple fluids as they flow within a porous medium is central to many geological, environmental, and industrial processes. It is assumed that the flow pathways of each phase are invariant when modelling subsurface flow using Darcys law extended to multiphase flow; a condition that is assumed to be valid during [...]
Complex Rupture of an Immature Fault Zone: A Simultaneous Kinematic Model of the 2019 Ridgecrest, CA Earthquakes
Published: 2019-10-24
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
The July 4, 2019 Mw6.4 and subsequent July 6, 2019 Mw7.1 Ridgecrest Sequence earthquakes ruptured orthogonal fault planes in the Little Lake Fault Zone, a low slip rate (1 mm/yr) dextral fault zone in the area linking the Eastern California Shear Zone and Walker Lane. This region accommodates nearly one fourth of plate boundary motion and has been proposed to be an incipient transform fault [...]