Preprints
Filtering by Subject: Geophysics and Seismology
A physics-based approach of deep interseismic creep for viscoelastic strike-slip earthquake cycle models
Published: 2019-04-24
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Most geodetic inversions of surface deformation rates consider the depth distribution of interseismic fault slip-rate to be time invariant. However, some numerical simulations show down-dip penetration of dynamic rupture into regions with velocity-strengthening friction, with subsequent up-dip propagation of the locked-to-creeping transition. Recently, Bruhat & Segall (2017) developed a new [...]
A Scalable Algorithm for Cross-correlations of Compressed Ambient Seismic Noise
Published: 2019-04-17
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Companies and academic geophysicists are increasingly collecting continuous seismic data on denser arrays, and are looking to a variety of lossy compression methods to store and quickly access this data. Some researchers turn to ambient noise interferometry for low-cost near-surface imaging to avoid to cost and permitting required for active source experiments, but the computation can be very [...]
Finite frequency inversion of cross-correlation amplitudes for ambient noise source directivity estimation
Published: 2019-04-15
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
We present a new method for determining the azimuthal variation of ambient seismic noise sources, that combines the computational speed and simplicity of traditional approaches with the rigour of waveform-inversion-based approaches to noise-source estimation. This method is based on a previously developed theoretical framework of sensitivity kernels for cross-correlation amplitudes. It performs a [...]
Efficient 3D large-scale forward-modeling and inversion of gravitational fields in spherical coordinates with application to lunar mascons
Published: 2019-04-11
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
An efficient forward modeling algorithm for calculation of gravitational fields in spherical coordinates is developed for 3D large‐scale gravity inversion problems. 3D Gauss‐Legendre quadrature (GLQ) is used to calculate the gravitational fields of mass distributions discretized into tesseroids. Equivalence relations in the kernel matrix of the forward‐modeling are exploited to decrease storage [...]
Characterising strong force networks produced during granular shear using percolation methods: Revealing the bridge between local grain scale processes and macroscopic sliding
Published: 2019-04-08
Subjects: Earth Sciences, Geology, Geophysics and Seismology, Other Earth Sciences, Physical Sciences and Mathematics, Physics, Tectonics and Structure
Faults, landslides and subglacial till often contain accumulations of granular debris. Their macroscopic motion is at least to some extent determined by the processes operating in this sheared granular material. A valid question in these environments is how the local behaviour at the individual granular contacts actually sums up to influence macroscopic sliding. Laboratory experiments and [...]
Fast non-linear gravity inversion in spherical coordinates with application to the South American Moho
Published: 2019-04-06
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Estimating the relief of the Moho from gravity data is a computationally intensive non-linear inverse problem. What is more, the modeling must take the Earths curvature into account when the study area is of regional scale or greater. We present a regularized non-linear gravity inversion method that has a low computational footprint and employs a spherical Earth approximation. To achieve this, we [...]
Comment on “Earthquake-induced prompt gravity signals identified in dense array data in Japan” by Kimura et al.
Published: 2019-04-05
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
A recent work by Kimura et al. (2019) (hereafter referred to as K19) claims to provide the first observational constraints on the prompt elastogravity signals (PEGS) induced by an earthquake. To make their claim, the authors argue that the observations shown in Vallée et al. (2017) (hereafter referred to as V17) are spurious and their modeling inaccurate. Here we show that K19’s claim is invalid [...]
Earthquake cycle modeling of the Cascadia subduction zone
Published: 2019-04-05
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
The Cascadia subduction zone hosts great $\mathrm{M}_\mathrm{W} > 8.5$ earthquakes, but studying these events is hindered by our short observational record. Earthquake cycle simulation provides an alternative window into the behavior of the subduction zone. Here, we present simulations over 3,800 years, 14 ruptures and hundreds of slow slip events on a high-fidelity geometric representation of [...]
Ridge Subduction and Afterslip Control Aftershock Distribution of the 2016 Mw 7.8 Ecuador Earthquake
Published: 2019-04-02
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
We characterise the aftershock sequence following the 2016 Mw=7.8 Pedernales earthquake. More than 10,000 events were detected and located, with magnitudes up to 6.9. Most of the aftershock seismicity results from interplate thrust faulting, but we also observe a few normal and strike-slip mechanisms. Seismicity extends for more than 300 km along strike, and is constrained between the trench and [...]
Boundary element methods for earthquake modeling with realistic 3D geometries
Published: 2019-04-01
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Boundary element methods have become a foundational tool in earthquake science for the modeling of earthquake cycle kinematics. Despite their wide use and convenience typical rectangular and triangular constant slip dislocation methods produce stress singularities at the edges of every element rendering these models physically unrealistic. As we demonstrate, in an earthquake cycle simulation [...]
Observation and explanation of spurious seismic signals emerging in teleseismic noise correlations
Published: 2019-04-01
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Deep body waves have been reconstructed from seismic noise correlations in recent studies. The authors note their great potential for deep-Earth imaging. In addition to the expected physical seismic phases, some spurious arrivals having no correspondence in earthquake seismograms are observed from the noise correlations. The origins of the noise-derived body waves have not been well understood. [...]
Role of strain-dependent weakening memory on the style of mantle convection and plate boundary stability
Published: 2019-03-28
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
How plate tectonic surface motions relate to the convecting mantle remains one of the major problems in geosciences. In particular, the cause and consequence of strain localization at plate boundaries remains debated, even though strain memory, i.e. the ability to preserve and reactivate tectonic inheritance over geological time, appears to be a critical feature in plate tectonics. Here, we [...]
Seismic expression of shear zones: insights from 2-D convolution seismic modelling
Published: 2019-03-28
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
During extension, compression or strike-slip motion, shear zones accommodate large amountsof strain in the crust. Our understanding of these processes critically depends on our ability torecognize shear zones in the subsurface. The exact signature of shear zones in seismic reflectiondata is however not well understood. To advance our understanding, we simulate how threeoutcrop examples of [...]
Outer Trench Slope Flexure and Faulting at Pacific Basin Subduction Zones
Published: 2019-03-22
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Flexure and fracturing of the seafloor on the outer trench wall of subduction zones reflects bending of the lithosphere beyond its elastic limit. To investigate these inelastic processes, we have developed a full non-linear inversion approach for estimating the bending moment, curvature, and outer trench wall fracturing using shipboard bathymetry and satellite altimetry derived gravity data as [...]
Numerical wave propagation through ice-covered regions
Published: 2019-03-19
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
In recent years, seismic station coverage in polar regions has been increasing steadily, providing new insight into the deep structure and dynamics of these remote parts of the globe. Numerical seismic wave propagation through polar regions is complicated by the presence of ice sheets. At periods relevant for regional-scale waveform tomography, the ice acts as a thin layer that, for an exact [...]