Preprints
Filtering by Subject: Geophysics and Seismology
A geodynamic and mineral physics model of a solid-state ultralow-velocity zone
Published: 2019-09-06
Subjects: Earth Sciences, Geophysics and Seismology, Mineral Physics, Physical Sciences and Mathematics
Recent results (Wicks et al., 2010) suggest that a mixture of iron-enriched (Mg,Fe)O and ambient mantle is consistent with wavespeed reductions and density increases inferred for ultralow-velocity zones (ULVZs). We explore this hypothesis by simulating convection to deduce the stability and morphology of such chemically-distinct structures. The buoyancy number, or chemical density anomaly, [...]
Enhanced Convection and Fast Plumes in the Lower Mantle Induced by the Spin Transition in Ferropericlase
Published: 2019-09-06
Subjects: Earth Sciences, Geophysics and Seismology, Mineral Physics, Physical Sciences and Mathematics
Using a numerical model we explore the consequences of the intrinsic density change (Δρ/ρ ≈ 2–4%) caused by the Fe2+ spin transition in ferropericlase on the style and vigor of mantle convection. The effective Clapeyron slope of the transition from high to low spin is strongly positive in pressure‐temperature space and broadens with high temperature. This introduces a net spin‐state driving [...]
Frictional heterogeneities can promote disordered slip evolution on faults
Published: 2019-09-04
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
We consider that a slip instability nucleates an earthquake. Past studies found blow-up solutions for diverging slip velocities. Prior stability analyses, considering heterogeneous frictional properties revealed that stable blow-up solutions can predictably dictate earthquake-nucleating instabilities. In this prior analysis, the focus remained mainly on the attraction to stable blow-up [...]
Cohesive-Zone Effects in Hydraulic Fracture Propagation
Published: 2019-08-23
Subjects: Earth Sciences, Engineering, Engineering Mechanics, Engineering Science and Materials, Environmental Sciences, Geophysics and Seismology, Oil, Gas, and Energy, Physical Sciences and Mathematics
Hydraulic fracture presents an interesting case of crack elasticity and fracture propagation non-linearly coupled to fluid flow. Hydraulic fracture (HF) is often modeled using the Linear Elastic Fracture Mechan- ics (LEFM), which assumes that the damaged zone associated with the rock breakage near the advancing fracture front is small compared to the lengthscales of other physical processes [...]
Accelerating Numerical Wave Propagation by Wavefield Adapted Meshes, Part II: Full-Waveform Inversion
Published: 2019-08-23
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
We present a novel full-waveform inversion approach which can reduce the computational cost by up to an order of magnitude compared to conventional approaches, provided that variations in medium properties are sufficiently smooth. Our method is based on the usage of wavefield-adapted meshes which accelerate the forward and adjoint wavefield simulations. By adapting the mesh to the expected [...]
The anelasticity of zinc and its implications for the Earth’s inner core
Published: 2019-08-21
Subjects: Earth Sciences, Geophysics and Seismology, Mineral Physics, Physical Sciences and Mathematics
The Earth’s inner core exhibits significant anisotropy in both seismic velocity and attenuation as well as hemispherical and depth variations. These observations point to an inner core that is both complex and dynamic. However, interpretation of these observations without knowledge of the attenuation processes active in the inner-core is difficult. To address this we have used zinc, as a [...]
Review paper: The 2nd June 1979 Mw 6.1 Cadoux surface rupturing earthquake, Australia
Published: 2019-08-18
Subjects: Earth Sciences, Geology, Geophysics and Seismology, Physical Sciences and Mathematics, Tectonics and Structure
The 2nd June 1979 moment magnitude (Mw) 6.1 Cadoux earthquake caused a complex, multi-fault surface rupture consisting of six mapped scarps: (from south to north) the 8 km long west dipping Robb scarp, 3 km long south dipping Cumming scarp, the Lone Tree, Carter and Tank scarps (which together define an east-dipping arcuate rupture) and the 2.5 km long southwest-dipping Kalajzic scarp. Surface [...]
Review paper: The 10th March 1970 Mw 5.0 Calingiri surface rupturing earthquake, Australia
Published: 2019-08-18
Subjects: Earth Sciences, Geology, Geophysics and Seismology, Physical Sciences and Mathematics, Tectonics and Structure
The 10th March 1970 moment magnitude (Mw) 5.0 Calingiri earthquake surface rupture is 3.3 km long with a maximum vertical displacement of 0.4 m. The fault as defined by surface measurements is a shallow-dipping reverse fault (~ 20° east) with a probable shallow hypocentre (< 1 km). This is consistent with published hypocentral depths, though large uncertainties exist within the seismological [...]
Review paper: The 30th March 1986 Mw 5.7 Marryat Creek surface rupturing earthquake, Australia
Published: 2019-08-18
Subjects: Earth Sciences, Geology, Geophysics and Seismology, Physical Sciences and Mathematics, Tectonics and Structure
The 30th March 1986 Mw 5.7 Marryat Creek earthquake produced a highly arcuate 13 km long surface rupture with maximum vertical displacement of 0.9 m. Sinistral displacement on the NE-SW limb, dextral displacement on the NNE-SSW limb, and maximum vertical displacement in the central apex of rupture supports SW over NE movement of a hanging-wall block. Epicentre locations are poorly constrained and [...]
Review paper: The 14th October 1968 Mw 6.6 Meckering surface rupturing earthquake, Australia
Published: 2019-08-18
Subjects: Earth Sciences, Geology, Geophysics and Seismology, Physical Sciences and Mathematics, Tectonics and Structure
The 14th October 1968 MW 6.6 Meckering earthquake surface rupture is comprised of a main 37 km long concave Meckering scarp (with a 1.5 km wide dextral step-over along the Burges en-echelon rupture complex) and a minor 9 km long rupture on the Meckering scarp foot-wall (the Splinter scarp, also with a 1.5 km dextral step-over). We recommend a total surface rupture length of 44.4 km for [...]
Review paper: The 20th May 2016 Mw 6.1 Petermann surface rupturing earthquake, Australia
Published: 2019-08-18
Subjects: Earth Sciences, Geology, Geophysics and Seismology, Physical Sciences and Mathematics, Tectonics and Structure
The 20th May 2016 Mw 6.1 Petermann earthquake produced a 21 km long surface rupture with a maximum vertical offset of 0.9 m. Geological and geophysical data provide strong evidence that rupture occurred along a mylonite foliation plane with an orientation defined by deformation from the nearby Woodroffe Thrust, a major Neoproterozoic terrane suture. The most geologically and seismologically [...]
Review paper: The 23rd March 2012 Mw 5.2 Pukatja surface rupturing earthquake, Australia
Published: 2019-08-18
Subjects: Earth Sciences, Geology, Geophysics and Seismology, Physical Sciences and Mathematics, Tectonics and Structure
The 23rd March 2012 Mw 5.2 Pukatja earthquake produced an arcuate surface rupture 1.6 km long with a maximum vertical offset of 0.48 m. We reclassify its length to 1 km based on application of orientation and kinematic criteria used previously to measure other historic Australian surface ruptures. Epicentres are poorly constrained and inaccurate, located up to 17 km from the surface rupture with [...]
Real-Time High-Rate GNSS Displacements: Performance Demonstration During the 2019 Ridgecrest, CA Earthquakes
Published: 2019-08-17
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Traditional real-time seismology has relied on inertial sensors to characterize ground motions and earthquake sources, particularly for hazards applications such as warning systems. In the past decade, a revolution in high-rate, real-time Global Navigation Satellite System (GNSS) displacement have provided a new source of data to augment traditional measurement devices. The Ridgecrest, California [...]
Empirical Green’s Function Retrieval using Cross-correlation of Ambient Noise Correlations (C2)
Published: 2019-08-13
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Empirical Greens function (EGF) retrieval commonly relies on cross-correlating the long-term ambient seismic wavefield that is simultaneously recorded at multiple stations. Recent studies have demonstrated observationally that cross-correlating the coda of ambient noise cross-correlation functions (C3) enables reconstruction of the EGFs, regardless of the operating time of the stations. In this [...]
Small baseline InSAR time series analysis: Unwrapping error correction and noise reduction
Published: 2019-08-07
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
We present a review of small baseline interferometric synthetic aperture radar (InSAR) time series analysis with a new processing workflow and software implemented in Python, named MintPy (https://github.com/insarlab/MintPy). The time series analysis is formulated as a weighted least squares inversion. The inversion is unbiased for a fully connected network of interferograms without multiple [...]