Preprints
Filtering by Subject: Earth Sciences
Probability density functions for radial anisotropy: implications for the upper 1200 km of the mantle
Published: 2017-11-04
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
The presence of radial anisotropy in the upper mantle, transition zone and top of the lower mantle is investigated by applying a model space search technique to Rayleigh and Love wave phase velocity models. Probability density functions are obtained independently for S-wave anisotropy, P-wave anisotropy, intermediate parameter η, Vp, Vs and density anomalies. The likelihoods for P-wave and S-wave [...]
A Bayesian approach to assess the importance of crustal corrections in global anisotropic surface wave tomography
Published: 2017-11-03
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Several recent studies have demonstrated the importance of crustal corrections when inverting surface wave data to model lateral variations in mantle radial anisotropy. It has also been shown that the choice of the prior crustal model to correct the data can strongly influence the anisotropy model and potentially lead to different geodynamic interpretations. In comparing tomographic models of [...]
Surface wave array tomography in SE Tibet from ambient seismic noise and two-station analysis - II. Crustal and upper-mantle structure
Published: 2017-11-03
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
We determine the 3-D shear wave speed variations in the crust and upper mantle in the southeastern borderland of the Tibetan Plateau, SW China, with data from 25 temporary broad-band stations and one permanent station. Interstation Rayleigh wave (phase velocity) dispersion curves were obtained at periods from 10 to 50 s from empirical Greens function (EGF) derived from (ambient noise) [...]
The signal of mantle anisotropy in the coupling of normal modes
Published: 2017-11-03
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
We investigate whether the coupling of normal mode (NM) multiplets can help us constrain mantle anisotropy.We first derive explicit expressions of the generalized structure coefficients of coupled modes in terms of elastic coefficients, including the Love parameters describing radial anisotropy and the parameters describing azimuthal anisotropy (Jc, Js, Kc, Ks, Mc, Ms, Bc, Bs, Gc, Gs, Ec, Es, Hc, [...]
Probability density function for radial anisotropy from fundamental mode surface wave data and the Neighbourhood Algorithm,
Published: 2017-11-03
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
We applied Sambridges Neighbourhood Algorithm (NA) to degree-8 fundamental mode Love and Rayleigh wave phase velocity maps between 40 and 150 s to find models of radial anisotropy in the upper 220 km of the mantle. The NA is a powerful tool to explore a multidimensional model space and retrieve an ensemble of models from which statistical inferences (posterior probability density functions [...]
P and S tomography using normal-mode and surface waves data with a neighbourhood algorithm
Published: 2017-11-03
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Traditionally P- and S-wave tomography has been based on the inversion of data that are sensitive to the desired Earth structure, and model covariance is estimated from imperfect resolution and data error propagation. This analysis ignores the usually large null-spaces, and hence the significant non-uniqueness of the solution encountered in seismic tomography problems. Here we perform a model [...]
Locating Seismicity on the Arctic Plate Boundary Using Multiple-Event Techniques and Empirical Signal Processing
Published: 2017-11-03
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
The oceanic boundary separating the Eurasian and North American plates between 70 and 84 degrees North hosts large earthquakes which are well recorded teleseismically, and many more seismic events at far lower magnitudes that are well recorded only at regional distances. Existing seismic bulletins have considerable spread and bias resulting from limited station coverage and deficiencies in the [...]
The Applicability of Incoherent Array Processing to IMS Seismic Arrays
Published: 2017-11-02
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
The seismic arrays of the International Monitoring System (IMS) for the Comprehensive Nuclear-Test-Ban Treaty (CTBT) are highly diverse in size and configuration, with apertures ranging from under 1 km to over 60 km. Large and medium aperture arrays with large inter-site spacings complicate the detection and estimation of high-frequency phases lacking coherence between sensors. Pipeline detection [...]
The 11 October 2010 Novaya Zemlya Earthquake: Implications for Velocity Models and Regional Event Location
Published: 2017-11-02
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Characterizing the seismicity of Novaya Zemlya and the surrounding Arctic seas requires accurate event‐location estimates. Low‐magnitude events in this region are currently observed only by a small number of stations in the European Arctic, with a large azimuthal gap, making the accuracy of regional velocity models all the more important. Regional travel‐time calibration is difficult given the [...]
Formation of a cohesive floodplain in a dynamic experimental meandering river
Published: 2017-11-02
Subjects: Earth Sciences, Geomorphology, Physical Sciences and Mathematics
Field studies suggest that a cohesive floodplain is a necessary condition for meandering in contrast to braided rivers. However, it is only partly understood how the balance between floodplain construction by overbank deposition and removal by bank erosion and chutes leads to meandering. This is needed because only then does a dynamic equilibrium exist and channels maintain meandering with low [...]
Compositional Signatures in Acoustic Backscatter Over Vegetated and Unvegetated Mixed Sand-Gravel Riverbeds
Published: 2017-11-02
Subjects: Civil and Environmental Engineering, Earth Sciences, Engineering, Environmental Monitoring, Environmental Sciences, Geomorphology, Hydraulic Engineering, Physical Sciences and Mathematics, Statistical Models, Statistics and Probability
Multibeam acoustic backscatter has considerable utility for remote characterization of spatially heterogeneous bed sediment composition over vegetated and unvegetated riverbeds of mixed sand and gravel. However, the use of high-frequency, decimeter-resolution acoustic backscatter for sediment classification in shallow water is hampered by significant topographic contamination of the signal. In [...]
Accurate relative location estimates for the North Korean nuclear tests using empirical slowness corrections
Published: 2017-11-02
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Declared North Korean nuclear tests in 2006, 2009, 2013 and 2016 were observed seismically at regional and teleseismic distances. Waveform similarity allows the events to be located relatively with far greater accuracy than the absolute locations can be determined from seismic data alone. There is now significant redundancy in the data given the large number of regional and teleseismic stations [...]
Illuminating the seismicity pattern of the October 8, 2005, M = 7.6 Kashmir earthquake aftershocks
Published: 2017-11-02
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
The M=7.6 October 8, 2005, Kashmir earthquake generated thousands of aftershocks. Existing catalogs are coarse, omitting data from key stations and not correcting bias. We target arrivals on unexploited regional stations with optimized signal processing. A multiple event Bayesian relocation results in far more structured clusters of seismicity. All arrival data for the Bayesloc program is [...]
A systematic study of earthquake detectability using Sentinel-1 Interferometric Wide-Swath data
Published: 2017-11-01
Subjects: Earth Sciences, Geophysics and Seismology, Other Earth Sciences, Physical Sciences and Mathematics
The Sentinel-1 mission comprises two synthetic aperture radar satellites, each with a 12 day orbital repeat, orbiting 6 days apart within a narrow tube. The mission design promises the ability to respond quickly to earthquakes with InSAR, and to facilitate production of interferograms with good interferometric correlation globally. We report on our efforts to study global seismicity using [...]
Location and probability of shoal margin collapses in a sandy estuary
Published: 2017-11-01
Subjects: Earth Sciences, Geomorphology, Physical Sciences and Mathematics
Channel bank failure, collapses of shoal margins and beaches due to flow slides have been recorded in Dutch estuaries for the past 200 years but have hardly been recognized elsewhere. Current predictions lack forecasting capabilities, because they were validated and calibrated for historic data of cross-sections in specific systems, allowing local hindcast rather than location and probability [...]