Preprints
Filtering by Subject: Geophysics and Seismology
Seismic anisotropy changes across upper mantle phase transitions
Published: 2017-11-03
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
The mantle transition zone is believed to play an important role in the thermochemical evolution of our planet and in its deep water cycle. Constraining mantle flow at these depths can help elucidate its nature and better understand mantle dynamics and the history of plate tectonics. Seismic anisotropy, i.e., the directional dependence of seismic wave velocity, provides us with the most direct [...]
Depth constraints on azimuthal anisotropy in the Great Basin from Rayleigh-wave phase velocity maps
Published: 2017-11-03
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
We present fundamental-mode Rayleigh-wave azimuthally anisotropic phase velocity maps obtained for the Great Basin region at periods between 16 s and 102 s. These maps offer the first depth constraints on the origin of the semi-circular shear-wave splitting pattern observed in central Nevada, around a weak azimuthal anisotropy zone. A variety of explanations have been proposed to explain this [...]
Probability density functions for radial anisotropy: implications for the upper 1200 km of the mantle
Published: 2017-11-03
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 [...]
Accurate relative location estimates for the North Korean nuclear tests using empirical slowness corrections
Published: 2017-11-01
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: 2017-11-01
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 [...]
Geological applications of digital terrain analysis
Published: 2017-11-01
Subjects: Earth Sciences, Geochemistry, Geographic Information Sciences, Geography, Geology, Geomorphology, Geophysics and Seismology, Physical Sciences and Mathematics, Remote Sensing, Social and Behavioral Sciences, Spatial Science, Tectonics and Structure, Volcanology
Editorial to the IJGIS Special Issue on "Geological applications of digital terrain analysis". In this volume, the modern advances in the field of geological terrain analysis are presented, while emphasis is given to the quantitative analysis of modern datasets.