Random noise attenuation via the randomized canonical polyadic decomposition     

Wenlei Gao  Mauricio D. Sacchi 《Geophysical Prospecting》2020,68(3):872-891

Tensor algebra provides a robust framework for multi-dimensional seismic data processing. A low-rank tensor can represent a noise-free seismic data volume. Additive random noise will increase the rank of the tensor. Hence, tensor rank-reduction techniques can be used to filter random noise. Our filtering method adopts the Candecomp/Parafac decomposition to approximates a N-dimensional seismic data volume via the superposition of rank-one tensors. Similar to the singular value decomposition for matrices, a low-rank Candecomp/Parafac decomposition can capture the signal and exclude random noise in situations where a low-rank tensor can represent the ideal noise-free seismic volume. The alternating least squares method is adopted to compute the Candecomp/Parafac decomposition with a provided target rank. This method involves solving a series of highly over-determined linear least-squares subproblems. To improve the efficiency of the alternating least squares algorithm, we uniformly randomly sample equations of the linear least-squares subproblems to reduce the size of the problem significantly. The computational overhead is further reduced by avoiding unfolding and folding large dense tensors. We investigate the applicability of the randomized Candecomp/Parafac decomposition for incoherent noise attenuation via experiments conducted on a synthetic dataset and field data seismic volumes. We also compare the proposed algorithm (randomized Candecomp/Parafac decomposition) against multi-dimensional singular spectrum analysis and classical prediction filtering. We conclude the proposed approach can achieve slightly better denoising performance in terms of signal-to-noise ratio enhancement than traditional methods, but with a less computational cost.  相似文献   

GHR1 Zircon – A New Eocene Natural Reference Material for Microbeam U‐Pb Geochronology and Hf Isotopic Analysis of Zircon     

Michael P. Eddy  Mauricio Ibaez‐Mejia  Seth D. Burgess  Matthew A. Coble  Umberto G. Cordani  Joel DesOrmeau  George E. Gehrels  Xianhua Li  Scott MacLennan  Mark Pecha  Kei Sato  Blair Schoene  Victor A. Valencia  Jeffrey D. Vervoort  Tiantian Wang 《Geostandards and Geoanalytical Research》2019,43(1):113-132

We present multitechnique U‐Pb geochronology and Hf isotopic data from zircon separated from rapakivi biotite granite within the Eocene Golden Horn batholith in Washington, USA. A weighted mean of twenty‐five Th‐corrected ²⁰⁶Pb/²³⁸U zircon dates produced at two independent laboratories using chemical abrasion‐isotope dilution‐thermal ionisation mass spectrometry (CA‐ID‐TIMS) is 48.106 ± 0.023 Ma (2s analytical including tracer uncertainties, MSWD = 1.53) and is our recommended date for GHR1 zircon. Microbeam ²⁰⁶Pb/²³⁸U dates from laser ablation‐inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS) and secondary ion mass spectrometry (SIMS) laboratories are reproducible and in agreement with the CA‐ID‐TIMS date to within < 1.5%. Solution multi‐collector ICP‐MS (MC‐ICP‐MS) measurements of Hf isotopes from chemically purified aliquots of GHR1 yield a mean ¹⁷⁶Hf/¹⁷⁷Hf of 0.283050 ± 17 (2s, n = 10), corresponding to a εHf₀ of +9.3. Hafnium isotopic measurements from two LA‐ICP‐MS laboratories are in agreement with the solution MC‐ICP‐MS value. The reproducibility of ²⁰⁶Pb/²³⁸U and ¹⁷⁶Hf/¹⁷⁷Hf ratios from GHR1 zircon across a variety of measurement techniques demonstrates their homogeneity in most grains. Additionally, the effectively limitless reserves of GHR1 material from an accessible exposure suggest that GHR1 can provide a useful reference material for U‐Pb geochronology of Cenozoic zircon and Hf isotopic measurements of zircon with radiogenic ¹⁷⁶Hf/¹⁷⁷Hf.  相似文献   

Acceleration strategies for elastic full waveform inversion workflows in 2D and 3D     

Jean Kormann  Juan E. Rodríguez  Miguel Ferrer  Albert Farrés  Natalia Gutiérrez  Josep de la Puente  Mauricio Hanzich  José M. Cela 《Computational Geosciences》2017,21(1):31-45

Full waveform inversion (FWI) is one of the most challenging procedures to obtain quantitative information of the subsurface. For elastic inversions, when both compressional and shear velocities have to be inverted, the algorithmic issue becomes also a computational challenge due to the high cost related to modelling elastic rather than acoustic waves. This shortcoming has been moderately mitigated by using high-performance computing to accelerate 3D elastic FWI kernels. Nevertheless, there is room in the FWI workflows for obtaining large speedups at the cost of proper grid pre-processing and data decimation techniques. In the present work, we show how by making full use of frequency-adapted grids, composite shot lists and a novel dynamic offset control strategy, we can reduce by several orders of magnitude the compute time while improving the convergence of the method in the studied cases, regardless of the forward and adjoint compute kernels used.  相似文献   

Monitoring the 2004 andesitic block-lava extrusion at Volcán de Colima,México from seismic activity and SO₂ emission     

Vyacheslav M. Zobin  Nicholas R. Varley  Miguel González  Justo Orozco  Gabriel A. Reyes  Carlos Navarro  Mauricio Bretón 《Journal of Volcanology and Geothermal Research》2008

The 2004 andesitic block-lava extrusion at Volcán de Colima, México was accompanied and followed by numerous seismic signals associated with rockfalls, pyroclastic flows and explosive events. We analyze temporal variations in the number of rockfalls and explosions, the seismic signal duration of rockfalls and the energy of the explosion and compare this with both the rate of magma discharge and SO₂ emission. Characteristics of seismic signals and SO₂ emission are compared with those observed during the 1998–1999 Volcán de Colima block-lava extrusion. For both eruptions, the explosive activity was low during the lava extrusion and increased after its termination. The variation in the daily number and the total duration of rockfall seismic signals gives a good reflection of the development of the lava emission process. An increase in magmatic degassing (SO₂ flux) was observed some days before the onset of lava extrusion. The degassing strongly decreased some days before the peak in the rate of the 1998–1999 lava emission but reached its peak together with the peak in the rate of the 2004 lava emission. These features of seismic activity and SO₂ emission demonstrate that they are good tools for monitoring the extrusion process.  相似文献   

The synrift phase of the early Domeyko Basin (Triassic,northern Chile): Sedimentary,volcanic, and tectonic interplay in the evolution of an ancient subduction‐related rift basin     

Mauricio Espinoza  Diego Montecino  Vernica Oliveros  Natalia Astudillo  Paulina Vsquez  Robinson Reyes  Christopher Celis  Rodrigo Gonzlez  Juan Contreras  Christian Creixell  Amancay Martínez 《Basin Research》2019,31(1):4-32

The geodynamic setting along the SW Gondwana margin during its early breakup (Triassic) remains poorly understood. Recent models calling for an uninterrupted subduction since Late Palaeozoic only slightly consider the geotectonic significance of coeval basins. The Domeyko Basin initiated as a rift basin during the Triassic being filled by sedimentary and volcanic deposits. Stratigraphic, sedimentological, and geochronological analyses are presented in order to determine the tectonostratigraphic evolution of this basin and to propose a tectonic model suitable for other SW Gondwana‐margin rift basins. The Domeyko Basin recorded two synrift stages. The Synrift I (~240–225 Ma) initiated the Sierra Exploradora sub‐basin, whereas the Synrift II (~217–200 Ma) reactivated this sub‐basin and originated small depocentres grouped in the Sierra de Varas sub‐basin. During the rift evolution, the sedimentary systems developed were largely controlled by the interplay between tectonics and volcanism through the accommodation/sediment supply ratio (A/S). High‐volcaniclastic depocentres record a net dominance of the syn‐eruptive period lacking rift‐climax sequences, whereas low‐volcaniclastic depocentres of the Sierra de Varas sub‐basin developed a complete rift cycle during the Synrift II stage. The architecture of the Domeyko Basin suggests a transtensional kinematic where N‐S master faults interacted with ~NW‐SE basement structures producing highly asymmetric releasing bends. We suggest that the early Domeyko Basin was a continental subduction‐related rift basin likely developed under an oblique convergence in a back‐arc setting. Subduction would have acted as a primary driving mechanism for the extension along the Gondwanan margin, unlike inland rift basins. Slab‐induced dynamic can strongly influence the tectonostratigraphic evolution of subduction‐related rift basins through controls in the localization and style of magmatism and faulting, settling the interplay between tectonics, volcanism, and sedimentation during the rifting.  相似文献   

MEPBAY and SMC: Software tools to support different operational levels of headland-bay beach in coastal engineering projects     

André L.A. Raabe  Antonio H. da F. Klein  Mauricio González  Raul Medina 《Coastal Engineering》2010

This paper presents MEPBAY and SMC software tools that allow comprehending and solving problems in headland-bay beach through a parabolic model. These tools can be employed as coastal engineering design tools (including nourishment designs) and also for academic purposes. They are oriented to different end-users, including coastal technicians, scientists and undergraduates and as coastal engineering design tools, they can be applied to different operational levels (pre-design and design). The aim of the paper is to present design guidelines, the capabilities of the tools, their potential use and applications. Both tools were applied to analyze San Lorenzo Beach and demonstrate their ability at different project levels.  相似文献   

Modelling of shallow landslides with machine learning algorithms     

Zhongqiang Liu  Graham Gilbert  Jose Mauricio Cepeda  Asgeir Olaf Kydland Lysdahl  Luca Piciullo  Heidi Hefre  Suzanne Lacasse 《地学前缘(英文版)》2021,12(1):385-393

This paper introduces three machine learning(ML)algorithms,the‘ensemble'Random Forest(RF),the‘ensemble'Gradient Boosted Regression Tree(GBRT)and the Multi Layer Perceptron neural network(MLP)and applies them to the spatial modelling of shallow landslides near Kvam in Norway.In the development of the ML models,a total of 11 significant landslide controlling factors were selected.The controlling factors relate to the geomorphology,geology,geo-environment and anthropogenic effects:slope angle,aspect,plan curvature,profile curvature,flow accumulation,flow direction,distance to rivers,water content,saturation,rainfall and distance to roads.It is observed that slope angle was the most significant controlling factor in the ML analyses.The performance of the three ML models was evaluated quantitatively based on the Receiver Operating Characteristic(ROC)analysis.The results show that the‘ensemble'GBRT machine learning model yielded the most promising results for the spatial prediction of shallow landslides,with a 95%probability of landslide detection and 87%prediction efficiency.  相似文献   

Resonance tongues in the linear Sitnikov equation     

Mauricio Misquero 《Celestial Mechanics and Dynamical Astronomy》2018,130(4):30

In this paper, we deal with a Hill’s equation, depending on two parameters \(e\in [0,1)\) and \(\varLambda >0\), that has applications to some problems in Celestial Mechanics of the Sitnikov type. Due to the nonlinearity of the eccentricity parameter e and the coexistence problem, the stability diagram in the \((e,\varLambda )\)-plane presents unusual resonance tongues emerging from points \((0,(n/2)^2),\ n=1,2,\ldots \) The tongues bounded by curves of eigenvalues corresponding to \(2\pi \)-periodic solutions collapse into a single curve of coexistence (for which there exist two independent \(2\pi \)-periodic eigenfunctions), whereas the remaining tongues have no pockets and are very thin. Unlike most of the literature related to resonance tongues and Sitnikov-type problems, the study of the tongues is made from a global point of view in the whole range of \(e\in [0,1)\). Indeed, an interesting behavior of the tongues is found: almost all of them concentrate in a small \(\varLambda \)-interval [1, 9 / 8] as \(e\rightarrow 1^-\). We apply the stability diagram of our equation to determine the regions for which the equilibrium of a Sitnikov \((N+1)\)-body problem is stable in the sense of Lyapunov and the regions having symmetric periodic solutions with a given number of zeros. We also study the Lyapunov stability of the equilibrium in the center of mass of a curved Sitnikov problem.  相似文献   

Sediment dynamics modulated by burrowing crab activities in contrasting SW Atlantic intertidal habitats     

Mauricio Escapa  Gerardo M.E. Perillo  Oscar Iribarne 《Estuarine, Coastal and Shelf Science》2008

Biogenic bottom features, animal burrows and biological activities interact with the hydrodynamics of the sediment–water interface to produce altered patterns of sediment erosion, transport and deposition which have consequences for large-scale geomorphologic features. It has been suggested that depending on the hydrodynamic status of the habitat, the biological activity on the bottom may have a variety of effects. In some cases, different bioturbation activities by the same organism can result in different consequences. The burrowing crab Neohelice granulata is the most important bioturbator at SW Atlantic saltmarshes and tidal plains. Because of the great variety of habitats that this species may inhabit, it is possible to compare its bioturbation effects between zones dominated by different hydrodynamic conditions. Internal marsh microhabitats, tidal creeks bottoms and basins, and open mudflats were selected as contrasting zones for the comparison on a large saltmarsh at Bahía Blanca Estuary (Argentina). Crab burrows act as passive traps of sediment in all zones, because their entrances remain open during inundation periods at high tide. Mounds are generated when crabs remove sediments from the burrows to the surface and become distinctive features in all the zones. Two different mechanisms of sediment transport utilizing mounds as sediment sources were registered. In the first one, parts of fresh mound sediments were transported when exposed to water flow during flooding and ebbing tide, with higher mound erosion where currents were higher as compared to internal marsh habitats and open mudflats. In the second mechanism, mounds exposed to atmospheric influence during low tide became desiccated and cracked forming ellipsoidal blocks, which were then transported by currents in zones of intense water flow in the saltmarsh edge. Sedimentary dynamics varied between zones; crabs were promoting trapping of sediments in the internal saltmarsh (380 g m⁻² day⁻¹) and open mudflats (1.2 kg m⁻² day⁻¹), but were enhancing sediment removal in the saltmarsh edge (between 10 and 500 g m⁻² day⁻¹ in summer). The implication is that biologically mediated sedimentological changes could be different among microhabitats, potentially leading to contrasting geomorphologic effects within a particular ecosystem.  相似文献   

Multi‐millennial scale climate variability during MIS 3 and MIS 2 inferred from luminescence dating of coastal sand dunes and buried paleosol sequences in central Chile, 32°S     

Juan‐Luis García  Belisario Andrade  Mauricio Caldern  Christopher Lüthgens 《第四纪科学杂志》2019,34(3):203-214

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