Paleomagnetism and magnetic fabrics of Mio-Pliocene hypabyssal rocks of the Combia event,Colombia: tectonic implications     

Victor A. Piedrahita  Roberto S. Molina-Garza  Gloria M. Sierra  José F. Duque-Trujillo 《Studia Geophysica et Geodaetica》2017,61(4):772-800

Mio-Pliocene hypabyssal rocks of the Combia event in the Amagá basin (NW Andes-Colombia), contain a deformational record of the activity of the Cauca-Romeral fault system, and the interaction of terranes within the Choco and northern Andean blocks. Previous paleomagnetic studies interpreted coherent counterclockwise rotations and noncoherent modes of rotation about horizontal axes for the Combia intrusives. However, rotations were determined from in-situ paleomagnetic directions and the existing data set is small. In order to better understand the deformational features of these rocks, we collected new paleomagnetic, structural, petrographic and magnetic fabric data from well exposed hypabyssal rocks of the Combia event. The magnetizations of these rocks are controlled by a low-coercivity ferromagnetic phase. Samples respond well to alternatingfield demagnetization isolating a magnetization component of moderate coercivity. These rocks do not have ductile deformation features. Anisotropy of magnetic susceptibility and morphotectonic analysis indicate that rotation about horizontal axes is consistently to the south-east, suggesting the need to apply a structural correction to the paleomagnetic data. The relationships between magnetic foliations and host-rock bedding planes indicate tectonic activity initiated before ~10 Ma. We present a mean paleomagnetic direction (declination D = 342.8°, inclination I = 12.1°, 95% confidence interval α₉₅ = 12.5°, precision parameter k = 8.6, number of specimens n = 18) that incorporates structural corrections. The dispersion S = 27° of site means cannot be explained by secular variation alone, but it indicates a counterclockwise rotation of 14.8° ± 12.7° relative to stable South America. Paleomagnetic data within a block bounded by the Sabanalarga and Cascajosa faults forms a more coherent data set (D = 336.5°, I = 17.4°, α₉₅ = 11.7°, k = 12.5, n = 14), which differs from sites west of the Sabanalarga fault and shows a rotation about a vertical axis of 20.2° ± 10.7°. Deformation in the Amagá basin may be tentatively explained by the obduction of the Cañas Gordas terrane over the northwestern margin of the northern Andean block. However, it can also be related to the local effects of the Cauca-Romeral fault system.  相似文献   

A direct scaling analysis for the sea level rise     

Giuseppe?Roberto?Tomasicchio  Letizia?Lusito  Felice?D’AlessandroEmail author  Ferdinando?Frega  Antonio?Francone  Samuele?De?Bartolo 《Stochastic Environmental Research and Risk Assessment (SERRA)》2018,32(12):3397-3408

The estimation of long-term sea level variability is of primary importance for a climate change assessment. Despite the value of the subject, no scientific consensus has yet been reached on the existing acceleration in observed values. The existence of this acceleration is crucial for coastal protection planning purposes. The absence of the acceleration would enhance the debate on the general validity of current future projections. Methodologically, the evaluation of the acceleration is a controversial and still open discussion, reported in a number of review articles, which illustrate the state-of-art in the field of sea level research. In the present paper, the well-proven direct scaling analysis approach is proposed in order to describe the long-term sea level variability at 12 worldwide-selected tide gauge stations. For each of the stations, it has been shown that the long-term sea level variability exhibits a trimodal scaling behaviour, which can be modelled by a power law with three different pairs of shape and scale parameters. Compared to alternative methods in literature, which take into account multiple correlated factors, this simple method allows to reduce the uncertainties on the sea level rise parameters estimation.  相似文献   

The 2014 Earthquake Model of the Middle East: seismogenic sources     

Laurentiu Danciu  Karin Şeşetyan  Mine Demircioglu  Levent Gülen  Mehdi Zare  Roberto Basili  Ata Elias  Shota Adamia  Nino Tsereteli  Hilal Yalçın  Murat Utkucu  Muhammad Asif Khan  Mohammad Sayab  Khaled Hessami  Andrea N. Rovida  Massimiliano Stucchi  Jean-Pierre Burg  Arkady Karakhanian  Hektor Babayan  Mher Avanesyan  Tahir Mammadli  Mahmood Al-Qaryouti  Doğan Kalafat  Otar Varazanashvili  Mustafa Erdik  Domenico Giardini 《Bulletin of Earthquake Engineering》2018,16(8):3465-3496

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Probabilistic leak detectability assessment via state estimation in water transport networks     

Sarai?DíazEmail authorView author&#;s OrcID profile  Roberto?Mínguez  Javier?González 《Stochastic Environmental Research and Risk Assessment (SERRA)》2018,32(7):2111-2128

Leak detectability or leakage awareness refers to the capability of sensing losses from a water supply system. Several methods exist in the technical literature to tackle this problem, but only few address it with a state estimation approach. The aim of this paper is to present a new methodology that enables probabilistic assessment of the extent to which water loss could be detected using state estimation by only analysing a single hydraulic state, i.e. one time period. Significant leaks are sensed by identifying unusually high normalised state estimation residuals, which can be identified based on the largest normalised residual test. More specifically, the probability of detecting leaks is computed here by working with the multivariate distribution among measurements and estimates to take into account the noisy nature of measurements with an analytical approach rather than with sampling experiments, which are time-consuming. The methodology set out herein also provides a procedure to systematically assess the minimum leak that could be detected in different parts of the network for a specific measurement setting and operating condition. The method has been applied to a water transport network case study to show its potential and to highlight the usefulness of such a tool for practitioners. The limitations of such a methodology are also discussed, including its possible use for on-line leak detection strategies.  相似文献   

The impact of submersed aquatic vegetation on the development of river mouth bars     

Sara Lera  William Nardin  Lawrence Sanford  Cindy Palinkas  Roberto Guercio 《地球表面变化过程与地形》2019,44(7):1494-1506

This work is inspired by the sudden resurgence of the submersed aquatic vegetation (SAV) bed in the Chesapeake Bay (USA). Because the SAV bed occurs at the mouth of the Bay's main tributary (Susquehanna River), it plays a significant role in modulating sediment and nutrient inputs from the Susquehanna to the Bay. Previous model studies on the impact of submersed aquatic vegetation on the development of river mouth bars lacked a complete mechanistic understanding. This study takes advantage of new advances in 3D computational models that include explicit physical-sedimentological feedbacks to obtain this understanding. Specifically, we used Delft3D, a state-of-the-art hydrodynamic model that provides fine-scale computations of three-dimensional flow velocity and bed shear stress, which can be linked to sediment deposition and erosion. Vegetation is modeled using a parameterization of hydraulic roughness that depends on vegetation height, stem density, diameter, and drag coefficient. We evaluate the hydrodynamics, bed shear stresses, and sediment dynamics for different vegetation scenarios under conditions of low and high river discharge. Model runs vary the vegetation height, density, river discharge, and suspended-sediment concentration. Numerical results from the idealized model show that dense SAV on river mouth bars substantially diverts river discharge into adjacent channels and promotes sediment deposition at ridge margins, as well as upstream bar migration. Increasing vegetation height and density forms sandier bars closer to the river mouth and alteration of the bar shape. Thus, this study highlights the important role of SAV in shaping estuarine geomorphology, which is especially relevant for coastal management. © 2019 John Wiley & Sons, Ltd.  相似文献   

Classifying zones of suitability for manual drilling using textural and hydraulic parameters of shallow aquifers: a case study in northwestern Senegal     

F. Fabio Fussi  Letizia Fumagalli  Francesco Fava  Biagio Di Mauro  Cheik Hamidou Kane  Magatte Niang  Souleye Wade  Barry Hamidou  Roberto Colombo  Tullia Bonomi 《Hydrogeology Journal》2017,25(8):2263-2279

A method is proposed that uses analysis of borehole stratigraphic logs for the characterization of shallow aquifers and for the assessment of areas suitable for manual drilling. The model is based on available borehole-log parameters: depth to hard rock, depth to water, thickness of laterite and hydraulic transmissivity of the shallow aquifer. The model is applied to a study area in northwestern Senegal. A dataset of boreholes logs has been processed using a software package (TANGAFRIC) developed during the research. After a manual procedure to assign a standard category describing the lithological characteristics, the next step is the automated extraction of different textural parameters and the estimation of hydraulic conductivity using reference values available in the literature. The hydraulic conductivity values estimated from stratigraphic data have been partially validated, by comparing them with measured values from a series of pumping tests carried out in large-diameter wells. The results show that this method is able to produce a reliable interpretation of the shallow hydrogeological context using information generally available in the region. The research contributes to improving the identification of areas where conditions are suitable for manual drilling. This is achieved by applying the described method, based on a structured and semi-quantitative approach, to classify the zones of suitability for given manual drilling techniques using data available in most African countries. Ultimately, this work will support proposed international programs aimed at promoting low-cost water supply in Africa and enhancing access to safe drinking water for the population.  相似文献   

Low Angle Contact Between the Oaxaca and Juárez Terranes Deduced From Magnetotelluric Data     

Jorge A. Arzate-Flores  Roberto Molina-Garza  Fernando Corbo-Camargo  Víctor Márquez-Ramírez 《Pure and Applied Geophysics》2016,173(10-11):3357-3371

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Source Characterization and Tsunami Modeling of Submarine Landslides Along the Yucatán Shelf/Campeche Escarpment,Southern Gulf of Mexico     

Jason D. Chaytor  Eric L. Geist  Charles K. Paull  David W. Caress  Roberto Gwiazda  Jaime Urrutia Fucugauchi  Mario Rebolledo Vieyra 《Pure and Applied Geophysics》2016,173(12):4101-4116

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Pyroclastic density currents at Stromboli volcano (Aeolian Islands,Italy): a case study of the 1930 eruption     

A. Di Roberto  A. Bertagnini  M. Pompilio  M. Bisson 《Bulletin of Volcanology》2014,76(6):1-14

Pyroclastic density currents (PDC) related to paroxysmal eruptions have caused a large number of casualties in the recent history of Stromboli. We combine here a critical review of historical chronicles with detailed stratigraphic, textural, and petrographic analyses of PDC deposits emplaced at Stromboli over the last century to unravel the origin of currents, their flow mechanism and the depositional dynamics. We focus on the 1930 PDC as they are well described in historical accounts and because the 1930 eruption stands as the most voluminous and destructive paroxysm of the last 13 centuries. Stromboli PDC deposits are recognizable from their architecture and the great abundance of fresh, well-preserved juvenile material. General deposit features indicate that Stromboli PDC formed due to the syn-eruptive gravitational collapse of hot pyroclasts rapidly accumulated over steep slopes. Flow channelization within the several small valleys cut on the flanks of the volcano can enhance the mobility of PDC, as well as the production of fine particles by abrasion and comminution of hot juvenile fragments, thereby increasing the degree of fluidization. Textural analyses and historical accounts also indicate that PDC can be fast (15–20 m/s) and relatively hot (360–700 °C). PDC can thus flow right down the slopes of the volcano, representing a major hazard. For this reason, they must be adequately taken into account when compiling risk maps and evaluating volcanic hazard on the Island of Stromboli.  相似文献   

On‐Site Vapor‐Phase Analysis as a Novel Approach for Monitoring Groundwater Wells     

David T. Adamson  Thomas E. McHugh  Michal W. Rysz  Roberto Landazuri  Mir Ahmad Seyedabbasi  Patrick E. Haas  Charles J. Newell 《Ground Water Monitoring & Remediation》2014,34(2):42-59

The results of comprehensive field testing of on‐site vapor‐phase‐based groundwater monitoring methods are presented to demonstrate their utility as a robust and cost‐effective approach for rapidly obtaining volatile organic compounds (VOCs) concentration data from a monitoring well. These methods—which rely on sensitive, commercially available field equipment to analyze vapor in equilibrium with groundwater—proved easy to implement and can be tailored to site‐specific needs, including multilevel sampling. During field testing, low‐flow groundwater concentrations could be reasonably estimated using submerged passive vapor diffusion samplers or field equilibration of collected groundwater (R² = 0.85 to 0.96). These two methods are not as reliant on in‐well mixing to overcome vertical stratification within wells as simpler headspace methods. The importance of well and aquifer‐specific factors on concentration data (and therefore method selection) is highlighted, including the effect of changing in‐well patterns due to seasonal temperature gradients. Results indicated that vertical stratification was relatively limited within the set of wells included in these studies, resulting in similar performance for short depth‐discrete passive vapor diffusion samplers (constructed from 40‐mL vials) and longer samplers (2.5 to 5 feet in length) designed to cover a larger portion of the screened interval. A year‐long, multi‐event evaluation demonstrated that vapor‐phase‐based monitoring methods are no more variable than conventional groundwater monitoring methods, with both types subject to similar spatial and temporal variability that can be difficult to reduce. Vapor sampling methods represent a promising approach for estimation of groundwater concentrations by reducing the cost liabilities associated with monitoring while providing a more sustainable approach.  相似文献