Quantifying the relationship between structural deformation and the morphology of submarine channels on the Niger Delta continental slope     

W. Hamish Mitchell  Alexander C. Whittaker  Mike Mayall  Lidia Lonergan  Marco Pizzi 《Basin Research》2021,33(1):186-209

The processes and deposits of deep‐water submarine channels are known to be influenced by a wide variety of controlling factors, both allocyclic and autocyclic. However, unlike their fluvial counterparts whose dynamics are well‐studied, the factors that control the long‐term behaviour of submarine channels, particularly on slopes undergoing active deformation, remain poorly understood. We combine seismic techniques with concepts from landscape dynamics to investigate quantitatively how the growth of gravitational‐collapse structures at or near the seabed in the Niger Delta have influenced the morphology of submarine channels along their length from the shelf edge to their deep‐water counterpart. From a three dimensional (3D), time‐migrated seismic‐reflection volume, which extends over 120 km from the shelf edge to the base of slope, we mapped the present‐day geomorphic expression of two submarine channels and active structures at the seabed, and created a Digital Elevation Model (DEM). A second geomorphic surface and DEM raster—interpreted to closer approximate the most recent active channel geometries—were created through removing the thickness of hemipelagic drape across the study area. The DEM rasters were used to extract the longitudinal profiles of channel systems with seabed expression, and we evaluate the evolution of channel widths, depths and slopes at fixed intervals downslope as the channels interact with growing structures. Results show that the channel long profiles have a relatively linear form with localized steepening associated with seabed structures. We demonstrate that channel morphologies and their constituent architectural elements are sensitive to active seafloor deformation, and we use the geomorphic data to infer a likely distribution of bed shear stresses and flow velocities from the shelf edge to deep water. Our results give new insights into the erosional dynamics of submarine channels, allow us to quantify the extent to which submarine channels can keep pace with growing structures, and help us to constrain the delivery and distribution of sediment to deep‐water settings.  相似文献   

Feeding habits of Solea senegalensis in earthen ponds in Sado estuary     

Maria Ana Castelo Branco  Marco A. Arruda  Sofia Gamito   《Journal of Sea Research》2010,64(4):446-450

The senegale sole, Solea senegalensis Kaup, 1858, is a commercially valuable fish and it is beginning to be cultured in a semi-intensive way in fish farms in southern European countries. The present study was initiated to investigate the diet of S. senegalensis under semi-extensive conditions. The feeding habits of sole were studied in two earthen ponds of a fish farm in the Sado estuary. In one earthen pond, artificial fish ration was given. S. senegalensis feeds on few prey items, its diet is mainly composed of insect larvae (Chironomus salinarus) and polychaeta (Hediste diversicolor). The diet composition of this species suggests feeding specialization, by consuming mainly annelids and insect larvae and by avoiding other items, extremely abundant in the environment, such as gastropods. In the water reservoir where ration was given, some fish consumed simultaneously benthic organism together with ration. However, benthic organisms seem to be the most important component of S. senegalensis diet.  相似文献   

Transtensional shear zones controlling volcanic eruptions: the Middle Pleistocene Mt Amiata volcano (inner Northern Apennines,Italy)     

Andrea Brogi  Domenico Liotta  Marco Meccheri  Lorenzo Fabbrini 《地学学报》2010,22(2):137-146

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Seasonal changes of antioxidant and oxidative parameters in the coral Pocillopora capitata on the Pacific coast of Mexico     

Marco A. Liñán‐Cabello  Laura A. Flores‐Ramírez  Tania Zenteno‐Savin  Norma O. Olguín‐Monroy  Ramón Sosa‐Avalos  Manuel Patiño‐Barragan  Aramis Olivos‐Ortiz 《Marine Ecology》2010,31(3):407-417

The physiological responses of the coral Pocillopora capitata to environmental conditions common in winter and summer were studied in 2007 during February–March (winter) and June–July (summer) at La Boquita reef (Manzanillo, Colima, Mexico). Shallow and deep sampling stations were established at different distances from a small jetty built next to the Juluapan Lagoon. We analyzed superoxide radicals () and lipid peroxidants (TBARS); the activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), and glutathione‐S‐transferase (GST); chlorophyll a (Chl a), zooxanthellae density (ZD); and mycosporine‐like amino acids (MAAs). Our results showed that the , TBARS, CAT, GST, MAAs, and Chl a, levels were significantly higher in summer (P < 0.05); no seasonal difference was found for GPx, GR or ZD. We found significant differences (P < 0.05) in winter only for Chl a and ZD at shallow sites and, in contrast, for at deeper sites. The results of this study indicate that increasing temperature and radiation associated with seasonal changes (from winter to summer), the efficiency of the enzymes GST, CR and GPX, and the production of MAAs together form a powerful mechanism for P. capitata to offset the detrimental effects of environmental change.  相似文献   

Complex dynamics of small-moderate volcanic events: the example of the 2011 rhyolitic Cordón Caulle eruption,Chile     

Marco?PistolesiEmail author  Raffaello?Cioni  Costanza?Bonadonna  Manuela?Elissondo  Valerie?Baumann  Antonella?Bertagnini  Laura?Chiari  Rafael?Gonzales  Mauro?Rosi  Lorella?Francalanci 《Bulletin of Volcanology》2015,77(1):3

After decades of repose, Puyehue-Cordón Caulle Volcano (Chile) erupted in June 2011 following a month of continuously increasing seismic activity. The eruption dispersed a large volume of rhyolitic tephra over a wide area and was characterized by complex dynamics. During the initial climactic phase of the eruption (24–30 h on 4–5 June), 11–14-km-high plumes dispersed most of the erupted tephra eastward towards Argentina, reaching as far as the Atlantic Ocean. This first eruptive phase was followed by activity of lower intensity, leading to the development of a complex stratigraphic sequence, mainly due to rapid shifts in wind direction and eruptive style. The resulting tephra deposits consist of 13 main layers grouped into four units. Each layer was characterized based on its dispersal direction, sedimentological features, and on the main characteristics of the juvenile fraction (texture, density, petrography, chemistry). The lowest part of the eruptive sequence (Unit I), corresponding to the tephra emitted between 4 and 5 June, is composed of alternating lapilli layers with a total estimated volume of ca. 0.75 km³; these layers record the highest intensity phase, during which a bent-over plume dispersed tephra towards the southeast-east, with negligible up-wind sedimentation. Products emitted during 5–6 June (Unit II) signaled an abrupt shift in wind direction towards the north, leading to the deposition of a coarse ash deposit in the northern sector (ca. 0.21 km³ in volume), followed by a resumption of easterly directed winds. A third phase (Unit III) began on 7 June and resulted in tephra deposits in the eastern sector and ballistic bombs around the vent area. A final phase (Unit IV) started after 15 June and was characterized by the emission of fine-grained white tephra from ash-charged plumes during low-level activity and the extrusion of a viscous lava flow. Timing and duration of the first eruptive phases were constrained based on comparison of the dispersal of the main tephra layers with satellite images, showing that most of the tephra was emitted during the first 72 h of the event. The analyzed juvenile material tightly clusters within the rhyolitic field, with negligible chemical variations through the eruptive sequence. Textural observations reveal that changes in eruption intensity (and consequently in magma ascent velocity within the conduit) and complex interactions between gas-rich and gas-depleted magma portions during ascent resulted in vesicular clasts with variable degrees of shear localization, and possibly in the large heterogeneity of the juvenile material.  相似文献   

Structural damage in the cities of Reggiolo and Carpi after the earthquake on May 2012 in Emilia Romagna   总被引：2，自引：2，他引：0  

Marco Andreini  Anna De Falco  Linda Giresini  Mauro Sassu 《Bulletin of Earthquake Engineering》2014,12(5):2445-2480

This paper addresses the structural damage to the main buildings of the cities of Reggiolo and Carpi after the primary earthquake shocks on May 20th and 29th, 2012, in Emilia Romagna. The damage survey, performed via form-based methods, highlights the different seismic behaviour of several types of buildings, especially those having historical features, and the consequences of the damage in terms of costs. Moreover, an analysis of some failure mechanisms activated in Reggiolo enables the evaluation of the local peak ground acceleration, due to the soil amplification.  相似文献   

The use of cholinesterase as potential biomarker: In vitro characterization in the polychaete Capitella teleta     

Isa D.L. Gomes  Marco F.L. Lemos  Amadeu M.V.M. Soares  Carlos Barata  Melissa Faria 《Marine pollution bulletin》2014

The ecological relevance of polychaetes coupled with their easy culture and maintenance in the laboratory, has led them to become increasingly used in marine ecotoxicological studies, raising the need to validate frequently applied monitoring tools at various biological levels. The present study was aimed to characterize the cholinesterases (ChE) activity in the polychaete Capitella teleta, using three substrates (acetylthiocholine iodide, propionylthiocholine iodide, and S-butyrylthiocholine iodide) and four known inhibitors (eserine hemisulfate, BW284c51, iso-OMPA and chlorpyrifos-oxon). Results showed that most of the measured cholinesterase activity was acetylcholinesterase (AChE). Inhibition of enzyme kinetic experiments denoted that sensitivity of C. teleta’s ChE to the organophosphorous metabolite chlorpyrifos-oxon (IC₅₀ = 60.72 nM) was analogous to some fish species. This study highlights the relevance of ChE characterization before its use as a biomarker in ecotoxicology and biomonitoring studies.  相似文献   

Visual Event Screening of Continuous Seismic Data by Supersonograms     

Benjamin Sick  Marco Walter  Manfred Joswig 《Pure and Applied Geophysics》2014,171(3-5):549-559

We present a new visualization method for human inspection of seismic data called supersonograms, which maximizes the amount of time and stations visible on screen while retaining the possibility to detect short and low-signal to noise ratio (SNR) signals. This visualization approach is integrated into a seismological software suite used in the seismic aftershock monitoring system (SAMS) of Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) on-site inspections (OSI) to detect suspicious events eventually representing aftershocks from an underground nuclear explosion (UNE). During an OSI, huge amounts of continuous waveform data accumulate from up to 50 six-channel mini-arrays covering an inspection area of 1,000 square kilometers. Sought-after events can have magnitude as low as $\hbox{M}_{\rm L}\,{-2.0}$ and duration of just a few seconds, which makes it particularly hard to discover them in large, noisy datasets. Therefore, the data visualization is based on nonlinearly scaled, noise-adapted spectrograms, i.e., sonograms, which help to distinguish weak signal energy from stationary background noise. Four single-trace sonograms per mini-array can be combined into supersonograms, since the array aperture is small and sonograms suppress differences of local site noise, allowing an analyst to check array-wide signal coherence quickly. In this paper, we present the supersonograms and the software on the basis of a dataset from a creeping, inhabited landslide in Austria where the same station layout is used as in an OSI. Detected signals are fracture processes in the sedimentary landslide, i.e., slidequakes, with $\hbox{M}_{\rm L}\,{-0.5} \,\hbox{\,to}\,{-2.5}$ between July 2009 and July 2011. These signals are comparable in magnitude and duration to expected weak UNE aftershocks.  相似文献   

Catchment-scale storm velocity: quantification,scale dependence and effect on flood response     

Efthymios I. Nikolopoulos  Marco Borga  Davide Zoccatelli  Emmanouil N. Anagnostou 《水文科学杂志》2014,59(7):1363-1376

Abstract

The concept of “catchment-scale storm velocity” quantifies the rate of storm motion up and down the basin accounting for the interaction between the rainfall space–time variability and the structure of the drainage network. It provides an assessment of the impact of storm motion on flood shape. We evaluate the catchment-scale storm velocity for the 29 August 2003 extreme storm that occurred on the 700 km²-wide Fella River basin in the eastern Italian Alps. The storm was characterized by the high rate of motion of convective cells across the basin. Analysis is carried out for a set of basins that range in area from 8 to 623 km² to: (a) determine velocity magnitudes for different sub-basins; (b) examine the relationship of velocity with basin scale and (c) assess the impact of storm motion on simulated flood response. Two spatially distributed hydrological models of varying degree of complexity in the representation of the runoff generation processes are used to evaluate the effects of the storm velocity on flood modelling and investigate model dependencies of the results. It is shown that catchment-scale storm velocity has a non-linear dependence on basin scale and generally exhibits rather moderate values, in spite of the strong kinematic characteristics of individual storm elements. Consistently with these observations and for both models, hydrological simulations show that storm motion has an almost negligible effect on the flood response modelling.

Editor Z.W. Kundzewicz; Guest editor R.J. Moore

Citation Nikolopoulos, E.I., Borga, M., Zoccatelli, D., and Anagnostou, E.N., 2014. Catchment-scale storm velocity: quantification, scale dependence and effect on flood response. Hydrological Sciences Journal, 59 (7), 1363–1376. http://dx.doi.org/10.1080/02626667.2014.923889  相似文献   

An integrated approach for investigating geomorphic response to extreme events: methodological framework and application to the October 2011 flood in the Magra River catchment,Italy          下载免费PDF全文

Massimo Rinaldi  William Amponsah  Marco Benvenuti  Marco Borga  Francesco Comiti  Ana Lucía  Lorenzo Marchi  Laura Nardi  Margherita Righini  Nicola Surian 《地球表面变化过程与地形》2016,41(6):835-846

A high‐magnitude flash flood, which took place on 25 October 2011 in the Magra River catchment (1717 km²), central‐northern Italy, is used to illustrate some aspects of the geomorphic response to the flood. An overall methodological framework is described for using interlinked observations and analyses of the geomorphic impacts of an extreme event. The following methods and analyses were carried out: (i) hydrological and hydraulic analysis of the event; (ii) sediment delivery by event landslide mapping; (iii) identification and estimation of wood recruitment, deposition, and budgeting; (iv) interpretation of morphological processes by analysing fluvial deposits; (v) remote sensing and geographic information system (GIS) analysis of channel width changes. In response to the high‐magnitude hydrological event, a large number of landslides occurred, consisting of earth flows, soil slips, and translational slides, and a large quantity of wood was recruited, in most part deriving from floodplain erosion caused by bank retreat and channel widening. The most important impact of the flood event within the valley floor was an impressive widening of the overall channel bed and the reactivation of wide portions of the pre‐event floodplain. Along the investigated (unconfined or partly confined) streams (total investigated length of 93.5 km), the channel width after the flood was up to about 20 times the channel width before the event. The study has shown that a synergic use of different methods and types of evidence provides fundamental information for characterizing and understanding the geomorphic effects of intense flood events. The prediction of geomorphic response to a flood event is still challenging and many limitations exist; however a robust geomorphological analysis can contribute to the identification of the most critical reaches. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献