Geotechnical zonation and soil–structure interaction at Puerto Vallarta,México     

Escudero  Christian R.  Ramirez Gaytan  Alejandro  Zamora Camacho  Araceli  Preciado  Adolfo  Flores  Karen L.  Gomez Hernandez  Adan 《Natural Hazards》2022,110(1):247-267

Natural Hazards - We performed a seismic vulnerability assessment that involves geotechnical and building structure analysis for Puerto Vallarta, Mexico, a city located along the pacific coast....  相似文献   

The effects of dredging operations on the hydrodynamics of an ebb tidal delta: Oka Estuary,northern Spain     

P. Liria  E. Garel  A. Uriarte 《Continental Shelf Research》2009,29(16):1983-1994

The hydrodynamics associated with the Mundaka Sandbar are described. The sandbar (ebb tidal delta) is responsible for the formation and the quality of a “world famous” surfing wave, at the mouth of the Oka Estuary in the Urdaibai Biosphere Reserve. The primary factor controlling the shape of the sandbar is the shoreline configuration. In turn the size of the sandbar is controlled by the volume of the tidal outflow and the wave energy. Periods of tidal dominance occur during summer (associated with sandbar accretion); with mixed energy conditions during winter and wave dominance under storms (sandbar erosion).The surfing wave lost its characteristics following, intensive dredging along the estuary, combined with beach nourishment, in May 2003. Between May 2005 and April 2006, the outer part of the estuary was monitored, to understand the processes controlling recent morphological changes over the area.Recent studies undertaken in the mouths of estuaries, together with the results of the monitoring are described; these are complemented by the numerical modelling of wave hydrodynamics under medium and extreme sea states. Analyses of the wave and current survey data, combined with the modelling outputs, have demonstrated that the changes were not irreversible. As such, the natural shape of the sandbar has recovered gradually, as has the quality of the Mundaka surfing wave.  相似文献   

C₂₅ and C₃₀ biogenic alkenes in sediments and detritus of a New England salt marsh     

Adolfo G. Requejo  James G. Quinn 《Estuarine, Coastal and Shelf Science》1985,20(3):281-297

As part of a geochemical study of C₂₅ and C₃₀ biogenic alkenes in estuarine environments, distributions of these compounds in detritus and sediments collected from a New England salt marsh (Round Swamp on Conanicut Island in Narragansett Bay, Rhode Island) have been determined. The alkene assemblages detected, consisting primarily of four acyclic C₂₅ dienes and trienes and a C₃₀ bicyclic diene, qualitatively resemble those previously reported for other sediments in which anoxic conditions were prevalent. These similarities exist despite significant differences in the principal sources of sedimentary organic matter, suggesting that the occurrence of these specific alkenes is more likely associated with an in situ process common to anoxic environments than with a direct input from a specific source. Size fractionation (> 840 μm and < 840 μm to 1·2 μm) of marsh detritus revealed that the larger size fraction, consisting primarily of decaying Spartina debris, contains significant amounts of alkenes. This result, together with alkene subsurface profiles which show high surface concentrations decreasing to near-background levels by 20 cm, suggest that anaerobic bacteria are mediating in situ production of these compounds. Previous studies of bacterial hydrocarbons have not reported the presence of these C₂₅ and C₃₀ alkenes, although similar compounds have been isolated from several species of methanogenic bacteria. However, attempts to induce alkene synthesis by decomposing Spartina anaerobically in the laboratory were unsuccessful. In light of this result, the exact source of alkenes in marsh sediments remains uncertain. The absence from marsh sediments of other C₂₅ alkenes whose sedimentary distributions had been previously correlated with the presence of marine (planktonic) organic matter implies the existence of different origins for structurally related constituents of this hydrocarbon series.  相似文献   

An improved approach for assigning pumping rates to heterogeneous aquifer models     

Pinales A  Chavez A  Llerar G  Manzanares L  Keer A 《Ground water》2005,43(2):274-279

A common assumption of ground water models formulated using a block-centered finite-difference method is that a well is located at the center of a cell regardless of its actual location. Due to this assumption, errors are introduced in the spatial distribution of simulated heads. This paper presents an alternative approach for assigning the pumping rates of wells that are located off cell centers. This approach consists of assigning the pumping rate not only to the cell in which the well is located but also to adjacent cells, taking into account the length of the well screen, the hydraulic conductivity, and the distance from the well to the center of its cell. The advantage of this alternative approach over the conventional one is illustrated with a test problem of a synthetic aquifer. Statistical measures of error indicate a much better model fit when pumping rates of wells are distributed over several cells.  相似文献   

Reconstructions of the Mediterranean Outflow Water during the quaternary based on the study of changes in buried mounded drift stacking pattern in the Gulf of Cadiz     

Estefania Llave  Francisco J. Hernández-Molina  Dorrik A. V. Stow  Mari Carmen Fernández-Puga  Margarita García  Juan T. Vázquez  Adolfo Maestro  Luis Somoza  Victor Díaz del Río 《Marine Geophysical Researches》2007,28(4):379-394

Contourite deposits in the central sector of the middle slope of the Gulf of Cadiz have been studied using a comprehensive acoustic, seismic and core database. Buried, mounded, elongated and separated drifts developed under the influence of the lower core of the Mediterranean Outflow Water are preserved in the sedimentary record. These are characterised by depositional features in an area where strong tectonic and erosive processes are now dominant. The general stacking pattern of the depositional system is mainly influenced by climatic changes through the Quaternary, whereas changes in the depositional style observed in two, buried, mounded drifts, the Guadalquivir and Huelva Drifts, are evidence of a tectonic control. In the western Guadalquivir Drift, the onset of the sheeted drift construction (aggrading QII unit) above a mounded drift (prograding QI unit) resulted from a new Lower Mediterranean Core Water hydrodynamic regime. This change is correlated with a tectonic event coeval with the Mid Pleistocene Revolution (MPR) discontinuity that produced new irregularities of the seafloor during the Mid- to Late-Pleistocene. Changes in the Huelva Drift from a mounded to a sheeted drift geometry during the Late-Pleistocene, and from a prograding drift (QI and most part of QII) to an aggrading one (upper seismic unit of QII), highlight a new change in oceanographic conditions. This depositional and then oceanographic change is associated with a tectonic event, coeval with the Marine Isotope Stage (MIS) 6 discontinuity, in which a redistribution of the diapiric ridges led to the development of new local gateways, three principal branches of the Mediterranean Lower Core Water, and associated contourite channels. As a result, these buried contourite drifts hold a key palaeoceanographic record of the evolution of Mediterranean Lower Core Water, influenced by both neotectonic activity and climatic changes during the Quaternary. This study is an example of how contourite deposits and erosive elements in the marine environment can provide evidence for the reconstruction of palaeoceanographic and recent tectonic changes.  相似文献   

The relation of the southern trade winds to upwelling processes during the last 75,000 years     

Adolfo Molina-Cruz 《Quaternary Research》1977,8(3):324-338

In the equatorial Pacific, between the Galapagos Islands and the coast of South America, two kinds of upwelling of oceanic waters occur. One is related to coastal upwelling and the other to surfacing of the Equatorial Undercurrent. Both of those processes are associated with the development of the southeast trade winds blowing in this area. Coastal upwelling is increased when the trade winds are intensified, and the surfacing of the Equatorial Undercurrent occurs when the trades weaken. The development of coastal upwelling and the surfacing of the Equatorial Undercurrent are inferred from the radiolarian assemblages in the sediments. The abundance of quartz, opal, and radiolarian assemblages in the deep-sea sediments of this area, as well as the distance from the sample locations to land and to the quartz source, is correlated with the intensity of the trade winds (in February and August) through multiple regression analysis. The chronostratigraphy of core V1929 (3°35′S, 83°56′W), used in this study, is inferred on basis of its δ¹⁸0 record. During the last 75,000 years, the fluctuations in intensity of the trade winds have been concurrent with or preceded the fluctuations in the amount of ice stored on the continents. In general, the wind velocity of the winter trades has been intensified during cool climatic stages of the earth (δ¹⁸0 stages 4 and 2) and they have been relaxed during warm stages (δ¹⁸0 stages 3 and 1). Seasonal contrast of the trade winds has also fluctuated within time, having been relatively high during the upper part of δ¹⁸0 stage 3.  相似文献   

Geomechanical characterisation of rock masses in Alpine regions: the Basque Arc (Basque-Cantabrian basin, Northern Spain)   总被引：1，自引：0，他引：1  

Toms Morales  Gorka Uribe-Etxebarria  Jesús A. Uriarte  Iigo Fernndez de Valderrama 《Engineering Geology》2004,71(3-4):343-362

The geomechanical characterisation of rock masses in Alpine regions is one of the main challenges currently facing rock mechanics. These rock masses, made up of very different materials and frequently tectonically disturbed, are affected by engineering works, giving rise to potentially important problems. Thus, in the Basque Country, these materials are at the cause of important fatalities occurring in recent years. In this context, we aim at characterising these materials with the ultimate purpose of predicting their behaviour. The characterisation is initially approached based on the GSI, m_i and σ_ci parameters, following the Hoek-Brown failure criterion. This information is supplemented with field and laboratory measurements, and by obtaining the RQD and RMR indices. Using the information obtained from 99 metering stations, we develop a graphic classification procedure, which allows us to distinguish materials based on their characteristics, behaviour, type and degree of associated problems, and type and effectiveness of solutions provided. Eight classes of material are established.  相似文献   

Ductility of wide-beam RC frames as lateral resisting system     

Fernando Gómez-Martínez  Adolfo Alonso-Durá  Flavia De Luca  Gerardo M. Verderame 《Bulletin of Earthquake Engineering》2016,14(6):1545-1569

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On the devil's tracks: unexpected news from the Foresta ichnosite (Roccamonfina volcano,central Italy)     

Adolfo Panarello  Maria Rita Palombo  Italo Biddittu  Mauro Antonio Di Vito  Gennaro Farinaro  Paolo Mietto 《第四纪科学杂志》2020,35(3):444-456

The Foresta ichnosite is well known for preserving some of the oldest human fossil footprints recorded in Europe so far. This research aims to: i) describe new footprints that are larger than those already reported, some of which form a new trackway that moves in the opposite direction to all the others; ii) announce the discovery of some stone tools also in the surroundings of the Foresta ichnosite. The new results increase the total number of human fossil footprints to at least 81, specify the direction and the number of footprints of Trackway C, and identify three new directions of walking at the site. More compelling and complete estimates of the dimensional range of all ichnological evidence enables us, furthermore, to estimate the number of trackmakers walking on the trampled surface as a minimum of five, one of them likely being an adult male. The general shape of all the recorded footprints suggests that the Foresta trackmakers share some similarities with those at Sima de los Huesos, and belong to the same taxonomical group as the Ceprano skull. All the new evidence enables us to better understand the presence of hominin populations in the Roccamonfina volcano area during the Middle Pleistocene. © 2020 John Wiley & Sons, Ltd.  相似文献   

Effective run‐off flow length over biological soil crusts on silty loam soils in drylands          下载免费PDF全文

Roberto Lázaro  Adolfo Calvo‐Cases  Amparo Lázaro  Isabel Molina 《水文研究》2015,29(11):2534-2544

Surface hydrological behaviour is important in drylands because it affects the distribution of soil moisture and vegetation and the hydrological functioning of slopes and catchments. Microplot scale run‐off can be relatively easily measured, i.e. by rainfall simulations. However, slope or catchment run‐off cannot be deduced from microplots, requiring long‐time monitoring, because run‐off coefficients decrease with increasing drainage area. Therefore, to determine the slope length covered by run‐off (run‐off length) is crucial to connect scales. Biological soil crusts (BSCs) are good model systems, and their hydrology at slope scale is insufficiently known. This study provides run‐off lengths from BSCs, by field factorial experiments using rainfall simulation, including two BSC types, three rain types, three antecedent soil moistures and four plot lengths. Data were analysed by generalized linear modelling, including vascular plant cover as covariates. Results were the following: (i) the real contributing area is almost always much smaller than the topographical contributing area; (ii) the BSC type is key to controlling run‐off; run‐off length reached 3 m on cyanobacterial crust, but hardly over 1 m on lichen crust; this pattern remained through rain type or soil moisture; (iii) run‐off decreased with BSC development because soil sealing disappears; porosity, biomass and roughness increase and some changes occur in the uppermost soil layer; and (iv) run‐off flow increased with both rain type and soil moisture but run‐off coefficient only with soil moisture (as larger rains increased both run‐off and infiltration); vascular plant cover had a slight effect on run‐off because it was low and random. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献