Hydraulic conductivity characterization of a karst recharge area using water injection tests and electrical resistivity logging     

Bárbara Angulo  Tomás Morales  Jesús A. Uriarte  Iñaki Antigüedad 《Engineering Geology》2011,117(1-2):90-96

Water injection tests and electrical logging are particularly useful techniques in the characterization of geological media in engineering works. In this paper these techniques in conjunction with cracks measurements obtained from drilling cores, were used in the characterization of a singular location in a karst massif. The aim of our work is to determine the hydraulic characteristics of the investigated site, as well as to establish the relationship between the data obtained by the different techniques used. Thus, electrical resistivity records and fracture data were obtained from two boreholes of 100 and 120 m depth. Hydraulic conductivity was calculated from 25 low-pressure water injection tests (LPT) carried out at different depths in both boreholes. The relationship between hydraulic conductivity and fracture frequency was not very statististically significant (R²: 0.062–0.672; σ_est: 0.61–1.575). Conversely, electrical resistivity and hydraulic conductivity had a great relationship (R²: 0.725–0.935; σ_est: 0.159–0.738), so the electrical resistivity may be related to the functionality of the fractures. Finally, the LPT is shown as a very practical tool for determining the degree of the hydraulically interconnection with the surroundings, for establishing the hydraulic conductivity profile and for obtaining a measure of soil erosionability according to the significance of the fracture washing out processes recorded.  相似文献   

Tectonic evolution of a restricted ocean basin: the Powell Basin (Northeastern Antarctic Peninsula)     

José Rodriguez-Fernandez  Juan-Carlos Balanya  Jesús Galindo-Zaldivar  Andrés Maldonado 《Geodinamica Acta》2013,26(4):159-174

Abstract

The Powell Basin is one of the few present-day examples of a small isolated ocean basin largely surrounded by blocks of continental crust. The continental blocks in this basin result from the fragmentation of the northern Antarctic Peninsula. This basin was created by the eastward motion of the South Orkney microcontinent relative to the Antarctic Peninsula. The axial rift, identified by multichannel seismic profiles obtained during the HESANT 92/93 cruise, and the gravimetric anomalies of the basin plain, together with the transcurrent faults along the northern and southern margins, indicate a predominant WSW-ENE trend of basin extension. The South Orkney microcontinent was incorporated into the Antarctic Plate during the Miocene as a consequence of the end of basin spreading. The eastern and western margins are conjugate and have an intermediate crust in the region of transition to the basin plain. The differences in the basement structure and the architecture of the depositional units suggest that the extensional process was asymmetrical. The southern transtensive margin and the northern transcurrent margin are rectilinear and steep, without any intermediate crust in the narrow fault zone between the base of the continentalblocks slope and the oceanic crust. The multichannel seismic profiles across the central sector of the basin reveal a spreading axis with a double ridge and a central depression filled with sediments. The geometry of the reflectors in this depression indicates that the ponded deposits belong to the early stages of oceaniccrust accretion. This structure is similar to the overlapping spreading centres observed in fast-spreading oceanic axes, where the spreading axis has relay and overlapping segments.

The depositional units of the margins and basin plain have been grouped into four depositional sequences, comprising the classic stages in the formation of an ocean basin: pre-rift (S1), syn-rift (S2), syn-drift (S3), and post-drift (S4). The pre-rift sequence has deformed reflectors and is observed in the southern and eastern margins. The syn-rift sequence, tectonically disrupted, fills depressions bounded by faults and is well-developed in the eastern margin where it is truncated by an erosive surface identified as the break-up unconformity. The syn-drift sequence is wedge-shaped in the basin, thickening towards the margins and having onlap relations on the flanks of the spreading ridge. The post-drift sequence is the thickest unit and is characterised by a cyclic pattern of alternating packages of high-amplitude reflectors, very continuous, and low-amplitude reflectors. Towards the western and eastern margins, the same sequence has channel-levee complexes and channelised, wedged bodies attributed to turbiditic deposits of submarine fans derived from canyons located in the slope and outer shelf. The cyclic nature of this sequence is probably related to advancing and receding grounded ice sheets in the continental shelf since the latest Miocene.  相似文献   

Temporal evolution of surface humidity in Spain: recent trends and possible physical mechanisms   总被引：1，自引：0，他引：1  

Sergio M. Vicente-Serrano  Cesar Azorin-Molina  Arturo Sanchez-Lorenzo  Enrique Morán-Tejeda  Jorge Lorenzo-Lacruz  Jesús Revuelto  Juan I. López-Moreno  Francisco Espejo 《Climate Dynamics》2014,42(9-10):2655-2674

We analyzed the evolution of surface relative humidity (RH) and specific humidity (q) in Spain, based on complete records available from the State Meteorological Agency of Spain. The surface RH records used span the period 1920–2011, but because of spatial and temporal constraints in the dataset we used a subset of the data, covering the period 1961–2011. The subset contained 50 monthly series of RH, which were created through a process of quality control, reconstruction and homogenization. The data shows that there was a large decrease in RH over mainland Spain from 1961 to 2011, which was greatest in spring and summer. In contrast, there was no overall change in the specific humidity in this period, except in spring, when an increase was observed. The decrease in RH affected the entire country, but the changes in specific humidity were less homogeneous. For specific humidity there was a general increase in the northern and eastern parts of Spain, whereas negative trends dominated in the central and southern areas, mainly during the summer months. The results suggest that an increase in the water holding capacity of the atmosphere as a consequence of warming during recent decades has not been accompanied by an increase in the surface water vapor content, probably because the supply of water vapor from the main terrestrial and oceanic areas has been constrained. We discuss the implications of these findings for evapotranspiration processes, precipitation and water management in Spain.  相似文献   

Climatic Indices Influencing the Long-Term Variability of Mediterranean Heat and Water Fluxes: The North Atlantic and Mediterranean Oscillations     

Francisco Criado-Aldeanueva  F. Javier Soto-Navarro  Jesús García-Lafuente 《大气与海洋》2014,52(2):103-114

Interannual to interdecadal precipitation (P), evaporation (E), water deficit (E-P), and total heat flux have been correlated with North Atlantic Oscillation (NAO) and Mediterranean Oscillation (MO) indices to explore the influence of large-scale atmospheric forcing on the variability of the Mediterranean water and heat budgets. Basin-averaged precipitation decrease from the mid-1960s to the late 1980s clearly corresponds to a switch from a low to a high state of both indices. The variability of E-P is not so well correlated with the atmospheric indices because of the different sensitivity of E and P that leads to correlations of opposite sign in the eastern and western sub-basins. The effectiveness of the NAO and MO indices is quite similar for P and E-P but the regional MO index has turned out to be a more successful indicator of interdecadal evaporation and net heat flux because, from the mid-1970s to the early 1990s, correlation with the NAO index decreases considerably. Because the MO centre remains relatively steady, it influences most of the Mediterranean Sea year round, so it is more suitable for monitoring long-term water and especially heat budget variability.  相似文献   

Temporal patterns of deforestation and fragmentation in lowland Bolivia: implications for climate change     

Jesús N. Pinto-Ledezma  Mary Laura Rivero Mamani 《Climatic change》2014,127(1):43-54

The lowlands of eastern and northeastern Bolivia are characterized by a transition between the humid evergreen forests of the Amazon Basin and the deciduous thorn-scrub vegetation of the Gran Chaco. Within this landscape lies one of the world’s best preserved areas: the ecoregion known as the Chiquitano dry forest, where deforestation patterns over a 30 year period were analyzed. Results indicate that the area of the natural cover was reduced from 97.21 % before 1976 to 82.10 % in 2008, causing significant change in the landscape, especially in the spatial configuration of forest cover. The density of forest fragments increased from 0.073 patches per 100 ha before 1976 to 0.509 in 2008, with a mean distance between patches of 151 and 210 m over the same period, leading to a considerable reduction in the fragment sizes, from 1,204 ha before 1976 to a mere 54 in 2008. This pattern, observed in forests, does not occur in the savannas because, on one hand the savanna area is much lower compared to that of forests, and on the other because the deforestation process tended to be concentrated within forested areas. Based on the observed patterns, it is possible that in the future the natural landscapes will be substituted principally by anthropic landscapes, if there is no change in the economic and land distribution policies. If this process continues, it will stimulate the expansion of mechanized agriculture and the colonization of new areas, which will lead to further deforestation and landscape fragmentation.  相似文献   

Characterization of ground motions using recurrence plots     

Silvia R. García  Miguel P. Romo  Jesús Figueroa-Nazuno 《Geofísica Internacional》2013,52(3):209-227

The current analysis of earthquakes is typically based on linear mathematical models that may fail to describe and forecast particular behaviors, because in many cases the data complexity may induce a highly non linear behavior. In this paper the implementation of an alternative method for seismic time series analysis is presented. The RPs (Recurrence Plots) enables recognition and treatment of measured accelerations. An RP obtained from seismic data allows a more efficient interpretation of the ground motions and this explanation contributes to characterize materials and responses. The nonlinear attributes from RPs analysis can be used as filters to reveal patterns or be combined to predict a seismic property. Automated seismic data characterization, based on nonlinear seismic attributes, could rewrite the rules of earthquake phenomena interpretation. The objective of this work is to establish a new methodology for practical application of nonlinear dynamics in seismic pattern/attributes recognition, an evolving and challenging engineering field.  相似文献   

Offshore Occurrences of Heavy-Mineral Placers,Northwest Galicia,Spain     

Malcolm Richard Gent  Mario Menéndez Alvarez  Jesús José María García Iglesias  Javier TaraÑo Álvarez 《Marine Georesources & Geotechnology》2013,31(1-2):39-59

ABSTRACT

Results of offshore water-jet sediment sampling demonstrate the potential for interstadial placer deposits of industrial minerals in the shore-face to inner-shelf of Cape Ortegal, NW Spain. Placer deposition is interpreted to have occurred during glacial interstadials since the Last Glacial Maximum, and deposits sampled at 24 to 42 m. BSL were formed during the Younger Dryas, and subsequently preserved as a result of very rapid rising sea-levels. The sediments are almost entirely terrestrially derived with a particularly high heavy mineral content (Sp. Gr. >2.9), of more than 75% in all samples. Reworked garnet from earlier-sedimentary deposits constitutes an important fraction of the placer deposits identified but is generally absent in other sediments. Indications of the presence of +5 m-thick paleo-placer deposits with sections include:

• Placer garnet + spinel grades increase with depth in those sediments at 24 to 42 m BSL to the ocean-floor.

• The d50 of sediments with background grades decrease with depth while those of placer deposits do not display any significant trend.

• Garnets in non-mineralized sediments are almost entirely angular, whereas in placer enriched sediments they vary in form from well-rounded to angular. Some grains in the latter display surface morphologies typical of reworked sediment while none of the former do.

Sediments deposited during glacial interstadials at depths of up to 130 m BSL may represent important, undeveloped exploration targets for offshore placer deposits of industrial minerals. Industrial mineral exploration should extend the depths of investigations to those corresponding to major interstadial periods.  相似文献   

Electrochemical Degradation of Carbamazepine in Aqueous Solutions – Optimization of Kinetic Aspects by Design of Experiments          下载免费PDF全文

Patricia Palo  Joaquin R. Dominguez  Jesús Sánchez‐Martín  Teresa González 《洁净——土壤、空气、水》2014,42(11):1534-1540

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Introduction to Mathematics and Geosciences: Global and Local Perspectives,Volume I     

Rafael Orive  María L. Osete  Jesús I. Díaz  José Fernández 《Pure and Applied Geophysics》2015,172(1):1-5

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Coupling patterns between para‐glacial and permafrost degradation responses in Antarctica          下载免费PDF全文

Marc Oliva  Jesús Ruiz‐Fernández 《地球表面变化过程与地形》2015,40(9):1227-1238

The recently deglaciated environments in maritime permafrost regions are usually affected by very active paraglacial processes. Elephant Point is an ice‐free area of 1.16 km2 located in the SW of Livingston island (South Shetland Islands, Antarctica). Between 1956–2010 the retreat of the ice cap covering most part of this island has exposed 17.3% of the land surface in this peninsula. Two geomorphological units were identified in this new ice‐free area: a moraine extending from the western to the eastern coastlines and a relatively flat proglacial surface. The glacier in 1956 sat in contact with the northern slope of the moraine, but its accelerated retreat ‐ in parallel to the warming trend recorded in the Antarctic Peninsula ‐ left these areas free of glacier ice. Subsequently, the postglacial evolution was controlled by the relaxation phase typical of paraglacial systems. The typology and intensity of geomorphological processes show a significantly different dynamics between the southern and northern slopes of the moraine. This pattern is related to the different stage of paraglacial adjustment in both slopes. In the southern side, on coarser sediments, pronival ramparts, debris flows and alluvial fans are distributed, with a low to moderate activity of slope processes. In the northern side, mass wasting processes are extremely active on fine‐grained unconsolidated sediments. Ice‐rich permafrost is being degraded by thermokarst processes. Landslides and mudflows transfer large amounts of sediments down‐slope. The surface affected by retrogressive‐thaw slumps in the moraine has been quantified in 24,172 m2, which accounts for 9.6% of its surface. The abundance of kettle‐lakes is also indicative of the degradation of the ground ice. Paraglacial processes are expected to continue in the moraine and proglacial area in the near future, although their intensity and duration will depend on the magnitude and rate of future climate trends in the northern Antarctic Peninsula. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献