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This study addresses the influence of landslide dams on surface water drainage and groundwater flow. In the study area of Scanno Lake and Sagittario River (Central Italy), a limestone rockslide‐avalanche formed a lake, which has an outlet that is occasionally active, showing infiltration into the rockslide dam. Several springs are present at the lake's base and are partly fed by seepage through the rockslide debris. Piezometric surveys, discharge measurements, pumping tests and chemical analyses are tools used to build a conceptual model of the groundwater flow and to evaluate the flow through the rockslide debris. Seasonal water isotopic signatures validate the assumed model, showing a mixing of infiltration recharge and groundwater seepage throughout the rockslide debris. Various recharge areas have been found for springs, pointing out those directly fed by the rockslide debris aquifer. Hypotheses about seasonal groundwater mixing between the regional carbonate aquifer and the rockslide debris aquifer are supported by isotope results. Seasonal changes in groundwater table level due to recharge and surface losses from seasonal outlet have been correlated with isotopic groundwater composition from the rockslide debris aquifer and the downstream springs; this relationship highlights the role of the rockslide dam body on the hydrodynamics of the studied area. Relationships between surface waters and groundwater in the area have been completely understood on the basis of water isotopic fingerprinting, finally obtaining a complete evaluation of groundwater renewable resources and its regimen. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   
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The Buenos Aires (Argentina) and Venice (Italy) coastlands have experienced significant saltwater contamination of the phreatic aquifer, coastal erosion, hydrodynamic changes and relative sea level rise processes due to natural and man-induced factors. These factors expose coastal areas to morpho-hydro-geological hazards, such as soil desertification, frequency and degree of flooding, littoral erosion, and the silting of river mouths and channels. Man-made interventions and actions, such as beach mining, construction of coastal structures and exploitation of aquifers without an adequate knowledge of the hydrology setting and an adequate management program, worsen these natural hazards. Uncontrolled human activity induces environmental damage to the overall coastal plains. The coastal plains play an important role in the social/economic development of the two regions based on land use, such as agriculture, horticulture, breeding, and tourism, as well as industry. Results of investigations on saltwater contamination, sea level rise and morphological changes recently performed in these two coastal areas are presented here.  相似文献   
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A high‐resolution method to image the horizontal boundaries of gravity and magnetic sources is presented (the enhanced horizontal derivative (EHD) method). The EHD is formed by taking the horizontal derivative of a sum of vertical derivatives of increasing order. The location of EHD maxima is used to outline the source boundaries. While for gravity anomalies the method can be applied immediately, magnetic anomalies should be previously reduced to the pole. We found that working on reduced‐to‐the‐pole magnetic anomalies leads to better results than those obtainable by working on magnetic anomalies in dipolar form, even when the magnetization direction parameters are not well estimated. This is confirmed also for other popular methods used to estimate the horizontal location of potential fields source boundaries. The EHD method is highly flexible, and different conditions of signal‐to‐noise ratios and depths‐to‐source can be treated by an appropriate selection of the terms of the summation. A strategy to perform high‐order vertical derivatives is also suggested. This involves both frequency‐ and space‐domain transformations and gives more stable results than the usual Fourier method. The high resolution of the EHD method is demonstrated on a number of synthetic gravity and magnetic fields due to isolated as well as to interfering deep‐seated prismatic sources. The resolving power of this method was tested also by comparing the results with those obtained by another high‐resolution method based on the analytic signal. The success of the EHD method in the definition of the source boundary is due to the fact that it conveys efficiently all the different boundary information contained in any single term of the sum. Application to a magnetic data set of a volcanic area in southern Italy helped to define the probable boundaries of a calderic collapse, marked by a number of magmatic intrusions. Previous interpretations of gravity and magnetic fields suggested a subcircular shape for this caldera, the boundaries of which are imaged with better detail using the EHD method.  相似文献   
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The transfer equations for the Stokes parameters, as derived under the assumption of LTE and in the general case of anomalous Zeeman multiplet, are solved by a perturbative method that reduces the system of four coupled linear differential equations to an iterative series of well known linear differential equations. The perturbation parameter turns out to be of the order of magnitude of the ratio of the Larmor frequency to the line Doppler half-width, so that the method appears to be particularly suitable for small magnetic fields.Some qualitative results on the importance of Faraday rotation and the orders of magnitude of the line profiles of the Stokes parameters are obtained.  相似文献   
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An effective approach to understanding the dynamics of explosive volcanic eruptions and the conduit systems that drive them is through synergy of multiple data sets. Three data sets that lend themselves to ease of integration are seismic, infrasonic and thermal. Although approaches involving these data have been used to record volcanological phenomena since 1862, 1955 and 1965, respectively, their integrated use has only developed since 1999. When combined, these three data sets allow constraint of shallow system geometry and the dynamics of the explosive events that occur within that system. Using Stromboli volcano (Italy) as a case study, we review the complete range of geochemical and geophysical studies that can be applied. In doing so, we aim to show how integration of these diverse studies allows insights into a plumbing system and the dynamics of the eruptive activity that the system feeds. When combined at Stromboli, these data provide constraint of multiple system parameters including chamber depths, gas and magma fluxes, shallow system magma residence times, explosion source depths, and the rise/ejection velocities of ascending gas slugs and ejecta. In turn, these results allow various conduit and eruption dynamic models to be applied and tested.The persistent and repeated mildly explosive events that characterize Stromboli have been modeled in terms of the coalescence of gas within the magma to form large gas slugs that ascend the remaining portion of the conduit to burst at the free surface. Our integrated seismic, infrasonic and thermal data sets indicate that gas coalescence occurs at a depth of ∼260 m, with a typical event frequency of ∼9/h. Infrasonic and thermal data show the explosion source to be located 20-220 m below the vent. Thermal data give emission velocities for the ejected fragments of 8-20 m/s, which converts to gas jet velocities of 23-39 m/s. Tracking these parameters in space and time shows that, although eruptions at Stromboli can be grouped into two characteristic types (simple and complex-each of which characterizes a particular crater, NE and SW, respectively), events within each type show significant short-term variability. The system does, however, appear robust, maintaining its characteristic strombolian eruption style after significant effusive phases and more energetic explosive events.  相似文献   
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