Structural features of Panarea volcano in the frame of the Aeolian Arc (Italy): Implications for the 2002–2003 unrest     

Valerio Acocella  Marco Neri  Thomas R. Walter   《Journal of Geodynamics》2009,47(5):288-292

Panarea, characterized by gas unrest in 2002–2003, is the volcanic island with the least constrained structure in the eastern-central Aeolian Arc (Italy). Based on structural measurements, we define here its deformation pattern relative to the Arc. The main deformations are subvertical extension fractures (63% of data), normal faults (25%) and dikes (12%). The mean orientation of the extension fractures and faults is N38°E, with a mean opening direction of N135° ± 8°, implying extension with a moderate component of dextral shear. These data, matched with those available for Stromboli volcano (pure opening) and Vulcano, Lipari and Salina volcanoes (predominant dextral motions) along the eastern-central Arc, suggest a progressive westward rotation of the extension direction and an increase in the dextral shear. The dextral shear turns into compression in the western arc. The recent unrest at Panarea, coeval to that of nearby Stromboli, may also be explained by the structural context, as both volcanoes lie along the portion of the Arc subject to extension.  相似文献   

Coordinate mapping of analytical contaminant transport solutions to non-uniform flow fields     

James R. Craig  Thomas Heidlauf 《Advances in water resources》2009

Existing analytical solutions to 2D and 3D contaminant transport problems are limited by the mathematically convenient assumption of uniform flow. An approximate method is developed herein for coordinate mapping of 2D (vertically-averaged) transport solutions to non-uniform steady-state irrotational and divergence-free flow fields in single-layer aquifers. The method enables existing analytical transport solutions to be applied to aquifer systems with wells, non-uniform saturated thickness, surface water features, and (to a limited degree) heterogeneous hydraulic conductivity and recharge. This mass-conservative coordinate mapping approach is inexact in its approximation of the dispersion process but is still sufficiently accurate for many simple flow systems. The degree of model error is directly proportional to the variation of velocity magnitude within the domain. These mapped analytical solutions are compared to numerical simulation results and the coordinate mapping errors are investigated. The methods described herein may be used in the traditional capacity of analytical transport models, i.e., screening and preliminary site assessment, without sacrificing accuracy by assuming locally uniform flow conditions or applying an ad-hoc coordinate transformation. The solutions benefit from the traditional advantages of analytical methods, particularly the removal of artifacts due to spatial and temporal discretization: no time-stepping or numerical discretization is required.  相似文献   

Potential impact of climate change on aquatic insects: A sensitivity analysis for European caddisflies (Trichoptera) based on distribution patterns and ecological preferences   总被引：1，自引：1，他引：0  

Daniel Hering  Astrid Schmidt-Kloiber  John Murphy  Sofie Lücke  Carmen Zamora-Muñoz  Manuel Jesús López-Rodríguez  Thomas Huber  Wolfram Graf 《Aquatic Sciences - Research Across Boundaries》2009,71(1):3-14

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Comparison of polar mesospheric cloud measurements from the Cloud Imaging and Particle Size experiment and the solar backscatter ultraviolet instrument in 2007     

Susanne Benze  Cora E. Randall  Matthew T. DeLand  Gary E. Thomas  David W. Rusch  Scott M. Bailey  James M. Russell  William McClintock  Aimee W. Merkel  Chris Jeppesen 《Journal of Atmospheric and Solar》2009,71(3-4):365-372

We compare measurements from the Aeronomy of Ice in the Mesosphere (AIM) Cloud Imaging and Particle Size (CIPS) experiment to the NOAA-17 solar backscatter ultraviolet (SBUV/2) instrument during the 2007 Northern Hemisphere polar mesospheric cloud (PMC) season. Daily average Rayleigh scattering albedos determined from identical footprints from the CIPS nadir camera and SBUV/2 agree to better than ～5% throughout the season. Average PMC brightness values derived from the two instruments agree to within ±10%. PMC occurrence frequencies are on average ～5% to nearly a factor of two higher in CIPS, depending on latitude. Agreement is best at high latitudes where clouds are brighter and more frequent. The comparisons indicate that AIM CIPS data are valid for scientific analyses. They also show that CIPS measurements can be linked to the long time series of SBUV/2 data to investigate long-term variability in PMCs.  相似文献   

Sensitivity of climate response to variations in freshwater hosing location     

Thomas Kleinen  Timothy J. Osborn  Keith R. Briffa 《Ocean Dynamics》2009,59(3):509-521

In a recent intercomparison of the response of general circulation models (GCMs) to high-latitude freshwater forcing (Stouffer et al., J Climate 19(8):1365–1387, 2006), a number of the GCMs investigated showed a localised warming response in the high-latitude North Atlantic, as opposed to the cooling that the other models showed. We investigated the causes for this warming by testing the sensitivity of the meridional overturning circulation (MOC) to variations in freshwater forcing location, and then analysing in detail the causes of the warming. By analysing results from experiments with HadCM3, we are able to show that the high-latitude warming is independent of the exact location of the additional freshwater in the North Atlantic or Arctic Ocean basin. Instead, the addition of freshwater changes the circulation in the sub-polar gyre, which leads to enhanced advection of warm, saline, sub-surface water into the Greenland–Iceland–Norwegian Sea despite the overall slowdown of the MOC. This sub-surface water is brought to the surface by convection, where it leads to a strong warming of the surface waters and the overlying atmosphere.  相似文献   

Towards continuous long-term measurements of suspended particulate matter (SPM) in turbid coastal waters   总被引：1，自引：1，他引：0  

Thomas H. Badewien  Elke Zimmer  Alexander Bartholomä  Rainer Reuter 《Ocean Dynamics》2009,59(2):227-238

The dynamics of sediment transport in the East Frisian Wadden Sea are important for the coastal zone and for ecosystem functioning. The tidal inlets between the East Frisian islands connect the back-barrier intertidal flats to the North Sea. Here, concentrations of suspended particulate matter (SPM) in the water column are highly variable, depending on weather conditions and tides. In order to estimate the nature and quantity of sediment transport, in situ measurements were carried out at a Time Series Station in the tidal inlet between the islands of Spiekeroog and Langeoog. This study shows the suitability of multispectral transmissometry (MST) for obtaining long-term SPM measurements with high resolution. The comparability of this technique to the standard filter method and the laser diffraction method [laser in situ scattering and transmissometry (LISST)] is demonstrated. In addition, the Junge coefficients derived from both MST and LISST measurements are compared. A time series of SPM data covering nearly 4 months is presented. As a major result, the data reveal that a single storm surge can have less impact on SPM dynamics than longer-lasting gales. This high-resolution long-term data set is very valuable for modelling suspended matter flux. It also provides background information for studying the influence of SPM dynamics on coastal sediments.  相似文献   

Frictional sliding in serpentine at very high pressure     

Haemyeong Jung  Yingwei Fei  Paul G. Silver  Harry W. Green 《Earth and Planetary Science Letters》2009,277(1-2):273-279

Using a new four-channel system for detecting acoustic emissions in a multianvil apparatus, we have assessed the pressure–temperature range for such emissions, as well as the role of dehydration, by deforming samples of extensively serpentinized peridotite. We show that in the absence of dehydration and for samples initially faulted at low pressure, acoustic emissions occurred well outside the expected pressure–temperature field of unassisted brittle failure. Emissions were also detected during and after dehydration of serpentine. Microstructures of post-run specimens revealed fault slip with offsets up to ~ 500 μm, regardless of whether or not dehydration took place. Dehydration appears to effectively stop slip on pre-existing faults and create new ones. Analysis of P-wave travel times from the four sensors confirmed that the acoustic emissions originated within the specimen during fault slip. These observations suggest that earthquakes can be triggered by slip along an existing fault containing serpentine under significantly higher pressure and temperature conditions than previously thought possible without dehydration.  相似文献   

IGCP 368 International Field Workshop in Eastern Zimbabwe and Western Mozambique     

Bob Thomas 《Gondwana Research》1999,2(2):318

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Short contribution: Buried Canopic channel identified near Egypt's Nile delta coast with radar (SRTM) imagery     

Jean‐Daniel Stanley  Thomas F. Jorstad 《Geoarchaeology》2006,21(5):503-514

Shuttle Radar Topography Mission (SRTM) data, with ground‐based geologic investigations, define the geographic position of the relict Canopic channel in Egypt's NW Nile delta. Two sinuous channel segments south of Abu Qir Bay are observed on a radar image: a more sinuous trace (36 km in length) west of Idku lagoon, and an eastern one (˜20 km), reaching the lagoon's southeast corner. Sediment cores recovered along channel traces show sand‐rich deposits (to > 4 m thick) beneath the surface, in contrast with silty muds in areas away from channels. Historic and archaeological findings indicate that the Ptolemaic Roman city of Schedia once lay directly along the Canopic that channeled water from the 3rd to 2nd centuries B.C. until ˜5th century A.D., after which Nile water was displaced to the east via Bolbitic and, later, Rosetta branches. Identification of buried, but well‐defined, Canopic channels provides baselines for renewed archaeological exploration in this delta sector. © 2006 Wiley Periodicals, Inc.  相似文献   

Integration of GIS and Spatio-temporal Simulation Models: Interoperable Components for Different Simulation Strategies   总被引：1，自引：0，他引：1  

Lars Bernard  & Thomas Krüger 《Transactions in GIS》2000,4(3):197-215

New technologies for distributed object computing (DOC) challenge new approaches to integrate Geographical Information Systems (GIS) and simulation tools for spatio-temporal modeling. Several standardization initiatives work on specifying interfaces and defining service architectures for appropriate components. Currently, the most promising attempts are represented by the OpenGIS and the High Level Architecture. This paper gives a brief survey of the current state of the emerging standards, highlights the advantages and shortcomings of these attempts, and defines a possible framework for GIS-integrated simulation of spatio-temporal processes. Two abstraction layers provide interfaces for different GIS kernels and allow the integration of different simulation models. A prototype implementation of the specified interfaces shows the integration of analysis tools and two different simulation strategies: a mesoscale boundary layer model based on the Navier-Stokes equation and a cellular automata to simulate air pollutant dispersion.  相似文献