Multifractal analysis of three large earthquakes in Chile: Antofagasta 1995, Valparaiso 1985, and Maule 2010     

Denisse Pastén  Diana Comte 《Journal of Seismology》2014,18(4):707-713

A multifractal analysis of seismicity of three large earthquakes in Chile is made: the Central Zone 1985 (M _W = 8.0), Antofagasta 1995 (M _W = 8.1), and Maule 2010 (M _W = 8.8) earthquakes. The analysis shows that the fractal dimension spectrum D _q decreases with time before an earthquake. This fact suggests that the spatial distribution of seismic events could form a cluster before a main shock.  相似文献   

Analysis of nodal point pollution,variability, and sustainability in mesohaline tidal creeks     

Andrew Muller  Diana Muller 《Marine pollution bulletin》2014

Mesohaline tidal creeks are critical since they may lie at the crossroads of aquatic habitat and urban/sub-urban pressures. The emphasis of this study was to determine the water quality stressor variations within and between tidal creeks and determine whether they serve as nodes of pollutants into the sub-estuary. Measurements of water quality stressors were conducted over a six-year period. The study revealed that characterizing the variability of individual tidal creeks is critical to understanding the process and impacts of stressors in sub-estuarine environments and that the tidal creeks are actually nodal points of sediment and nutrient pollution. This results in hypoxia being controlled within tidal creeks rather than being imported from the parent estuary. The calculated metrics were then used to create a Sustainability Characterization Map. Methods incorporated in this study would be of value to restoration managers, and in the decision-making process of urban and suburban watershed planners.  相似文献   

Three-dimensional kinematic depth migration of converted waves: application to the 2002 Molise aftershock sequence (southern Italy)   总被引：1，自引：0，他引：1  

Diana Latorre  Pasquale De Gori  Claudio Chiarabba  Alessandro Amato  Jean Virieux  Tony Monfret 《Geophysical Prospecting》2008,56(4):587-600

Migration techniques, currently used in seismic exploration, are still scarcely applied in earthquake seismology due to the poor source knowledge and sparse, irregular acquisition geometries. At the crustal scale, classical seismological studies often perform inversions based on the arrival time of primary phases (P- and S-waves) but seldom exploit other information included in seismic records. Here we show how migration techniques can be adapted to earthquake seismology for converted wave analysis. As an example, we used data recorded by a dense local seismic network during the 2002 Molise aftershock sequence. In October and November 2002, two moderate magnitude earthquakes struck the Molise region (southern Italy), followed by an aftershock sequence lasting for about one month. Local earthquake tomography has provided earthquake hypocenter locations and three-dimensional models of P and S velocity fields. Strong secondary signals have been detected between first-arrivals of P- and S-waves and identified as SP transmitted waves. In order to analyse these waves, we apply a prestack depth migration scheme based on the Kirchhoff summation technique. Since source parameters are unknown, seismograms are equalized and only kinematic aspects of the migration process are considered. Converted wave traveltimes are calculated in the three-dimensional (3D) tomographic models using a finite-difference eikonal solver and back ray tracing. In the migrated images, the area of dominant energy conversion corresponds to a strong seismic horizon that we interpreted as the top of the Apulia Carbonate Platform and whose geometry and position at depth is consistent with current structural models from existing commercial seismic profiles, gravimetric and well data.  相似文献   

Dynamics of a Prorocentrum minimum bloom along the northern coast of Sinaloa,Mexico     

Aída Martínez-López  Diana Cecilia Escobedo-Urías  Ana Elsi Ulloa-Pérez  Raul Aguirre 《Continental Shelf Research》2008

To investigate the relative importance of mesoscale physical events, such as upwellings and physical and chemical variables during an algae bloom of Prorocentrum minimum, 25 sampling sites were established offshore of the Navachiste Lagoon Complex on the east side of the Gulf of California. Samples were analyzed for phytoplankton concentration, water chemistry, and temperature during November 1999, January, March, April, May, and August 2000. Satellite imagery of sea surface temperature (SST) for April 2000 was processed to obtain a synoptic view of the area during the extraordinary bloom of P. minimum in the open waters of the Gulf of California. The bloom was associated with change of oceanographic conditions from moderate winds to calm period, temperature increase and high nitrate (NO₃⁻-N) and ammonia (NH₄⁺-N) content in the offshore waters. Depletion of these nutrients during the bloom suggests that this species uses both types of nitrogen substrates. Cysts in the northernmost sampling stations in January and March indicate that upwelling water, rich in nitrates, also carried a seed stock population of P. minimum. SST patterns in the satellite imagery suggest wind-forcing as the responsible mechanisms triggering the algal bloom offshore of the Navachiste Lagoon Complex.  相似文献   

Evaluating different GCMs for predicting spatial recharge in an irrigated arid region     

Michael W. Toews  Diana M. Allen   《Journal of Hydrology》2009,374(3-4):265-281

Groundwater systems in arid regions will be particularly sensitive to climate change owing to the strong dependence of rates of evapotranspiration on temperature, and shifts in the precipitation regimes. Irrigation use in these arid regions is typically a large component of the water budget, and may increase due to changes in soil moisture resulting from higher temperatures and changes in the timing of precipitation events. In this study, future predicted climate change scenarios from three global climate models (CGCM1 GHG+A1, CGCM3.1 A2, and HadCM3 A2) are used to determine the sensitivity of recharge to different climate models in an irrigated agricultural region. The arid Oliver region (annual precipitation 300 mm) in the Okanagan Basin, British Columbia, is used to demonstrate the approach. Irrigation return flow, as a contribution to total diffuse recharge, is simulated by calculating the daily applied irrigation based on estimates of seasonal crop water demand and the forecasted precipitation and evaporation data. The relative contribution of irrigation return flow to groundwater recharge under current and future climate conditions is modelled. Temperature data were downscaled using Statistical Downscaling Model (SDSM), while precipitation and solar radiation changes were estimated directly from the GCM data. Shifts in climate, from present to future predicted, were applied to a stochastic weather generator, and used to force a one-dimensional hydrologic model, HELP 3.80D. Results were applied spatially, according to different soil profiles, slope and vegetation, over a 22.5 km by 8.6 km region. Changes to recharge in future time periods for each GCM result in modest increases of recharge with the peak recharge shifting from March to February. Lower recharge rates and higher potential evapotranspiration rates are similarly predicted by all three models for the summer months. All scenarios show that the potential growing season will expand between 3 and 4 weeks due to increases in temperature. However, the magnitude of the change varies considerably between models. CGCM3.1 has the largest increases of recharge rates, CGCM1 has very minor increases, and HadCM3 is relatively stable (as indicated by the near-zero changes between climate states). The significant differences between these three models indicate that prediction of future recharge is highly dependent on the model selected. The minor increase of annual recharge in future predicted climate states is due the shift of peak recharge from increased temperature. Irrigation rates dominate total recharge during the summer months in this arid area. Recharge in irrigated areas is significantly higher than natural recharge, with irrigation return flow between 25% and 58%. A comparison of recharge results for the least efficient and the most efficient irrigation systems indicates that the latter are more sensitive to choice of GCM.  相似文献   

Assessing impacts of invasive phytoplankton: The Baltic Sea case     

Irina Olenina  Norbert Wasmund  Iveta Jurgensone  Janina Kownacka  Diana Vaiciūt? 《Marine pollution bulletin》2010,60(10):1691-1700

There is an increasing understanding and requirement to take into account the effects of invasive alien species (IAS) in environmental quality assessments. While IAS are listed amongst the most important factors threatening marine biodiversity, information on their impacts remains unquantified, especially for phytoplankton species. This study attempts to assess the impacts of invasive alien phytoplankton in the Baltic Sea during 1980-2008. A bioinvasion impact assessment method (BPL - biopollution level index) was applied to phytoplankton monitoring data collected from eleven sub-regions of the Baltic Sea. BPL takes into account abundance and distribution range of an alien species and the magnitude of the impact on native communities, habitats and ecosystem functioning. Of the 12 alien/cryptogenic phytoplankton species recorded in the Baltic Sea only one (the dinoflagellate Prorocentrum minimum) was categorized as an IAS, causing a recognizable environmental effect.  相似文献   

Periglacial landscape evolution and environmental changes of Arctic lowland areas for the last 60 000 years (western Laptev Sea coast, Cape Mamontov Klyk)     

Lutz Schirrmeister  Guido Grosse  Viktor Kunitsky  Diana Magens  Hanno Meyer  Alexander Dereviagin  Tatyana Kuznetsova  rei Andreev  Olga Babiy  Frank Kienast  Mikhael Grigoriev  Pier Paul Overduin  & Frank Preusser 《Polar research》2008,27(2):249-272

Non-glaciated Arctic lowlands in north-east Siberia were subjected to extensive landscape and environmental changes during the Late Quaternary. Coastal cliffs along the Arctic shelf seas expose terrestrial archives containing numerous palaeoenvironmental indicators (e.g., pollen, plant macro-fossils and mammal fossils) preserved in the permafrost. The presented sedimentological (grain size, magnetic susceptibility and biogeochemical parameters), cryolithological, geochronological (radiocarbon, accelerator mass spectrometry and infrared-stimulated luminescence), heavy mineral and palaeoecological records from Cape Mamontov Klyk record the environmental dynamics of an Arctic shelf lowland east of the Taymyr Peninsula, and thus, near the eastern edge of the Eurasian ice sheet, over the last 60 Ky. This region is also considered to be the westernmost part of Beringia, the non-glaciated landmass that lay between the Eurasian and the Laurentian ice caps during the Late Pleistocene. Several units and subunits of sand deposits, peat–sand alternations, ice-rich palaeocryosol sequences (Ice Complex) and peaty fillings of thermokarst depressions and valleys were presented. The recorded proxy data sets reflect cold stadial climate conditions between 60 and 50 Kya, moderate inderstadial conditions between 50 and 25 Kya and cold stadial conditions from 25 to 15 Kya. The Late Pleistocene to Holocene transition, including the Allerød warm period, the early to middle Holocene thermal optimum and the late Holocene cooling, are also recorded. Three phases of landscape dynamic (fluvial/alluvial, irregular slope run-off and thermokarst) were presented in a schematic model, and were subsequently correlated with the supraregional environmental history between the Early Weichselian and the Holocene.  相似文献   

Rotation broadening of spectral features from star spots     

Diana P. Kjurkchieva 《Astrophysics and Space Science》1995,232(1):185-194

This paper presents an extension of the method of the characteristic points by Kjurkchieva (1987, 1989). This method for the analysis of light curves of spotted stars is further developed by including spectral information. Expressions describing the variation of the rotation broadening of spectral features arising from a star spot are derived for a known spot configuration. The results are used in the solution of the inverse problem by the method of the characteristic points. It is shown that the rotation broadening of spectral features from star spots can be used to easily determine the angular size and the polar distance of a circular spot. It turns out that the equatorial velocity and radius of the spotted star can be obtained in some cases by the combined analysis of the photometric and spectral data.  相似文献   

B and R photometry of AM her during 1993     

Diana P. Kjurkchieva  Dragomir V. Marchev 《Astrophysics and Space Science》1995,234(2):207-215

The results from the simultaneous observations in B and R colours of AM Her are presented. Analysis of these data shows the following: (a) There are always two clear minima in the R light curves, while the secondary minimum in B light curves sometimes is not well defined; (b) The times of the minima in R and B colour nearly coincide; (c) The photometric period changes remarkably from cycle to cycle but its mean value remains constant; (d) Short stillstands on the increasing branches of the two minima are seen similar to those visible in UX UMa-type cataclysmic stars; (e) Besides the irregular flickering with time scale of a few minutes, a variability with a period 20.28 min in the two colours is established.  相似文献   

Late Pliocene–Quaternary tectonics in the frontal part of the SE Carpathians: Insights from tectonic geomorphology     

Diana Necea  W. Fielitz  L. Matenco   《Tectonophysics》2005,410(1-4):137-156

The Romanian East Carpathians display large-scale heterogeneities along the mountain belt, unusual foredeep geometries, significant post-collisional and neotectonic activity, and major variations in topography, mostly developed in the aftermath of late Miocene (Sarmatian; 11 Ma) subduction/underthrusting and continental collision between the East European/Scythian/Moesian foreland and the inner Carpathians Tisza-Dacia unit. In particular, the SE corner of the arcuate orogenic belt represents the place of still active large-scale differential vertical movements between the uplifting mountain chain and the subsiding Focşani foredeep basin. In this key area, we have analysed the configuration of the present day landforms and the drainage patterns in order to quantify the amplitude, timing and kinematics of these post-collisional late Pliocene–Quaternary vertical movements. A river network is incising in the upstream a high topography consisting of the external Carpathians nappes and the Pliocene–Lower Pleistocene sediments of the foreland. Further eastwards in the downstream, this network is cross-cutting a low topography consisting of the Middle Pleistocene–Holocene sediments of the foreland. Geological observations and well-preserved geomorphic features demonstrate a complex succession of geological structures. The late Pliocene–Holocene tectonic evolution is generally characterised by coeval uplift in the mountain chain and subsidence in the foreland. At a more detailed scale, these vertical movements took place in pulses of accelerated motion, with laterally variable amplitude both in space and in time. After a first late Pliocene uplifting period, subsidence took place during the Earliest Pleistocene resulting in a basal Quaternary unconformity. This was followed by two, quantifiable periods of increased uplift, which affected the studied area at the transition between the Carpathians orogen and the Focşani foreland basin in the late Early Pleistocene and the late Middle to late Pleistocene. Both large-scale deformation events affected the western Focşani basin flank, tilting the entire structure with 9° during the late Early Pleistocene and uplifted it as a block during the early Late Pleistocene. The late Early Pleistocene tilting resulted in 750 m uplift near the frontal monocline and by extrapolation in a presumed 3000 m uplift near the central parts of the Carpathians. The late Middle to late Pleistocene cumulative uplift reaches 250 m and correlates with a contemporaneous progradation of the uplifted areas towards the Focşani Basin. The uplifting events are separated by a second Quaternary unconformity. On the whole, the late Pliocene–Quaternary evolution of the Carpathians orogen/Focşani basin structure indicate large-scale differential uplift during the latest stages of a continuous post-collisional orogenic evolution.  相似文献