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991.
Earthquake mechanisms of the Adriatic Sea and Western Greece: implications for the oceanic subduction-continental collision transition 总被引:3,自引:0,他引:3
Calum Baker Denis Hatzfeld Hélène Lyon-Caen Elephteria Papadimitriou Alexis Rigo † 《Geophysical Journal International》1997,131(3):559-594
We present 21 focal solutions (magnitude > 5.5) reliably computed by body-wave modelling for the western Hellenic arc from Yugoslavia to the southern Peloponnese. Mechanisms located within the Aegean show normal faulting, the T-axis trending N-S in the centre and parallel to the active boundary in the external part. Mechanisms associated with the Keffalinia fault are consistent with dextral strike-slip motion. Reverse mechanisms located along the active boundary are remarkably consistent and do not depend on the nature of the active boundary (continental collision or oceanic subduction). The consistency in azimuth of the slip vectors and of the GPS velocity relative to Africa, all along the active boundary, suggests that the deformation is related to the same motion. The discrepancy between seismic-energy release and the amount of shortening confirms that the continental collision is achieved by seismic slip on faults but the oceanic subduction is partially aseismic. The northward decrease in velocity between continental collision and oceanic subduction suggests the continental collision to be a recent evolution of the active subduction. 相似文献
992.
Mira MoroviĆ 《Journal of Earth System Science》2002,111(3):215-225
Spatial and temporal variability of pigments was studied from the CZCS satellite data and fromin situ chlorophyll and transparency for the period 1979-1985. The three Adriatic sites, Northern, Middle, and Southern Adriatic
are differently influenced by meteorological, hydrological and oceanographic parameters. The differences between seasonalin situ chlorophyll and remotely sensed pigment concentrations (from CZCS satellite data) from the Adriatic are large in winter.
Through the correlation analysis, pigments were compared to meteo-oceanographic and hydrological parameters from different
Adriatic sites. The PCA (principal component analysis) was applied to the pigment data series and significant components were
compared. Different correlations are obtained for warm and cold periods of the year pointing to seasonal differences in the
underlying mechanism of pigment variability. The first PC is influenced mainly by temperature. In the warm period more parameters
seem to influence the pigment field, than in the cold period. The pigments in the Adriatic are in good correlation to a number
of hydrologic and meteo-oceanographic factors. 相似文献
993.
Zhuang XU Alaa SALEM Zhongyuan CHEN Weiguo ZHANG Jing CHEN Zhanghua WANG Qianli SUN Daowei YIN 《Frontiers of Earth Science》2008,2(4):434-438
This paper examines the Burullus lagoon deposits of the Nile delta coast and the distribution of Pb-210 and Cs-137. Three
vibrocores from the lagoon have revealed densely concentrated shell fragments of brackish water origin in the upper (<ca.
15cm, in general) core sediments. Pb-210 and Cs-137 are in general measurable above this sediment core horizon, but, the rest
downcore remains as an irregular distribution pattern, probably incurred due to secondary sediment transport or seawater seepage
related processes. The present study of Pb-210 and Cs-137 and associated sediment nature of Burullus lagoon prefers sediments
of <15 cm in vibrocores to after Aswan High Dam constructed in 1964, with sedimentation rate of 0.42-0.56 cm/a. 相似文献
994.
INTRODUCTIONThemangroveswamPisaInaoransySteInwherespedallyadaptalplantSgrowintheintertidalbetattheinterfacebetweenlandandaninthetropiesandsub-tropies.ThernangrovefonstplaySrnanyrolessuchascoastalstabilizer,disperseroftheeneryofst0me,tida1boresandwinds,baniert0invasionofinlandarmbysaltwatCr,produoerofnutrientSandfoastresounasuchasfuel,chaimal,fodder,tirnberandsomeirnPor-tantanbeIsoferenoAncvalue.TheongoingintheiveandextenSivedestruCtion0frnangrovesbymankindseVereydarnagestemetrialandn… 相似文献
995.
Flash floods associated with heavy precipitation has become a hazardous phenomenon along the Mediterranean coasts of Turkey in recent years. During 3 and 4 November 1995 heavy and intense rainstorm activity over the Aegean coast led to flash flooding in the city of zmir. Damage exceeded $50 million and 61 people died as a result of the flood. The Karyaka district suffered the most severe damage. This study presents an analysis of the meteorological settings that led to the development of these intense storms and describes the role of the terrain features involved in the zmir flood.The important mesoscale features which initiated the severe weather outbreak included pronounced low-level advection, positive vorticity and strong upper level divergence. A surface low centered over the Aegean Sea enhanced the advection of warm and moist unstable air masses coming from the southwest over the Mediterranean Sea along a southwesterly low level jet (LLJ). A squall line oriented NE-SW over the Aegean Sea also contributed to the storm development, and intensity of the storms was further enhanced by the orographic effect. The presence of a frontal system, the stability indices associated with the event, and other meteorological features are all reminiscent of the synoptic type flash floods identified by Maddox. While the pressure and moisture patterns were favorable for severe storm activity, nonmeteorological factors including the topography, geomporphology, and and land-use contributed to the flooding to a great extent. Settling in the flood-prone zone, insufficient floodwater structures, and the lack of channel improvements in the creeks enhanced flood damage to the city. Many of the deaths occurred in the settlements located in the flood-prone zone of the Ilca and Dallk creeks. 相似文献
996.
Abstract. A four-year oceanographic data set from the Northern Adriatic Sea identified the factors favoring development of the nanoplankton or microplankton components of the phytoplankton crop. Latitudinally atypical summer nanoplankton blooms, perhaps of recent origin, develop under vertically stratified conditions in the presence of high nutrient concentrations (including silicates). Including the summer blooms, the nanoplankton were responsible for more than half the total phytoplankton production about 90% of the time. No single mechanism governed phytoplankton cell size or size succession, but rather a number of mechanisms which were not mutually exclusive. 相似文献
997.
While acetate is generally regarded as an important intermediate in the mineralization of organic matter in anoxic sediment systems, some quantitative studies in marine systems (including our own) have measured acetate oxidation rates in excess of sulphate reduction rates where sulphate is known to be the principal electron acceptor. We revisited Skan Bay, Alaska, where we had previously made such observations, for a reexamination of acetate turnover. Measurements of acetate concentrations, production rate, oxidation rate and sulphate reduction rate as well as bioenergetic considerations led to the conclusion that acetate oxidation rate in 15–18-cm deep sediment is 1·1–1·5 μM h−1. The possibility that previous measurements were high because of a non-citric-acid-cycle pathway of acetate oxidation (suggested by recent laboratory studies) was excluded. It appears that our previous turnover measurements were high mainly because of high acetate concentrations. Procedures used for the isolation of porewater for acetate determination may influence results to an extent not previously recognized. 相似文献
998.
The activity of three Malacostraca (Decapoda), Crangon crangon, Carcinus aestuarii and Paleamon squilla, was studied following rapid environmental changes in a Mediterranean lagoon linked temporarily with the sea. Nekton was sampled every 2–3 days using fixed fyke nets. A canonical analysis and a stepwise multiple regression were computed to determine which factor(s) can predict or account for the catch of these three decapods. In spite of rapid environmental changes no exceptional mortality was observed in each of the three species. Temperature is the environmental factor with major impact on the activity of C. crangon. Activity of P. squilla is controlled by water depth. At a depth of less than 20 cm two factors, salinity and phase of the moon, have a significant influence on the activity of this species. At depths deeper than 20 cm the activity is inhibited. There is only a weak relationship between the catch of C. aestuarii and salinity. Additional data on the life cycle of these species are given. The limitations of a monthly sampling period are discussed and the need for more short-term, consecutive sampling periods is stressed in order to understand the dynamics of systems with rapid environmental fluctuations. 相似文献
999.
1000.
Abstract. A three-year set of data from six stations is analysed in order to monitor the environmental quality by use of macrobenthos in addition to chemical data. The communities differ along the depth gradient and no seasonal cycle is evident. Stronger temporal differences in community composition are evident when examining a four-year cycle at one of the stations in connection with an improvement of environmental parameters. 相似文献