Seismic hazard impact of the Lower Tagus Valley Fault Zone (SW Iberia)   总被引：5，自引：1，他引：5  

Susana P. Vilanova  Joao F.B.D. Fonseca 《Journal of Seismology》2004,8(3):331-345

The seismic hazard of SW Iberia is composed of two contributions: offshore, large to very large events on the plate boundary between Africa and Eurasia such as the Lisbon earthquake of 1755 or the Gorringe Bank earthquake of 1969; and onshore, moderate to strong intraplate earthquakes on inherited crustal fractures. One of these zones of crustal weakness is the Lower Tagus Valley (LTV) fault zone, which displays the highest level of seismic hazard in Western Iberia. In this paper we review the active tectonics and seismicity of the LTV, integrating previous geophysical data with recent results of paleoseismological investigations, and discuss its impact on the seismic hazard of SW Iberia. We conclude that the seismic zonation for hazard assessment currently in force in the building code is biased towards the scenario of distant offshore rupture, and does not take adequately into account the LTV seismic source.  相似文献   

Stratospheric final warmings in the Southern Hemisphere and their energetics     

V. B. Rao  M. B. Rosa  J. P. Bonatti  S. H. Franchito 《Meteorology and Atmospheric Physics》2003,83(1-2):35-49

Summary.  Using 9 years (1985–1993) data, final stratospheric warmings in the Southern Hemisphere are studied. Interannual variations in the onset date and the temperatures are noted. In 1985 the stratosphere was colder by about 5 K and the wave activity was less. This year the final warming got delayed. In contrast in 1988 the final warming occurred earlier when compared with the mean picture and the wave activity was more. An examination of Eliassen-Palm fluxes showed the important role of planetary waves in the wave-mean flow interaction. In the energetics the most spectacular change is the reduction of zonal kinetic energy. Before the warming the energy exchanges were P_z → P_e → K_e → K_z ← P_z and after the warming they were P_z ← P_e ← K_e → K_z ← P_z. The dramatic reduction of zonal kinetic energy seems to be due to two effects: the reduction in K_e → K_z conversion and the weakening of direct meridional circulation. Received October 3, 2001; revised June 5, 2002  相似文献   

Crustal melting in the lower parts of island arcs: an example from the Bremanger Granitoid Complex,west Norwegian Caledonides   总被引：4，自引：0，他引：4  

Jogvan Hansen  Kjell P. Skjerlie  Rolf B. Pedersen  Jesús De La Rosa 《Contributions to Mineralogy and Petrology》2002,143(3):316-335

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Effect of isolation temperature on the characteristics of extracellular proteases produced by Antarctic bacteria   总被引：1，自引：0，他引：1  

Susana C. Vazquez  Walter P. Mac Cormack 《Polar research》2002,21(1):63-71

Protease-producing psychrotolerant bacteria were isolated from Antarctic biotopes on casein agar plates using different incubation temperatures. Most of the isolates were non-spore-forming Gram-negative motile rods with catalase activity, 30% were pigmented and none of them were glucose fermenters. All the strains were grown in liquid cultures at 20°C and protease secretion was tested using the azocasein method. Despite their capacity for production of a clear zone of hydrolysis in agar plates, some strains did not produce detectable levels of proteolytic activity in liquid cultures. The lowest apparent optimum temperature for protease activity found in culture supernatants was 40°C. Almost all the strains showed activation energy values about 10-20 kJ-mol⁻¹ lower than that observed for a mesophilic Subtilisin. Most of the proteases showed optimal activity at neutral or alkaline pH values and developed a multiple-band profile on gelatine-SDS-PAGE. It was observed that the lower the strain isolation temperature was, the more stongly cold-adapted–in terms of optimal temperature and activation energy–were the proteases produced by them. This dependence of the characteristics of the proteases on the isolation temperature is an important factor to take into account in the design of screening programmes directed towards the isolation of psychrotolerant bacteria able to produce proteases strongly or weakly adapted to work in the cold. The Antarctic area explored proved to be a promising source of proteolytic bacteria with potential use in industrial processes to be carried out at low or moderate temperatures.  相似文献   

Variations in the pallial organ sizes of the invasive oyster, Crassostrea gigas, along an extreme turbidity gradient     

Mickaël Dutertre  Laurent Barillé  Peter G. Beninger  Philippe Rosa  Yves Gruet 《Estuarine, Coastal and Shelf Science》2009

Spatial size variations of labial palps, gills and the adductor muscle of the invasive feral oyster, Crassostrea gigas, were studied along two gradients of suspended particulate matter (SPM) concentrations in the temperate macrotidal Bourgneuf Bay, (annual mean SPM concentration gradient of 21.0–154.0 mg l⁻¹) and the adjacent Loire Estuary (annual mean SPM concentration gradient of 24.1–630.4 mg l⁻¹) on the French Atlantic Coast. The gill-to-palp (G:P) ratios decreased with increasing turbidity, both in the bay and the estuary. Changes in G:P ratios were chiefly related to palp area variations, increasing gradually from low turbidity to very high-turbidity sites, while gill area showed no clear relationship with turbidity conditions. The G:P ratio, showing a significant relationship (r² = 0.97) with SPM concentrations, is proposed as a pallial organ index of oyster acclimation to turbidity conditions. The area of the striated part of the adductor muscle was always greater than that of the smooth one, and adductor muscle area tended to decrease when SPM concentration increased. These observations show the morphological capacity of the oyster C. gigas to tolerate SPM concentrations above the feeding cessation thresholds previously determined experimentally. They also suggest that pallial organ size variations could help explain the success of recent feral oyster invasions in temperate turbid ecosystems.  相似文献   

The impact of sediment burial and erosion on seagrasses: A review   总被引：1，自引：0，他引：1  

Susana Cabao  Rui Santos  Carlos M. Duarte 《Estuarine, Coastal and Shelf Science》2008,79(3):354-366

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Buoyancy-controlled eruption of magmas at Mt Etna     

Rosa Anna Corsaro  Massimo Pompilio 《地学学报》2004,16(1):16-22

Buoyancy controls the ability of magma to rise, its ascent rate and the style of the eruptions. Geophysical, geological and petrological data have been integrated to evaluate the buoyancy of magmas at Mt Etna. The density difference between host rocks and magmas is mainly related to the amount of H₂O dissolved in the magma and to the bubble‐liquid separation processes. In the depth interval 22–2 km b.s.l. highly hydrated (H₂O ～ 3%) basaltic magmas or mixtures of bubbles + liquid have positive buoyancy and rise rapidly. Conversely, bubble‐depleted liquids, with an intermediate H₂O content (～ 1.5%), having neutral buoyancy, will spread out and form magmatic reservoirs at different depths until cooling/crystallization further modify composition and density. These different processes account for the magma compositions, location of magmatic reservoirs as determined by geophysical methods, and the complex eruptive cycles (slow effusions, fire fountains and Plinian eruptions) that have been observed in the history of the volcano.  相似文献   

Comments on the development of new macroalgal indices to assess water quality within the Mediterranean Sea: A reply     

Enric Ballesteros  Susana Pinedo  Raquel Arévalo 《Marine pollution bulletin》2007,54(5):628-630

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Cyanobacterial blooms in estuarine ecosystems: characteristics and effects on Laeonereis acuta (Polychaeta, Nereididae)     

da Rosa CE  de Souza MS  Yunes JS  Proença LA  Nery LE  Monserrat JM 《Marine pollution bulletin》2005,50(9):956-964

In January of 2003, a cyanobacterial bloom in the Patos' Lagoon (Southern Brazil) (32 degrees 05'S-52 degrees 12'W) was observed. Water samples were taken to identify the composition and abundance of the bloom, as well as the occurrence of toxins. The effects of this occurrence on the estuarine worm Laeonereis acuta (Polychaeta, Nereididae) was also evaluated. Predominance of cyanobacteria, particularly Anabaena trichomes ( approximately 2.5.10(6) individuals per liter) was observed, and low concentrations of microcystins and anticholinesterasic toxins were detected. Augmented levels of lipid hydroperoxides (LPO) and glutathione-S-transferase activity, and lowering of total protein content were also observed in organisms collected during the bloom event. Although non-toxic, the cyanobacterial bloom could augment the cycle of hyper-oxygenation and hypoxia in the water. During hyperoxia, L. acuta, an oxyconformer, should consume more oxygen, thus augmenting the rate of reactive oxygen species generation. A repeated cycle of hyper-oxygenation and hypoxia would finally induce oxidative stress, as evidenced by the high levels of LPO and glutathione-S-transferase activity.  相似文献   

Effects of artificial and natural recharge on chemical equilibrium in the Cerro Prieto reservoirs, Baja California, México     

Enrique Portugal  Rosa María Barragn  Jesús de Len 《Journal of Geochemical Exploration》2006,89(1-3):339

Chemical equilibrium modeling studies of two aquifers in the western part of the Cerro Prieto (CP-I) geothermal field were performed to obtain the activities of the main ions and complexes by using the EQQYAC program. The results provided a pH of 6.44 for the deep aquifer, which is slightly higher than the value of 5.5 found for the shallower reservoir. In the northern part of the field, the reservoir pH has decreased up to 1.5 units compared to that modeled for 1990. Variations of pH with respect to time were also found to occur in the southern part of the field. In spite of the large changes in hydrodynamic conditions occurring in the reservoir due to exploitation, the equilibrium between both K- and Na-feldspars and between K-feldspar and K-mica seems to control the chemical composition of the fluids, in both reservoirs.  相似文献