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Regional source tsunamis pose a potentially devastating hazard to communities and infrastructure on the New Zealand coast. But major events are very uncommon. This dichotomy of infrequent but potentially devastating hazards makes realistic assessment of the risk challenging. Here, we describe a method to determine a probabilistic assessment of the tsunami hazard by regional source tsunamis with an “Average Recurrence Interval” of 2,500-years. The method is applied to the east Auckland region of New Zealand. From an assessment of potential regional tsunamigenic events over 100,000 years, the inundation of the Auckland region from the worst 100 events is modelled using a hydrodynamic model and probabilistic inundation depths on a 2,500-year time scale were determined. Tidal effects on the potential inundation were included by coupling the predicted wave heights with the probability density function of tidal heights at the inundation site. Results show that the more exposed northern section of the east coast and outer islands in the Hauraki Gulf face the greatest hazard from regional tsunamis in the Auckland region. Incorporating tidal effects into predictions of inundation reduced the predicted hazard compared to modelling all the tsunamis arriving at high tide giving a more accurate hazard assessment on the specified time scale. This study presents the first probabilistic analysis of dynamic modelling of tsunami inundation for the New Zealand coast and as such provides the most comprehensive assessment of tsunami inundation of the Auckland region from regional source tsunamis available to date. 相似文献
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Sea lice treatments on salmon farms have no adverse effects on zooplankton communities: a case study
The long-term effects of the sea lice treatment products Excis and Slice on zooplankton communities in a Scottish sea loch were investigated at a commercially operating salmon farm over 31 months. Cypermethrin and emamectin benzoate are the active ingredients in Excis and Slice respectively, which are widely used to control ectoparasitic sea lice on farmed salmon. Excis and Slice treatments did not cause basin-wide effects on the zooplankton community. For both formulations, no adverse affects on zooplankton were detected, instead observed changes in zooplankton abundance and community composition displayed natural seasonal cycles of abundance. Water column concentrations of cypermethrin and emamectin benzoate following sea lice treatments at the fish farm were predicted using models. Cypermethrin concentrations of 3000 ng/l were predicted for short periods immediately after each cage treatment assuming no particle adhesion. The 3-h and 24-h Environmental Quality Standards (EQS) were exceeded for 10 h and 32 h respectively on the second day when five cages were treated. However, cypermethrin concentrations higher than 0.5 ng/l (24-h EQS) were predicted to occur over <2% of the total basin area on each treatment day. The 3-h EQS (16 ng/l) was exceeded in <0.3% of the basin on each treatment day. The concentration of soluble emamectin benzoate present in the water column was predicted from modelled deposition footprints and sediment concentrations to be of order 10(-3) ng/l. Predicted concentrations of both chemicals were generally lower than those causing toxicity to copepods in previous laboratory studies and further support the results of this field study that environmental concentrations of Excis and Slice do not adversely impact zooplankton communities. 相似文献
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Pavle TAN?I? Radovan DIMITRIJEVI? Maja POZNANOVI? Aleksandar PA?EVSKI Slobodanka SUDAR 《《地质学报》英文版》2012,86(6):1524-1538
The crystal structure of ludwigite from Vranovac ore deposit (Boranja Mt., Serbia) was refined using the X-ray powder diffraction (XRPD) Rietveld method in the space group Pbam to a final RB=7.45% and RF=5.26%. It has the unit cell dimensions of: a=9.2515(2) ?; b=12.3109(2) ?; c=3.03712(7) ?; and V=345.91(1) ?3. The calculated distances and angles are mostly in good agreement with the Mg2+-Fe2+ substitutions across the M(1) and M(3) sites, as well as with the Fe3+-Al3+ replacement in the M(4) site. However, the mean observed M(2)-O distance is considerably shorter than prescribed, due to a slight increase of the Fe3+ content in the M(2) site. Such replacement was compensated by slight increase of the Fe2+ content in the M(4) site, resulting in the (Mg1.48Fe2+0.46Fe3+0.05Mn0.02)2.01(Fe3+0.94Fe2+0.04Al0.02)1.00B1.00O5 composition. The formation temperature was estimated to be about 500–600°C. The influences of the various chemical compositions to the crystallographic parameters, M-O distances, M(3) and M(4) sites shift, distortion parameters and estimated valences, were also studied and compared with other reference samples. 相似文献
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A.H.C. Thean T.I. Gillibrand A. Pedlar M.J. Kukula 《Monthly notices of the Royal Astronomical Society》2001,327(2):369-384
We present new 1.6-GHz (18-cm) MERLIN maps of 15 Seyfert galaxies, with angular resolutions typically 0.1 to 0.3 arcsec. These and previous observations are used to investigate the properties of 19 of the 24 CfA Seyfert galaxies brighter than 2 mJy at 8.4 GHz. This is the first time a significant fraction of the CfA sample has been mapped at this frequency with subarcsecond resolution, and our observations provide the highest resolution radio maps available for several sources. We use our observations to measure the two-point spectral indices of compact radio components, and we investigate the correlation between infrared and radio emission shown by Seyfert galaxies.
Our results can be summarized as follows. Resolved structures as small as 20 pc are found in three previously unresolved radio sources, and only four sources show single, unresolved radio components. The mean 1.6 to 8.4 GHz spectral index of 31 radio components is , and approximately 25 per cent of the components have a spectral index flatter than . The spectral index distributions of type 1 and type 2 Seyferts are statistically indistinguishable. The cores of multiple-component sources tend to have flatter radio spectra than secondary components. The low-resolution infrared ( IRAS ) emission from Seyfert galaxies is usually dominated by kiloparsec-scale, extranuclear emission regions. 相似文献
Our results can be summarized as follows. Resolved structures as small as 20 pc are found in three previously unresolved radio sources, and only four sources show single, unresolved radio components. The mean 1.6 to 8.4 GHz spectral index of 31 radio components is , and approximately 25 per cent of the components have a spectral index flatter than . The spectral index distributions of type 1 and type 2 Seyferts are statistically indistinguishable. The cores of multiple-component sources tend to have flatter radio spectra than secondary components. The low-resolution infrared ( IRAS ) emission from Seyfert galaxies is usually dominated by kiloparsec-scale, extranuclear emission regions. 相似文献
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William Power Xiaoming Wang Emily Lane Philip Gillibrand 《Pure and Applied Geophysics》2013,170(9-10):1621-1634
Regional source tsunamis represent a potentially devastating threat to coastal communities in New Zealand, yet are infrequent events for which little historical information is available. It is therefore essential to develop robust methods for quantitatively estimating the hazards posed, so that effective mitigation measures can be implemented. We develop a probabilistic model for the tsunami hazard posed to the Auckland region of New Zealand from the Kermadec Trench and the southern New Hebrides Trench subduction zones. An innovative feature of our model is the systematic analysis of uncertainty regarding the magnitude-frequency distribution of earthquakes in the source regions. The methodology is first used to estimate the tsunami hazard at the coastline, and then used to produce a set of scenarios that can be applied to produce probabilistic maps of tsunami inundation for the study region; the production of these maps is described in part II. We find that the 2,500 year return period regional source tsunami hazard for the densely populated east coast of Auckland is dominated by events originating in the Kermadec Trench, while the equivalent hazard to the sparsely populated west coast is approximately equally due to events on the Kermadec Trench and the southern New Hebrides Trench. 相似文献
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A particle transport model is described that is being used to simulate the dispersal of salmon lice (Lepeophtheirus salmonis) larvae in the waters of Loch Torridon. A hydrodynamic model, forced by tides and winds, drives the transport model. Particle movements are strongly influenced by winds, which can lead to formation of lice concentrations in coastal areas several kilometres from the source. Idealised constant wind simulations have been used to locate areas that larval lice may potentially reach from given source locations. Detailed analysis of simulations forced with real wind data is required to assess areas that larval lice from these sources are likely to reach. Further field and experimental work on the viability of lice is required to assess infection risk. 相似文献
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PA Franklin 《新西兰海洋与淡水研究杂志》2013,47(1):112-126
Maintenance of suitable conditions in lowland rivers for both fish passage and resident species is crucial to ensuring the long-term sustainability of fish populations. The dissolved oxygen concentration of water is a key factor controlling habitat quality for fish and a critical measure of stream health. Continued land use intensification and greater exploitation of water resources has contributed towards increasing the frequency and duration of low dissolved oxygen events in lowland rivers and the associated risk of adverse effects on fish communities. Revised guidelines are therefore proposed to support setting of biologically relevant dissolved oxygen limits for the protection of New Zealand freshwater fish communities. These guidelines account for both event magnitude and duration, identify different protection levels based on the risk of negative impacts and are based on current scientific knowledge on the tolerances of New Zealand fish species. 相似文献