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1.
Tide gauges distributed all over the world provide valuable information for monitoring mean sea level changes. The statistical models used in estimating sea level change from the tide gauge data assume implicitly that the random model components are stationary in variance. We show that for a large number of global tide gauge data this is not the case for the seasonal part using a variate-differencing algorithm. This finding is important for assessing the reliability of the present estimates of mean sea level changes because nonstationarity of the data may have marked impact on the sea level rate estimates, especially, for the data from short records.  相似文献   

2.
State‐of‐the‐art technology is presently being used for the acquisition of water level and meteorological data in the Intra‐Americas Sea to support the Global Sea Level Observing System (GLOSS) network of sea‐level monitoring stations. GLOSS stations provide data for the investigation of regional relative sea level change in areas of complex tectonic motion, national geodetic vertical datums, near real‐time data for input to climatic diagnostic numerical models, calibration of satellite altimeter and scatterometer data, and the evaluation of the feasibility of producing synoptic mean sea level charts for the prediction of climatic trends, long‐range weather forecasts, and ocean processes.  相似文献   

3.
The physical and chemical features of Pupu Springs (40 51’ S, 172° 46’ E), near Takaka, the largest cold springs in New Zealand and one of the largest in the world, were investigated by scuba diving. The springs have a maximum depth of 6.9 m and a mosaic of substrate types (bedrock, boulders, and gravel). The temperature of the springs water is constant at 11.7°C, water velocities are generally moderate to very strong (25–100 cm.s‐1), and average water discharge is about 9.6 m3.s‐1. Mean holding time for water in the springs is 4.4 min. The water is extremely clear, with a vertical extinction coefficient (log10) of 0.09. The springs water flows from an artesian basin in Arthur Marble and is low in dissolved oxygen. The water is rich in calcium (64 g.m‐3), with a high specific conductivity (65 mS.m‐1). Information on water temperature, discharge, and chemistry is provided for five other cold springs in New Zealand: Hamurana Springs, Rotorua; Otangaroa Springs, near Putaruru; Three Springs, near Fairlie; Western Springs, Auckland; and a spring at Lake Hayes, Queenstown.  相似文献   

4.
Abstract

It has been observed that earthquake‐induced settlement depends on the excess pore water pressure accumulated during an earthquake. In particular, in the case where a clay layer is overconsolidated, excess pore water pressure is produced and settlement occurs by dissipation of the excess pore water pressure, which is very large in comparison with the coefficient of secondary compression. Therefore, if the settlement of clay ground induced by secondary compression becomes a serious problem, careful consideration of the earthquake‐induced settlement is needed. In this article, the settlement characteristics of a clay layer induced by cyclic shear are discussed, including the effects of loading period, the threshold shear strain below which no excess pore pressure or no settlement takes place, and the relationships between uniform shear strain cycles and irregular strain‐time histories. Then a calculation procedure for estimating the earthquake‐induced settlement is developed and applied to three soil profile cases, including the clay layers in Mexico City and Osaka Bay in Japan. In the case of a soil profile in Mexico City, settlements of about 0–3 cm are estimated and these values agree reasonably with the leveling results for the Mexico City earthquake of 1985. Furthermore, it is pointed out that the settlement induced by earthquakes is considerably affected by differences in the accelerograms.  相似文献   

5.
Abstract

The tsunami travel‐time charts that are presently in use by the Tsunami Warning Center were constructed originally in 1948 based on the hydrographic data available in the mid 1940s. Even the revised charts of 1971 made use of essentially the same data. It is shown here that the travel times deduced by these charts could be in error by as much as two hours in some cases. Even worse, the compiled travel times as deduced from these charts are generally greater than the observed travel times, which is a dangerous situation from a tsunami warning point of view.  相似文献   

6.
We investigated temporal (day‐to‐day and season) and spatial (reach) variability of drift with the aim of guiding sampling protocol for quantifying drift at the whole river or reach scale. Overall, we found aquatic drift density and biomass varied considerably seasonally (CV = 72.9, 88.1) and to a lesser extent spatially (CV = 31.3, 30.7) and from day‐to‐day (CV = 45.2, 39.4). Although spatial and day‐to‐day variation in drift density and biomass were similar, sampling logistics suggest spatial sampling would be more cost‐effective and less time consuming. Drift density and biomass estimated from top samplers was often higher than estimates from samplers near the streambed or mid‐water column. A reliable estimate of mean densities and biomass at a site may require only two samplers— a top sampler and either a middle or bottom sampler. In our study, we calculated that sampling at four sites over 1 or 4 days at one site would be required to obtain a 95% CI within 50% of the mean drift density. Eight sites over 1 or 10 days at one site would be required to achieve a 95% CI within 25% of the mean drift density.  相似文献   

7.
2‐phenoxyethanol was tested as a preservative for plankton samples intended for electrophoretic analysis of enzymes. Esterase, α‐glycerophosphate dehydrogenase, glucosephosphate isomerase, isocitrate dehydrogenase, lactate dehydrogenase, malate dehydrogenase, phospho‐glucomutase, and superoxide dismutase were tested in starch gels. Adult skeletal muscle tissues retained enzyme activity for five of the enzymes tested. No activity was detected in eight larval species analysed for the same eight enzymes. 2‐phenoxyethanol is unsuitable as a biochemical preservative for plankton samples but may find an application for adult muscle tissues.  相似文献   

8.
Breeding seasons and sizes at first maturity for nine species of fish in the Avon‐Heathcote Estuary, Christchurch, New Zealand, were: sand flounder, Rhombosolea plebeia, mid‐winter to spring at 200 mm+; yellow‐bellied flounder, Rhombosolea leporina, winter and spring at 260 mm+; common sole, Peltorhamphus novaeieelandiae, did not breed in the estuary but reached first maturity at 220 mm +; yellow‐eyed mullet, Aldrichetta forsteri, spawned twice a year, winter and summer, at 220 mm +; kahawai, Arripis trutta, bred outside the estuary at 520–540 mm +; spotty, Pseudolabrus celidotus, spring to autumn at 200 mm for males and 160 mm for females; cockabully, Tripterygion nigripenne, spring and early summer at 52–57 mm +; common bully, Gobiomorphus basalis, spring and early summer at 45–50 mm+; and globefish, Speroides richei, spring to autumn at 147 mm + for males and 120 mm + for females. The successive stages in gonad development are described for these species.

In pelagic species, e.g., flatfish and kahawai, x2 analyses showed that for most months females are more numerous than males, and that migration is of major importance. In (littoral species, e.g., common bully and cockabully, there is a 1 : 1 sex ratio in the breeding season, but this ratio subsequently breaks down.

The Avon‐Heathcote estuary was used mainly as a nursery area by juvenile fish, although some species, such as sand flounder, yellow‐bellied flounder, yellow‐eyed mullet, and cockabully spawned in the estuary.  相似文献   

9.
Details are given of gut‐content analyses for nine fish species from the Avon‐Heathcote Estuary, Christchurch, New Zealand: sand flounder, Rhombosolea plebeia (Richardson); yellow‐bellied flounder, R. leporina (Hutton); common sole, Peltorhamphus novaezeelandiae (Gunther); yellow‐eyed mullet, Aldrichetta forsteri (Cuvier & Valenciennes); kahawai, Arripis trutta (Bloch & Schneider); spotty, Pseudolabrus celidotus (Bloch and Schneider); cockabully, Tripterygion nigripenne (Cuvier & Valenciennes); common bully, Gobiomorphus basalis (Gray); and globefish, Spheroides richei (Freminville). The percent occurrences of each food type recorded over Ihe sampling period (April 1965‐April 1966) for each species are compared. Monthly food tables are given for those species of which suitably large samples were obtained (sand flounder, yellow‐bellied flounder, common sole, yellow‐eyed mullet, and globefish). Where possible, the dietary occurrence of different food types is related to environmental and other factors observed or considered likely to influence food selection.  相似文献   

10.
Characteristic organisms are tabulated, and the substrate conditions briefly described for seven habitats in the Avon‐Heathcote Estuary, Christchurch, New Zealand. Temperatures and water movements within the estuary are outlined.

From April 1965 to April 1966, samples were collected by short otter‐trawl shots, gill netting, beach seine hauls, and dip netting; the limitations of the gear are noted. The distributions and movements are recorded for nine fish species : sand flounder, Rhombosolea plebeia (Richardson) ; yellow‐bellied flounder, Rhombosolea leporina (Hutton) ; common sole, Peltorhamphus novae‐zeelandiae (Gunther) ; ye'llow‐eyed mullet Aldrichetta forsteri (Cuvier and Valenciennes); kahawai, Arripis trutta (Bloch and Schneider); spotty, Pseudolabrus celidotus (Bloch and Schneider); cockabully, Tripterygion nigripenne (Cuvier and Valenciennes) ; common bully, Gobiomorphus basalis (Gray); and globe fish, Spheroides richei (Freminville).

Length‐frequency distributions showed that most of the nine species of fish used the estuary as a feeding area for adults and as a nursery area. Only two species did not migrate to and from the sea.

Length‐weight relationships for eight species showed that weight was a function of length approximately cubed, and that the exponential equation could be used to predict weight from length.

Regressions of caudal fin length on standard length for four species gave a positive correlation (r = +0.95). Relative proportions of body length to caudal fin length were related to habitat; fish of benthic habits had proportionally shorter caudal fins than pelagic fish.  相似文献   

11.
Let A,B,C denote three mainland‐stations whose positions are unknown. Let D,E,F denote the positions of a moving ship at three different moments of time. At any of the locations D,E,F, the three azimuths to the target‐stations A,B,C are measured. The problem is to determine from these nine measurements the mutual positions of all stations A,B,C,D,E,F up to a common shift and a change of scale. The problem was formulated by J. H. Lambert in 1765. He also specified a mathematical solution. In this paper so‐called “critical configurations”; are investigated. It is shown that there are nontrivial configurations of the six stations A to F, such that solution of the problem is not unique (critical configuration of the first kind). There is a larger set of configurations, such that the linearized problem admits of an infinity of solutions (critical configurations of the second kind). In the latter case, the original nonlinear problem may be solvable, but the solution is highly unstable with respect to perturbations of the measurements. The main result obtained is as follows. If all stations A to F are located on a second degree curve, i.e., on a conic section, then the configuration is critical, at least of the second kind. The configuration continues to be critical if arbitrarily many observations and target‐points are added which are all situated on the second‐degree curve.  相似文献   

12.
Short‐term effects of deposit feeding on benthic micro‐organisms are known from several marine environments, but longer‐term influences of deposit feeders have not been extensively investigated. The long‐term microbial response to deposit feeding by the gastropod Amphibola crenata was monitored in a 10‐month field study where deposit feeding intensity was controlled in artificial enclosures. The presence of the snail resulted in a minor decrease in bacterial numbers and a slight increase in heterotrophic activity relative to bacterial cell numbers. This effect may have been the long‐term signature of a previously reported pulse in bacterial production during the recolonisation of Amphibola faeces. Normal snail density had a strong inhibitory effect on primary productivity by the benthic microalgae, reducing CO2 fixation to 29–47% of levels that could be attained when snails were excluded. Variations in the effect of deposit feeding on micro‐organisms over the experimental period suggest that it may be modified by seasonal factors acting on benthic communities. In a similar interaction of influences, seasonal changes in microbial biomass and activity appeared to vary with snail density.  相似文献   

13.
Zi Jun Gan  C. C. Tung 《Marine Geodesy》2013,36(3-4):293-301
Abstract

In 1980, Murty and Loomis proposed a new, objective tsunami magnitude scale based on total tsunami energy. A list of 178 tsunamigenic earthquakes during the period 1815 to 1974 was given along with estimated tsunami magnitudes. In this study, we derived the probability distribution function of tsunami magnitudes based on the assumptions that (1) the occurrences of tsunamigenic earthquakes are a Poisson process, and (2) tsunami energy is a polynomial function of tsunami recurrence time. Using the data given by Murty and Loomis, the parameters of the distribution function are estimated. Comparison with the data shows that the derived distribution is a good representation of the distribution of the Murty‐Loomis tsunami magnitude.  相似文献   

14.
Abstract

Marine positioning is relevant for several aspects of tsunami research, observation, and prediction. These include accurate positioning of instruments on the ocean bottom for determining the deep‐water signature of the tsunami, seismic observational setups to measure the earthquake parameters, equipment to determine the tsunami characteristics during the propagation phase, and instruments to map the vertical uplift and subsidence that occurs during a dip‐slip earthquake.

In the accurate calculation of coastal tsunami run‐up through numerical models, accurate bathymetry is needed, not only near the coast (for tsunami run‐up) but also in the deep ocean (for tsunami generation and propagation). If the bathymetry is wrong in the source region, errors will accumulate and will render the numerical calculations inaccurate. Without correct and detailed run‐up values on the various coastlines, tsunami prediction for actual events will lead to false alarms and loss of public confidence.  相似文献   

15.
Abstract

The distributions of infaunal Peracarida (Crustacea) and their correlation with sediment type, tidal height, and degree of exposure were studied in winter (June) at five beaches on Stewart Island, New Zealand. The beaches were selected lo cover a range of exposures to wind and wave action and substrate sorting. Substrate and infauna samples were taken at four tidal levels from each, with a 0.0625 m2 quadrat.

Sieve separation and statistical analysis of the substrate samples indicated predominantly sand‐sized particles from all beaches, with median diameters in the range +1.52 to +2.92 ? (phi) units. Substrates were well sorted throughout the size range: ? quartile deviation ranged from 0.26 to 0.71, skewness from —0.18 to +0.07 ?.

Peracarid fauna was generally abundant, with a maximum of 29 136 per m2sampled in a more sheltered beach. Cumacea was the most abundant group, followed by Amphipoda, Isopoda, and Tanaidacea; dominance followed a similar sequence, being 78%, 19%, 2% and 1% respectively. Frequency of occurrence at the 19 stations was headed by Amphipoda (100%), with Isopoda 53%, Cumacea 32% and Tanaidacea 11%.  相似文献   

16.
Summary

Lake Pupuke, situated in the North Island of New Zealand near Auckland (Latitude 36° 53'S, Longitude 174° 52'E), is a small, circular body of water (maximum width 1.2 km, maximum depth 55 m). From November 1966 to November 1967 observations on its physico‐chemical factors were made twice monthly.

The range of temperatures in the year was 12.0–24.2°c at the surface and 11.3–14.5°c at 40 m. A thermocline farmed between early October and early January, when it became strongly developed at about 17 m and persisted until late April. Between early May and late June the stratification was breaking down and between mid July and mid September the lake was isothermal.

The values for light transmitted per metre through the water were high from mid August to mid December (53–76% per metre), very low from mid December until mid February (23–49% per metre), high in March (75% per metre) and relatively constant over the winter months (53–64% per metre). The amount of light transmitted depended closely on the density of phytoplankton. Changes in the depth at which a Secchi disc disappeared paralleled the light transmission values, and the mean Secchi depth was 2.2 m, range 1.0–5.2 m.

Oxygen concentrations down to 30 m were highest at all depths from mid November to early January (112–134% saturation). From early January to late April oxygen was strongly stratified (epilimnion 55–100% saturation, hypolimnion 24–77% saturation). During winter oxygen values gradually increased at all depths.

The range of pH was 7.8–9.5 units at the surface and 7.8–8.6 units at 30 m. From early January to late April pH values were strongly stratified but from mid July to mid August they were nearly uniform. The range of alkalinity (mainly HCO3 ? ions) was 76.0–80.8 ppm CaCO3 and values showed stratification in summer. Carbonate ion was present from early October to mid June, but free carbon dioxide was only found in trace amounts.

The range of nitrate ion concentrations was 0.05–0.31 ppm; nitrate became obviously depleted in summer. Only one nitrite value was significant, 0.25 ppm. other nitrite values never exceeded 0.10 ppm. The concentration of ammoniacal nitrogen built up to a summer maximum of 0.95 ppm in the hypolimnion (annual range 0–0.95 ppm); values for albuminoid ammonia (0.016–1.03 ppm of nitrogen) varied with the quantity of living matter present.

The annual mean for total ion concentration (3.30 meq./1) was high and the order of ions was Na+>Mg2+>Ca2+>K+ and HCO3 ?>CI?>SO4 2?. Such dissolved salts may have arrived as airborne particles, dissolved in rain, or as sea spray.  相似文献   

17.
The distribution of adult Trichoptera in light traps was investigated alongside nine streams draining catchments under native forest, pine forest, or pasture near Hamilton, Waikato, New Zealand. The aim of the study was to determine the relationship between abundance, taxonomic richness, and community composition with respect to land use during summer, and to evaluate the use of adult Trichoptera compared with benthic invertebrates as potential bio‐indicators of the effectiveness of land‐management changes. Adult Trichoptera faunas alongside the native streams were dominated by Hydrobiosidae, Conoesucidae, and Helicopsychidae (each >10% of total Trichoptera numbers for at least two of the three sites), whereas Leptoceridae, Oeconescidae, and Hydrobiosidae were relatively abundant alongside at least two of the pine sites. Adult Trichoptera faunas at the pasture sites were strongly dominated by Hydroptilidae which made up 47–85% of numbers caught at all sites. The mean number of individuals and taxa caught in light traps increased from November to January and then declined in February for all land‐use types. Overall, total numbers and taxonomic richness of adult Trichoptera were significantly lower at the pine sites compared to the pasture or native sites. TWINSPAN classification of benthic invertebrates collected in November clearly differentiated sites based on land use for presence/absence and percentage abundance data. A similar pattern was evident for most sites when adult Trichoptera faunas were used for the four sampling dates combined, suggesting that light trapping has potential as a tool for bio‐monitoring.  相似文献   

18.
Lake Ototoa is a warm monomictic lake at 36° 31’ S, 174° 14'E. During a year's study (March 1969‐March 1970), the lake became thermally stratified in November, the metalimnion being between depths of 12 m and 16 m. Surface temperatures ranged between 10.2°c (in August) and 25.2°c (in late January), and bottom temperatures between 9.7°c and 17.5°c. The annual heat budget was calculated to be 642 354 KJ.m‐2 (15 500 cal.cm‐2) and the work of the wind in distributing the heat income 1.730 KJ.m‐2 (1766 g.cm.cm‐2). Secchi disc transparencies ranged between 5 m and 9.2 m (mean 7.07 m) and were greatest in the summer. Light transmission per metre was also high, ranging between 61% and 87%. Surface waters were normally supersaturated with oxygen, but during summer stratification oxygen concentrations in the bottom waters dropped to a minimum of 2.3 mg.litre‐2 and a positive heterograde distribution of oxygen with depth was found. The oxygen deficit was 0.015 mg.cm‐2.day‐1 and showed the lake to be oligotrophic. Mean surface pH was 7.82, and the ionic composition of the waters was similar to that of other small New Zealand and Australian lakes located near the sea. Compared with other New Zealand lakes PO4‐P concentrations (range 1.00–10.20 μg.litre‐1) were low and NO3—N concentrations (range 0.12–0.60 mg.litre‐1) high.  相似文献   

19.
A technique is currently under development a the Naval Research Laboratory for imaging of backscatterec acoustic returns from ocean basin topography. The method is straightforward. An explosive sound source is detonated near the center of an ocean basin and the round‐trip travel time from source to reflectors and return is measured. Distance to back‐scattering topography is assumed to be proportional to round‐trip time, with a proportionality constant equal to half the sound speed. A multielement receiving array is used to determine the azimuthal directions to topographic features. Reverberation data are output to an imaging system to study the spatial distribution of sea bottom reverberation. The images are in the form of two‐dimensional maps of backscattered acoustic energy. Typical maps are larger than 2,000 km x 2,000 km (or area coverage greater than 4 x 106 km2). After correction of maps from individual shot detonations for range‐dependent propagation losses, we average ("integrate") maps together on a pixel by pixel basis for a clear picture of major basin reverberators.  相似文献   

20.
Geomorphological features (derived from 16,000 lkm of echo‐sounding and bathymetric data) and deep‐seated tectonic structures of the continental margin off NW India are presented. The shelf break over the entire region occurs between 80 to 154 m water depth, and adjacent to Saurashtra and Bombay High the depth and orientation of the shelf edge show marked variations. The boundary of the slope is shallower in the northern portion (about 1450 m in the vicinity of the Indus) than in the southern region (2900 m off Bombay).

The steep slope off the Gulf of Kachchh has relatively smooth physiography due to higher input of fluvial sediment and burial of structures. The gentler slope off Saurashtra and the Bombay High area has numerous complex features, the most prominent among them being benches at depths of 180–230 m (width 2–10 km) and 650–780 m and a series of bathymetric highs and lows. Slope breaks are also observed between 400 and 600 m off Bombay and between 560 and 960 m off Saurashtra. These features are surface manifestations of the anticlinal features extending along the shelf in this region. Unevenness (order of 100–300 m) due to slumping is also observed at the base of the slope.

Based on the correlation between tectonic structures of this area and these subphysiographic features, extension of the Saurashtra Anticline onto the slope, a new strike slip fault (the southern boundary fault of Narmada graben) and an along‐shelf anticlinal structure off Saurashtra are delineated.  相似文献   

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