Short-term seaward fish migration in the Messolonghi–Etoliko lagoons (Western Greek coast) in relation to climatic variables and the lunar cycle     

George Katselis  Katerina Koukou  Evagelos Dimitriou  Constantin Koutsikopoulos 《Estuarine, Coastal and Shelf Science》2007,73(3-4):571-582

In the present study we analysed the daily seaward migratory behaviour of four dominant euryhaline fish species (Mugilidae: Liza saliens, Liza aurata, Mugil cephalus and Sparidae: Sparus aurata) in the Messolonghi–Etoliko lagoon system (Western Greek coast) based on the daily landings' time series of barrier traps and assessed the relationship between their migratory behaviour and various climatic variables (air temperature and atmospheric pressure) and the lunar cycle. A 2-year time series of daily fish landings (1993 and 1994), a long time series of daily air temperature and daily temperature range (1991–1998) as well as a 4-year time series of the daily atmospheric pressure (1994–1997) and daily pressure range were used. Harmonic models (HM) consisting of annual and lunar cycle harmonic components explained most (R² > 0.80) of the mean daily species landings and temperature variations, while a rather low part of the variation (0.18 < R² < 0.27) was explained for pressure, daily pressure range and daily temperature range. In all the time series sets the amplitude of the annual component was highest. The model values of all species revealed two important migration periods (summer and winter) corresponding to the spawning and refuge migrations. The lunar cycle effect on species' daily migration rates and the short-term fluctuation of daily migration rates were rather low. However, the short-term fluctuation of some species' daily migration rates during winter was greater than during summer. In all species, the main migration was the spawning migration. The model lunar components of the species landings showed a monthly oscillation synchronous to the full moon (S. aurata and M. cephalus) or a semi-monthly oscillation synchronous to the new and full moon (L. aurata and L. saliens). Bispectral analysis of the model values and the model residuals' time series revealed that the species daily migration were correlated (coherencies > 0.6) to the daily fluctuations of the climatic variables at seasonal, mid and short-term scales.  相似文献   

Algebraic estimation of the specific storage from slug tests in confined aquifers in the overdamped case     

Mazi  Katerina  Akylas  Evangelos  Koussis  Antonis D. 《Hydrogeology Journal》2021,29(7):2545-2553

Hydrogeology Journal - A simple method is presented for estimating the specific storage of a confined aquifer from an overdamped slug test in a fully penetrating well. This method is based on the...  相似文献   

Empirical relationships between aftershock area dimensions and magnitude for earthquakes in the Mediterranean Sea region     

Konstantinos I. Konstantinou  Gerassimos A. Papadopoulos  Anna Fokaefs  Katerina Orphanogiannaki 《Tectonophysics》2005,403(1-4):95-115

Fault dimension estimates derived from the aftershock area extent of 36 shallow depth (≤ 31 km) earthquakes that occurred in the Mediterranean Sea region have been used in order to establish empirical relationships between length, width, area and surface-wave/moment magnitude. This dataset consists of events whose aftershock sequence was recorded by a dense local or regional network and the reported location errors did not exceed on average 3–5 km. Surface-wave magnitudes for these events were obtained from the NEIC database and/or published reports, while moment magnitudes as well as focal mechanisms were available from the Harvard/USGS catalogues. Contrary to the results of some previously published studies we found no evidence in our dataset that faulting type may have an effect on the fault dimension estimates and therefore we derived relationships for the whole of the dataset. Comparisons, by means of statistical F-tests, of our relationships with other previously published regional and global relationships were performed in order to check possible similarities or differences. Most such comparisons showed relatively low significance levels (< 95%), since the differences in source dimension estimates were large mainly for magnitudes lower than 6.5, becoming smaller with increasing magnitude. Some degree of similarity, however, could be observed between our fault length relationship and the one derived from aftershock area lengths of events in Greece, while a difference was found between our regional and global fault length relationships. A calculation of the ratio defined as the fault length, derived from our relationships, to the length estimated from regional empirical relationships involving surface ruptures showed that it can take a maximum value of about 7 for small magnitudes while it approaches unity at Ms 7.2. When calculating the same ratio using instead global empirical relationships we see the maximum value not exceeding 1.8, while unity is reached at Mw 7.8, indicating the existence of a strong regional variation in the fault lengths of earthquakes occurring in the Mediterranean Sea region. Also, a relationship between the logarithms of the rupture area and seismic moment is established and it is inferred that there is some variation of stress drop as a function of seismic moment. In particular, it is observed that for magnitudes lower than 6.6 the stress drop fluctuates around 10 bar, while for larger magnitudes the stress drop reaches a value as high as 60 bar.  相似文献   

A Maastrichtian palaeomagnetic pole for the Pacific plate from a skewness analysis of marine magnetic anomaly 32     

Katerina E. Petronotis  & Richard G. Gordon 《Geophysical Journal International》1999,139(1):227-247

The asymmetry (skewness) of marine magnetic anomaly 32 (72.1–73.3  Ma) on the Pacific plate has been analysed in order to estimate a new palaeomagnetic pole. Apparent effective remanent inclinations of the seafloor magnetization were calculated from skewness estimates of 108 crossings of anomaly 32 distributed over the entire Pacific plate and spanning a great-circle distance of ~12  000  km. The data were inverted to obtain a palaeomagnetic pole at 72.1°N, 26.8°E with a 95 per cent confidence ellipse having a 4.0° major semi-axis oriented 98° clockwise of north and a 1.8° minor semi-axis; the anomalous skewness is 14.2° ± 3.7°. The possible dependence of anomalous skewness on spreading rate was investigated with two empirical models and found to have a negligible effect on our palaeopole analysis over the range of relevant spreading half-rates, ~25 to ~90  mm  yr⁻¹ . The new pole is consistent with the northward motion for the Pacific plate indicated by coeval palaeocolatitude and palaeoequatorial data, but differs significantly from, and lies to the northeast of, coeval seamount poles. We attribute the difference to unmodelled errors in the seamount poles, mainly in the declinations. Comparison with the northward motion inferred from dated volcanoes along the Hawaiian–Emperor seamount chain indicates 13° of southward motion of the Hawaiian hotspot since 73  Ma. When the pole is reconstructed with the Pacific plate relative to the Pacific hotspots, it differs by 14°–18° from the position of the pole relative to the Indo–Atlantic hotspots. This has several possible explanations including bias in one or more of the palaeomagnetic poles, motion between the Pacific and Indo–Atlantic hotspots, and errors in plate reconstructions relative to the hotspots.  相似文献   

Reverse flood and pollution routing with the lag-and-route model     

Antonis D. Koussis  Katerina Mazi 《水文科学杂志》2013,58(10):1952-1966

ABSTRACT

Reverse routing can be used to transfer flood- or pollution-related information monitored at a downstream gauging station to an ungauged upstream cross-section. This signal identification problem is ill-posed and, as such, is sensitive to perturbations in the data to be inverted; therefore, the amplification of errors, e.g., those befalling measurements, must be controlled. Storage routing models are parsimonious diffusion wave substitutes and well suited for conversion to direct reverse routers. We present efficient inversion frameworks based on the lag-and-route (single reservoir plus exact reverse lag-step) and the reservoirs-in-series models. In both cases we invert a centred finite difference scheme of the reservoir storage balance equation that involves only one value of the unknown signal; signal values identified in previous reverse time steps, which would carry perturbations, are absent. This simple structure endows the reverse scheme with robustness. Procedures are verified with perfect and with error-seeded data; solution oscillations caused by the latter are damped by low-pass filtering. Both inverse routing models regain the upstream signals with high fidelity. Reverse storage routing is exemplified in a demonstration of reservoir control and in a field case of solute transport in a stream.