Source mechanism and source parameters of May 28, 1998 earthquake,Egypt

On May 28, 1998, a moderate size earthquake of mb 5.5 occurred offshore the northwestern part of Egypt (latitude 31.45°N and longitude 27.64°E). It was widely felt in the northern part of Egypt. Being the largest well-recorded event in the area for which seismic data from the global digital network are available, it provides an excellent opportunity to study the tectonic process and present day stress field occurring along the offshore Egyptian coast. The source parameters of this event are determined using three different techniques: modeling of surface wave spectral amplitudes, regional waveform inversion, and teleseismic body waveform inversion. The results show a high-angle reverse fault mechanism generally trending NNW–SSE. The P-axis trends ENE–WSW consistently with the prevailed compression stress along the southeastern Hellenic arc and southwestern part of the Cyprean arc. This unexpected mechanism is most probably related to a positive inversion of the NW trending offshore normal faults and confirms an extension of the back thrusting effects towards the African margin. The estimated focal depth ranges from 22 to 25 km, indicating a lower crustal origin earthquake owing to deep-seated tectonics. The source time function indicates a single source with rise time and total rupture duration of 2 and 5 s, respectively. The seismic moment (M _o) and the moment magnitude (M _w) determined by the three techniques are 1.03 × 10¹⁷ Nm, 5.28; 1.24 × 10¹⁷ Nm, 5.33; and 1.68 × 10¹⁷ Nm, 5.42; respectively. The calculated fault radius, stress drop, and the average dislocation assuming a circular fault model are 7.2 km, 0.63 Mpa, and 0.11 m, respectively.     

Conceptual examination of climate–soil controls upon rainfall partitioning in an open-fractured soil II: Response to a population of storms

A simple two-domain bucket model of fractured soil was coupled with a stochastic model of rainfall variability, in order to investigate the climate and soil controls upon the stochastic properties of the triggering of fracture flow and surface runoff, and the partitioning of rainfall between the matrix and fracture domains and surface runoff. Conventionally, soils are regarded as time domain filters between rainfall and hydrological response. This investigation highlights an additional type of threshold filtering especially important in understanding the infiltration behaviour of fractured soils, for which an event-based characterisation of rainfall in modelling is crucial. A priori-definable indices were derived which are capable of describing elements of this threshold filtering, by allowing the statistical properties of fracture flow- and surface runoff-triggering storms (i.e., mean and variance of storm duration, intensity and effective inter-storm period, as well as cumulative partitioning of rainfall), to be inferred directly from average storm and soil properties. Using these indices, the long-term response of fractured soils, including the long-term hydrological importance of fractures, can be estimated without simulation.     

Cryptosporidium Oocysts in Drinking Water Supply of Chennai City,Southern India

Cryptosporidium is an enteric parasitic protozoan capable of causing chronic diarrhea. One of the most common modes of transmission is through faeces‐contaminated water. This study determines the distribution of Cryptosporidium oocysts for the first time in Chennai City's drinking water supply. 199 drinking water samples were collected from ten zones of the city. In the water samples Cryptosporidium, a common pathogenic protozoan of the gastrointestinal tract, has been analyzed physico chemically as well as microbiologically for heterotrophic organisms and total coliforms (TC). The studies revealed that three zones of the city were highly contaminated with coliforms and parasitic protozoa. A statistical analysis was done to find any correlation between heterotrophic organisms, total coliforms, and oocysts. Even though a positive correlation exists between oocysts and bacteriological parameters, a regression equation shows that heterotrophic plate count (HPC) and total coliforms were only 20% responsible for the presence of oocysts. The level of Cryptosporidium oocysts isolated from the water samples may present a public health hazard although no major outbreaks have so far been reported in Chennai City. Routine surveillance of water quality throughout the city is needed to curb the pollutants.     

Zoobenthos of Lake Uluabat,a Ramsar Site in Turkey,and Their Relationship with Environmental Variables

The numerical and proportional distributions of zoobenthos in lake Uluabat, which is located in the Northwestern part of Turkey and having international importance according to the Ramsar Convention, were determined from August 2004 to July 2005 at monthly intervals (except for December 2004, January and February 2005) at 12 different stations. Thirty‐three taxonomic groups were recorded. It was found that the zoobenthos consisted of 35.6 % Oligochaeta, 27.7 % Nematoda, 12.3 % Chironomidae larvae, 10.7 % Gastropoda, 3.6 % Ostracoda, and 10.1 % Varia by numbers (Bivalvia, Ceratopogonidae, Hirudinea, Odonata, Ephemeroptera, Asilidae, Hydraacarina, Hemiptera, Argulidae, and Gammaridae). The average number of invertebrates was 160 individuals for 33 taxa at the 12 different stations. Also some environmental parameters of the lakewater were analyzed (temperature, pH, dissolved oxygen, biochemical oxygen demand, chemical oxygen demand, NO₂–N, NO₃–N, NH₃–N, PO₄^–3, fecal coliform, and total coliform). The relationships between the dynamics of the Oligochaeta and the physicochemical variables were supported by the Pearson correlation index and the canonical correspondence analysis (CANOCO). It was found that the relation between the average number of P. hammoniensis and P. albicola (p < 0.05, r = 0.590 and 0.593, respectively) and L. hoffmeisteri (p < 0.01, r = 0.777) was directly proportional while the relation between the average number of some taxa Trichodrillus sp., Rhyacodrilus coccineus, Nais communis, N. variabilis, and N. barbata and NO₃–N (p < 0.05, r = –0.685) was inversely proportional.     

Analysis of Physical and Chemical Parameters for Discrimination of Water Origin in a Hydroelectric Reservoir

Seventeen physical and chemical parameters were obtained from a hydroelectric reservoir located in a tropical region in the south of Brazil. Multivariate Principal Component Analysis (PCA) and Hierarchical Group Analysis (HGA) were used to identify the parameters discriminating the origin of water from the Tibagi and the Primeiro de Maio River, after it has passed the mixing region. The study was conducted during the dry and rainy seasons in July 2002 and February 2003 at three depths and three sampling sites located 0, 5, and 10 km away from the mixing region. The statistical methods showed to be appropriate for identifying the contribution of each tributary in the water mixing site of a complex water system. The most important discriminating parameter was the absorbance relation A(253 nm)/A(203 nm), followed by the concentrations of Fe(III), Mn(III), and Ni(II). An anthropogenic interference was found in the reservoir due to high Ni(II) and orthophosphate concentrations caused by a nearby town sewage discharge. The interference was more important during the dry periods due to the lower dispersion of the pollutants. Urgent initiatives should be taken from the state government to build treatment stations for the wastewater of the small cities around the Capivara hydroelectric reservoir to prevent the drinking water quality from deteriorating.     

Analysis of the weightiness of site effects on reinforced concrete (RC) building seismic behaviour: The Adra town example (SE Spain)

The damage distribution in Adra town (south‐eastern Spain) during the 1993 and 1994 Adra earthquakes (5.0 magnitude), that reached a maximum intensity degree of VII (European Macroseismic Scale (EMS scale)), was concentrated mainly in the south‐east zone of the town and the most relevant damage occurred in reinforced concrete (RC) buildings with four or five storeys. In order to evaluate the influence of ground condition on RC building behaviour, geological, geomorphological and geophysical surveys were carried out, and a detailed map of ground surface structure was obtained. Short‐period microtremor observations were performed in 160 sites on a 100m × 100m dimension grid and Nakamura's method was applied in order to determine a distribution map of soil predominant periods. Shorter predominant periods (0.1–0.3 s) were found in mountainous and neighbouring zones and larger periods (greater than 0.5 s) in thicker Holocene alluvial fans. A relationship T = (0.049 ± 0.001)N, where T is the natural period of swaying motion and N is the number of storeys, has been empirically obtained by using microtremor measurements at the top of 38 RC buildings (ranging from 2 to 9 storeys). 1‐D simulation of strong motion on different soil conditions and for several typical RC buildings were computed, using the acceleration record in Adra town of the 1993 earthquake. It is noteworthy that all the aforementioned results show the influence of site effects in the degree and distribution of observed building damage. Copyright © 2007 John Wiley & Sons, Ltd.     

Prediction of surface horizontal displacements, and gravity and tilt changes caused by filling the Three Gorges Reservoir

 Horizontal displacements, and gravity and tilt changes induced by filling the Three Gorges Reservoir are modeled using elastic loading Green functions. When the water surface reaches its highest level, the effects become maximum on the reservoir banks. The longitudinal and latitudinal components of the horizontal displacements reach −8.2 and 7.7 mm respectively, gravity is increased by up to 3.4 mGal, and the prime vertical and meridian components of the tilt changes are −7.8 and −17.5 arcseconds respectively. Accordingly, the filling of the reservoir will influence values observed from global positioning system (GPS), gravimetry and tilt measurements in the area. The results given can be used to provide important corrections for extracting earthquake-related signals from observed data. Received: 19 January 2001 / Accepted: 3 September 2001     

湛江港邻近海域台风浪的模拟研究

对第三代近岸海浪数值模式SWAN及包含的物理过程进行了简要介绍，利用该模式对影响南海湛江港海域的二次台风浪过程进行了模拟研究：由藤田台风风场模型同化相应时刻的台风要素、NCAR/NCEP网格点资料、单站观测资料后，提供模式所需风场；利用自嵌套的方式，提供模式波谱边界条件；两次模拟结果与实际海浪观测资料相符较好，可以为该海域台风浪的模拟预报提供较为重要的参考。     

南沙群岛岛礁地形地貌TM影像特征分析

根据南沙海区的地形地貌特征，利用TM图像，对不同的珊瑚礁、珊瑚沙发育状况和岛礁的地质特征与生态特征进行了分析，研究了水下礁、滩的物质组份、发育程度及TM影像特征，提出了30m以浅岛礁分类方法，查清了南沙海域岛、礁、滩、沙的形态和分布，细化并完善了南沙群岛岛礁分类。