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11.
Source parameters and ground motion of the Suez-Cairo shear zone earthquakes,Eastern Desert,Egypt 总被引：1，自引：0，他引：1
Three felt earthquakes with local magnitudes 4.0 (June 29th, 2000), 4.2 (July 07th, 2005) and 3.7 (October 30th, 2007) occurred
to the southeast of Cairo along the Suez-Cairo shear zone. Being the most well recorded events by the Egyptian National Seismic
Network (ENSN) in this area, they provide us an excellent opportunity to study the tectonics, the stress field, the source
parameters, and the expected ground motion at Cairo. The focal mechanisms of the three events based on the first motion P-wave
polarities indicate mainly normal faulting with a slight strike-slip component along nodal planes trending nearly EW and NW–SE.
The three focal solutions imply a rejuvenation of the pre-existing EW and NW–SE faults due to a partly transfer of rifting
deformation from the Red Sea-Gulf of Suez along these trends. Dynamic source parameters of these events are estimated from
the P-wave spectra of the closest ENSN stations. The average values of the seismic moment, stress drop, rupture radius, and
fault dislocation are estimated from six stations and interpreted in the context of the tectonic setting. These parameters
in addition to the effects of site and path are used to synthesize the ground motion seismograms using stochastic modeling
technique at the recorded stations and at some strategic sites. 相似文献
12.
13.
Alteration Patterns Related to Hydrothermal Gold Mineralizaition in Meta-andesites at Dungash Area, Eastern Desert, Egypt 总被引：3，自引：0，他引：3
Abstract: The hydrothermal alteration patterns associating with the gold prospect hosted by metavolcanics in the Dungash area, Eastern Desert of Egypt, were investigated in order to assign their relationship to mineralization. The metavolcanics of andesitic composition are generated by regional metamorphism of greenschist facies superimposed by hydrothermal activity. Epidote and chlorite are metamorphic minerals, whereas sericite, carbonates, and chlorite are hydrothermal alteration minerals. The auriferous quartz vein is of NEE‐SWW trend and cuts mainly the andesitic metavolcanics, but sometimes extends to the neighbouring metapyroclastics and metasediments. Quartz‐sericite, sericite, carbonate‐sericite, and chlorite‐sericite constitute four distinctive alteration zones which extend outwards from the mineralized quartz vein. The quartz‐sericite and sericite zones are characterized by high contents of SiO2, K2O, Rb, and As, the carbonate‐sericite zone is by high contents of CaO, Au, Cu, Cr, Ni, and Y, and the chlorite‐sericite zone is by high contents of MgO, Na2O, Zn, Ba, and Co. Gold and sulphide minerals are relatively more abundant in the carbonate‐sericite zone followed by the sericite one. The geochemistry of the alteration system was investigated using volume‐composition and mass balance calculations. The volume factors obtained for the different alteration zones, mentioned above (being 1.64, 1.19, 1.17, and 1.07, respectively), indicate that replacement had taken place with a volume gain. The mass balance calculations revealed addition of SiO2, K2O, As, Cu, Rb, Ba, Ni, and Y to the system as a whole and subtraction of Fe2O3 from the system. Initial high aK+ and aH+ for the invading fluids is suggested. As the fluids migrated into wallrocks, they became more concentrated in Mg, Ca, and Na with increasing activities of CO2 and S. The calculated loss‐gain data are in agreement with the microscopic observations. Breakdown of ferromagnesian minerals and feldspars in the quartz‐sericite, sericite, and chlorite‐sericite zones accompanied by loss in Mg, Fe, Ca, and Na under acidic conditions and low CO2/H2O ratio may obstruct the formation of carbonates and sulphides, and the precipitation of gold in these zones. The role of metamorphic fluids in the area is expected to be restricted to the liberation of Au and some associated elements from their hosts. 相似文献
14.
Relationship between point rainfall, average sampled rainfall and ground truth at the event scale in the Sahel 总被引：1，自引：0，他引：1
Geostatistical techniques are used to quantify the reference mean areal rainfall (ground truth) from sparse raingaugenetworks.
Based on the EPSAT-Niger event cumulative rainfall, a linear relationship between the ground truth considered as the mean
area rainfall estimated from the densely available raingauge network and the area rainfall estimated from sparse network are
derived. Also, a linear relationship between the ground truth and point rainfall is established. As it was reported experimentally
by some authors, the slope of these relationships is less than one. Based on the geostatistical framework, the slope and the
ordinate at the origin can be estimated as a function of the spatial structure of the rainfall process. It is shown that the
slope is smaller than one. For the special case of one gauge inside a fixed area or a Field Of View (FOV), an areal reduction
factor is derived. It has a limit value which depends only on the size of the area and the spatial structure of the rainfall
process. The relative variance error of estimating the FOV cumulative rainfall from point rainfall is also given. 相似文献
15.
Sorption of dissolved Fe2+ on bentonite was studied using a batch technique. The distribution coefficient, Kd , was evaluated for a bentonite-iron system as a function of contact time, pH, sorbent and sorbate concentrations, and temperature. Sorption results were interpreted in terms of Freundlich's and Langmuir's equations. Thermodynamic parameters for the sorption system were determined at three temperatures: 298°, 308°, and 318°K. The values of ΔH°(-4.0 kjmol−1 ) and ΔG°(-2.46 Kjmol−1 ) at 298°K (25°C) suggest that sorption of iron on bentonite is an exothermic and a spontaneous process. The ΔG° value became less negative at higher temperatures and, therefore, less iron was sorbed at higher temperatures. The desorption studies with 0.01 M CaCl2 and deionized water at iron loading on bentonite showed that more than 90 wt% of the iron is irreversibly sorbed, probably due to the fixation of the iron by isomorphous replacement in the crystal lattice of the sorbent. 相似文献
16.
Examination of the stellar spectrum of this star reveals that it has a composite spectrum. It could be classified as (A7V+G5V). It contains three forbidden [Feii] lines which are of the essential features of η Carinae stars. The spectrum also contains H, Hei, Feii, Mni, Tiii, and other different lines. The K-line seems to be sharp double line while other lines appear single ones which suggest early component may be double. This also seems to be true according to radial velocity measurements. 相似文献
17.
A new C15 acetogenin, cyclic enyne (12E)‐cis‐maneonene‐E ( 1 ) and (12Z)‐trans‐maneonene‐B ( 2 ), together with different secondary metabolites including sesquiterpenoid 2,10‐dibromo‐3‐chloro‐α‐chamigrene ( 3 ) and fatty acid aldehydes ( 4–8 ) were isolated from the petroleum ether extract of a red alga, identified as Laurencia papillosa, collected from the Saudi Red Sea coast. The L. papillosa crude extract and its active ingredient acetogenin ( 1 ) have been evaluated for the ability to control two main economically important pests, the confused flour beetle larvae Tribolium confusum and Culex pipiens mosquito larvae. Compound 1 showed high potential as a natural insecticide against these two pests. In the case of T. confusum larvae, the LD50 values were 0.21 and 0.16% after 6 and 12 days of treatment with crude extract and acetogenin, respectively. On the other hand, the resulting LC50 values of mosquito larvae bioassay were 30.7, 36.9, and 41.8 ppm after 24 h treatment against 2nd, 3rd, and 4th larval instars, respectively. Also, an increase of the insecticidal effects against mosquito larvae was recorded after extending treatment time to 48 h. 相似文献
18.
Ras Banas Peninsula is a large triangular tract of land jutting out into the Red Sea. It extends about 40 km eastward out of the general trend of the Red Sea coast of Egypt, covering an area of about 600 km2. Three sandy spits are jutting out from the main body of the peninsula into the Red Sea, possibly representing relics of structural trends, two of which are located at the western part and the third one is extending from the eastern edge forming a further seaward extension of the main body. A series of isometric and contour maps of the whole area under investigation are provided in digitized visual form of geomorphologic features, landforms and slope configuration. According to difference in relief, the study area can be subdivided into three topographic divisions, namely coastal plain (<50 m), medium-height land (50–150 m) and hinterland (>150 m). Drainage and lineament maps of the drainage networks were prepared from the topographic map and satellite images of the area. The prepared lineament map shows four main trends that control the configuration of the drainage system in the study area. These trends are Aqaba trend (NE–SW to NNE–SSW), Red Sea trend (NW–SE to NNW–SSE), Nubian trend (N–S), and Tethyan trend (E–W). It is clear that the structural trends, lithology and general slope are the main controls of developing parallel and dendritic drainage patterns in the area. Both geomorphology and drainage system configuration have great influences on the land use and natural hazards affecting the peninsula especially torrential floods and sea level fluctuations. 相似文献
19.
Mikhail Ezersky et al. have published the article “Geophysical prediction and following development sinkholes in two Dead Sea areas, Israel and Jordan” (February 2013) in which the paper “Salt karst and tectonics: sinkholes development along tension cracks between parallel strike-slip faults, Dead Sea, Jordan” published by Closson D, Abou Karaki N, Hallot F in 2009 (Earth Surface Processes and Landforms, 34(10), 1408–1421) is questioned. In this short paper, we propose some clarifications and discuss the criticisms of these authors. 相似文献
20.
Data of hourly interplanetary plasma (field magnitude, solar wind speed, and ion density), solar (sunspot number, solar radio
flux), and geomagnetic indices (Kp, Ap) over the period 1970-2010, have been used to examine the asymmetry between the solar
field north and south of the heliospheric current sheet (HCS). A persistent yearly north-south asymmetry of the field magnitude
is clear over the considered period, and there is no magnetic solar cycle dependence. There is a weak N-S asymmetry in the
averaged solar wind speed, exhibited well at times of maximum solar activities. The solar plasma is more dense north of the
current sheet than south of it during the second negative solar polarity epoch (qA < 0). Moreover, the N - S asymmetry in solar activity (Rz) can be statistically highly significant. The sign of the average N - S asymmetry depends upon the solar magnetic polarity.
The annual magnitudes of N - S asymmetry depend positively on the solar magnetic cycle. Most of the solar radio flux asymmetries
occurred during the period of positive IMF polarity. 相似文献