Liquefaction resistance evaluation of soils using artificial neural network for Dhaka City,Bangladesh

Natural Hazards - Soil liquefaction resistance evaluation is an important site investigation for seismically active areas. To minimize the loss of life and property, liquefaction hazard analysis is...     

Influence of natural and anthropogenic factors on the water quality of the coastal waters around the South Andaman in the Bay of Bengal

During the last decade, the Andaman and Nicobar Islands (ANI) have witnessed a marginal population growth with associated variations and degradation in the water quality of the inhabited coastal region. Monthly water quality data collected from six coastal locations in ANI were used to evaluate the anthropogenic influence in an otherwise pristine island environment. Exceptionally low dissolved oxygen (0.7–2.0 mg/L) at the Phoenix Jetty (PJ) and mangrove site indicates hypoxic conditions. Among the nutrients, nitrate shows high values at PJ due to heavy nutrient loading from domestic sewage. The cluster analysis segregated PJ from the remaining sites, indicating deterioration in the water quality. On the other hand, water quality at Sippighat, a low-intensity aquaculture site, does not indicate any deterioration. Apart from the large modulations in the water quality of the study area by the Bay of Bengal waters, the effect of domestic waste discharges significantly affects the coastal waters of Andaman. Though the present water quality at most of the study sites appears acceptable, the increased volume of tourism and allied activities poses a potential threat to the island ecosystem. Besides the anthropogenic influences, the long-term trends in oceanographic factors were analyzed in order to decipher the expected natural effect on future water quality of the region. Based on the increasing sea surface temperature as well as the decreasing chlorophyll-a, eddy kinetic energy, and zonal kinetic energy, we propose that the combined effect of both natural and anthropogenic factors can ultimately distress the present ambient water quality of ANI.     

Spectral characteristics of natural and artificial seismic events in the Lop Nor test site, China

Seismic discriminants based on the spectral seismogram and spectral magnitude techniques have been tested to discriminate between three events; a nuclear explosion which took place in Lop Nor, China with m _b 6.1 and two earthquakes from the closest area with m _b 5.5 and 5.3, respectively. The spectral seismogram of the three events shows that the frequency content of the nuclear explosion differs from that of the earthquakes where the P wave is richier in high frequency content in the nuclear explosion than the corresponding earthquakes. It is also observed that the energy decays more rapidly for the nuclear explosion than for the earthquakes. Furthermore, the spectral magnitudes reveal significant differences in the spectra between the nuclear explosion and the two earthquakes. The observed differences appear to be quite enough to provide a reliable discriminant. The estimated stress drop from the magnitude spectra indicates a higher stress drop of the nuclear explosion relative to the earthquakes of the same tectonic region.     

A Study of Largest Active Region AR12192 of 24th Solar Cycle Using Fractal Dimensions and Mathematical Morphology

Solar System Research - An active region (AR) of the sun is an area of strong magnetic field. Sunspots are frequently formed in an AR. Solar activity exhibits in the form of solar flares and...     

A Preliminary Study on the Aghbolaq(Fe,Cu) Skarn Deposit,Oshnavieh, NW Iran: Constraints on Metasomatic Fluid Evolution

The Aghbolaq skarn deposit is located in the Urumieh-Golpayegan plutonic belt,NW Iran.The garnetite skarn(stage I) has been intensely cross-cut by the magnetite-garnet skarn (stage II) which were,in turn,cut and offset by the orehosting quartz veins/veinlets (stage III).The predominance of andradite (Adr_(82.5–89.1)) and its high Fe~(3+)/Al ratio (up to 1685)apparently supports the high f O_2,salinity and prevalence of magmatic/hydrothermal fluids involved,rather than meteoric waters,during the magnetite-garnet skarn formation.Two major groups of fluid inclusions,namely aqueous (LV,LVS) and aqueous–carbonic (LV_C,LL_CV_C),were recognized in garnet and quartz veins that,especially in growth zones and along intra-granular trails,better display fluid inclusion assemblages (FIAs) than those in clusters.The prograde magnetite-garnet skarn was formed by the metasomatic fluid at relatively high T_h (209–374℃),under a lithostatic pressure of～200 bars.The retrograde mineralized quartz veins were formed at temperatures ranging from 124℃to 256℃,by dilute and less saline(2.57–11.93 wt%Na Cl eq.) hydrothermal fluids under a hydrostatic pressure of～80 bars.The fluid evolution of the Aghbolaq skarn began with an earlier simple cooling of metasomatic fluid during the prograde stage,followed by the later influx of low salinity meteoric fluids during the retrograde stage.     

Bedouin farms in the Saint Katherine mountainous area(South Sinai,Egypt)

This study aims to assess the natural and cultivated plant species in 26 Bedouin farms in Saint Katherine Protectorate(SKP),identify their soil and water characteristics,and assess the suitability of these farms for the cultivation of some wild medicinal plants.The farms were selected to represent wide wadis with deep sand and clay deposits,gorge-like wadis covered with rock fragments of different sizes,spot-like oases,and the Al Q'aa Plain.Using TWINSPAN(two-way indicator species analysis)and DCA(detrended correspondence analysis)techniques,the 26 farms were classified into 5 groups(Ⅰ-Ⅴ)based on their floristic composition of wild plants.These groups reflect an elevation gradient among the farms above sea level from a mean of 119 m to a mean of1,865m.A total of 73 wild species were recorded,with47 in groupⅡ(500-1,000 m)and 25 in group V(1,700 m).The common target species were Artemisia judaica,Acacia tortilis subsp.raddiana,Origanum syriacum subsp.sinaicum and Varthemia montana(34.6%-26.9%).The cultivated speciesnumbered 25,with 17 in groupⅡ(500-1,000 m) andⅡin groupⅣ(1,500-1,700 m).The common fruit trees were olive,grape,fig,apple,palm,almond,apricot and pomegranate(73.0%-42.3%).Based on the soil characteristics,13 farms belong to soil class 2that describes good soils with moderate limitations,and 12 belong to soil class 3 that describes moderately good soils,which can be used regularly for crops after proper treatment.     

Stochastic ground-motion simulation of two Himalayan earthquakes: seismic hazard assessment perspective

The earthquakes in Uttarkashi (October 20, 1991, M _w 6.8) and Chamoli (March 8, 1999, M _w 6.4) are among the recent well-documented earthquakes that occurred in the Garhwal region of India and that caused extensive damage as well as loss of life. Using strong-motion data of these two earthquakes, we estimate their source, path, and site parameters. The quality factor (Q _β ) as a function of frequency is derived as Q _β (f) = 140f ^1.018. The site amplification functions are evaluated using the horizontal-to-vertical spectral ratio technique. The ground motions of the Uttarkashi and Chamoli earthquakes are simulated using the stochastic method of Boore (Bull Seismol Soc Am 73:1865–1894, 1983). The estimated source, path, and site parameters are used as input for the simulation. The simulated time histories are generated for a few stations and compared with the observed data. The simulated response spectra at 5% damping are in fair agreement with the observed response spectra for most of the stations over a wide range of frequencies. Residual trends closely match the observed and simulated response spectra. The synthetic data are in rough agreement with the ground-motion attenuation equation available for the Himalayas (Sharma, Bull Seismol Soc Am 98:1063–1069, 1998).