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71.
Ali Aghaei Asadollah Mahboubi Reza Moussavi Harami Mahdi Nadjafi Govind Joseph Chakrapani 《Journal of the Geological Society of India》2014,83(3):311-328
The upper Jurassic carbonate settings in Iran are widely exposed in north and northeastern parts. Five stratigraphic columns were selected in the north eastern Iran. Their thickness ranges from 330 to 500 m. The various diagenetic processes identified include, micritization, cementation, compaction (physical and chemical), dissolution, neomorphism, pyritization, hematitization, silicification and dolomitization, which affected these carbonates. Elemental and stable isotopes analysis indicated that these deposits have undergone both meteoric and burial diagenesis in a relatively open system with moderate water-rock interaction. The positive trend between trace elements and oxygen isotope depletion also support these burial conditions. Lighter δl8O values of the dolomite samples may be related to an increase in temperature during the burial, which correspond to coarser euhedral crystals. Relatively higher δ18O values in finer dolomite crystals indicate their formation at lower burial depths relative to coarser crystals. Petrographic evidences such as coarse euhedral crystals with bright and dull zonation prove this interpretation. Chert nodules also have lighter 18O values relative to carbonate host rock, thus indicating the influence of burial diagenetic processes in their formation. The average environmental palaeotemperature was estimated to be 26°C on the basis of oxygen isotope values of less altered lime-mudstones. 相似文献
72.
Earthquakes have a greater effect on society than most people think. These effects range from structural damages to economic impacts and fatalities. An earthquake only lasts for a few seconds and the aftershocks may continue for days, but the damage does continue for years. Residential site safety and earthquake damage assessment studies play a crucial role in developing reliable rehabilitation and development programs, improving preparedness and mitigating losses in urbanized areas. The extremely densely populated metropolis of Tehran, which totals of 7,768,561 for 22 districts (according to the 2006 population census), coupled with the fragility of houses and infrastructure, highlight the necessity of a reliable earthquake damage assessment based on essential datasets, such as building resistance attributes, building population, soil structures, streets network and hazardous facilities. This paper presents a GIS-based model for earthquake loss estimation for a district in Tehran, Iran. Damages to buildings were calculated only for the ground shaking effect of one of the region's most active faults, the Mosha Fault in a likely earthquake scenario. Earthquake intensity for each building location was estimated based on attenuation relation and the ratio of damage was obtained from customized fragility curves. Human casualties and street blockages caused by collapsed buildings were taken into account in this study, as well. Finally, accessibility verification found locations without clear passages for temporary settlements by buildings via open streets. The model was validated using the 2003 Bam earthquake damages. The proposed model enables the decision-makers to make more reliable decisions based on various spatial datasets before and after an earthquake occurs. The results of the earthquake application showed total losses as follows: structural damages reaching 64% of the building stock, a death rate of 33% of all the residents, a severe injury rate reaching 27% of the population and street closures upwards of 22% due to building collapse. 相似文献
73.
Mahdi Rasouli Maleki 《Rock Mechanics and Rock Engineering》2011,44(6):695-710
Havasan dam site is located in northwest of Iran. The planned concrete dam is to be built on Cretaceous limestone. Faulted
and fractured limestone is exposed at the dam abutments and in the reservoir area. Rock mass properties including the deformation
modulus and uniaxial compressive strength were calculated using different rock mass classification systems (RMR, Q, GSI and
DMR). Laboratory tests indicate that joint filling materials contain clay with low to high plasticity (CL to CH) and low to
medium potential swelling pressures. X-ray diffraction analysis confirms that the reason for potential swelling of joint fillings
is the existence of clay minerals (such as illite and montmorillonite). The study results about the shear strength of clay-filled
joints show that under JRC–JCS condition (laboratory scale), JRC
n
–JCS
n
(large scale) and normal stress equal to 0.25–4 MPa, the range of shear strength of clay-filled joints will be equal to 0.2–2.17
and 0.14–1.72 MPa. In some areas dissolution along the joints results in high permeability, especially in the right abutment.
Three dominant joint sets occur in the exploration galleries which have been excavated in the right abutment. The maximum
aperture of these joints varies from 7 to 9 cm, and the joints are typically filled with clay. Preliminary analysis shows
that the presence of open joints which will cause seepage of water, combined with the impact of the clay-filled joints and
forces acting on the slopes, could lead to slope failures and rock falls. In addition, the assessment of slope stability results
in abutments using limited equilibrium method and Swedge software under dynamic and static conditions shows that two wedges
formed on the slopes of the abutment by the natural joints are potentially unstable. The rock wedge on the left abutment is
smaller but presents higher sliding potential. In addition, there is no probability of planar failure due to the geological
condition of the dam abutments. This paper summarizes the site investigation and subsequent analysis, which resulted in a
recommendation not to construct this site. We offer some potential mitigation plans to consider if a dam were to be built
at this site. 相似文献
74.
Mahdi Zoorabadi Serkan Saydam Bruce Hebblewhite 《Geotechnical and Geological Engineering》2013,31(2):783-791
Penetration rate prediction of Tunnel Boring Machine (TBM) is the first step to advance prediction process of mechanized tunnelling. In this research, influence of effective parameters on TBM penetration rate is investigated by sensitivity analysis of three main TBM performance prediction methods; Norwegian University of Science and Technology (NTNU), rock mass index (RMi) and QTBM. Based on these analyses, it is shown that applied thrust per disc and joint spacing in NTNU and RMi models have more influence on penetration rate. In QTBM model, Q value, applied thrust per disc and induced biaxial stress are more effective. 相似文献
75.
Field and dual magnetic susceptibility proxies for heavy metal pollution assessment in the urban soil of Al-Karak City, South Jordan 总被引：1，自引：1，他引：0
A total of 115 urban soil samples collected on grid bases from Al-Karak, South Jordan, were investigated for their field and dual-frequency magnetic susceptibility (χ field, χ d) and heavy metal content using Bartington susceptibility meters and ICP-MS. The upper soils have higher magnetic susceptibility values than lower soils, and large particles contain more heavy metals and higher magnetic susceptibility than smaller particles. This might be attributed to the lack of pedogenesis due to arid climate influence. Within the upper soil all heavy metal showed positive significant correlation with upper soil low-frequency χ dlf. This was evident from the distribution maps produced by Surfer 9.0 for χ dlf and heavy metals. The results showed that higher χ dlf is associated with traffic-dominated sites more than other areas. The frequency-dependent susceptibility (χfd %) falls between 2 and 10 %, which indicate the presence of admixture of fine supermagnetic particles. Mildly correlation exists between χfd % and χ dlf, which implies that soils contain anthropogenic multi-domain grains. Selected samples have been analyzed for their mineral constituents; the results indicate the presence of magnetite as the main magnetic mineral. This confirms the anthropogenic source of pollution mainly from the vehicle-related materials. The results indicate the applicability of magnetic susceptibility for pollution detection. 相似文献
76.
Comparison of cokriging and adaptive neuro-fuzzy inference system models for suspended sediment load forecasting 总被引：1，自引：0，他引：1
Mehdi Vafakhah 《Arabian Journal of Geosciences》2013,6(8):3003-3018
The present research was carried out by using artificial neural network (ANN), adaptive neuro-fuzzy inference system (ANFIS), cokriging (CK) and ordinary kriging (OK) using the rainfall and streamflow data for suspended sediment load forecasting. For this reason, the time series of daily rainfall (mm), streamflow (m3/s), and suspended sediment load (tons/day) data were used from the Kojor forest watershed near the Caspian Sea between 28 October 2007 and 21 September 2010 (776 days). Root mean square error, efficiency coefficient, mean absolute error, and mean relative error statistics are used for evaluating the accuracy of the ANN, ANFIS, CK, and OK models. In the first part of the study, various combinations of current daily rainfall, streamflow and past daily rainfall, streamflow data are used as inputs to the neural network and neuro-fuzzy computing technique so as to estimate current suspended sediment. Also, the accuracy of the ANN and ANFIS models are compared together in suspended sediment load forecasting. Comparison results reveal that the ANFIS model provided better estimation than the ANN model. In the second part of the study, the ANN and ANFIS models are compared with OK and CK. The comparison results reveal that CK was a better estimation than the OK. The ANFIS and ANN models also provided better estimation than the OK and CK models. 相似文献
77.
Mohammad Zare Hamid Reza Pourghasemi Mahdi Vafakhah Biswajeet Pradhan 《Arabian Journal of Geosciences》2013,6(8):2873-2888
Landslide susceptibility and hazard assessments are the most important steps in landslide risk mapping. The main objective of this study was to investigate and compare the results of two artificial neural network (ANN) algorithms, i.e., multilayer perceptron (MLP) and radial basic function (RBF) for spatial prediction of landslide susceptibility in Vaz Watershed, Iran. At first, landslide locations were identified by aerial photographs and field surveys, and a total of 136 landside locations were constructed from various sources. Then the landslide inventory map was randomly split into a training dataset 70 % (95 landslide locations) for training the ANN model and the remaining 30 % (41 landslides locations) was used for validation purpose. Nine landslide conditioning factors such as slope, slope aspect, altitude, land use, lithology, distance from rivers, distance from roads, distance from faults, and rainfall were constructed in geographical information system. In this study, both MLP and RBF algorithms were used in artificial neural network model. The results showed that MLP with Broyden–Fletcher–Goldfarb–Shanno learning algorithm is more efficient than RBF in landslide susceptibility mapping for the study area. Finally the landslide susceptibility maps were validated using the validation data (i.e., 30 % landslide location data that was not used during the model construction) using area under the curve (AUC) method. The success rate curve showed that the area under the curve for RBF and MLP was 0.9085 (90.85 %) and 0.9193 (91.93 %) accuracy, respectively. Similarly, the validation result showed that the area under the curve for MLP and RBF models were 0.881 (88.1 %) and 0.8724 (87.24 %), respectively. The results of this study showed that landslide susceptibility mapping in the Vaz Watershed of Iran using the ANN approach is viable and can be used for land use planning. 相似文献
78.
79.
Coseismic slip model of the 2007 August Pisco earthquake (Peru) as constrained by Wide Swath radar observations 总被引：1，自引：0，他引：1
Mahdi Motagh Rongjiang Wang Thomas R. Walter Roland Bürgmann Eric Fielding Jan Anderssohn Jochen Zschau 《Geophysical Journal International》2008,174(3):842-848
The Pisco earthquake ( M w 8.0; 2007 August 15) occurred offshore of Peru's southern coast at the subduction interface between the Nazca and South American plates. It ruptured a previously identified seismic gap along the Peruvian margin. We use Wide Swath InSAR observations acquired by the Envisat satellite in descending and ascending orbits to constrain coseismic slip distribution of this subduction earthquake. The data show movement of the coastal regions by as much as 85 cm in the line-of-sight of the satellite. Distributed-slip model indicates that the coseismic slip reaches values of about 5.5 m at a depth of ∼18–20 km. The slip is confined to less than 40 km depth, with most of the moment release located on the shallow parts of the interface above 30 km depth. The region with maximum coseismic slip in the InSAR model is located offshore, close to the seismic moment centroid location. The geodetic estimate of seismic moment is 1.23 × 1021 Nm ( M w 8.06), consistent with seismic estimates. The slip model inferred from the InSAR observations suggests that the Pisco earthquake ruptured only a portion of the seismic gap zone in Peru between 13.5° S and 14.5° S, hence there is still a significant seismic gap to the south of the 2007 event that has not experienced a large earthquake since at least 1687. 相似文献
80.
This article presents a comparison between two two-dimensional finite volume flood propagation models: SRH-2D and Hydro_AS-2D. The models are compared using an experimental dam-break test case provided by Soares-Frazão (J Hydraul Res, 2007. doi: 10.1080/00221686.2007.9521829). Four progressively refined meshes are used, and both models react adequately to mesh and time step refinement. Hydro_AS-2D shows some unphysical oscillations with the finest mesh and a certain loss of accuracy. For that test case, Hydro_AS-2D is more accurate for all meshes and generally faster than SRH-2D. Hydro_AS-2D reacts well to automatic calibration with PEST, whereas SRH-2D has some difficulties in retrieving the suggested Manning’s roughness coefficient. 相似文献