• Volume 128, Issue 2

March 2019

• Propagation and coalescence of en-echelon cracks under a far-field tensile stress regime: An experimental study

Experiments were carried out to observe the variation in propagation and linkage of parallel en-echelon cracks with varying orientation of the crack array and different relative position of the cracks within the array in an extensional regime. Two-layered analogue model, with a basal layer of pitch overlain by a layer of kaolin paste was used in the experiments. En-echelon cracks were pre-cut within the kaolin layer maintaining specific geometrical parameters of the cracks (e.g., length, centre spacing, separation) in such a manner that there was a weak (though not negligible) local tip-induced stress favouring curvature of adjacent crack tips towards one another. The results obtained were matched with natural pattern of linkage of veins, rift basins and spreading ridges, as described in the relevant literature. The experimental results showed that the final pattern of linkage between the cracks was a result of initial deflection of crack tip from its plane due to combined effect of local and far-field stress. When the deflection of tip from the crack plane was between 0$^{\circ}$ to 45$^{\circ}$, a ‘tip to wall’ linkage took place between adjacent cracks isolating a rhombohedral area in the interaction zone. The resultant structure could be geometrically comparable to a micro-plate-like structure isolated due to linkage of ridge segments initially forming an overlapping spreading centre (OSC). When the deflection of tip from the crack plane was greater than 45$^{\circ}$, a ‘tip to tip’ linkage between adjacent cracks took place resulting in a structure similar to a transform fault between spreading ridges and or rift basins. When effect of the remote stress opposed the tip induced stress, no linkage took place between the adjacent cracks, and finally the tips propagated straight along a plane perpendicular to the remote extension direction.

• Groundwater quality in a semi-arid region of India: Suitability for drinking, agriculture and fluoride exposure risk

Fluoride exposure through consumption of drinking water was studied in a heavily industrialised area and suitable measures were suggested to control the fluorosis risk to residents. Groundwater quality conforms to World Health Organization (WHO) criterion for drinking except for fluoride and is also suitable for irrigation. Fluoride concentration ranges from 0.1 to 4.4 mg/l and 39% of the total samples measured were found to be contaminated as per WHO limits (1.5 mg/l). The fluoride intake through drinking water was calculated to be 0.10 mg/kg/d for infants, 0.09 mg/kg/d for children and 0.05 mg/kg/d for adults with a corresponding exposure dose exceeding 2.1, 1.9 and 1.1 times for infants, children and adults, respectively, compared to the minimum risk value of 0.05 mg/kg/d. The fluorosis risk map indicates that with a few exceptions of some western and northwestern parts, the entire study area is prone to fluorosis and the highest being in the south central part. The fluoride exposure dose suggests the risk of mottled enamel among residents if untreated groundwater is provided for drinking for a long time. Considering the hydrogeological setup of this region, various amelioration methods to help mitigate the ill effects of high fluoride were evaluated and better nutrition containing calcium and vitamin C was found to be the most effective and viable option.

• Establishment of digital 3D map based on discrete elevation point data measured in the field

This study established a survey zone digital elevation model (DEM) using highly precise and regularly updated three-dimensional coordinates of the surface of barchan dunes using CASS9.0 software. Two contour plots were drawn, one for the entire survey zone drawn with a contour interval of 0.005 m and one for an individual sand dune drawn with a contour interval of 0.001 m. ArcMap10 was used to define the projection of the created contour lines in DWG format and export the data into shape files to enable the creation of a triangulated irregular network (TIN). Next, TIN data was converted into raster data to facilitate our analysis and data processing. We created the final TIN by using an additional smoothing processing on the desired area that had been clipped out. We added the TIN data to the ArcScene module to establish the final 3D numerical model of barchan dunes. This model extracts and analyzes the changes in the characteristic parameters of the barchan dune as its topography changes in real time so researchers can visualize dune migration and evolution. Their understanding is enhanced by comparing and superposing the various 3D dune models on different days.

• Mapping of groundwater spring potential zone using geospatial techniques in the Central Nepal Himalayas: A case example of Melamchi–Larke area

Studies assessing the groundwater spring potential in the Himalayan mountain slopes are very important for sustainable water resources management and build climate resilience in mountains, but such studies are few in the Himalayas. Hence, this paper attempts to identify the groundwater spring potential zone in the Central Himalayas of Nepal. About 412 groundwater springs were surveyed, which were mainly originated from the weathered, jointed or fractured rock aquifers in the high-grade metamorphosed rocks. Eleven influencing factors, viz., altitude, slope gradient, slope shape, relative relief, flow accumulation, drainage density, geology, lineament density, land use and vegetation density were considered in assessing the groundwater spring potential using the weight of evidence method. Weight indicating the probability of groundwater spring occurrence on multiple classes of each factor was calculated and finally summed up to determine the groundwater spring potential. Gentle slope, low relative relief, high flow accumulation, north- and east-facing slopes, denser lineament density, altitude class of 1500–2500 m, high vegetation density, and forest demonstrated a higher likelihood of spring occurrence. Validation of the groundwater spring potential map was successful, which implies the method can be replicated in a similar biophysical environment, where the hydrogeological or geophysical surveyed data is not available.

• Co-seismic grace gravity-based 11-layered 3-D thrust fault model for the Sumatra earthquake 2004

Our co-seismic Gravity Recovery and Climate Experiment gravity data (level 2 ‘RL_05’ data product ‘GX-OG-_2-GSM) for the Sumatra earthquake 2004 is obtained by differencing monthly gravity field average for November 2004 from that of January 2005 and band-pass filtering (17${-}$30$^{\circ}$ and orders) in the spectral domain. Here, we propose a 11-layered three-dimensional (3-D) thrust fault gravity model based on different co-seismic rupture models in the literature. It honours co-seismic deformation of the ocean surface, ocean bottom and subsurface earth medium, different earthquake parameters and hypocentre information (${\sim}$ 35 km below mean sea level). Our forward gravity response matches well with the observed gravity (RMS error of 0.06257 $\mu$gal (6.26%)) data and our model allowed an independent computation of rupture length, instantaneous velocity, average seismic moment and momentum, which are, respectively, 1560 km, 2.9 km/s, 4.53 $\times$ 10$^{22}$ N m and 9.7 $\times$ 10$^{17}$ kg m/s. These parameters fairly agree with those in the literature. The computed momentum indeed corresponds to an area pulse (9.7 $\times$ 10$^{17}$ kg m/s) at ocean bottom that led to a tsunami generation. Thus, the proposed multi-layered 3-D gravity model in traditional fashion fully accounts for co-seismic gravity signal of the Sumatra earthquake 2004.

• Shear creep characteristics of weak carbonaceous shale in thick layered Permian limestone, southwestern China

Several weak intercalations of carbonaceous shale, which are commonly developed in the Permian thick limestone strata in Wulong County, Chongqing, southwestern China, form a structure of alternating layers of soft and hard rocks, which control the stability of massive layered rockslides. We focus on the Permian carbonaceous shale and analyse its mineral composition, microstructure and shear creep characteristics during the three evolutionary stages. The analysis results indicate the following: (i) During the evolutionary process of the carbonaceous shale, the microstructure changed from compact to loose, and the clay mineral content gradually increased from less than 5% in the original soft rock to 5–10% in the interlayer shear zone, and finally to greater than 10% in the sliding zone. (ii) Under the identical shear stress, the creep displacement and rate gradually increase nonlinearly. Under the identical normal stress, the long-term shear strength gradually decreases, and the drop in cohesion is greater than the internal friction angle. (iii) We established an improved Burgers nonlinear damage creep model, which fully reflected the creep deformation process of the carbonaceous shale. The fitting curve of the model matched the experimental results well.

• Investigating suspended-sediment transport in a shallow lake using a three-dimensional hydrodynamic and sediment model

A three-dimensional, unstructured-grid hydrodynamic and suspended-sediment transport model was developed to simulate the temporal and spatial variations of suspended sediment and was applied to the subtropical subalpine Tsuei-Feng Lake (TFL) of Taiwan. The model was validated with measured water level and suspended-sediment concentration in 2009, 2010 and 2011. The overall model simulation results are in quantitative agreement with the observational data. The validated model was then applied to explore the most important parameter that affects the suspended-sediment concentration and to investigate the effect of wind stress on the mean current and suspended-sediment distribution in this shallow lake. Modelling results of the sensitivity analysis revealed that the settling velocity is a crucial parameter and the erosion rate is less important in the suspended-sediment transport model. Remarkable lake circulation was found based on the strength of wind speed and wind direction. A strong wind would result in a higher mean current in the top layer and suspended-sediment distribution in the top and bottom layers. This study demonstrated that wind stress played a significant influence on mean circulation and suspended-sediment transport in a shallow lake.

• A new neuro-fuzzy-based classification approach for hyperspectral remote sensing images

Hyperspectral images are widely used in many applications. However, finding the appropriate hyperspectral image classification technique is a challenge. In this paper, we propose a new method by using an artificial intelligence-based method for hyperspectral image classification. The system has two parts: first, a pre-processing step, which helps the training phase to work faster; and second, the training part, which consists of calculating the neuro-fuzzy parameters. The prepared system is then applied to the classification of images. Three well-known hyperspectral datasets, including Pavia University from reflective optics system imaging spectrometer, the Botswana image from Hyperion and the Indian Pine image from airborne visible/infrared imaging spectrometer, were chosen to test the method. The final results of the experiments show that this system outperforms two classical methods of hyperspectral classification: support vector machine and spectral angle mapper. The comparison of the final results was made using two different metrics: overall accuracy and total disagreement. The proposed method increases the overall accuracy by about 5% for the Pavia University dataset, 2% for the Botswana dataset and 7% for the Indian Pine dataset. The total disagreement was reduced by about 0.01 for the Pavia University, 0.03 for the Botswana and 0.1 for the Indian Pine dataset when the proposed method was applied.

• INSAT-3D low-level atmospheric motion vectors: Capability to capture Indian summer monsoon intra-seasonal variability

In India, Atmospheric Motion Vectors (AMVs) are derived operationally from the advanced Indian meteorological geostationary satellite INSAT-3D since July 2013 over Indian Ocean region and are used in the numerical model for forecast improvement. In this study, first-time the low-level monsoon winds derived from INSAT-3D satellite have been used to see how these winds are successful in capturing the intra-seasonal variability over the Indian Ocean region for the year 2016. A validation of AMVs is done on regular basis. In this study, the validation of low-level AMVs with National Center for Environmental Prediction (NCEP) analysis winds carried out during June to September 2016. The observed mean monthly features of the Indian Summer Monsoon (ISM) in July and August 2016 from low-level AMVs from INSAT-3D match well with those of NCEP analysis winds. INSAT-3D low-level AMVs are quite successful in capturing the northward propagation of low level jet and their locations during active and break monsoon conditions which are known features of the ISM. They are also able to explain the two dominant modes of variability: (i) one with a periodicity between 32 and 64 days, and (ii) another with a periodicity between 8 and 16 days, for the monsoon season of 2016 when Morlet wavelet transform analysis is performed for time series analysis. An EOF analysis is performed for the study of the spatial structure of intra-seasonal variability and temporal variability of INSAT-3D low-level AMVs over the Indian Ocean region for ISM 2016 and quantifies the results of EOF analysis by performing RMSE analysis between EOFs of INSAT-3D and NCEP wind data.

• Petrology and geochemistry of a boninite dyke from the western Bastar craton of central India

The Dongargarh Supergroup along with the basal Amgaon Gneissic Complex constitutes the northwestern part of the central Indian Bastar craton. In the present study, we report a new finding of a boninite dyke intruded in the Amgaon gneisses of this area. The dyke composed of mainly pyroxenes, amphiboles and subordinate amount of plagioclase. The higher contents of SiO$_{2}$ (51–54 wt.%), MgO (12–14 wt.%), Ni (375–473 ppm), Cr (1416–1580 ppm) and very low TiO$_{2}$ (0.2–0.4 wt.%) are consistent with the boninite nature of the dyke as well as the unevolved primary nature of the source magma. The extraordinarily high CaO content (15.97–17.7 wt.%) with higher CaO/Al$_{2}$O$_{3}$ (3.13–3.96) ratios classifies it as high-Ca boninite. The trace element ratios including Zr/Ti, Ti/V, Ti/Sc and Ti/Yb further show its geochemical similarity with the Archaean boninite. The dyke also shows negative high-field strength element (Nb, Ta and Ti) anomalies which are the characteristics of the boninite rocks reported elsewhere and along with the enriched light rare earth element pattern, it shows more affinity particularly with the northern Bastar boninite dyke. The mineralogical and geochemical similarities of the boninite dykes from the Bastar craton indicate a widespread boninitic event during the Palaeoproterozoic having a similar origin. These boninite dykes indicate the preservation of subduction-related signatures in the lithospheric mantle beneath the Bastar craton at the time of its evolution or may be during the convergence of the Bastar and Bundelkhand cratons.

• A comparative study of conceptual rainfall-runoff models GR4J, AWBM and Sacramento at catchments in the upper Godavari river basin, India

Accurate catchment level water resource assessment is the base for integrated river basin management. Due to the complexity in model structure and requirement of a large amount of input data for semi-distributed/distributed models, the conceptual models are gaining much attention in catchment modelling these days. The present study compares the performance of three conceptual models, namely GR4J, Australian Water Balance Model (AWBM) and Sacramento for runoff simulation. Four small catchments and one medium catchment in the upper Godavari river basin are selected for this study. Gap-filled daily rainfall data and potential evapotranspiration (PET) measured from the same catchment or adjacent location are the major inputs to these models. These models are calibrated using daily Nash–Sutcliffe efficiency (NSE) with bias penalty as the objective function. GR4J, AWBM and Sacramento models have four, eight and twenty-two parameters, respectively, to optimise during the calibration. Various statistical measures such as NSE, the coefficient of determination, bias and linear correlation coefficient are computed to evaluate the efficacy of model runoff predictions. From the obtained results, it is found that all the models provide satisfactory results at the selected catchments in this study. However, it is found that the performance of GR4J model is more appropriate in terms of prediction and computational efficiency compared to AWBM and Sacramento models.

• Geoelectric versus MASW for geotechnical studies

We explore the role of non-invasive multi-electrode electrical resistivity imaging (ERT) and induced polarisation imaging (IPI) as an alternative to multichannel analysis of surface waves (MASW) for geotechnical site characterisation in view of their higher near-surface spatial resolution. By using regression equations, we assess the relative performance of ERT, IPI and MASW in predicting geotechnical test results (standard penetration test (SPT), dynamic cone penetration test (DCPT) and static cone penetration test (SCPT)) in a site investigation on our IIT Roorkee Campus, India. The results indicate that the average root mean square (RMS) errors in predicting SPT based on ERT, IPI and MASW are 16.95%, 21.9% and 28.03%, respectively. Likewise, the average RMS errors in predicting DCPT based on ERT, IPI and MASW are 15.4%, 15.3% and 56.99%, respectively, and the average RMS errors in predicting SCPT based on ERT, IPI and MASW are 20.15%, 18.65% and 36.49%, respectively. In view of higher resolution for near-surface investigations, ERT/IPI seems to score over MASW in geotechnical site investigation studies. So, a leading role for non-invasive and cost-effective ERT/IPI in geotechnical site investigations is envisaged.

• Establishing a daily rainfall occurrence simulation model for the Langat River catchment, Malaysia

For the study of water resources of a catchment, an immediate task would be to establish a good model for predicting the probable daily rainfall occurrence and rainfall amount. This study presents the simulation of daily rainfall occurrence using the generalized linear model (GLM), the non-homogeneous hidden Markov model (NHMM) and the bootstrap aggregated classification tree (BACT) model. The major challenge of NHMM is the determination of optimum number of hidden states, which can be achieved using the Bayesian information criterion score. While the determination of number of grown tree is another challenge for BACT model, this critical task can be achieved with the help of out-of-bag classification error. Both the NHMM and BACT model outperformed the GLM to capture the rainfall persistence and spell lengths distribution. Through the validation phase, the BACT model exhibited better performance with the higher indices of probability of detection, critical success index, Heidke skill score and Peirce skill score, than other models. The prediction ability of the NHMM is equivalent to an unskilled random forecast with the skill scores nearly equal to zero. At the end, the BACT model was recommended as the appropriate daily rainfall occurrence model for this study.

• Monitoring of severe weather events using RGB scheme of INSAT-3D satellite

In this study, real-time analysis of products and information dissemination (RAPID), a web-based quick visualisation and analysis tool for INSAT satellite data on a real-time basis has been introduced for identification of pre-monsoon severe weather events. The tool introduces the next generation weather data access and advanced visualisation. The combination of channels using red–green–blue (RGB) composites of INSAT-3D satellite and its physical significant value contents are presented. The solar reflectance and brightness temperatures (BTs) are the major components of the RGB composite. The solar reflectance component of the shortwave thermal infrared (IR) (1.6 $\mu$m), visible (0.5 $\mu$m) and thermal IR channels (10.8 $\mu$m) representing the cloud microstructure is known as Day Microphysics (DMP) RGB and the BT differences between 10.8, 12.0 and 3.9 $\mu$m is known as Night Microphysics (NMP) RGB. The threshold technique has been developed separately for both the RGB products of the year 2015–2016 and 2016–2017 of March–June, prior to the event (1–3 hr) for the detection of the thunderstorms. A validation analysis was conducted using the Forecast Demonstration Project of Storm Bulletins for pre-monsoon weather systems prepared by the India Meteorological Department and RADAR observations, demonstrating that this approach is extremely useful in recognising the area of convection prior to the occurrence of the events by the RGB thresholds. The validation of these thresholds has been carried out for March–June 2017. Both the RGBs i.e., DMP and NMP have a reasonable agreement with the ground-based observations and RADAR data. This threshold technique yields a very good probability of thunderstorm detection more than 94% and 93% with acceptable false alarm conditions, less than 3% and 5% for DMP and NMP, respectively. Furthermore, the limitations of these RGB products are additionally highlighted, and the future extent of refinement of these products in perspective of a rapid scan strategy is proposed. The threshold techniques are found to be useful for nowcasting application and are being used operationally using the RAPID tool.

• Sedimentological characteristics and controlling factors on fluvial styles of the Guantao Formation, Kongdian Oilfield, China

The Kongdian Oilfield is located in eastern China. More than 30 years have passed since the oil field was discovered in 1979. The majority of the oil is produced from reservoirs of the Guantao Formation (Miocene). A detailed description and interpretation of core, well-logging and 3-D seismic stratal slices data was carried out to analyze sedimentological characteristics of the Guantao Formation and two fluvial styles have been identified encompassing braided channel and meandering channel. Seven main facies associations were defined: (i) upward-fining channel, (ii) braided channel with mid-channel bar, (iii) meandering channel with point bar, (iv) levee, (v) floodplain, (vi) minor channel, (vii) swamp. Vertical changes in fluvial styles of the Guantao Formation were recognized by variations in preserved thickness, channels stacking pattern, regional paleoflow directions, and channel/floodplain ratios. The fluvial succession is 50–70 m thick in the lower Guantao Formation, composed of braided channels and high channel/floodplain ratio. The alluvial succession is 60 m in thickness in the upper Guantao Formation, the dominant fluvial styles change to meandering channels and channel/floodplain ratio reduces. The main factor that may have affected the fluvial style is the base-level changes. With the rise of the base level the fluvial style is believed to have changed from braided channels to meandering channels.

• Amphibolites in the rare metal- and tin-bearing Bastar–Malkangiri pegmatite belt in Chhattisgarh and Odisha, India

Amphibolites and Abukuma-type low-grade and low-pressure meta-sedimentary rocks (MSR) host mineralised rare metal (Nb–Ta, Be and Li)- and Sn-bearing granite pegmatites and their parental, fertile S-type granites in the Bastar–Malkangiri Pegmatite Belt (BMPB) in the SE part of the Bastar craton in parts of Chhattisgarh and Odisha, India. Amphibolites, based on their field relationship (as sills in MSR), mineral assemblage and textural features, are broadly classified into three types: (i) tremolite-, (ii) hornblende–actinolite-, and (iii) hornblende-bearing amphibolites. Petrochemically, amphibolite types (i–iii) show a regular decrease in their Mg content and related trace elements such as Cr (81–1731 ppm), Ni (135–379 ppm) and Co (23–68 ppm) and, hence, are designated, respectively, as high-, intermediate- and low-Mg amphibolites. All the three types show slight enrichment in Si, Fe and P, reflected in their normative quartz, hypersthene and lesser diopside, magnetite, ilmenite and apatite, but no olivine. They are relatively enriched in incompatible elements such as Rb (16–526 ppm), Ba (15–538 ppm), Zr (56–147 ppm) and Nb (3–44 ppm), with relatively a higher concentration of these elements in those near to the contacts with pegmatites, thereby demonstrating some influence of the pegmatites on the chemistry of the host amphibolites. In spite of these, the three types of amphibolites show regular differentiation trends, reflected by their systematic decrease of Ni, Cr and Co with a decrease of Mg, and also show Fe-enrichment in their alkalies (Na$_{2}$O + K$_{2}$O) ${-}$ (FeO + Fe$_{2}$O$_3$) ${-}$ MgO (AFM) plot. The field, petrography and major–minor trace elements petrochemistry, including rare earth elements with slight negative to no Eu-anomaly, and their chemical patterns cumulatively point out that these amphibolites are ortho-type and sub-alkaline in nature, with quartz tholeiitic magmatic affinity, and the formation due to more of fractional crystallisation and less of 5–25% partial melting of an enriched primordial mantle magma (enriched mid-oceanic ridge basalt – E-MORB), emplaced at a deduced shallow depth of 10–25 km, with the main controlling phases being olivine, plagioclase, clinopyroxene and apatite.

• Palaeoecological significance of a palynofloral assemblage from Surma Group (Late Miocene) of Tamenglong area, Manipur, northeast India

A Late Miocene palynofloral assemblage is recorded for the first time from the sediments of Surma Group exposed at Tamenglong area of Manipur. The assemblage mainly consists of fungal spores and Microthyriaceous ascostromata, algal remains, pteridophytic spores, gymnospermous and angiospermous pollen. The quantitative analysis indicates the dominance of bisaccate gymnosperm pollen (61%) mainly represented by Podocarpidites and Pinuspollenites, followed by pteridophytic spores (23%), algal and fungal remains (11%) and angiosperm pollen grains (5%). Abundance of Hammenisporis spp., fungal conidia and ascostromata along with Zygnemataceous zygospores in the assemblage indicates a warm, humid climate and freshwater depositional environment for the Surma sediments in the present area of investigation. Recorded palynofloral assemblage with the characteristic fungal Microthyriaceous ascostromata suggests a pro-delta to shoreface depositional environment. Representatives of families Parkeriaceae, Cyatheaceae, Gleicheniaceae, Hymenophyllaceae, Podocarpaceae, Araceae and Malvaceae indicate the prevalence of tropical–subtropical climate. The Tamenglong palynofloral assemblage has been compared with some other assemblages known from the Mio-Pliocene sediments of India. The occurrences of abundant Pinuspollenites, Tsugaepollenites, Hibisceaepollenites and Parmathyrites in the present assemblage suggest a Late Miocene age.

• Investigating daytime and night-time differences with the seasonal trend and sources of inorganic fine aerosols in Indo-Gangetic plain

This study investigates the seasonal distribution of inorganic aerosols in Central New Delhi and identifies their potential source regions using concentration weighted trajectories (CWTs). Secondary inorganic aerosols (NO$_{3}^{-}$, SO$_{4}^{2-}$, NH$_{4}^{+}$) are the largest contributors to fine particulate matter in New Delhi, India. The concentrations of secondary inorganic aerosols showed very distinct seasonal patterns with higher concentrations in winter and post-monsoon seasons. Inorganic ions Ca$^{2+}$, Mg$^{2+}$ and K$^{+}$ were also examined to understand their temporal trends. The primary aerosols were found to have smaller diurnal differences than secondary aerosols. The higher coefficient of divergence for secondary aerosols indicated a significant difference in their chemistry and/or meteorology during daytime and night-time, respectively. The backward trajectory analysis revealed the advection of ionic species from distant sources responsible for their significant seasonality. The highest concentrations of K$^{+}$ during the post-monsoon season were mainly influenced by air masses arriving from Punjab and Haryana regions resulting from the prominent agricultural crop residue burning in these areas. CWT also identified the Thar Desert and Punjab as potential regions for enhanced levels of Ca$^{2+}$ and K$^{+}$, respectively. Also, the brick kilns located in western UP were observed as the major potential sources for NO$_{3}^{-}$ and SO$_{4}^{2-}$.

• Multistage gedrite in gedrite–hypersthene-bearing high-grade granulites from Daltonganj, Chhotanagpur granite–gneissic complex, Jharkhand, as evident from TEM and textural relations

The studied rock consists of mineral phases garnet–cordierite–gedrite–hypersthene–biotite–quartz and lies nearly 14 km southwest of Daltonganj in the western part of Chhotanagpur granite–gneissic complex. Textural relations of mineral phases, mineral chemistry and transmission electron microscopy (TEM) analyses of the rock samples suggest the early (gedrite1), middle (gedrite2) and late stages (gedrite3) formation of gedrite. Hypersthene appears through the metamorphic reaction gedrite $+$ quartz $=$ orthopyroxene $+$ garnet $+$ cordierite $+$ H$_{2}$O due to the breakdown of gedrite3 at the thermal peak of 869$^{\circ}$C/7.79 kbar. The bundles, prismatic and fibrous forms of three gedrites have been observed in the TEM images. TEM images and selected area electron diffraction patterns show the distribution of metallic element position at the different lattice site. The P–T estimates of the rock from garnet–orthopyroxene, garnet–cordierite and garnet–biotite exchange geothermometers and garnet–sillimanite–cordierite–quartz geobarometers vary from 775$^{\circ}$ to 869$^{\circ}$C, 642$^{\circ }$ to 703$^{\circ }$C, 480$^{\circ }$ to 617$^{\circ }$C and 6.76 to 7.79 kbar, respectively.

• Landslide prediction capability by comparison of frequency ratio, fuzzy gamma and landslide index method

This study presented the prediction capability of three methods including the frequency ratio (FR), fuzzy gamma (FG) and landslide index method (LIM) to produce landslide-prone areas in the Sari-Kiasar watershed, Mazandaran Province of Iran. In the first step, 105 landslide locations were selected and were randomly divided into two groups of 75% (78 locations) and 25% (27 locations) as training and testing datasets. Then the 17 landslide conditioning factors including land use/land cover, Differential Vegetation Index (DVI), lithology and distance from faults, elevation, slope aspect, slope angle, tangential curvature, profile curvature and plane curvature, distance from drainage, rainfall, Stream Power Index, Sediment Transport Index and temperature, and distance from road, density of settlement were considered for the proposed modelling approach. Finally, by applying the training dataset, three landslide susceptibility maps were constructed by using the FR, FG and LIM methods. The prediction capability of the performed model was evaluated by the area under the receiver operating curve or AUC for both training (success rate) and testing (prediction rate) datasets. The results showed that the AUC for success rate of FR, FG and LIM models was 82.04%, 81.08% and 73.61% and for prediction rate was 82.72%, 79.09% and 65.45%, respectively. The results showed that the FR model has a higher prediction accuracy than the FG and LIM methods. This study revealed that the most important factors in landslide occurrence are rainfall, slope and vegetation. The result of the present study can be possibly useful for land use planning and watershed management.

• # Journal of Earth System Science

Volume 129, 2020
All articles
Continuous Article Publishing mode

• # Editorial Note on Continuous Article Publication

Posted on July 25, 2019