Trapped waves of the 27 November 1945 Makran tsunami: observations and numerical modeling   总被引：1，自引：1，他引：0  

S. Neetu  I. Suresh  R. Shankar  B. Nagarajan  R. Sharma  S. S. C. Shenoi  A. S. Unnikrishnan  D. Sundar 《Natural Hazards》2011,59(3):1609-1618

The 27 November 1945 earthquake in the Makran Subduction Zone triggered a destructive tsunami that has left important problems unresolved. According to the available reports, high waves persisted along the Makran coast and at Karachi for several hours after the arrival of the first wave. Long-duration sea-level oscillations were also reported from Port Victoria, Seychelles. On the other hand, only one high wave was reported from Mumbai. Tide-gauge records of the tsunami from Karachi and Mumbai confirm these reports. While the data from Mumbai shows a single high wave, Karachi data shows that high waves persisted for more than 7 h, with maximum wave height occurring 2.8 h after the arrival of the first wave. In this paper, we analyze the cause of these persistent high waves using a numerical model. The simulation reproduces the observed features reasonably well, particularly the persistent high waves at Karachi and the single high wave at Mumbai. It further reveals that the persistent high waves along the Makran coast and at Karachi were the result of trapping of the tsunami-wave energy on the continental shelf off the Makran coast and that these coastally-trapped edge waves were trapped in the along-shore direction within a ∼300-km stretch of the continental shelf. Sensitivity experiments establish that this along-shore trapping of the tsunami energy is due to variations in the shelf width. In addition, the model simulation indicates that the reported long duration of sea-level oscillations at Port Victoria were mainly due to trapping of the tsunami energy over the large shallow region surrounding the Seychelles archipelago.  相似文献   

Particle Filter-based assimilation algorithms for improved estimation of root-zone soil moisture under dynamic vegetation conditions   总被引：1，自引：0，他引：1  

Karthik Nagarajan  Jasmeet JudgeWendy D. Graham  Alejandro Monsivais-Huertero 《Advances in water resources》2011,34(4):433-447

In this study, we implement Particle Filter (PF)-based assimilation algorithms to improve root-zone soil moisture (RZSM) estimates from a coupled SVAT-vegetation model during a growing season of sweet corn in North Central Florida. The results from four different PF algorithms were compared with those from the Ensemble Kalman Filter (EnKF) when near-surface soil moisture was assimilated every 3 days using both synthetic and field observations. In the synthetic case, the PF algorithm with the best performance used residual resampling of the states and obtained resampled parameters from a uniform distribution and provided reductions of 76% in root mean square error (RMSE) over the openloop estimates. The EnKF provided the RZSM and parameter estimates that were closer to the truth than the PF with an 84% reduction in RMSE. When field observations were assimilated, the PF algorithm that maintained maximum parameter diversity offered the largest reduction of 16% in root mean square difference (RMSD) over the openloop estimates. Minimal differences were observed in the overall performance of the EnKF and PF using field observations since errors in model physics affected both the filters in a similar manner, with maximum reductions in RMSD compared to the openloop during the mid and reproductive stages.  相似文献   

Controlling NOx Emission of Crude Rice Bran Oil Blend for Sustainable Environment     

Subramani Saravanan  Govindan Nagarajan  Radhakrishnan Ramanujam  Santhanam Sampath 《洁净——土壤、空气、水》2011,39(6):515-521

The main objective of this work is to investigate the factors influencing the NOx control of a stationary diesel engine fuelled with crude rice bran oil blend with lesser effect on smoke density and brake thermal efficiency (BTE). Fuel injection timing, percentage of EGR, and fuel injection pressure are chosen as the factors for the objective and NOx emission, smoke density, and BTE are considered as the response variables. To critically analyze the effects of the chosen factors on the objective three levels were chosen in each factor and the experiments were designed by following the design of experiments method. Taguchi's L₉ orthogonal array was used to conduct the tests with different combination of factor levels. Through analysis of variance (ANOVA) method, the most influencing factors and also the significance of each factor affecting each response variable were found out. Response graph was drawn for each response variable to determine the optimum combination of factor levels in achieving the objective and the obtained combination was confirmed experimentally.  相似文献   

Occurrence of Nummulitic coralline limestone from offshore Palar Basin,Bay of Bengal,India     

S. Ramesh  K. Nvv Murthy  S. M. Hussain  S. Ramasamy  G. A. Ramadass 《Marine Georesources & Geotechnology》2020,38(1):57-63

Abstract

Palar basin is located between Pennar and Cauvery sedimentary basins of East coast of India in Bay of Bengal, northeast Indian Ocean. Sea floor drill (Wire-line Autonomous Coring System – WACS) with operational capability of up to 3000?m water depth was developed to collect long cores from deep sea floor for geotechnical and ocean resource assessment studies. During the drilling operation it encountered Nummulitic coralline limestone of Lower Eocene age at 18 meters below the seafloor (mbsf) at 850?m water depth indicating carbonated platform presence for the first time at the study region. Bathymetry contour from Naval Hydrography Chart and General Bathymetric Chart of the Oceans (GEBCO) has revealed the presence of shallow mounds from 50 to 200?m depth closure contour near the sampling site at 850?m water depth which might be a submerged carbonated structure. Since, Nummulites are shallow water dwelling fauna (<20?m depth) but its occurrence at 18 mbsf in 850?m water depth is recorded because of the advancement in technology tool for long core sampling by means of sea floor drill.  相似文献   

Hydrogeochemistry and microbial contamination of groundwater from Lower Ponnaiyar Basin, Cuddalore District, Tamil Nadu, India   总被引：1，自引：1，他引：0  

M. Jeevanandam  R. Nagarajan  M. Manikandan  M. Senthilkumar  S. Srinivasalu  M. V. Prasanna 《Environmental Earth Sciences》2012,67(3):867-887

Groundwater is the major source of fresh water in regions where there is inadequate surface water resources. Forty-seven groundwater samples were collected from Lower Ponnaiyar basin, Cuddalore District, south India, during the premonsoon (PRM) and postmonsoon (POM) seasons of 2005. Out of 47 groundwater samples, 15 samples showing higher nitrate concentration were those collected during PRM 2005. Microbial analysis of these samples was carried out by employing 16S rRNA gene sequence tool. Detailed analysis was conducted to determine the hydrogeochemical processes and microbial contamination responsible for deterioration of quality. The abundance of the ions during PRM and POM are in the following order: Na?>?Ca?>?Mg?>?K?=?Cl?>?HCO₃?>?SO₄?>?CO₃. The dominant water types in PRM are in the order of NaCl?>?CaMgCl?>?mixed CaNaHCO₃, whereas during POM NaCl?>?CaMgCl?>?mixed CaNaHCO₃, and CaHCO₃. However, NaCl and CaMgCl are major water types in the study area. The quality of groundwater in the study area is mainly impaired by surface contamination sources, mineral dissolution, ion exchange and evaporation. Groundwater chemistry was used to assess quality to ensure its suitability for drinking and irrigation, based on BIS and WHO standards. Suitability for irrigation was determined on the basis of the diagram of US Salinity Laboratory (USSL), sodium absorption ratio (SAR), residual sodium carbonate (RSC), and Na%. According to SAR and USSL classification, 27.66% (PRM) and 40.43% (POM) of samples fall under C3S2 category, indicating high salinity and medium sodium hazard, which restrict its suitability for irrigation. Microbiological analysis and its effects on the water quality were also addressed. The 16S rRNA gene sequences of 11 bacterial contaminants exhibited five groups with 11 operational taxonomic units with aerobic and facultatively anaerobic organisms. The presence of aerobic organisms in the groundwater samples reflects the active conversion of ammonia to nitrite by Nitrosomonas sp. which is further converted to nitrates by other organisms. Further the presence of nitrate reducers could also play a role in the process of conversion of nitrate to ammonia and nitrate to molecular nitrogen.  相似文献   

Assessment of groundwater potential zones using GIS technique   总被引：1，自引：0，他引：1  

M. Nagarajan  Sujit Singh 《Journal of the Indian Society of Remote Sensing》2009,37(1):69-77

A case study was conducted to find out the groundwater potential zones in Kattakulathur block, Tamil Nadu, India with an aerial extent of 360.60 km². The thematic maps such as geology, geomorphology, soil hydrological group, land use / land cover and drainage map were prepared for the study area. The Digital Elevation Model (DEM) has been generated from the 10 m interval contour lines (which is derived from SOI, Toposheet 1:25000 scale) and obtained the slope (%) of the study area. The groundwater potential zones were obtained by overlaying all the thematic maps in terms of weighted overlay methods using the spatial analysis tool in ArcGIS 9.2. During weighted overlay analysis, the ranking has been given for each individual parameter of each thematic map and weights were assigned according to the influence such as soil −25%, geomorphology − 25%, land use/land cover −25%, slope − 15%, lineament − 5% and drainage / streams − 5% and find out the potential zones in terms of good, moderate and poor zones with the area of 49.70 km², 261.61 km² and 46.04 km² respectively. The potential zone wise study area was overlaid with village boundary map and the village wise groundwater potential zones with three categories such as good, moderate and poor zones were obtained. This GIS based output result was validated by conducting field survey by randomly selecting wells in different villages using GPS instruments. The coordinates of each well location were obtained by GPS and plotted in the GIS platform and it was clearly shown that the well coordinates were exactly seated with the classified zones.  相似文献   

Remote sensing- and GIS-based runoff modeling with the effect of land-use changes (a case study of Cochin corporation)     

M. Nagarajan  George Basil 《Natural Hazards》2014,73(3):2023-2039

A study was conducted to estimate the runoff in urbanized zone using Soil Conservation Services Curve Number (SCS-CN) method through remote sensing and GIS techniques. In this study, the region was identified as Cochin Corporation (Kerala State, India) with an aerial extent of 96.44 km². The spatial and non-spatial data were collected from different sources, and the thematic layers of soil hydrologic group and land-use maps were prepared and overlaid with one other. The overlaid output results were assigned by curve numbers with respect to soil and land-use categories, and the CN map was prepared with the help of Visual Basic (VB) language in ArcGIS platform. Through supervised classifications, 13 different land-use classes were identified from Quickbird data for the year of 2005 and 2010. The most prominent land-use classes were water bodies, residential, mixed crops, commercial and industrial, and 3 types of soil hydrologic groups were identified namely A, B, and C categories. The B group is most prominent occupying 60 km² of the study area. The CN map shows the ranges that 92–100 is the major CN area with high runoff potential zone of the study region. At the final stage, the runoff was estimated by the maximum successive rainfall received in this study area in two different years—2005 and 2010 along with their land-use pattern. The runoff model is applied for temporal variation in land-use change, and impact of runoff was studied. The study area showed significant changes in land-use pattern between 2005 and 2010 particularly in the land-use change from agricultural into industrial, commercial, and residential (high density). The area covered by the highest runoff depth with the range of 92–100 CN values increased from 43.87 to 45.32 km² from 2005 to 2010. The volume of runoff was increased from 135.56 to 141.49 Mm³ from 2005 to 2010 due to the land-use change pattern.  相似文献   

Enrichment pattern of leachable trace metals in roadside soils of Miri City,Eastern Malaysia     

R. Nagarajan  M. P. Jonathan  Priyadarsi D. Roy  M. V. Prasanna  A. Elayaraja 《Environmental Earth Sciences》2014,72(6):1765-1773

This article presents the results on distribution and enrichment pattern of acid-leachable trace metals (ALTMs) from roadside soil of Miri city, Sarawak, East Malaysia. The city is one of the fastest developing in the Malaysian region with huge petroleum resources. ALTMs Fe, Mn, Cr, Cu, Ni, Co, Pb, Zn and Cd along with organic carbon and carbonates (CaCO₃) were analyzed in 37 soil sediments collected from roadside. The enrichment of ALTMs [especially Cu (0.4–13.1 μg g^?1), Zn (9.3–70.7 μg g^?1), Pb (13.8–99.1 μg g^?1)] in the roadside soils indicate that these metals are mainly derived from sources related to traffic exhausts, forest fires and oil refineries. The comparative study and enrichment pattern of elements indicates that Mn, Cu, Zn and Pb are enriched multi-fold than the unpolluted soil and Ni, Pb, Cd in some samples compared to Sediment Quality Guidelines like Lowest Effect Level (LEL) and Effects Range Low (ERL) in the region which is mainly due to the recent industrial developments in the region.  相似文献   

Franck-condon factors and -centroids for certain band systems of astrophysical molecular ions CN+ and N+2     

N. Rajamanickam  K. Nagarajan  V. Raja 《Astrophysics and Space Science》2000,274(4):725-731

The Franck-Condon factors and r-centroids, which are very closelyrelated to relative vibrational transition probabilities, have beenevaluated by the more reliable numerical integration procedure forthe bands of c ¹ - a ¹ and f ¹ - a ¹ systems of CN ⁺ and C ^{2 +} _u- X ^{2 +} _g and D ² _g- A ² _u systems of N ⁺ ₂ molecular ions of astrophysical interest,using a suitable potential.  相似文献   

Tectonic evolution of early precambrian south indian shield (rocks) using remotely sensed data     

S M Ramasamy  S Balaji  C J Kumanan 《Journal of the Indian Society of Remote Sensing》1999,27(2):91-104

The interpretation of satellite imagery of part of South India falling South of 15 degree North latitude shows that the regional anticlines, synclines, domes and basins of the Precambrian group of metamorphites are aligned in three major hill ranges/domains such as Chitra-durga domain in the north, the Mangalore-Ootacamund-Bangalore domain in the centre and the Cochin-Cape Comorin-Madurai-Chittoor domain in the south. These hills are crescent shaped with their axes of elongation oriented in NNW-SSE direction. The lineaments with ENE-WSW, NE-SW/WNW-ESE and NNW-SSE azimuthal frequencies respectively exhibit extensional, shear and release geometries. Such deformational fabric shows that the tectonic evolution of South India was controlled by two major compressive forces, the first one aligned in N-S direction and the second in ENE-WSW direction.  相似文献