GPS measurements of postseismic deformation due to October 8, 2005 Kashmir earthquake

Relaxation of the coseismic stresses following an earthquake causes postseismic crustal deformation, which can last for days to years. Continuous monitoring of postseismic deformation facilitates the understanding of the mechanism of deformation and postseismic relaxation and viscous rheology. After the October 8, 2005 Kashmir earthquake, global positioning system data for 8 months, starting from October, 2005 have been analyzed from three continuous sites located at Gulmarg, Amritsar, and Jaipur. The average velocity during the observation period at Gulmarg (8.6 cm/year) is significantly higher than the Indian plate velocity exhibiting postseismic crustal deformation. The velocity at Amritsar (5.9 cm/year) and Jaipur (5.1 cm/year) is comparable to the Indian plate velocity. At Gulmarg, the logarithmic function fits well to the north–south component of postseismic transients (~in the coseismic slip direction). The nature of decay in these transients suggests that the deformation is mainly due to an afterslip, and the second possible contribution may be from the viscous relaxation process. This paper presents the characteristics of postseismic transients and possible contributions from various postseismic mechanisms subsequent to the Kashmir earthquake.     

The influence of barrier beach on sediment transportation in the Kakinada Bay

Summary Studies upon the changes of bottom topography in the vicinity of Godavari point and Kakinada Bay indicates recession of contours towards the shore as a result of net loss of sediment since the formation of Kakinada Bay. The sand spit has been growing in the north-westerly direction reducing the width of the opening between the Kakinada Bay and the open Ocean. The currents across the opening strengthen resulting rapid erosion of the bottom of the Bay. The beach to the north of the Kakinada Bay entrance channel is building up. In the present investigation, the authors made an attempt to explain the shore line changes and changes in bottom topography in the Kakinada Bay from the currents measured under different tidal conditions around the sand spit (Godavari Point.)     

Geology of Pulikonda and Dancherla alkaline complexes,Andhra Pradesh

Geological studies on saturated to oversaturated and subsolvus aegirine-riebeckite syenite bodies of the Pulikonda alkaline complex and Dancherla alkaline complex were carried out. The REE distribution of the Dancherla syenite shows a high fractionation between LREE and HREE. The absence of Eu anomaly suggests source from garnet peridotite. The Pulikonda syenite shows moderate fractionation between LREE and HREE as reflected by enrichment of HREE and moderate enrichment of LREE. The negative Eu anomaly indicates role of plagioclase fractionation.Three distinct co-eval primary magmas i.e. mafic syenite-, felsic syenite- and alkali basalt magmas — all derived from low-degrees of partial melting of mantle differentiates and enriched metasomatised lower crust played a major role in the genesis and emplacement of the syenites into overlying crust along deep seated regional scale trans-lithospheric strike-slip faults and shear zones following immediately after late-Archaean calc-alkaline arc magmatism at different time-space episodes i.e. initially at craton margin and later on into the thickened interior of the Eastern Dharwar craton. The ductile sheared and folded Pulikonda alkaline complex was evolved dominantly from the magmas derived from partial melting of lower crust and minor juvenile magmas from mantle. Differentiation and fractionation by liquid immiscibility of mafic magma and commingling-mixing of intermediate and felsic magmas followed by fractionational crystallisation under extensional tectonics during waning stages of calc-alkaline arc magmatism nearer to the craton margin were attributed as the main processes for the genesis of Pulikonda syenite complex. Commingling and limited mixing of independent mantle derived mafic and felsic syenitic magmas and accompanying fractionation resulting into soda rich and potash rich syenite variants was tentatively deduced mechanism for the origin of Dancherla, Danduvaripalle, Reddypalle syenites and other bodies belonging to Dancherla alkaline complex at the craton interior. The Peddavaduguru syenite was formed by differentiation of alkali mafic magma (gabbro to diorite) and it’s simultaneous mingling with fractionated felsic syenitic magma under incipient rift. Vannedoddi and Yeguvapalli syenites were derived due to desilicification and accompanying alkali feldspar mestasomatism of younger potash rich granites along Guntakal-Gooty fault and along Singanamala shear zone respectively.     

Managed aquifer recharge (MAR) by the construction of subsurface dams in the semi-arid regions: A case study of the Kalangi river basin, Andhra Pradesh

Overuse of groundwater in coastal areas, due to high population and agricultural activity results in seawater intrusion into the coastal aquifer. This paper presents the control measures taken to manage aquifer recharge (MAR) and also to overcome the problem of seawater intrusion into the coastal aquifer along the Kalangi river, Nellore district of Andhra Pradesh, India having connectivity with Pulicat (saltwater) lake estuary. Due to overexploitation of groundwater and less rainfall in past years, adjacent seawater has started intruding in the Kalangi river sub-surface and deteriorating groundwater quality up to 11.6 km from the confluence of the river with Pulicat lake. To prevent this situtation, subsurface dams were constructed in traditional manner using local earth material in three different places across the Kalangi river near Sullurpet town. The water storage capacities calculated after the sub-surface dams’ construction are 1.28 mcft at GK Engineering College, 6.23 mcft at Challamagudi and 3.143 mcft at Holy Cross School sites. The Holy Cross School sub-surface dam is the first full scale dam-cum-check dam constructed to prevent salt water intrusion in the Kalangi river at Sullurpet, Nellore district, Andhra Pradesh. At the Kalangi river estuary portion (at the mouth of sea) a groyne was reconstructed over old groyne site with the introduction of clay bed and wooden sheet piles at down stream. Apart from prevention of sea water entry into Kalangi river sub-surface (during seasons) the groyne top level was raised to prevent mixing of high sea water tides with fresh water and ensuring additional storage of fresh water at upstream side. The reconstructed groyne was serving the purpose of obstructing the surface seawater entry in the Kalangi river and water quality has improved in the river as well as in the wells. After construction of sub-surface dam, as per the Simpson ratio classification, there is substantial improvement of water quality in the SHAR infiltration well situated near the Holy Cross School sub-surface dam.     

A microstructural and argon laserprobe study of shear zone development at the western margin of the Nanga Parbat–Haramosh Massif,western Himalaya

A sample of banded amphibolite from the western margin of the Nanga Parbat–Haramosh Massif as Sassi has been studied using microstructural and ⁴⁰Ar/³⁹Ar laserprobe techniques to investigate the relationship between deformation and argon isotope variations in a natural system. Amphibolite-grade deformation occurred during south-directed overthrusting of the Kohistan arc over India along the Main Mantle Thrust and was overprinted by extensional reactivation of the earlier fabric and the formation of biotite-rich shear zones. Subsequent deformation along discrete fine-grained fault zones was characterised by the formation of scapolite, chlorite and K-feldspar, early plastic deformation and later cataclasis. Different minerals developed during this history show a wide range in apparent ⁴⁰Ar/³⁹Ar ages. Biotite, chlorite and scapolite exhibit much lower concentrations of excess argon, indicating their equilibration in a fluid relatively poor in excess argon. A `true' age of ca. 8 Ma from biotite represents a minimum age for deformation associated with formation of the Nanga Parbat Syntaxis and also precludes Pliocene metamorphism in this area of the syntaxis. Both high- and low-closure temperature minerals (amphiboles and feldspars) record apparent ages which are associated with the incorporation of excess argon within the mineral lattice. Although differential thermal resetting of minerals at different closure temperatures is important, variations in the inherited ⁴⁰Ar/³⁶Ar ratio throughout the sample is dominated by deformation and fluid infiltration. Consequently it appears that within deforming metamorphic rocks, areas with significantly different argon isotope compositions may be present and need not be homogenised by diffusion. Received: 6 July 1994 / Accepted: 24 December 1996     

Tidal eddies in a semi-enclosed basin: a model study

A modeling study has been carried out to support a Marine Management Plan for the Gulf of Kachchh, India and here the hydrodynamic part of the programme is described. The hydrodynamic model accurately predicts the tides and tidal currents present in the Gulf and these have been validated with the measured data, albeit at only a few locations. The time averaged residual currents obtained from the model for one lunar cycle clearly reproduce the complex, small-scale, topographically induced flows with several eddies. The existence of a dynamic barrier along Sikka-Mundra section, which divides the Gulf into two distinct dynamic systems, is very evident. The model is further used to predict the movement of surface floating particles launched at different locations in the Gulf, as an aid to determining floating pollutants. The results indicate that industries discharging wastes upstream of the barrier should use extreme caution, as these will remain in the vicinity for at least one lunar cycle.     

The M w 8.6 Indian Ocean earthquake on 11 April 2012: Coseismic displacement, Coulomb stress change and aftershocks pattern

The M _w 8.6 Indian Ocean earthquake occurred on April 11, 2012 near the NW junction of three plates viz. Indian, Australian and Sunda plate, which caused widespread coseismic displacements and Coulomb stress changes. We analyzed the GPS data from three IGS sites PBRI, NTUS & COCO and computed the coseismic horizontal displacements. In order to have in-depth understanding of the physics of earthquake processes and probabilistic hazard, we estimated the coseismic displacements and associated Coulomb stress changes from two rectangular parallel fault geometries, constrained by Global Positioning System (GPS) derived coseismic displacements. The Coulomb stress changes following the earthquake found to be in the range of 5 to ?4 bar with maximum displacement of ～11 m near the epicenter. We find that most of the aftershocks occurred in the areas of increased Coulomb stress and concentrated in three clusters. The temporal variation of the aftershocks, not conformed to modified Omori’s law, speculating poroelastic processes. It is also ascertained that the spatio-temporal transient stress changes may promote the occurrence of the subsequent earthquakes and enhance the seismic risk in the region.     

Geoenvironmental appraisal in a developing urban area

The area between Endada and Bhimunipatnam, an urban expansion of the Visakhapatnam Metrocomplex Region, Andhra Pradesh, India, is mainly underlain by the Eastern Ghats of Precambrian age. Geomorphologic units delineated are denudational, colluvial, fluvial and coastal plains. Geoenvironmental appraisal has been made with respect to the geomorphologic units. Geoenvironmental hazards include soil and rock characteristics, drainage conditions, structural features, slope stability, gully erosion, beach erosion, sea spray, depth to water table and groundwater quality, which impart considerable restraints on the urbanization of the area. Effective land use management measures are suggested to avoid the adverse impacts on the area for sustainable development.     

Utilization of Banana Stem Juice as a Feedstock Material for Bioethanol Production

Bananas are widely cultivated in tropical and subtropical countries and about 220 tons of biomass waste is produced per hectare of banana plantation. Banana pseudostem contains nearly 90% of moisture and about 4–5 m³ sap is generated from one ton of dried stem with high chemical oxygen demand(COD) and biological oxygen demand (BOD). The feasibility of using banana sap as a feedstock to produce ethanol is evaluated in this study. Banana sap is obtained by crushing the pseudostems and concentrated ten times and supplementing with other industrial byproducts such as corn steep liquor(CSL), spent wash (SW), and yeast extract (YE) for ethanol production. Acid and alkali hydrolyzes are performed to enhance the sugar levels of the sap before fermentation. Two different strains of Saccharomyces cerevisiae (MTCC170 and MTCC180) are used for fermentation. In general, supplementation of banana sap with industrial byproducts significantly enhanced the ethanol production. The maximum ethanol production (2.5 g ^?1) is observed with concentrated banana sap supplemented with 25% SW (v/v) with MTCC170, which is 16‐fold higher than banana sap alone. Theethanol content is also higher in alkali‐hydrolyzed banana sap supplemented with 25% SW compared to control. These results suggest that banana sap can be used as a renewable source to produce ethanol by supplementing with other industrial byproducts.     

The Chemical Nature of Phosphorus in Subtropical Lake Sediments

The phosphorus (P) composition of sediment profiles in three subtropical lakes of contrasting trophic state in Florida, USA, was determined by sequential fractionation and solution ³¹P NMR spectroscopy. Sediment from Lake Annie, an oligo-mesotrophic sinkhole with moderately acidic sediment (pH 5.4; loss on ignition 58 %), contained higher total P concentrations than sediment from eutrophic Lake Okeechobee (pH 7.7, loss on ignition 36 %) and hyper-eutrophic Lake Apopka (pH 7.5, loss on ignition 69 %). The chemical nature of sediment P varied markedly among the three lakes, suggesting the predominance of different diagenetic processes. Lake Okeechobee sediment was dominated by inorganic P, indicating the dominance of abiotic reactions; Lake Annie sediment contained abundant organic P throughout the sediment profile, indicating the importance of organic P stabilization at acidic pH; Lake Apopka contained almost half of its sediment P in microbial biomass, indicating the importance of biotic processes in regulating P dynamics. Solution ³¹P NMR spectroscopy of NaOH–EDTA extracts revealed that organic P occurred mainly as phosphomonoesters in all lakes. However, sediment from Lake Apopka also contained abundant phosphodiesters and was the only lake to contain detectable concentrations of polyphosphate, perhaps due to a combination of alternating redox conditions and high concentrations of inorganic phosphate and organic carbon. Organic P concentrations determined by sequential fractionation and solution ³¹P NMR spectroscopy were similar for all lakes when microbial P was included in values for sequential fractionation. We conclude that the chemical nature of sediment P varies markedly depending on trophic state and can provide important information on the dominant processes controlling P cycling in subtropical lakes.