Extreme Rainfall Events and Associated Natural Hazards in Alaknanda Valley, Indian Himalayan Region   总被引：2，自引：0，他引：2  

JOSHI Varun KUMAR Kireet 《山地科学学报》2006,3(3):228-236

Introduction The Himalaya is considered to be the youngest mountains on the earth, and is tectonically very active, and hence inherently (geologically) vulnerable to hazards. Extreme rainfall events, landslides, debris flows, torrents and flash floods due…  相似文献   

Coal fire mapping of East Basuria Colliery,Jharia coalfield using vertical derivative technique of magnetic data     

S K PAL  JITENDRA VAISH  SAHADEV KUMAR  ABHAY KUMAR BHARTI 《Journal of Earth System Science》2016,125(1):165-178

The present study deals with the coal fire mapping of East Basuria Colliery, Jharia coalfield, India, using the magnetic method. It is based on the fact that rise in temperature would result significant changes in magnetic susceptibility and thermo-remanent magnetization (TRM) of the overlying rocks. Magnetism increases slowly with the rise of temperature until the Curie temperature. Generally, rock/ overburden loses magnetization and becomes paramagnetic due to heating to Curie temperature, which results with significant reduction in magnetic susceptibility. However, magnetism increases significantly after cooling below the Curie temperature. Several data processing methods such as diurnal correction, reduction to pole (RTP), first and second vertical derivatives have been used for analysis of magnetic data and their interpretation. It is observed that the total magnetic field intensity anomaly of the area varies approximately from 44850 to 47460 nT and the residual magnetic anomaly varies approximately from ?1323 to 1253 nT. The range of the magnetic anomaly after RTP is approximately 1050–1450 nT. About 20 low magnetic anomaly zones have been identified associated with active coal fire regions and 11 high magnetic anomaly zones have been identified associated with non-coal fire regions using vertical derivative techniques.  相似文献   

Investigation of dominant modes of monsoon ISO in the northwest and eastern Himalayan region     

Sandipan Mukherjee  Srabanti Ballav  Sandeep Soni  Kireet Kumar  Utpal Kumar De 《Theoretical and Applied Climatology》2016,125(3-4):489-498

This study investigates the altitudinal variation of dominant modes of summer monsoon intra-seasonal oscillation (ISO) over the Northwest (NWH) and Eastern Himalayan (EH) region using (i) spatially scattered 133 number of station rainfall observations and (ii) latitudinal transect-wise (LT) rainfall variation, obtained from an observed interpolated gridded rainfall data for the period 1995–2004. The altitudinal variation of dominant modes of monsoon ISO were investigated by exploring the strong and weak phases of the principal components of 10–90 days bandpass rainfall data of June to September with respect to location specific station height. Investigation of frequency of days for light and moderate rainfall along with the occurrence of total seasonal rainy days has revealed existence of a rainfall maximum around 2100 m height for the NWH region. Similarly, the total seasonal rainy days of EH region was found to have maxima between 1100 and 1400 m height. Analyses of the spatially scattered station rainfall observation for the NWH region showed that the strong periods of ISO modes exist around 747.9 (±131.7) m and 2227.2 (±100.2) m heights. Over the EH region, the dominant modes of the monsoon ISO were found to be centred around 1200 m. Significant alterations of strong and weak phases of monsoon ISO as a response to altitudinal variation in the mountain surface were observed when latitudinal transect-wise variation of monsoon ISO modes were investigated.  相似文献   

ON THE EFFECTS OF THICKNESS OF THE HALF-PLANE MODEL IN HLEM INDUCTION PROSPECTING OVER SULPHIDE DYKES IN A HIGHLY RESISTIVE MEDIUM1     

M. S. JOSHI  O. P. GUPTA  J. G. NEGI 《Geophysical Prospecting》1988,36(5):551-558

In the quantitative data interpretation for HLEM induction prospecting, a vertical half-plane model in an insulating medium is widely employed. For this assumption to be valid, the steeply dipping massive sulphide dykes must have large strike lengths and depth extents, but small thickness. We report investigations, using the laboratory scale-modelling method, on the response variation of large vertical conductors as the thickness is varied. We conclude that a steeply dipping large dyke can be approximated by a half-plane model only if its thickness is less than half the skin depth. An inductively thick conductor produces larger amplitudes and relatively higher quadrature compared to a thin conductor, even if both have the same induction number.  相似文献   

Geothermobarometry of mafic granulites and metapelite from the Palghat Gap, South India: petrological evidence for isothermal uplift and rapid cooling   总被引：1，自引：0，他引：1  

C. R. RAVINDRA. KUMAR  T. CHACKO 《Journal of Metamorphic Geology》1994,12(4):479-492

The Palghat Gap region is located near the centre of the large southern Indian granulite terrane. at the northern edge of the Kodaikanal charnockite massif. The dominant rock types in the region are hornblende-biotite ± orthopyroxene gneisses and charnockites along with minor amounts of intercalated mafic granulite, metapelite and calc-silicate. The P-T estimates from garnetiferous mafic granulites and metapelite samples are generally in the range 9-10 kbar and 800-900 C using both conventional thermobarometric methods and the TWEEQU thermobarometry program. These P-T estimates, which should be taken as minimum values, are among the highest yet reported for South Indian and Sri Lankan granulites. The occurrence of orthopyroxene + plagioclase symplectites around embayed garnet grains in the mafic granulites and cordierite rims around garnet grains in metapelite suggest an isothermal decompression-type path. Similarly, a core-rim P-T trajectory indicates c. 3 and 7 kbar decompression at high temperature in the mafic granulites and metapelite, respectively. In both rock types, the key to the determination of the retrograde P-T path was the recognition of small amounts of second generation plagioclase with a more anorthitic composition than the matrix plagioclase. The preservation of high garnet-pyroxene temperatures in the mafic granulites (despite small garnet grain size) suggests rapid cooling of the terrane. Calculated minimum cooling rates range from 8 to 80 C Ma^-1. Such cooling rates are more rapid than those associated with normal isostatic processes and suggest that the terrane was tectonically exhumed at high temperature.  相似文献   

Response of climate to regional emissions of ozone precursors: sensitivities and warming potentials   总被引：2，自引：0，他引：2  

T. K. BERNTSEN  J. S. FUGLESTVEDT  M. M. JOSHI †  K. P. SHINE  N. STUBER ‡  M. PONATER  R. SAUSEN  D. A. HAUGLUSTAINE  L. LI 《Tellus. Series B, Chemical and physical meteorology》2005,57(4):283-304

  相似文献   

SOME RESULTS OF EXPERIMENTAL GEOPHYSICAL SURVEYS FOR LOCATION OF ANCIENT GOLD WORKINGS,KOLAR, INDIA *     

SHIKHAR C. JAIN  R. KUMAR  A. ROY 《Geophysical Prospecting》1973,21(2):229-242

On an experimental basis, observations were made with various geophysical methods to locate the ancient gold workings in Kolar Gold Fields, Kolar, India. The results of experimental surveys indicated that two-electrode resistivity surveys with two spacings followed by limited trenching would be able to locate about 70 percent of the ancient workings, at 55-60 percent of the cost of conventional trenching.  相似文献   

RESISTIVITY TYPE CURVES OVER OUTCROPPING VERTICAL DYKE—II *     

RAKESH KUMAR 《Geophysical Prospecting》1973,21(4):615-625

The theoretical horizontal resistivity profiles Over an outcropping vertical dyke with two-electrode and Schlumberger electrode systems are discussed. The two-electrode array seems very useful in locating the highly conducting thick or thin vein, while the Schlumberger (gradient) array is suited to detect the conducting vein of low and moderately high resistivity contrast and as well as the resistive vein of all widths and resistivity contrasts. Besides, the inline gradient array has a distinction of establishing a clue to evaluate the resistivity contrast of the vein.  相似文献   

Sedimentation in a closed trough north of the Iberia Abyssal Plain in the northeast Atlantic†     

SUNIT KUMAR ADDY  HIDEO KAGAMI 《Sedimentology》1979,26(4):561-576

Mirrol Trough of the northeast Atlantic contains five NNE-SSW trending, en echelon, turbidite-filled basins deeper than 5500 m, each ranging from 4 to 10 km in width and 19 to 65 km in length. Trough deposition has consisted mainly of turbidites from adjacent hills and ridges as indicated by the physiography of the region, sediment isopach map, the nature of the sediments in the trough, and benthic foraminiferal depth indicator species. The sedimentation rate on abyssal hills and ridges, as deduced from palaeomagnetic evidence, is 1.36 cm/10³ years. Using this sedimentation rate, it is estimated that Mirrol Trough subsided relative to the surrounding area and began receiving sediments between 8.3 and 11.5 m.y. ago; and the deposition of the most recent turbidite has occurred sometime between 29,000 and 44,000 years b.p. Tilting of the base of the most recent turbidite with respect to the basin floor is observed, and this is attributed to relative sinking of the eastern margin of the trough after the deposition of the most recent turbidite.  相似文献   

Contemporary deformation in the Kashmir–Himachal,Garhwal and Kumaon Himalaya: significant insights from 1995–2008 GPS time series     

Sridevi Jade  Malay Mukul  V. K. Gaur  Kireet Kumar  T. S. Shrungeshwar  G. S. Satyal  Rakesh Kumar Dumka  Saigeetha Jagannathan  M. B. Ananda  P. Dileep Kumar  Souvik Banerjee 《Journal of Geodesy》2014,88(6):539-557

We present new insights on the time-averaged surface velocities, convergence and extension rates along arc-normal transects in Kumaon, Garhwal and Kashmir–Himachal regions in the Indian Himalaya from 13 years of high-precision Global Positioning System (GPS) time series (1995–2008) derived from GPS data at 14 GPS permanent and 42 campaign stations between $29.5{-}35^{\circ }\hbox {N}$ and $76{-}81^{\circ }\hbox {E}$ . The GPS surface horizontal velocities vary significantly from the Higher to Lesser Himalaya and are of the order of 30 to 48 mm/year NE in ITRF 2005 reference frame, and 17 to 2 mm/year SW in an India fixed reference frame indicating that this region is accommodating less than 2 cm/year of the India–Eurasia plate motion ( ${\sim }4~\hbox {cm/year}$ ). The total arc-normal shortening varies between ${\sim }10{-}14~\hbox {mm/year}$ along the different transects of the northwest Himalayan wedge, between the Indo-Tsangpo suture to the north and the Indo-Gangetic foreland to the south indicating high strain accumulation in the Himalayan wedge. This convergence is being accommodated differentially along the arc-normal transects; ${\sim } 5{-}10~\hbox {mm/year}$ in Lesser Himalaya and 3–4 mm/year in Higher Himalaya south of South Tibetan Detachment. Most of the convergence in the Lesser Himalaya of Garhwal and Kumaon is being accommodated just south of the Main Central Thrust fault trace, indicating high strain accumulation in this region which is also consistent with the high seismic activity in this region. In addition, for the first time an arc-normal extension of ${\sim }6~\hbox {mm/year}$ has also been observed in the Tethyan Himalaya of Kumaon. Inverse modeling of GPS-derived surface deformation rates in Garhwal and Kumaon Himalaya using a single dislocation indicate that the Main Himalayan Thrust is locked from the surface to a depth of ${\sim }15{-}20~\hbox {km}$ over a width of 110 km with associated slip rate of ${\sim }16{-}18~\hbox {mm/year}$ . These results indicate that the arc-normal rates in the Northwest Himalaya have a complex deformation pattern involving both convergence and extension, and rigorous seismo-tectonic models in the Himalaya are necessary to account for this pattern. In addition, the results also gave an estimate of co-seismic and post-seismic motion associated with the 1999 Chamoli earthquake, which is modeled to derive the slip and geometry of the rupture plane.  相似文献