Introduction to the special volume on Bhuj earthquake     

B. K. Rastogi  J. R. Kayal  T. Harinarayana 《Natural Hazards》2013,65(2):1023-1025

  相似文献   

Production of Bauxite Certified Reference Material (BARC-B1201) for Nine Property Values (Al2O3, Fe2O3, SiO2, TiO2, V2O5, MnO,Cr2O3, MgO and LOI) Traceable to SI Units     

Ankam Durga Prasad  Lori Rastogi  Vinod Kumar Verma  Vasudevan Krishna Kumari  Sudhakar Yadlapalli  Kulamani Dash 《Geostandards and Geoanalytical Research》2023,47(3):629-636

The National Centre for Compositional Characterisation of Materials (NCCCM) / Bhabha Atomic Research Centre (BARC) and National Aluminium Company Limited (NALCO), India have produced an Indian origin bauxite certified reference material (CRM), referred to as BARC-B1201, certified for major (Al₂O₃, Fe₂O₃, SiO₂, TiO₂, loss on ignition - LOI) and trace contents (V₂O₅, MnO, Cr₂O₃, MgO). Characterisation was undertaken by strict adherence to ISO Guides. A method previously developed and validated in our laboratory, using single step bauxite dissolution and subsequent quantitation (of Al₂O₃, Fe₂O₃, SiO₂, TiO₂, V₂O_5, MnO, Cr₂O₃ and MgO) by ICP-AES (SSBD ICP-AES) was used for homogeneity studies and an inter-laboratory comparison exercise (ILCE) of the candidate CRM. LOI was determined by thermo-gravimetric analysis. Property values were assigned after an ILCE with participation from seventeen reputed government and private sector laboratories in India. The CRM was certified for nine property values: Al₂O₃, Fe₂O₃, SiO₂, TiO₂, V₂O_5, MnO, Cr₂O₃, MgO and LOI, which are traceable to SI units.  相似文献   

Investigations of June 7, 1988 earthquake of magnitude 4.5 near Idukki Dam in Southern India     

B. K. Rastogi  R. K. Chadha  C. S. P. Sarma 《Pure and Applied Geophysics》1995,145(1):109-122

A mildly damaging earthquake of magnitude 4.5 and intensity VI occurred 20 km east of the Idukki reservoir, Kerala in southern India. With a network of 5 seismic stations, the aftershocks which continued for 3 1/2 months were monitored. The hypocentral parameters, b value,M ₁/M ₀ ratio indicate that this earthquake sequence does not qualify to be categorized as induced. The trend of the aftershocks, composite fault plane solution and local tectonics point towards reactivation of a NW-SE fault along the Kallar river. The existence of such a fault is also supported by gravity studies.  相似文献   

Morphological aspects of a new type of counter electrojet event     

R. G. Rastogi 《Annales Geophysicae》1999,17(2):210-219

The study describes the time and space morphologies of a rather new type of counter electrojet event on the basis of data from the excellent chain of magnetic and ionospheric observatories along the Indo-Russian longitude sector. Abnormally large westward currents are observed during almost the whole of the daytime hours on a series of days. These events do not form any vortices in the current system and do not apparently seem to be associated with tidal effects or any solar magnetosphere events or geomagnetic disturbances. The existence of a westward electric field over the equatorial ionosphere has been confirmed by the absence of an equatorial type of sporadic E in the ionograms at Thumba precisely during the periods when H at Trivandrum minus H at Alibag is negative. The equatorial F region anomaly was also absent on the counter electrojet day. Such counter electrojet events during the northern winter months of low solar activity years are suggested to be the result of the modified wind system in the ionosphere associated with stratospheric warming events.  相似文献   

EM2INV — A finite difference based algorithm for two-dimensional inversion of geoelectromagnetic data     

P. K. Gupta  Sri Niwas  Anupma Rastogi 《Journal of Earth System Science》1999,108(4):233-253

The paper presents an efficient finite difference based 2D-inversion algorithm, EM2INV, for geoelectromagnetic data. The special features of the algorithm are

–	• optimal grid generation based on grid design thumb rules,
–	• finite domain boundary conditions,
–	• interpolation matrix that permits generation of response at observation points different from grid points,
–	• Gaussian elimination forward matrix solver, that enables reuse of already decomposed coefficient matrix,
–	• super-block notion that reduces the number of blocks with unknown resistivities and, in turn, the size of Jacobian matrix and
–	• bi-conjugate gradient matrix solver for inverse problem which circumvents the need of explicit Jacobian matrix computation.

The algorithm is tested rigorously by setting up exercises of diverse nature and of practical significance. The stability of the algorithm is established by inverting the synthetic response corrupted with Gaussian noise. The inversion experiments are aimed at studying

–	• relative performance of response functions,
–	• inversion quality of E- and B-polarization data,
–	• efficacy of single and multi-frequency data inversion,
–	• minimum number of frequencies and observation points needed for successful data inversion.

It has been observed that the Magneto-telluric data deciphers better the vertical position of the target and Geomagnetic Depth Sounding data deciphers the horizontal variations in a better way. The conductive and resistive bodies are better resolved by inversion of E- and B-polarization data respectively. The results of multi-frequency inversion imply that the increase in the number of frequencies does not necessarily enhance the inversion quality especially when the spread of observation points is sufficiently large to sense the target. The study of a minimum number of observation points highlights the importance of single point inversion that furnishes useful information about the inhomogeneity.  相似文献   

Magnitude estimation of Koyna-Warna earthquakes, India     

P. Mandal  B.K. Rastogi  C.S.P. Sarma  P.S. Raju  M. Kousalya 《Journal of Seismology》2002,6(4):447-458

The paper presents the current state of magnitude estimation for Koyna earthquakes exceeding magnitude 3.0. We estimate coda duration magnitude from analogue seismograms recorded on the short period vertical (SPZ) seismometer at Hyderabad seismic observatory HYB and determine moment magnitude using very broad-band (VBB) data from the Geoscope station (HYB)and short period digital data from the local seismic network of NationalGeophysical Research Institute (NGRI) around the Koyna and Warna reservoirs.Firstly, the seismograms of 97 Koyna earthquakes exceeding magnitude 4.0 havebeen used to establish a new empirical coda duration magnitude scale which includes the higher order terms of log₁₀, where is the coda length in seconds. Four background noise levels (1, 2, 6 and 10 mm) areconsidered to estimate the coda duration. We found that the duration magnitudes for 1 mm background level are more stable than those for 2, 6 and 10 mm. The new coda duration magnitude (M_dnew) scale, for 1 mmlevel, is:M_dnew = –0.594 + 2.04 log₁₀ – 0.0435 (log₁₀)²The estimated M_dnew are compatible with the reported M_S values of the NGRI observatory and the m_b values of the United States Geological Survey (USGS). These magnitudes can be obtained within the standard deviation of ± 0.26 units of M_S (NGRI). A new relatively homogeneous catalog for Koyna earthquakes of M_dnew 4.0 is obtained. The momentmagnitudes for 34 Koyna-Warna events of M_dnew ranging from 3.0 to 5.4 have been estimated using two techniques. The first utilizes amplitudes of band-pass filtered (between 15 and 30 sec) velocity traces of moderate Koyna-Warna earthquakes of M_W} 4.4 to 5.4, we abbreviate the magnitude using M_A. The second is based on the S-wave spectrum of short period seismograms of local earthquakes (M_W < 3.8). Moment magnitudes estimated by spectral analysis mainly depend on the estimation of event's long-period spectral level and appears to saturate for moderate Koyna-Warnaearthquakes (M_W > 3.8). We recommend the use of both techniques whenever possible. The estimated moment magnitudes and M_dnew show an almost linear relationship with a standard deviation of ± 0.05.  相似文献   

Delineation of Active Faults, Nucleation Process and Pore Pressure Measurements at Koyna (India)   总被引：1，自引：0，他引：1  

R. K Chadha  H. K Gupta  H. J Kumpel  P. Mandal  A. Nageswara Rao  N. Kumar  I. Radhakrishna  B. K Rastogi  I. P Raju  C. S. P Sarma  C. Satyamurthy  H. V. S Satyanarayana 《Pure and Applied Geophysics》1997,150(3-4):551-562

  相似文献   

Scintillations ofvhf radio beacons from two satellites     

R G Rastogi 《Journal of Earth System Science》1984,93(2):83-89

Analysis of scintillations ofvhf beacons from two very closely spaced geostationary satellites shows that the drift of irregularities is generally westward at the initial stages and changes to eastward during the later part of the night when the irregularities are fully developed or decaying.  相似文献   

Counter equatorial electrojet currents in the Indian zone     

R.G. Rastogi 《Planetary and Space Science》1973,21(8):1355-1365

The paper describes the phenomenon of afternoon depression of the geomagnetic H field on quiet days near the magnetic equator in the Indian zone. These events occur most frequently around 1600 solar hr and are localized in longitude; sometimes, not seen at stations separated by even 2 hr LT. The geomagnetic disturbance tends to decrease or destroy the identity of the phenomenon. The latitudinal extent of these events is confined to the equatorial electrojet region. The events do not seem to be caused mainly by the Moon, but their occurrences are modified by the lunar age, being most frequent around new and full Moon. These events are associated with the disappearance of the q type of E_s over the Equator for periods during which the H field is below the night-time level. The currents responsible for these events flow westward in the E-region and are within few degrees centred near the magnetic equator.  相似文献   

Morphometric evidence of seismicity around Wagad and Gedi Faults, eastern Kachchh, Gujarat     

Falguni Bhattacharya  B. K. Rastogi  Girish C. Kothyari 《Journal of the Geological Society of India》2013,81(1):113-121

Recent studies suggest that the eastern Kachchh is a potential zone for major earthquakes in the near future. Particularly, the E-W trending faults are considered capable of generating large magnitude earthquakes is further indicated by the recent concentration of the earthquake shocks, which, show two prominent clustering around west and north of the Wagad upland. In view of this, the conventional morphometric analyses of a terrain bounded by the E-W trending North Wagad Fault (NWF) and the Gedi Fault (GF) has been undertaken to ascertain the influence of seismicity in the evolution of the drainage basin. The study suggests that the fifth order drainage basins responded to the seismicity associated with both the NWF and GF. However, compared to the GF, the NWF seems to be more active. In addition to this, based on the stream morphology, we could identify two lineaments trending N-S and E-W. The former appears to be associated with the activity along the Manfara Fault (MF), whereas, the later seems to be the splays of the NWF. Further, a preferential westward shift of the streams suggests left lateral displacement of the E-W trending faults. Overall it can be suggested that the terrain is in juvenile stage implying tectonic instability.  相似文献