A
comparative study of ANN and Neuro-fuzzy for the prediction of dynamic constant of
rockmass
T N Singh1, R Kanchan2, A K Verma2 and K Saigal2
1Department of Earth Sciences, Indian Institute of Technology, Powai,
Mumbai 400 076, India.
e-mail: tnsingh@iitb.ac.in
2Institute of Technology, Banaras Hindu University, Varanasi 221 005,
India.
Physico{mechanical properties of rocks have great significance in all
operational parts in mining activities, from exploration to final
dispatch of material. Compressional wave velocity (p-wave velocity) and
anisotropic behaviour of rocks are two such properties which help to
understand the rock response under varying stress conditions. They also
in°uence the breakage mechanism of rock. There are different
methods to determine the p-wave velocity and anisotropy in situ and in
the
laboratory. These methods are cumbersome and time consuming. Fuzzy set
theory, Fuzzy logic and Neural Networks techniques seem very well
suited for typical geotechnical problems. In conjunction with
statistics and conventional mathematical methods, hybrid methods can be
developed that may prove to be a step forward in modeling geotechnical
problems. Here, we have developed and compared two di®erent models,
Neuro-fuzzy systems (combination of fuzzy and artificial neural
network systems) and Artificial neural network systems, for the
prediction of compressional wave velocity.
Facies,
dissolution seams and stable isotope compositions of the Rohtas Limestone (Vindhyan
Supergroup) in the Son valley
area, central India
S Banerjee1, S K Bhattacharya2 and S Sarkar3
1Department of Earth Sciences, Indian Institute of Technology Bombay,
Powai, Mumbai 400 076, India.
e-mail: santanu@iitb.ac.in
2Physical Research Laboratory, Ahmedabad, Navrangpura, Ahmedabad 380
009, India.
3Department of Geological Sciences, Jadavpur University, Kolkata 700
032, India.
The early Mesoproterozoic Rohtas Limestone in the Son valley area of
central India represents an overall shallowing-upward carbonate
succession. Detailed facies analysis of the limestone reveals outer- to
inner-shelf deposition in an open marine setting. Wave-ripples,
hummocky cross strat- ifications and edgewise conglomerates argue
against a deep marine depositional model for the Rohtas Limestone
proposed earlier. Stable isotope analysis of the limestone shows that
±13C and ±18O values are compatible with the early
Mesoproterozoic open seawater composition. The ribbon limestone facies
in the Rohtas Limestone is characterized by micritic beds, each
decoupled in a lower band enriched and an upper band depleted in
dissolution seams. Band-wise isotopic analysis reveals systematic
short-term variations. Comparative enrichment of the heavier isotopes
in the
upper bands is attributed to early cementation from sea water and water
derived from the lower band undergoing dissolution because of lowering
of pH at depth. The short-term positive shifts in isotopic compositions
in almost every upward gradational transition from a seamed band to a
non-seamed band support the contention that dissolution seams here are
of early diagenetic origin, although their formation was accentuated
under overburden pressure.
Compositional
variation and genesis of ferromanganese crusts of the Afanasiy{Nikitin Seamount, Equatorial Indian Ocean
R P Rajani, V K Banakar¤, G Parthiban, A V
Mudholkar and A R Chodankar
National Institute of Oceanography, Dona Paula, Goa 403 004, India.
¤e-mail: banakar@darya.nio.org
Eight ferromanganese crusts (Fe{Mn crusts) with igneous and sedimentary
substrates collected at different water depths from the
Afanasiy{Nikitin Seamount are studied for their bulk major, minor and
rare earth element composition. The Mn/Fe ratios < 1:5 indicate the
hydrogenetic accretion of the Fe{Mn hydroxides. These Fe{Mn crusts are
enriched in Co (up to 0.9%, average » 0:5%) and Ce. The
Ce-content is the highest reported so far (up to 3763 ppm, average
» 2250 ppm) for global ocean seamount Fe{Mn crusts. In spite of
general similarity in the range of major, minor, and strictly trivalent
rare earth element composition, the dissimilarity between the present
Fe{Mn crusts and the Paci¯c seamount Fe{Mn crusts in Co and Ce
associations with major mineral phases indicates inter-oceanic
heterogeneity and region-speci¯c conditions responsible for their
enrichment. The decrease in Ce-anomaly (from » 8 to »
1:5) with increasing water depth (from » 1:7km to » 3:2 km)
might suggest that the modern intermediate depth low oxygen layer was
shifted and sustained at a deeper depth for a long period in the past.
Development
and propagation of a pollution gradient in the marine boundary layer during INDOEX
(1999)
Matthew Simpson and Sethu Raman¤
Department of Marine, Earth, and Atmospheric Sciences, North Carolina
State University, Raleigh,
NC 27695-8208, USA.
¤e-mail: sraman@ncsu.edu
The development and propagation of a pollution gradient in the marine
boundary layer over the Arabian Sea during the Intensive Field Phase of
the Indian Ocean Experiment (1999) is inves- tigated. A hypothesis for
the generation of the pollution gradient is presented. Infrared
satellite images show the formation of the pollution gradient as the
leading edge of a polluted air mass
in the marine boundary layer and also its propagation over the Arabian
Sea and the northern Indian Ocean. Aerosol data measured from two
research vessels over the Arabian Sea show a varia- tion in the
concentrations caused by the passage of this pollution gradient. Depth
of the pollution gradient was found to be about 800 m. A numerical
model was used to simulate the development of this gradient and its
propagation over the ocean. Results show that its formation and
structure are significantly in°uenced by the diurnal cycle of
coastal sea-land breeze circulations along India's west coast.
Transport of aerosols and gases over the Arabian Sea in the lower
troposphere from land sources appears to be through this mechanism with
the other being the elevated land plume.
Biological
productivity, terrigenous in°uence and noncrustal elements supply to the Central
Indian Ocean Basin:
Paleoceanography during the past » 1 Ma
J N Pattan1¤, Toshiyuki Masuzawa2, D V Borole1, G
Parthiban1,
Pratima Jauhari1 and Mineko Yamamoto3
1National Institute of Oceanography, Dona Paula, Goa 403 004, India.
2Department of Hydrospheric{Atmospheric Sciences, Graduate School of
Environmental Studies, Nagoya
University, Nagoya 464-8601, Japan.
3Hydrospheric{Atmospheric Research Centre, Nagoya University, Nagoya
468-601, Japan.
¤e-mail: pattan@darya.nio.org
A 2 m-long sediment core from the siliceous ooze domain in the Central
Indian Ocean Basin (CIOB; 13±030S: 74±440E; water depth
5099 m) is studied for calcium carbonate, total organic carbon, total
nitrogen, biogenic opal, major and few trace elements (Al, Ti, Fe, K,
Mg, Zr, Sc,V, Mn, Cu, Ni, Zn, Co, and Ba) to understand the
productivity and intensity of terrigenous supply. The age model of the
sediment core is based on U{Th dating, occurrence of Youngest Toba
Tu® of » 74 ka and
Australasian microtektites of » 770 ka. Low carbonate content
(< 1%) of sediment core indicates deposition below the carbonate
com- pensation depth. Organic carbon content is also very low, almost
uniform (mean 0.2 wt%) and is of marine origin. This suggests a
well-oxygenated bottom water environment during the past » 1100
ka. Our data suggest that during » 1100 ka and » 400 ka
siliceous productivity was lower, complimented by higher supply of
terrigenous material mostly derived from the metasedimen- tary rocks of
High Himalayan crystalline. However, during the last » 400 ka,
siliceous productivity
increased with substantial reduction in the terrigenous sediment
supply. The results suggest that intensity of Himalayan weathering,
erosion associated with monsoons was comparatively higher prior to 400
ka. Manganese, Ba, Cu, Ni, Zn, and Co have around 90% of their supply
from noncrustal (excess) source and their burial to sea°oor
remained una®ected throughout the past » 1100 ka.
Seasonal
variability of physico{chemical characteristics of the Haldia channel of Hooghly estuary,
India
Y Sadhuram¤, V V Sarma, T V Ramana Murthy and B
Prabhakara Rao
National Institute of Oceanography, Regional Centre, Visakhapatnam,
India.
¤e-mail: sadhuram@darya.nio.org
Physical and chemical characteristics of the Hooghly estuary during
winter (December 1997{ January 1998), summer (May 1998) and
post-monsoon (November 1998) seasons have been stud-ied. Salinity
varied spatially and temporally and seasonally during ebb and °ood
tide conditions. Water temperature showed a di®erence of
10±C in winter to summer. Temperature did not vary much
vertically as it is a well-mixed estuary. Strong currents exceeding 100
cm s¡1 were observed during peak ebb and °ood tide conditions
irrespective of the season. Longitudinal eddy diffusion
coe±cient (Kx) was estimated as 757m s¡1 and 811m2
s¡1 during summer and post-monsoon sea-sons, respectively. The
vertical eddy di®usion coe±cient ("v) was estimated as
0:0337m2 s¡1 dur-ing post-monsoon season. The salinity and
current observations are compared with those obtained
from models reported earlier. Values of pH, Dissolved Oxygen and
Biological Oxygen Demand are within the threshold limits of the
estuarine environment. Nutrients show seasonal variation in the
estuarine environment. High values (160{2686 mg l¡1) of total
suspended matter were noticed both at surface and bottom in the study
region showing the impact of fresh water and sediment transportation.
A note on
2-D lithospheric deformation due
to a blind strike-slip fault
Sunita Rani1 and Sarva Jit Singh2
1Department of Applied Mathematics, Guru Jambheshwar University, Hisar
125 001, India.
e-mail: s¡b¡rani@redi®mail.com
2Department of Mathematics, University of Delhi, South Campus, New
Delhi 110 021, India.
e-mail: s¡j¡singh@yahoo.com
Analytical solution for the problem of a surface-breaking long
strike-slip fault in an elastic layer overlying an elastic half-space
is well known. The purpose of this note is to obtain the corresponding
solution for a blind fault. Since the solution is valid for arbitrary
values of the fault-depth and the dip angle, the effects of these two
important fault parameters can be studied numerically. The variation of
the parallel displacement and shear stress with the distance from the
fault is studied
numerically for different values of the fault-depth and dip angle.
Some characteristics of very heavy rainfall over
Orissa
during summer monsoon season
M Mohapatra1 and U C Mohanty2¤
1India Meteorological Department, Guwahati 781 015, India.
2Centre for Atmospheric Sciences, Indian Institute of Technology, Delhi
Hauz Khas, New Delhi 110 016, India.
¤e-mail: mohanty@cas.iitd.ernet.in
Orissa is one of the most °ood prone states of India. The °oods
in Orissa mostly occur during
monsoon season due to very heavy rainfall caused by synoptic scale
monsoon disturbances. Hence
a study is undertaken to ¯nd out the characteristic features of
very heavy rainfall (24 hours rainfall
¸ 125mm) over Orissa during summer monsoon season
(June{September) by analysing 20 years
(1980{1999) daily rainfall data of di®erent stations in Orissa. The
principal objective of this study
is to ¯nd out the role of synoptic scale monsoon disturbances in
spatial and temporal variability
of very heavy rainfall over Orissa.
Most of the very heavy rainfall events occur in July and August. The
region, extending from
central part of coastal Orissa in the southeast towards Sambalpur
district in the northwest, expe-
riences higher frequency and higher intensity of very heavy rainfall
with less interannual vari-
ability. It is due to the fact that most of the causative synoptic
disturbances like low pressure
systems (LPS) develop over northwest (NW) Bay of Bengal with minimum
interannual varia-
tion and the monsoon trough extends in west{northwesterly direction
from the centre of the
system. The very heavy rainfall occurs more frequently with less
interannual variability on the
western side of Eastern Ghat during all the months and the season
except September. It occurs
more frequently with less interannual variability on the eastern side
of Eastern Ghat during Sep-
tember. The NW Bay followed by Gangetic West Bengal/Orissa is the most
favourable region
of LPS to cause very heavy rainfall over di®erent parts of Orissa
except eastern side of East-
ern Ghat. The NW Bay and west central (WC) Bay are equally favourable
regions of LPS to
cause very heavy rainfall over eastern side of Eastern Ghat. The
frequency of very heavy rain-
fall does not show any signi¯cant trend in recent years over
Orissa except some places in north-
east Orissa which exhibit signi¯cant rising trend in all the
monsoon months and the season as a
whole.
Deformation of two welded elastic half-spaces
due to a long inclined tensile fault
Anil Kumar1, Sarva Jit Singh2;¤ and Jagdish Singh1
1Department of Mathematics, Maharshi Dayanand University, Rohtak 124
001, India.
2Department of Mathematics, University of Delhi South Campus, New Delhi
110 021, India.
¤e-mail: s¡j¡singh@yahoo.com
The calculation of the deformation caused by shear and tensile faults
is necessary for the inves-
tigation of seismic and volcanic sources. The solution of the
two-dimensional problem of a long
inclined shear fault in two welded half-spaces is well known. The
purpose of this note is to
present the corresponding solution for a tensile fault. Closed-form
analytical expressions for the
Airy stress function for a tensile line source in two welded
half-spaces are ¯rst obtained. These
expressions are then integrated analytically to derive the Airy stress
function for a long tensile
fault of arbitrary dip and ¯nite width. Closed-form analytical
expressions for the displacements
and stresses follow immediately from the Airy stress function. These
expressions are suitable for
computing the displacement and stress ¯elds around a long inclined
tensile fault near an internal
boundary.