Indian Journal of Marine Sciences
[ISSN: 0379-5136 CODEN : IJMNBF ]
Total visitors:683 since 29-05-07
VOLUME 36
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NUMBER 2
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JUNE 2007
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CONTENTS
Special Issue
on
Fractals in
Marine Sciences
|
Papers |
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Fractal
character of oceanic crustal magnetism determined from drill hole measurements |
97-104 |
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Power
law relation of bathymetry and gravity roughness with age of oceanic crust
below Ninety East Ridge |
105-109 |
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Fractal analysis of
gravity and bathymetry profiles across ridges in Indian Ocean
|
110-116 |
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Evidence
of continental crust in Laxmi Basin (Arabian Sea) using wavelet analysis |
117-121 |
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The
great Sumatra-Andaman earthquake of 26 December 2004 was predictable even from
seismicity data of mb≥4.5: A lesson to learn from nature
|
122-127 |
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|
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Tsunami
propagation of the 2004 Sumatra earthquake and the fractal analysis of the
aftershock acitivity |
128-135 |
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Application
of fractal in marine sciences : Study of
the 2004 Sumatra earthquake (Mw
9.3 ) sequence in Andaman-Nicobar Islands |
136-140 |
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||
Multifractal
thermal characteristics of the Western Philippine
Sea
upper layer
|
141-151 |
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|
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||
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Quantitative
characteristics of the Indian Ocean seafloor relief using fractal dimension Bishwajit
Chakraborty, Vasudev Mahale, K. Shashikumar &
K. Srinivas |
152-161 |
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|
|
|
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Fractal
dimensions of selected coastal water bodies in Kerala, SW coast of India - A
case study |
162-166 |
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Abstracts of the
Papers
Indian
Journal of Marine Sciences
Vol. 36(2), June 2007, pp.97-104
Fractal character of oceanic crustal magnetism
determined from
drill hole measurements
Mark
Pilkington
Geological
Survey of Canada, 615 Booth Street, Ottawa, K1A 0E9, Canada
[E-mail: mpilking@nrcan.gc.ca
]
Received 11 October 2006; revised 15 May 2007
A wide range of geophysical processes and rock properties has been
described in fractal or scaling terms. For continental crust, well log
susceptibilities, surface susceptibilities and aeromagnetic fields all tend to
support a model for a 3-D magnetization distribution having a radially-averaged
power spectrum proportional to some power of the spatial frequency. This simple
model of the scale-invariant behaviour of crustal magnetization and the
magnetic fields it produces can be exploited by several applications which
require information on such spatial variation. A more realistic power spectrum,
and equivalently, covariance model for continental crustal magnetization offers
many advantages over the geologically incorrect assumption of a white power
spectrum (equivalent to an uncorrelated distribution). Well log
susceptibilities and natural remanent magnetization intensities measured for
oceanic crust are shown here to exhibit scaling behaviour. Measurements from
Ocean Drilling Program holes 504B, 735B, 801C and holes CY1, CY4 in the Troodos
ophiolite sequence in Cyprus show overall values for the scaling exponent, ",
between -1.36 and -0.68 for susceptibilities and between -1.52 and -0.54 for
natural remanent magnetization intensities. Based on this small number of
samples, scaling exponents determined for basalt, sheeted dyke and gabbro
sequences within these logs show wide variation, indicating no apparent
correlation between rock type and scaling behaviour.
[Key words: Fractal, magnetic, oceanic
crust, drill hole]
**************************
Indian
Journal of Marine Sciences
Vol. 36(2), June 2007, pp.105- 109
Power law
relation of bathymetry and gravity roughness with age of
oceanic crust below Ninety East Ridge
Abhey
Ram Bansal*
National
Geophysical Research Institute, Uppal Road, Hyderabad – 500 007, India
*[E-mail:
a
bhey_bansal@ngri.res.in
]
Received 11 October 2006; revised 11 April 2007
In this
study altimeter gravity and ship track bathymetry data from National
Geophysical Data Center (NGDC) is explored to investigate the relation between
roughness of gravity and bathymetry data to the age of oceanic crust over 90°
E Ridge. The gravity and bathymetry profiles are selected over the ridge
at places of known ages from Deep Sea Drilling Project (DSDP) and Ocean
Drilling Program (ODP). The gravity and bathymetry data are gridded at sampling
interval
of 1’ 12’’ and profiles are extracted on the DSDP and ODP sites. The roughness
of gravity and bathymetry data is computed as the square root of the average
squared deviation about a linear trend. The roughness varies as a power –1.31
and -1.59 of age for bathymetry and gravity data. The mean fractal dimension is
found to be 1.54 and 1.46 for bathymetry and gravity data. The roughness of
bathymetry and gravity data varies with age with different power law. It is
also interesting to note that the roughness of bathymetry decreased with age,
which indicates modification of bathymetry data in the older (northern) portion
of the ridge with continuous depositions of Bengal fan sediments.
[Key
words: Gravity, bathymetry,
roughness and power law, age of oceanic crust, ninety east ridge, ODP, DSDP]
********************************
Indian
Journal of Marine Sciences
Vol. 36(2), June 2007, pp.110-116
Fractal analysis of gravity and bathymetry profiles across ridges in Indian Ocean
B.Ashalatha
National Geophysical Research Institute,
Hyderabad-500 007, India
[E-mail:
ashalatha_b@ngri.res.in ]
Received 11 October 2006
Fractal
analysis has been carried out for gravity and bathymetry profiles to examine
the nature of the short wavelength irregularities of the profiles which are not
generally explained by the linear models of ocean floor evolution. The Iterated
Function System has been used to generate synthetic profiles of known
dimensions and these are compared with the observed profiles. The results show
that the fractal dimensions for the data sets are in the range of 1.24-1.49. It
is observed that the fractal dimensions for the gravity profiles are lesser
than those of the bathymetry. The fractal dimensions for bathymetry and gravity
over spreading ridge are higher than those for the aseismic ridge. The fractal
nature is related to the chaotic behavior of dynamical systems which though
unpredictable are not random. The fractal dimensions obtained from the present
analysis show that the systems generating the signals can be represented by a
dynamical system of low order.
[Key
words: Fractal analysis, iterated function
system, Indian Ocean ridge]
********************************
Indian
Journal of Marine Sciences
Vol. 36(2), June 2007, pp.117-121
Evidence
of continental crust in Laxmi Basin (Arabian Sea) using
wavelet analysis
A.
Chamoli* & V.P.Dimri
National Geophysical Research Institute,
Hyderabad-500 007, India
*[E-mail:
chamoli_jp@rediffmail.com]
Received
11 October, 2006, revised 26 March 2007
The spectral analysis of bathymetry along
17°
12'N
latitude between the longitude ~60°
E
and 73°
E
has been done using wavelet transform. The profile covers all the major
features of the region including Western Basin, Laxmi Ridge, Laxmi Basin,
Panikkar Ridge, continental slope and continental shelf. The wavelet
coefficients at different scales a = 1, 2, 4, 8, 16, 32 showed that the
signatures are different on the left and right regions of the Laxmi Ridge. On
the basis of these signatures, the profile has been divided into different
sections and wavelet variance analysis for these sections has been done. The
calculated exponent β has the value ~2.0771 for whole data set and
~1.9367, 2.838, 2.9911 and 2.8750 corresponding to Western Basin, Laxmi Basin,
region from Laxmi Basin up to continental shelf and region covering continental
slope and continental shelf respectively. The fractal dimension corresponding
to these values are 1.53, 1.1, 1.0 and 1.06 respectively. The values of β
and fractal dimension show that the spectral behaviour of crust of Laxmi Basin
is near to continental shelf and slope, which indicates the nature of crust of
Laxmi Basin as continental.
[Key words: Wavelet transform, fractal dimension,
bathymetry, Laxmi Basin, spectral analysis, Arabian Sea, Laxmi ridge, Panikkar
ridge, crust]
*****************************
Indian
Journal of Marine Sciences
Vol. 36(2), June 2007, pp.122-127
The great Sumatra-Andaman
earthquake of 26 December 2004 was predictable even from seismicity data of mb≥4.5:
A lesson to learn from nature
S.S.Teotia*
& Dinesh Kumar
Department
of Geophysics, Kurukshetra University, Kurukshetra-136119, India
*[E-mail-
teotia_ss@rediffmail.com
]
Received
11 October 2006; revised 11 April 2007
The
spatial distribution of earthquakes is found to change before and after
occurrence of an earthquake of given size. The occurrence of an earthquake of
any size may be related with the self-organized criticality behavior of
turbulence in solids. This change is reflected in the temporal variation of
generalized dimension Dq or Dq spectra. Therefore, the
study of temporal variations of Dq and Dq spectra may be
used to study the changes in Seismicity structure before the occurrence of
earthquakes and hence multifractal study holds promise in forcasting earthquake
in the regions having potential to generate great earthquake. The study in this
paper deals with multifractal analysis of seismicity data of the region which
have resulted in great Sumatra-Andaman earthquake of 26 December 2004. The
significant increase in D-2 and Dq spectra has been
observed prior to occurrence of (mb=9, Mw =9.1 to 9.3)
great Sumatra-Andaman 26th December 2004 even with seismicity data having
completeness of catalogue for mb≥4.5. The monitoring of USGS
global network holds promise to reveal changes in Dq prior to
occurrence of great earthquakes even from earthquake catalogue which have their
completeness for magnitudes (i.e. mb≥4.5).
[Kew
words: Seismicity, self-organized criticality,
multifractal analysis, earthquake, Sumatra-Andaman]
***************************
Indian
Journal of Marine Sciences
Vol. 36(2), June 2007, pp.128-135
Tsunami
propagation of the 2004 Sumatra earthquake and
the fractal analysis of the aftershock activity
V.
P. Dimri* & Kirti Srivastava
National Geophysical Research Institute,
Hyderabad 500007, India
*[E-mail:
director@ngri.res.in
]
Received
28 March 2007; revised 18 April 2007
The 26 December 2004, earthquake of magnitude Mw~9.3 had generated
large tsunami waves that traveled large distances lying along the rim of the
Indian Ocean, Bay of Bengal and Arabian Sea and as far as the west coast of
Americas causing large scale devastation. The seismicity pattern of the fault
zone has been modeled by several authors, and it is seen that the fault rupture
can be divided into three segments. The aftershock sequences have been
analyzed, using the fractal approach, for three segments independently. The
first segment of 500 km long is the zone of the fastest rupture and has the
largest fractal dimension of about 2.10 implying that the fault rupture is two
dimensional. This region has a lower b value indicative of high stress regime.
In this paper the fastest rupture zone has been considered for the generation
and propagation of the tsunami waves. The tsunami wave propagation has been
modeled using the nonlinear form of long wave equations. The governing
equations are expressed as the partial differential equations which have been
solved numerically using the finite differences and the tsunami wave heights
have been computed at two Gauge locations i.e at Chennai and Visakhapatnam. The
wave heights at Chennai and Visakhapatnam have been compared with the tidal
data observed at two of these locations. Results show that the arrival times
and the magnitude of the wave heights are seen to be in agreement.
[Key words: Tsunami, fractals, gauges, seismicity, Sumatra, earthquake, aftershock activity]
******************
Indian
Journal of Marine Sciences
Vol. 36(2), June 2007, pp.136-140
Application of fractal in marine sciences: Study of the 2004 Sumatra earthquake (Mw 9.3) sequence in Andaman-Nicobar islands
Pankaj Mala Bhattacharya* & J.R.Kayal
Geophysics Division, Geological Survey of
India, 27 J.N Road, Kolkata-700 016, India
*[E-mail:
pankajmala2006@yahoo.com ]
Received
11 October 2006; revised 24 April 2007
Aftershock sequence of the 26 December
2004, Sumatra-Andaman mega thrust event (Mw 9.3) that resulted a rupture of
about 1300 km in the ocean floor, Sumatra to Andaman-Nicobar islands, is
studied to evaluate the fractal dimension of the oceanic tectonic features. A
large number of aftershocks (Mw ³
3.0) are recorded by temporary network that was established by the Geological
Survey of India (GSI) in the Indian state of Andaman-Nicobar islands. The
complex geological structures that include the Andaman trench, West Andaman
fault and the backarc spreading zone , Andaman spreading Ridge (ASR), in the
region generated a rupture area 800 ´
300 km2 below the Andaman – Nicobar islands. The Fractal dimension
was estimated using correlation dimension method and the box counting method.
Epicenters of 1100 well located earthquakes were considered for the analysis. A
prominent N-S trending contour with fractal dimension between 0.90 - 1.30
indicates that the epicenters are linear, or almost one dimensional that
correlates with the West Andaman fault. The box counting method estimated the
fractal dimension 1.17 for this linear fault that lie between the trench and
the back arc spreading zone in the ocean basin. The higher fractal dimension
(>1.5) contours on both sides of the West Andaman fault indicate the extent
of 2D heterogeneity of the Andaman Trench and the ASR. The fractal dimension
values for the entire region suggests that the faults are spatially distributed
in the whole region, and the whole region is seismically active.
[Key words: Fractal dimension, earthquake hypocenters, heterogeneity,
seismogenic]
************************
Indian
Journal of Marine Sciences
Vol. 36(2), June 2007, pp.141-151
Multifractal
thermal characteristics of the western Philippine Sea upper layer
*Peter
C. Chu & Chung-Ping Hsieh
Naval
Ocean Analysis and Prediction Laboratory, Department of
Oceanography, Naval Postgraduate School,
Monterey, California 93943, USA
*[E-mail:
pcchu@nps.edu
]
Received
11 October 2006; revised 11 April 2007
Multifractal characteristics of the upper layer
(above 140 m depth) thermal structure in the western Philippine Sea near Taiwan
are analyzed using high-resolution, digital thermistor chain data. The power
spectra at all the depths have multi-scale characteristics with the spectral
exponent
b
in the range of (1, 2), which
indicates nonstationary with stationary increments. The graph dimension varies
from higher values such as 1.71 (in sublayer: 60 m), to lower values such as
1.59 (in second thermocline: 120 m). However, the information dimension varies
slightly from 0.929 to 0.941. The multi-dimensional structure is stronger in
nonstationarity (graph dimension) than in intermittency (information
dimension). These results provide useful information for investigating
turbulence structure in the upper layer of the western Philippine Sea.
[Key
words: Multifractal structure, high-order structure function, singular
measure, power law, multifractal plane]
**************************
Indian
Journal of Marine Sciences
Vol. 36(2), June 2007, pp.152-161
Quantitative
characteristics of the Indian Ocean seafloor relief using
fractal dimension
*Bishwajit
Chakraborty, Vasudev Mahale, K. Shashikumar & K. Srinivas
National
Institute of Oceanography, Dona Paula, Goa-403 004, India
*[E-mail: bishwajt@nio.org ]
Received
11 October 2006; revised 3 April 2007
In this paper spectral technique has been
applied for seafloor topographic data analyses from three seafloor provinces of
the Indian Ocean. Study sites include West of the Andaman Island (WAI), Western
Continental Margins of India (WCMI) and Central Indian Ocean Basin (CIOB). The
analyses involved application of suitable gridding techniques to bathymetric
data of the multi-beam-Hydrosweep from these sites. Total eleven profiles i.e.,
three from two sites (A and B) and five from site C were used from varying
physiographic provinces. Segmentation
method is employed to non-stationary profile into homogenous or stationary
segments. Thereafter, estimation of spectral parameters (β) is carried out
for thirty-five segmented profiles and amplitude parameter (S) is computed.
Also, computation of Fractal Dimension (D) using spectral exponent parameter
was carried out and analyses is presented. Current investigation also includes
presentation of scatter plot between the β and S value for each site. The
computed Fractal Dimension (D) from sedimentary area of the
trench side of WAI site revealed very high D values i.e., higher roughness,
whereas varying fractal dimension values from remaining areas of this site are
indicative of moderate to lower seafloor roughness. Similarly, results form
WCMI (site B) area showed variable physiographic provinces from shelf (higher
D) to slope morphology which appears to have modified by presence of
physiographic highs and slump related features. Highest ‘D’ values for summit
of the highs indicate sub-aerial erosion and lower ‘D’ values for flanks across
the highs were also observed. Fractal Dimension (D) values from site C (CIOB)
also indicated moderate ‘D’ values for E-W and N-S profiles. However, scatter
plot between the β and S values for E-W and N-S profiles show interesting
demarcation in terms of clustering. In this work, application of Fractal
Dimension is demonstrated for quantitative characterization of the Indian Ocean
seafloor roughness.
[Key words: Seafloor relief, multi-beam bathymetry, fractal dimension, spectral techniques, Indian Ocean]
***********************
Indian
Journal of Marine Sciences
Vol. 36(2), June 2007, pp.162-166
Fractal
dimensions of selected coastal water bodies in Kerala,
SW coast of India - A case study
*Srikumar
Chattopadhyay & S. Suresh Kumar
Centre for Earth Science Studies,
Trivandrum-695 031, India
*(E-mail:
radresource@vsnl.com )
Received
11 October, 2006, revised 9 March 2007
Fractal
dimension (D) of shorelines of four coastal water bodies, namely Paravoor,
Ashtamudi, Kayamkulam and Vembanad have been worked out applying three methods.
The D values ranged from 1.09 to 1.40. Edge of Ashtamudi, which is genetically
different from the rest, is rougher compared to other water bodies as is
evident from the higher D values recorded by this water body. The method of log
N-log G plots appeared to be the most suitable for this study. Coast
perpendicular water body surrounded by laterites like Asthamudi estuary could
be well separated from the rest based on fractal dimension. It is suggested
that fractal dimensions may be used for classifying coastal water bodies as
linked to their genesis.
[Key
words: Fractal dimension, SW coast of india,
coastal water body, Kerala,
log N-log G plot ]
******************