Indian Journal of Marine Sciences

(www. niscair.res.in)

[ISSN: 0379-5136      CODEN  : IJMNBF ]

Total visitors:683        since 29-05-07

 

VOLUME  36

NUMBER 2

JUNE 2007

 

CONTENTS

 

Special Issue

on

Fractals  in  Marine  Sciences

 

 

Papers

 

Fractal character of oceanic crustal magnetism determined from drill hole measurements

      Mark Pilkington

97-104

 

 

Power law relation of bathymetry and gravity roughness with age of oceanic crust below Ninety East Ridge

      Abhey Ram Bansal

105-109

 

 

Fractal analysis of gravity and bathymetry profiles across ridges in Indian Ocean

      B.Ashalatha

110-116

 

 

Evidence of continental crust in Laxmi Basin (Arabian Sea) using wavelet analysis

      A. Chamoli & V.P.Dimri

117-121

 

 

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

122-127

 
 

Tsunami propagation of the 2004 Sumatra earthquake and the fractal analysis of the aftershock acitivity

      V.P. Dimri &  Kirti Srivastava

128-135

 

 

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

136-140

 

Multifractal thermal characteristics of the Western Philippine 

       Sea upper layer

      Peter C. Chu & Chung-Ping Hsieh

141-151

 

Quantitative characteristics of the Indian Ocean seafloor relief using fractal dimension

      Bishwajit Chakraborty, Vasudev Mahale, K. Shashikumar & K. Srinivas

152-161

 

 

Fractal dimensions of selected coastal water bodies in Kerala, SW coast of India - A case study

      Srikumar Chattopadhyay & S. Suresh Kumar

162-166

 

 

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]

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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]

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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]

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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]

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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]

 

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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 3.0) 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]

 

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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]

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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]

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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 ]

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