COVER ARTICLE

Photonirvachak

Journal of the Indian Society of Remote Sensing, Vol. 32, No. 3, 2004

USE OF SATELLITE DATA FOR TECTONIC INTERPRETATION, NW HIMALAYA

CHIRASHREE MOHANTY, DIBYA J. BARAL* AND JAVED N. MALIK Department of Civil Engineering,

Indian Institute of Technology, Kanpur-208 016, India

Mountain topography is the result of highly scale-dependent interactions involving climatic, tectonic and surface processes. Tectonic geomorphology deals with the geodynamics and geomorphic manifestation of crustal deformation processes. In Himalaya, bulk of the relief in mountainous region has been formed by uplift along thrust faults striking sub-parallel to the trace of the thrust zones. Therefore, there is an intimate link between uplift rates, material redistribution rates due to geomorphic processes, and the morphology of the area. By quantifying features the tectonic uplift rates and constrains geomorphic process rates can be inferred. To understand the complex inter- relationship of these elements in regional scale, there is a need to develop new approaches and methodologies. With significant improvement in resolution of available digital terrain data and computing resources, the evaluat ion of morphotectonic in a Geographical Information System (GIS) environment tends to be quantitative and more precise.

The evidence of neotectonic activities are commonly available through various geomorphic

signatures that can be studied using geological (such as lithology, proximity to active faults and lineament density) and geomorphological aspects (such as landform, slope, lateral erosion by streams, drainage texture, spring sapping, elevation difference between adjacent valleys, altitude and relief).

Numerous studies have been made to develop such relationship between the tectonics and morphology in the Himalaya and various other tectonic zones by conventional field methods e.g. river terrace study in river bank cross section, drilling, t renching, seismic profil ing, and sedimentological studies, radiometric dating etc. (Thakur, 1995; Burbank, 1999; Philip and Sah, 1999; Malik et al., 2003). But these are expensive, time consuming and only represent point and linear scale features in regional context. Analysis of DEM (Digital Elevation Model) in conjunction with remote sensing satellite data by numerical geomorphology provides a means for characterizing tectonic activity of an area in a quantitative way. Using digital terrain data in the form of DEM (Digital Elevation Model), and software tools have made the study easy and accessible everywhere. Under the frame work of GIS,

*Corresponding author : baral@iitk.ac.in

Received 20 June, 2004; in final form 28 July, 2004

242 Chirashree Mohanty et al.

analysis of geospatial data to derive inter- relationship becomes increasingly important.

An approach to study the regional variations in tectonic geomorphology along a segmented convergent plate boundary has been developed by Wells et al. (1988). Geomorphic observations of rivers in costal cordillera of northern Chile taking certain geomorphic parameters have been carried out by Riquelme et al. (2003). Another approach of studying the rate of upliftment taking the morphotectonic properties of the Lo River Fault near Tam Dao in North Vietnam was carried out by Cuong and Zuchiewicz (2001).

The study area within latitude 31~176 and longitude 76~176 is covered by the Survey of India Toposheet 53A in 250,000 scale and comprise of 9 districts of Punjab and Himachal Pradesh (Fig. 1). Physiographically, the study area consists of three major divisions the Siwaliks, Lesser Himalaya, and Higher Himalaya separated by the major thrust zones namely the Himalayan Frontal Fault, the Main Boundary Thrust and the Main Central Thrust, respectively. In the present study, analysis of the Himalayan terrain has been made using a Digital Elevation Model (DEM) and satellite data to evaluate different zones of active upliftment. North- western Himalaya presents a structurally complex

Fig. 1. Lineaments Mapped from Landsat TM over Study Area and Lineament Rose Diagram

Use of Satellite Data for Tectonic Interpretation... 243

landscape around the Kangra recess and the area west covering the Beas and Satluj valley. The structural in-homogeneities of NW Himalayan Mountain belt between reentrant and the frontal thrust provide the opportunity to study morphology and tectonics in an active compressional environment. Analyses have been carried out to highlight the variations of morphotectonic features and to illustrate the relative activities in different tectonic regimes for the study area.

Shuttle Radar Topographic Mission (SRTM) provided the elevation data needed to create a seamless DEM of 80% the world's landmass at different spatial resolution through the use of

synthetic aperture radar (SAR) technology. Extensive DEM data from a single source as with SRTM is especially desirable because it is consistent and comparable across large areas, compared to other high resolution DEMs derived from variable sources like individual satellite images. The SRTM data used for the present study area is having resolution 90 m and is able to provide greater variability of 1:50,000 scale map. For terrain cover data, Landsat TM, and IRS-ID LISS-III data in different spectral bands having resolution 28.5 and 23.5 m respectively have been used. Satellite terrain data can be draped over the digital terrain models that help to visualize and provide structural features in 3D perspective views (Fig. 2).

Fig. 2. 3D Perspective View from Landsat TM True Color Composite Image Draped Over DEM

244 Chirashree Mohanty et al.

The influence of subsurface structural features on channel patterns and the overall architecture of the watershed basins were studied. Regional analysis of drainage basin and river valley morphology helps to define differential uplift in many tectonically active regions. Linking of the geomorphological parameters with the hydrological characteristics of the basins provide a simple way to understand the tectonic behavior of different contiguous basins. The elevation models help calculation of hydrologic parameters (stream order, density, gradient, etc.) in a GIS database quickly which otherwise take years to calculate manually.

Hypsometry or the frequency distribution of elevation is often used in geomorphic analysis of form and process of a landscape. The hypsometric integral (HI) provides a means of quantifying a proportion of total drainage basin elevation relative to that of the total drainage basin area. The hypsometric curve and HI (integral of these curves) value obtained for an individual drainage basin are normalized quantit ies and therefore allow comparison of one basin to another, regardless of size. Recent studies have demonstrated the utility of hypsometric analysis in tectonic interpretation. High HI values have generally been associated with higher rates of tectonic activity and linear range fi-onts (McNamara et al., 1999).

Convex hypsometric curves with high value hypsometric integral reflect watershed basin with an important proportion of their surface located at high altitudes, i.e. incised watershed basin, whereas concave curves basin with an important proportion of their surface located at low altitudes. Large incision can be attributed to uplift of the area.

Drainage Density: Drainage density is the ratio of the total length of all channels in a given basin to the drainage area of the same basin. This number describes how densely a basin is channelized and in turn represents amount of tectonic uplift compared to stream down cutting (Jianjun et aI., 1998). Stream

Length (SL) Gradient Index. The stream length gradient index is the rate of change of slope along stream and correlates to stream power. Stream gradients of trunk channels provide a quantitative measure of tectonic activity or quiescence. High stream gradients are indicative of high rates of tectonic uplift. Lineament Density. Lineaments are mappable linear surface features which differ distinctly from the patterns of adjacent features and presumably reflect subsurface phenomena. The standard FCC generated from the satellite imagery is sharpened by edge enhancement filter before extracting the linear features. Major faults and l ineaments have been mapped by visual interpretation based on lithological dislocation, joints and fracture traces, truncation of outcrop, alignment of streams, sudden bending of streams (Figs 1, 5a).

For the study area the SRTM DEM (90 m) has been processed to delineate flow grid and channel links from automated drainage extraction processes as shown in the flow chart (Fig. 3). Various image- processing software / techniques have been employed to enhance the data in order to assist in the delineation of river basin boundaries, calculation of point attributes and interpolation for getting regional distribution in the map (Fig. 4).

Extracted drainage has been rasterized, gridded for 1 km pixels for stream length gradient index and drainage length density (Figs. 5b, d). To study the variations of intra and inter-river system tectonic- geomorphic analyses, basins of fourth order streams for major drainages were delineated. Area Elevation curve for each basin and HI for each basin is calculated and assigned to the central point. To map the distribution of each parameter over the study area, a moving average interpolation method was used (Fig. 5c). The Moving average operation is a point interpolation which values for the output pixels are the weighted averages of input point hypsometric integral values within radius of influence.

Use of Satellite Data for Tectonic Interpretation... 245

Fig. 3. Flow Chart for Drainage Network Extraction and Analysis

I E l e v a t i o n Data 1 I SRTM

RS T e r r a i n Data L a n d s a t / IRS

I I Slope, Aspec t , F l ow Gr id

V V I Drainage Network ]-.~ Drainage Basin ] I Lineaments 1

i

, . . . . . . . . . . . _%~/I . . . . . . . . . . . - I , . . . . . . . . . . . - V . . . . . . . . . . . " I , . . . . . . . . . . . - ~k / / . . . . . . . . . . . " I

' D r a i n a g e D e n s i t y m a p ', ] ', ' ~, ' H y p s o m e t r i c I n t e g r a l , ' L i n e a m e n t D e n s i t y M a p , ,~ S t r e a m L e n g t h G r a d I n d e x ', I , ', ,

. . . . . . . . . . . . . i . . . . . . . . . . . ~ . . . . . . . . . . . . ~ . . . . . . . . . . . . ~ . . . . . . . . . . . . ~ . . . . . . . . . . . .

, _ . . . . . . . . . _ v . . . . . . . . . . . . . . . . . . . . . . . . . v _ . . . . . . . . . . . . . . . . . . . . . . . . ~ . . . . . . . . . . . , I , L i tholocl ical / S t ruc tura l Map I I . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I

Fig. 4. Thematic Maps Derived from Satellite Data for Analysis

246 Chirashree Mohanty et al.

Fig. 5. Interpolated maps for (a) Lineament Density, (b) SL Gradient Index, (c) Hypsometric Integral and (d) Drainage Density

Each output interpolated thematic raster map was compared with the vector structural and lithological map of the area in a GIS environment. These relationships can be further used for the development of a suitable algorithm to be used a GIS environment. The zones pertaining to different tectonic activity in the study domain have been identified.

An attempt has been made to study the different morphometric parameters such as drainage and lineament density and hypsometric integral, which are consistent with an interpretat ion of the differential uplift within the area. Thematic maps produced for each of the parameters are analyzed discerning relationship of each layer to tectonic framework of the study area along NW Himalaya.

Use of Satellite Data for Tectonic Interpretation... 247

In the present study, three major divisions of the different landform settings were analyzed with a focus on the response of the fluvial systems to discrete tectonic perturbations. An attempt has been made to relate stream power, drainage density and hypsometric integral to explain the amount of erosion and behavior of structurally controlled mountain front with that of the tectonic uplift of the regions.

Utility of DEM and remote sensing data for regional scale tectonic studies has been shown. With the help of digital terrain data, important morphometric parameters are mapped and studied. Both the statistical and spatial variability of different parameters within the region and among the regions were investigated in detail and found to be in agreement with the existing structural models.

Thematic maps indicat ive of tectonic morphologies are prepared and have been used into the spatial database for further GIS analysis. The quantitative relations for combining the thematic maps for deriving the final activity zonation map for the study area are being worked out. This should enable us to collate the morphometric parameters in quantitatively to calculate the Tectonic Zonation Map. This map can be used in cross disciplinary study of Landslide Hazard, Earthquake, and Geotechnical studies in tec tonica l ly active Himalayan belt.

Acknowledgements

This work is a part of M. Tech dissertation of CM; DJB is thankful to TATA STEEL, Jamshedpur for partial financial grant. Financial support through research project (SR/FTP/ES-46/2001) sponsored by the Department of Science and Technology, New Delhi to JNM is duly acknowledged. Authors would like to thank Dr. R. P. Singh, Chief Editor for providing valuable suggestion to improve the original version of manuscript.

References

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Jianjun, H., Mukang, H., and Oilier, C.D., (1998). A morphometric method to determine neotectonic activity of the Weihe basin in northwestern China. Journal Himalayan Geology. 20:95-99.

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