Seismic assessment in southern Baromura hill, northeast India, considering geophysical aspects

ORIGINAL ARTICLE

Seismic assessment in southern Baromura hill, northeast India,considering geophysical aspects

Sudip Dey • Prasamita Sarkar • Chandrani Debbarma •

Sushmita Paul

Received: 29 March 2010 / Accepted: 15 July 2011 / Published online: 30 July 2011

� Springer-Verlag 2011

Abstract This paper aims to assess the geophysical sig-

natures like morphology and structure of a fault line, which

is situated in a part of southern Baromura hill of Tripura,

northeast India. In this work manual observations and

technical applications were adopted for understanding the

morphological and structural characters of the fault line. As

tectonic mapping is one of the main objectives of this

study, the remote sensing technique was used to prepare a

tectonic map of the study area. Geothermal range of the

area was measured by unsupervised classification of

Landsat TM thermal infrared band (band 6). The classified

thermal band was overlaid by another classified shortwave

infrared band (band 7 of Landsat TM), which explains the

structural evidences of the study area. In addition, an

automated digital elevation model (DEM) was prepared to

assess the morphological characters of the study area par-

ticularly near the confluence of R. Maharani and R. Gumti.

To analyse the structural condition of the faulted zone,

resistivity characters of the rocks were measured by

‘‘vertical electrical sounding’’ (VES) method. The electri-

cal resistivity character of this area strongly supports that a

displacement occurred in this place. Finally an attempt was

made to explain the character of faulting on the basis of

morphological signatures and structural evidences for

future disaster management planning.

Keywords Geophysical signature � Fault line �Unsupervised classification � Geothermal map �Structure-vertical electrical sounding

Introduction

Large-scale earthquakes occur due to movements of plates

along the destructive plate boundaries and faults that have

evolved through geological and tectonic processes.

Although occurrence of earthquake is a global phenome-

non, regional level geophysical setup is considered as a

very important factor from disaster management point of

view. Regional effect of tectonic hazards now has become

an important part in present geoscientific researches for

planning and management. During the current decade, the

concepts of probabilistic seismic risk assessment and

integrated approaches in disaster management have been

developed by many scholars like Asad et al (2001), Con-

sole and Murru (2001), Eftaxias et al. (2003), El-Hefnawy

et al. (2006), Korkmaz (2009, 2010), etc. In a very recent

work, Levi et al (2010) applied integrated approaches in

seismic disaster management using HAZUS-MH software

and successfully estimated earthquake loss in Israel. In

India, earthquake prediction researches started during the

early 1960s by the continuous efforts of seismologists and

several methods have been attempted for disaster mitiga-

tion (Tiwari 2000). However, it is a remarkable fact that

micro-regional to regional level authentic documentations

of all parts in India are still not available (Bilham 2004).

Thus, background studies on seismic hazards and associ-

ated natural disasters in India depend only on some current

S. Dey (&) � P. Sarkar � C. Debbarma � S. Paul

Department of Geography and Disaster Management, Tripura

University, Suryamaninagar 799130, India

e-mail: [email protected]

P. Sarkar


C. Debbarma


S. Paul


123

Environ Earth Sci (2012) 66:421–431

DOI 10.1007/s12665-011-1249-8

references and many of them are not authentic at all.

Recent observations have shown that earthquake events in

India have been increased over the last hundred years or so

(Singh and Sing 2007; Table 1). Therefore, the present

scenario demands proper planning by micro-regional to

regional-scale assessments for earthquake mitigation in

tectonically sensitive zones of this country such as the

Himalayan seismic belt and northeast India. Early resear-

ches by Gupta and Singh (1982), Guha and Bhattacharya

(1984), Agarwal (1986), Kayal (1987), Gupta and Singh

(1989), Gupta (1993) Kayal (1996,1998) and Bhattacharjee

(1998) strongly support that geophysically the northeastern

part of India is one of the most active tectonic zones in the

world and experiences frequent catastrophic earthquakes.

Considering the importance of regional level tectonic

assessment for disaster management planning in the seis-

mic regions, the present authors decided to perform a study

to delineate geophysical signatures of a faulted zone of

southern part of Baromura Hill in Tripura, northeast India.

Study area

The present study area is in the southern part of the

Baromura fold belt, east to Udaipur town of Tripura

(Fig. 1). Earlier, Dey et al. (2009a) conducted a study in

this place and detected a fault line (Udaipur fault) on the

basis of morphological signatures using remote sensing

technique. R. Maharani, a tributary of Gumti, is flowing

along the eastern end of this area. A small village, Hirapur,

which is near the confluence of R. Maharani with R. Gumti,

was selected for geoelectrical survey.

Geological setup

Tectonically the northeastern part of India remained very

dynamic during Tertiary and Quaternary periods, which is

related to the movement of Indian plate (Smith and Hallam

1970; McKenzie and Sclater 1971; Curray and Moore

Table 1 Some severe earthquakes in India

Date Place Geographical

location

Magnitude

Lat. Long.

October 8,

2005

Kashmir 34.43�N 73.54�E 7.6

December

26, 2004

Indian Ocean 3.30�N 95.87�E 9.0–9.3

January 26,

2001

Kutchh 23.6�N 69.8�E 6.9/7.9

September

29, 1993

Latur-Killari, 18.08�N 76.52�E 6.2

August 15,

1950

Arunachal Pradesh-

China border

28.5�N 96.7�E 8.5

January 15,

1934

Bihar, India 25�N 85�E 8.7

June 12,

1897

Shillong Plateau 26�N 91�E 8.7

Fig. 1 Location, geology and

environs of the study area

422 Environ Earth Sci (2012) 66:421–431

123

1974; Sclater and Fisher 1974; Falvey 1974 Curray et al.

1982; Valdiya 1984; Hutchison 1989; Klootwijk et al.

1992; Lee and Lawver 1995; Acharyya 1998; Varga 1997).

Geological evidences support that landform development

in this part started by sediment deposition during the

middle of the Miocene epoch (Mitra et al. 1968; Sinha and

Sastri 1973; Akram et al. 2004; Dey 2005). Structurally,

the present study area consists of un-metamorphosed upper

Tertiary sediments belonging to Miocene and Pliocene

depositions along with some recent alluviums (Table 2).

This area is characterised by plane beddings, which

were folded by late Tertiary and early Quaternary tectonic

movements. The dips of the fold are alternatively westward

and eastward. Alteration of thin sand and clay bands are

very common characteristics in the Tipam formation. Some

wave born ripple marks are observed in the lower Tipam

layers. Tidal ripple marks are found in upper Bokabil

formation. This deposition is dominated by thick beds of

clay (grey, blue and occasional green) with little sandy

compositions. Quartz is a very common mineral compo-

sition in Bokabil, Tipam and Dupitila formations (Dey

et al. 2009b, 2010). Blue clay, glass sand, etc., along with

occasional gypsum and lignite are also found in those

depositions.

Seismic status

The present study area falls in Zone V in the seismic hazard

map of India updated in 2000 by the Bureau of Indian Stan-

dards (BIS). In an early study, Gupta and Singh (1986)

detected a wide range of variation in b value (1–1.26) among

the major tectonic zones of northeast India, which indicates a

remarkable stress pattern variation (Steacy et al. 1996). In a

quantitative study, Dasgupta et al. (1998) systematically

assessed the level of spatial scale seismo-tectonic hazards in

the northeastern and eastern parts of India. Tiwari et al. (2004)

mentioned an alternative physical mechanism of earthquakes

like seasonal effect due to pore pressure generated by a sudden

change in water filtration. A spatial scale seismic microzo-

nation in some selected parts of northeast India (Sikkim

Himalayas and Gouhati region) was attempted by Nath et al.

(2008). Thingbaijam et al. (2008) assessed the recent seismic

character of northeast India on the basis of b value (for spatial

seismicity pattern) and fractal correlation dimension of

earthquake (DC) and finally divided northeast India into four

broad seismic zones namely Eastern Himalayas Zone (EHZ),

Mishmi Block Zone (MBZ), Eastern Boundary Zone (EBZ)

and Shillong Zone (SHZ). The EHZ is characterised by nor-

mal faulting mechanism and shallow earthquakes. MBZ and

SHZ are dominantly characterised by strike slip focal mech-

anism and shallow occurrence of earthquake. The Eastern

Boundary Zone (EBZ) is characterised by oblique reverse

faulting and intermediate depth epicentres.

The area under study in this research is a part of EBZ.

According to the available data, it can be stated that

earthquake activity in EBZ is mainly medium magnitude.

Some recent earthquake experiences of EBZ and adjoining

areas are shown in Table 3.

Methodology

Materials and data sources

The present work concentrates on identification of the

morphological as well as structural characters of a fault line

based on manual observation and technical applications.

Intensive field observations were done in the selected study

area from January 2008 to February 2010. Exposed struc-

tures were studied and some basic field maps were pre-

pared during the fieldwork. Dip angles and directions were

Table 2 Geological succession

of southern part of Tripura

Source Extracted from a

unpublished report of

Geological Survey of India,

Agartala, 2004 and field data)

Geological period Epoch Time Group Lithology

Quaternary Holocene 10,000 years Alluvium River born clayey silt,

clay with silt, sands, etc.Pleistocene 1.6 million years

Tertiary Pliocene 5.3 million years Dupi Tilla Estuarine brown clay sand,

mettled silty clay, white to

gray sandrock with silt band,

white clay

Line of unconformity

Tipam Marine-coastal and estuarine sand

rocks with shale and fossil

wood

Line of unconformity

Miocene 23.3 million years Bokabil Marine-coastal shale with minor

sandstone

Base not seen

Environ Earth Sci (2012) 66:421–431 423

123

measured by clinometer from the profiles of road cutting

and a dry and deep man-made channel. Ground control

points were fixed by GPS tool.

In this study technical work was directed towards the

assessment of fault morphology by applying remote sens-

ing and GIS technique and measurement of electrical

resistivity of rocks for understanding the structure of the

selected area. Several maps and images along with the field

maps were consulted (Table 4). Multi- sources data such as

Survey of India (SOI) topographic sheets (Scale: 1:50,000

and 1:63,360) and Geological map of Tripura (unpublished

map prepared by Geological Survey of India, scale:

1:50,000) were consulted. Apart from these, Landsat TM

images and Google Earth view were also studied primarily

for assessing morphological signatures. A tectonic map of

south Tripura prepared by Dey et al. (2009a) was also

consulted by the present authors.

Digital operation and digital data analysis

Applications of remote sensing and GIS techniques for

detecting the geological and tectonic features are very

common from the later parts of twentieth century and since

then it has played a remarkable role in hazard zoning and

planning for management (Gupta 1991). Henderson et al.

(1996) attempted to extract lineaments (faults and frac-

tures) from aerial photographs and satellite images.

Masoud and Koike (2006) used Landsat-7 ETM?/SRTM

DEM for assessing lineaments and their relationship with

hydrogeological setting in Siwa region of northwest Egypt.

Abdullah et al. (2009) worked with Landsat-5 TM and,

SPOT-5 satellite sensors and compared them for lineament

mapping in Hulu Lepar area. In the present research dif-

ferent bands of Landsat TM were used for detecting the

overall morphological signatures of tectonic structure in

the study area. As thermal radiance of the earth’s surface is

sensitive to the interrelated factors like vegetation cover,

slope, soil moisture, etc. (Doran and Parkin 1994; Bern-

stone et al. 1997), thermal range of the surface was con-

sidered as an effective tool for measuring morphological

signatures. It is well accepted that the pattern of vegetation

cover is changed sharply with the change of slope in the

hilly areas of Tripura (Dey et al. 2007). During the field-

work it has been observed that the high angle slopes (\50�)

are covered by dense mixed deciduous type forest while the

hill topes are mainly covered by dry type grasses and some

isolated trees. The low lands and river basins are covered

by dense grasses, bushes and some tropical trees. Thus,

geothermal mapping was adopted for assessing the mor-

phological condition of the study area.

Digital operation comprises four stages: (a) image

enhancement using linear stretching to obtain better visu-

alisations, (b) masking and preparing the digital classes/

groups (c) overlay operation and (d) vectorisation of

delineated fault lineament. In this research unsupervised

image classifications were done on thermal infrared band

of Landsat TM (band 6) to measure the spectral ranges of

the image, which indicates apparent temperature of the

surface. Short-wave infrared band (band-7) of the same

image was used to measure the geological pattern by

Table 3 Last hundred years earthquakes in Eastern Boundary Zone and its adjoining areas

Year Place Geographical locations Magnitude Severity

1920 West of Saitlan, Chin Division (Indo-Myanmar Border region) 22.20�N, 93.20�E 6.0 High

1950 NW of Srimangal, Chittagong Division (Bangladesh) 24.40�N, 91.70�E 6.3 High

1957 South of Silchar, Cachar District (Assam-Mizoram Border region) 24.50�N, 93.00�E 6.0 High

1967 NE of Agartala (Indo-Bangladesh Border region) Tripura 24.00�N, 91.50�E 5.1 Moderate

1968 NE of Agartala (Indo-Bangladesh Border region) Tripura 24.10�N, 91.60�E 5.2 Moderate

1971 East of Agartala (Tripura) 23.80�N, 91.80�E 5.4 Moderate

1984 SE of Agartala (Tripura) 23.6573�N, 91.5078�E 5.3 Moderate

1984 South of Silchar (Assam–Mizoram border region) 24.64�N, 92.89�E 6.0 High

1989 Tripura–Mizoram–Assam border region 24.4041�N, 92.4312�E 5.1 Moderate

1997 Southern Mizoram 22.212�N, 92.702�E 6.1 High

Table 4 Basic cartographic materials used in the present study

Sl no Cartographic materials Year of

publication

1. Survey of India Toposheet Nos

79M/10 and 79M/11

1968

2. Geological map (Geological survey

of India)

2002

3. Landsat TM Band 6a (Thermal infrared) 2008

4. Landsat TM Bands 4, 3, 2 and 2008

5 Band 7a and Band 5 2008

6. Tectonic map of southern Tripura

by Dey et al

2009

7. Google Earth view 2009

a Digital operation done on those bands


123

assessing hydrothermal alteration. On the basis of field

data, the numbers of classes were selected and again

unsupervised classification was done on band-7. For ther-

mal band, four main classes were selected on the basis of

vegetation cover and pattern of land objects. In case of

short-wave infrared band, a total of six classes were

selected. Overlay operation was performed with both the

classified raster images to delineate the structural influ-

ences on morphology (Fig. 2). In addition, an automated

digital elevation model (DEM) was prepared from SRTM

data, which was overlaid by Landsat TM band combina-

tions 7-5-4 (suitable to visualising water bodies; lower 50%

transparent,) and 5-4-3 (suitable for visualising geomor-

phology; upper 50% transparent).

Electrical resistivity survey

Electrical conductivity is a significant physical character

for understanding the resistivity nature of rocks. Earlier,

many investigations have been carried out on electric/

electromagnetic conductivity of various soils by McNeil

(1980), Palacky (1987), Dahlin (1993), Alfano (1993),

Dahlin (1996), Christensen and Sørensen (1996), Dahlin

and Loke (1997), George et al. (2008) and Akpan et al.

(2009), which strongly support the efficiency of this tech-

nique. The present authors applied ‘‘vertical electrical

sounding’’ (VES) method by earth resistivity meter

instrument for understanding the structural variation of this

area. After detailed observation of the exposed rock

structure of the study area, two places within 30 m distance

were selected for structural study by vertical electrical

sounding. Wenner’s configuration was adopted for vertical

electrical sounding and instrumental reading was taken up

to 15 m depth. The instrument was calibrated carefully.

Range of the instrument was fixed 910 (current 100 mA).

The resistivity was calculated by the simple formula:

q ¼ 2PAR ð1Þ

where q = resistivity of rocks in X m, A = spacing of

electrodes, R = range of the instrument 9 instrumental

reading

On the basis of the recorded resistivity characters, the

soil/rocks of this area were divided into four classes,

namely: topsoil layer (resistivity up to 15 X m), soft rocks

(resistivity below 60 X m), medium rocks (resistivity

below 100 X m) and hard rocks (resistivity 100 X m and

above) (Table 5; Fig. 3). In the western part of survey site,

a water bearing strata has been detected at 4 m depth. At

this depth the resistivity measured 07.536 X m (instrument

reading 0.303). Here, the upper layer resistivity is recorded

23.173 X m and lower layer resistivity is 16.328 X m.

Below 14 m of this side another water-bearing strata was

assumed where the resistivity has been measured

47.100 X m (instrument reading 0.05). In the eastern part,

water level assumed at 10 m-depth (measured resistivity

62.172 X m from instrument reading 0.106).

Results

Morphological signatures of fault line

Many misfit streamlets are found in this area, which is a

strong evidence of regional level complex geological

condition. From the classified geothermal image (Fig. 4) it

has been observed that R. Maharani extends northward

Fig. 2 Flow chart showing the

methodology of digital

operation


123

along a very straight line (Udaipur fault) before meeting

R. Gumti, which flows from an east to west direction across

the fault line. Remarkably no evidence of control of this

fault line on R. Gumti has been detected from field data and

digital data. It is quite evident that the R. Gumti was born

later than the development of this fault line. However,

some old channels of the river near Hirapur prove that

Gumti has changed its track several times in this past. This

Fig. 3 Resistivity characters of

western and eastern parts of the

surveyed areas in Hirapur

Table 5 Resistivity of rocks in

different depths

Source Field data generation

Western side Eastern side

Depth in

(m)

Instrument

reading

R in X q Depth in

(m)

Instrument

reading

R in X q

1 0.445 4.45 27.946 Erosion of upper alluvium by R. Maharani

2 0.205 2.05 25.748 1 0.079 0.79 04.961

3 0.123 1.23 23.173 2 0.096 0.96 12.058

4 0.303 0.3 07.536 3 0.258 2.58 48.607

5 0.052 0.52 16.328 4 0.243 2.43 45.781

6 0.091 0.91 34.289 5 0.198 1.98 62.172

7 0.126 1.26 55.399 6 0.182 1.82 68.578

8 0.094 0.94 47.226 7 0.159 1.59 69.896

9 0.069 0.69 38.999 8 0.152 1.52 76.365

10 0.054 0.54 33.912 9 0.148 1.48 83.649

11 0.068 0.68 46.974 10 0.106 1.06 66.568

12 0.087 0.87 65.563 11 0.163 1.63 112.60

13 0.109 1.09 88.988 12 0.119 1.19 89.768

14 0.199 1.99 174.96 13 0.106 1.06 86.538

15 0.05 0.5 47.100 14 0.091 0.91 80.007

15 0.089 0.89 83.838


123

may be due to the reactivation of the fault. On the basis of

the geological structure and associated morphological sig-

natures, it has been observed that this fault line extends

25 km from north to south (about 19 km is shown in

Fig. 4).

Characteristically, Maharani is a very narrow streamlet

(maximum 30 m wide near its confluence with R. Gumti)

and very few wide meanders are observed in its flow.

Interestingly, the valley of this narrow streamlet is 2.5 km

wide in the northern part and towards the south it gradually

becomes narrower. The streamlet is flowing along the

eastern corner of the wider valley near its confluence with

Gumti (Fig. 5). This might be due to the change of slope by

the early displacement, which resulted in eastward shifting

of the main flow of Maharani. Evidences of alluvial

depositions strongly support that once the streamlet used to

flow along the western margin of this valley. Spatial var-

iation of vegetation cover and elevation (57 m difference

has been measured during fieldwork) along the western

margin of the valley also support the geological compli-

cation between the western side and the eastern side of the

study area (Maharani Valley).

Fig. 4 Geothermal map

overlaid by geological map

showing geophysical condition

of the study area (base images:

Landsat TM band 6 and band 7

2008)

Fig. 5 DEM shows the

geomorphic condition and the

flow of maharani along the

eastern margin of its basin near

its confluence with R. Gumi


123

Electrical resistivity and evidence of rock

displacement:

The recorded resistivity data show a significant variation of

rock structure within 30 m surface distance (Fig. 6). In the

western part of the surveyed area top soil layer is very thin,

less than 1 m, because it was a high elevated area and

artificially levelled for the construction of road. This layer

is recognized as immature soil, which is covered by only

some dry types of grasses and bushes. Soft rock layers

(mainly sandy clay) have been found at 1m depth. From 1

to 3 m depth resistivity varies between 23 and 27 X m. Just

below the water-bearing strata (at 4 m depth) the rock

resistivity is very low, only 16.328 X m.

Soft rocks layers are found up to 11 m depth and

maximum resistivity of those soft layers is recorded

55.399 X m (at 7 m depth). Investigations show that these

are sandy to clay type of depositions. Medium hard rock

layers are recognised at 12 m (65.563 X m) and 13 m

depths (88.988 X m). At 14 m depth, maximum resistivity

in the study area (174.96 X m) has been measured, which

is the evidence of hard rock. This hard rock structure

exposed in the deep man-made channel only 300 m away

from the present VES station. Field observations show that

it is a hard slate layer, which formed a recumbent fold and

might be metamorphosed by huge pressure and tempera-

ture during tectonic activities.

The eastern part of the study area is about 1 m lower

than the western part due to early erosion of R. Maharani.

Now this place is used as a paddy field (Fig. 7a). The top

soil layer is very soft and wet. Thickness of soil layer

extends up to 2 m depth from the surface and resistivity

was recorded 12.058 X m. Just below the top soil layer

comparatively thin layers of soft rock have been found

(resistivity 48.607 and 45.781 X m) at the depths of 3 and

4 m. Remarkably, medium hard rock has been recognised

at 5 m depth. At 9 m the resistivity value was recorded

83.649 X m. Below the water level (10 m depth) a hard

rock layer has been detected which is characterised by

112.60 X m resistivity. This may be the extension of the

same slate layer, which was found in the western side.

From the above discussion it can be said that this part is

mainly composed of medium hard to hard rocks. The

remarkable variations of rock character in two different

parts of the surveyed area support that a displacement

occurred between the western and eastern parts of this area.

Apart from geoelectrical data, some evidences of local

strain effect have been identified from this study area

(Fig. 7c). These evidences also advocate the occurrence of

seismo-tectonic event in the past.

Discussion

The plane bedding pattern along with regular clay and sand

alterations (Fig. 7b) in Bokabil and Tipam formations of

this area prove that pre-tectonic deposition occurred under

stable environmental conditions. Line of unconformity

preserves the evidence of an early environmental shifting

between the periods of Bokabil and Tipam depositions.

Fig. 6 Structural plotting of the

study area by VES recording

(dip angles are measured by

clinometer from exposed layer

of the road cuttings)


123

Though Bokabil layer is characterised by thick marine-

coastal clayey depositions with prominent ripple marks,

two different folding evidences in different depths of this

formation prove the early tectonic activations during the

late Miocene. In the lower Bokabil a fold bed has been

observed which is followed by plane beddings. Another

fold layer (recumbent fold structure) was found in the

lower-middle Bokabil layer. Tipam layers formed there-

after under a very stable depositional environment, which

continued up to the latest tectonic activities.

Late Tertiary and Quaternary tectonic activities played a

very vital role for the development of upper (recent)

folding. The influence of the latest or late Tertiary–Qua-

ternary tectonic activities on the present geomorphology is

very clear in the study area. Generally, folds of this area are

characterised by alternatively eastward dips and westward

dips; however, along the western margin of the Maharani

Valley, only westward dip has been observed. In this place

no eastward dip has been found. It may be another valuable

evidence of geological complexity of this area.

In a very recent review work De and Bandyopadhyaya

(2010) attempted to explain the geophysical characters of

Maharani Valley on the only basis of surface erosion nat-

ure. However, structural analysis by electrical resistivity

data in this study area exposed the geological fact of sub-

surface displacement and nature of faulting along Maharani

Valley, which was earlier defined as Udaipur fault line by

Dey et al. (2009a). Observing the morphological characters

(misfits), it can be explained simply that the eastern side

might be slipped downward along the fault line; but the

resistivity data show a reverse feature beneath the soil

layers. A very close similarity was found between the rock

structures below 10 m depth of western side and rock

structures below 3 m depth of the eastern side. From that

structural condition a hypothetical conception has been

developed by the present authors, e.g. either the western

side moved downward or the eastern side moved upward

by faulting. Later Maharani might start eroding and the

eastern side became lower than the western block. It is

remarkable that Thingbaijam et al. (2008) also advocated

for the reverse faulting character in Eastern Boundary

Zone. Apart from the early tectonic evidences, some recent

evidence of active tectonic character has been detected in

this area from the changing nature R. Gumti. A compara-

tive study using SOI Toposheets of 1934, 1968, and current

satellite data show that R. Gumti remained very dynamic

even during the recent times in the present study area

particularly around Hirapur. Climatic factors and geomor-

phic process may play an additional role; but the influence

of tectonic factors cannot be ignored for shifting of this

river during the recent time as structural evidences shows

the probability of tectonic activeness.

Fig. 7 a Alluvial land on the eastern side of Maharani valley, b the exposed face along the line of displacement, c evidence of local strain effect

by early tectonic movement, d layer of recumbent fold


123

Conclusion and remark

The origin of a devastating earthquake depends on many

geophysical factors but proximity of the fault line in the

present study area may render a high-level hazard anytime.

From that standpoint, fault zonation mapping by satellite

data analysis strongly suggests that still though no big

tectonic occurrence has been found in this part of southern

Baromura hill from the available records, there remains a

certain possibility of an earthquake. It is a fact that due to

the lack of sufficient authentic data no awareness about the

risk from tectonic hazards has been developed in this area

at any level. As micro-regional scale geological complexity

was not reported previously, field data generated by elec-

trical survey along with the application of remote sensing

technique would be very helpful for developing a multi-

dimensional geophysical record and tectonic risk assess-

ment in the surroundings of Maharani basin. From meth-

odological point of view this study proves that without

multi-sources data it is very difficult to assess the risk

probability particularly in tectonically complicated zones.

It should be noted that the accuracy does not only mean the

technical accuracy but also appropriate simulation of

methodological application for field data generation.

Although the result worked out through the above-men-

tioned process of data simulation is satisfactory, some

further addition of data from different sources for geo-

processing is needed for a future version of advancement.

Hence, regular seismic data generation and change detec-

tion mapping by establishing permanent monitoring sta-

tions equipped by satellite technologies such as Geodetic

GPS and remote sensing in some selected places are

needed for more efficient earthquake disaster planning.

Acknowledgements The authors are grateful to Centre for Social

Exclusion and Inclusive Policy, Tripura University for partial funding

in this research and Global Land Cover Facility (GLCF) for providing

free satellite data. The authors are also grateful to the anonymous

reviewers whose technical advices helped to improve the manuscript.

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Seismic assessment in southern Baromura hill, northeast India, considering geophysical aspects

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