Ch5geology&Seismicity Tawang

7/31/2019 Ch5geology&Seismicity Tawang

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Environmental Impact Assessment Geology and Seismicity CISMHE

5GEOLOGY AND SEISMICITY

Tawang HE Project Stage-II is proposed in western Arunachal Pradesh in Tawang district

on river Tawang Chhu located within Higher Himalaya. A run of the river scheme has been

proposed to harness the hydro potential of river Tawang Chhu by constructing a barrage, 16 km

long HRT and an underground powerhouse. Further in order to harness the maximum potential of

the river, the powerhouse has been proposed near the confluence. The Himalayan state of Bhutan

is located towards south, west and south-west of the project and across the river Tawang Chhu

just downstream of the proposed power house.

5.1 REGIONAL GEOLOGY

Broadly, Arunachal Pradesh can be divided into four physiographic segments having

distinct stratigraphy and structures with major tectonic features/lineaments separating each

segment.

These are: Brahmaputra plains

Naga Patkoi ranges

Mishmi Hills

Himalayan Ranges

The Brahmaputra plains comprise quaternary deposits brought down by the mighty river

Brahmaputra and its tributaries. This physiographic segment is about 170 m south of the project.

The Naga Patkoi ranges are made up of PaleogeneNeogene sediments lying

unconformably over the concealed basement of Precambrian rocks. These are considered as the

eastern extension of the Shillong plateau. These ranges are made up of Tertiary sequence formed

during the last phase of Himalayan Orogeny. This physiographic segment is also far away from

the project and disposed in the south-western part of Arunachal Pradesh near the border with

Burma.

The NW - SE trending Mishmi hills are considered as northern continuation of Myanmar

Tawang H.E. Project Stage-II 5-1


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hills of Burma. Generally rocks of Precambrian age are exposed here. These hills abut against the

NagaPatkoi ranges of the ArakanYoma Mountain to the south along a tectonic plane known as

Mishmi Thrust. This physiographic segment is far away from the project and located in the

western part of Arunachal Pradesh bordering China.

The Himalayan ranges rise abruptly from Brahmaputra plains and merge with Tibetan

Plateau in the north covering about 350km of eastern most part of the Himalayas, (referred to as

Arunachal Himalaya) and extend from Bhutan in the west to Lohit valley in the east. The

Himalayan ranges abut against Myanmar- Arakan ranges. The Himalayan ranges here as in

western sector, are subdivided into following from north to south:

NORTHTrans Himalaya

Indus Tsangpo Suture Zone

Tethys Himalaya/ Tibetan Himalaya

Higher Himalaya

Main Central Thrust (MCT)

Lesser Himalaya

Main Boundary Thrust (MBT)

Sub-Himalaya

SOUTH

The Sub-Himalaya mostly comprise of sedimentaries known as Siwalik and are separated

from the Brahmaputra plains by Foothill thrust (FHT). The Siwaliks extend up to Bhalukpong

which is about 280 km from Tawang.

Towards north the Sub-Himalaya is thrusted over Lesser Himalaya along Main Boundary

Thrust. Lesser Himalaya is mainly formed by Upper Proterozoic to Lower Cambrian detrital

sediments from the passive Indian margin intercalated with some granites and acid volcanics

(1840 70 Ma). The Lesser Himalaya in the region is represented by Bhareli and Bichom

formations both of Gondwana Group, Bomdila group and Dirang Formations. The Lesser

Himalaya is observed up to Dirang which is located about 143 Km from Tawang. The LesserHimalaya towards the west abuts against Mishmi Hills while towards the north it is bounded by

the Main Central Thrust (MCT).



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Further north the Lesser Himalaya is overlain by Higher Himalaya and separated from it

by Main Central Thrust. The MCT appears between Dirang formation and the overlying Sela

Group of Higher Himalaya near Dirang. The Higher Himalaya is a 30 km thick medium to high

grade metamorphic sequence of meta sedimentary rocks which are intruded at many places by

granites of Ordovician (approx. 500 Ma) and early Miocene (approx. 22 Ma) age. Although most

of the meta-sediments forming the Higher Himalayan Crystalline Sequence (HHCS) are of late

Proterozoic to early Cambrian age, much younger meta-sediments can also be found in several

areas. The project area lies in Higher Himalaya belt and is located about 30 Km north of MCT

and about 100 Km south of Indus Tsangpo Suture Zone.

Further north the Higher Himalaya is overlain by Tethys or Tibetan Himalaya which

comprises of strongly folded and imbricated, weakly metamorphosed sedimentaries. Tethys

Himalaya is separated from overlying Trans Himalayan formations by Indus Tsangpo Suture

zone. The Indus Tsangpo Suture Zone (ISZ) defines the zone of collision between the Indian

plate and Eurasian plate. This suture zone is formed by the Ophiolite Mlanges, which are

composed of an intercalation of flysch and ophiolites from the Neotethys oceanic crust.

Lithostratigraphically, the rocks exposed in the area belong to Sela Group and Lumla

Formation. Das et al. (1975) introduced the term Sela Group to include garnetiferrous biotite

gneiss, lit par lit gneiss/migmatite, calc gneiss, high grade gneiss and schist etc. exposed around

Sela pass and high grade gneiss, schist, amphibolite, calc-silicate and migmatite extending from

Tawang up to 40 km NW of Sela. Jain & Tiwari (1977) divided the rocks of the area into the Sela

Group, the Bomdila Group and the Gipsu Formation, each separated by a prominent thrust. The

rocks around Lumla were classified by them as Gipsu Formation belonging to Bomdila Group.

Jain and Basu Roy (1978) classified the rock sequence exposed around Lumla into Lumla

Formation. Singh (1988) broadly followed the nomenclature given by Jain and Basu Roy (1978)

but made a few changes. The biotite gneiss which was considered to be a part of Bomdila Group

by the former was included in the Sela Group by Singh (1988). Moreover, the contact between

the Sela Group and the Lumla Formation was considered to be tectonic by the former but it was

refuted by Singh (1988) who considered the contact to be an unconformity. The contact between

Sela Group and Lumla Formation is marked by profuse intrusions of tourmaline granite and

pegmatites. Jamwal et al. (1996) subdivided the rocks of Sela Group into high grade gneisses,

high grade schists, amphibolite, calc-silicate, migmatite and younger granitoids. Tripathi et.al(1979) recorded sulphide mineralization (chalcopyrite, bornite, pyrite) in the biotite schist of



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Lumla Formation. The lithostratigraphic succession of the area provided by GSI in year 2006 is

as follows:

Age Group/Formation Lithology

Meso-Proterozoic

Lumla Formation Schistose quartzite garnetstaurolite biotite schist, and marblewith profuse intrusions of tourmaline granite and pegmatite.

Paleo-Proterozoic

Sela Group Silimanite gneiss and biotite gneiss with interbands of feldspathised garnet-biotite schist, amphibolite, migmatite andintrusions of tourmaline granite and pegmatite.

There are however varied opinions regarding the contact between Sela Group and Lumla

Formation and has been interpreted differently by various workers.

Gopendra Kumar (1997) and studies made by various workers regarding Lumla

Formation in Tawang-Woming La section (Singh, 1988) Takshing Formation and the Monigong

and Piddi Formations (Singh and De, 1989) have found that Lumla Formation rests over Sela

Group (Fig 5.1).

Santanu Bhattacharjee and others (2007) consider Lumla Formation equivalent to that of

Dirang Formation (Lesser Himalaya). They suggest that the Lumla Formation forms a tectonic

window within tectonic cover of Sela indicating thereby that the lithounits are thrust bound.

Exclusion of this window in Bhutan has not been discussed by these workers. The same needs

verification within adjoining Bhutan.

V. Srinivasan opines that these low grade meta-sedimentaries, namely Lumla Formation

occur in a regional synform extending towards Radi-Sakteng Basin in Bhutan (Srinivasan, 2001)

and form the base of Tethyan sedimentary sequence resting over Central Crystalline (ThimpuGroup in Bhutan or Sela Group in Arunachal Pradesh). In many places, they occur as narrow,

thin exposures surrounded by gneiss (Sela) with the contacts highly sheared. However in the

project area the contact between Sela and Lumla near Lumla is concealed.

The lithological description of the rocks belonging to Sela Group and Lumla Formation in

detail is as follows:



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5.1.1 Sela Group

Sela Group of rocks is the oldest sequence consisting of polyphase deformed high grade

metasediments of green schist to amphibolite facies. The rock types of Sela group include:

Sillimanite Gneiss: Sillimanite Gneiss is light grey, well foliated, hard, massive and profusely

jointed, characterized by thin layers of aggregate of sillimanite needles along the foliation planes

and joints. Thin veins of quartz as well as quartzo-feldspathic material are common along the

foliation and joint planes. Around Lohu, the sillimanite gneiss contains thin interbands of garnet

biotite schist and lenses of amphibolites. Amphibolite lenses are invariably characterized by

sulfide minerals in the form of fine disseminations. Microscopically sillimanite gneiss is

composed of quartz, orthoclase feldspar + plagioclase feldspar, sillimanite, biotite and garnet.

Biotite Gneiss: Biotite Gneiss is light grey in colour, well foliated, hard, massive and Jointed.

Interbands of feldspathised biotite schist are commonly recorded within the gneiss. At surface it is

generally weathered and friable. Quartzo-feldspathic veins showing pinch and swell structures are

commonly observed along the foliation planes. Locally the biotite gneiss is intruded by non-foliated,

medium grained massive biotite grantite along the structural discontinuities. At places it is

ganetiferours. Around Bomdir, highly weathered and feldspathised biotite schist interbands are

recorded within the gneiss. The boitite gneiss is principally composed of orthoclase feldspar,

plagioclase feldspar, quartz, muscovite and biotite. Opaques and garnet occur in subordinate amount.

Amphibolite: Amphibolite occurs as bands within the schist and in the form of lenses in biotite

gneiss along the foliation and joint Planes (Singh, 1988). The minerals present are hornblende

quartz, plagioclase, K-feldspar and opaques as accessory. In highly folded areas amphibolite

forms boudines on mesoscopic scale.

Calc-Silicate: Calc silicate is observed near Sarong Gompa and in the northern part of the area.

Calc silicate occurs in contact with schistose rock as well as gneiss. Some thin patches of

gneisses are observed within the calc-silicate as conformable bands. The rock is green and fine to

medium grained. The light green coloured bands are of quartz and feldspar. Mineral assemblage

of this litho-unit is hornblende quartz carbonate - feldspar + tremolite + epidote + sphene.

Migmatite: Migmatite occurs as patches and also as sporadic occurrences in the schist. They areespecially noticeable at the sites where gneiss and schist are closely associated and where



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younger granitoids intrude the country rocks. Genetically two types of migmatites are identified.

First type, which, occurs near gneiss patches within the schists or vice-versa. Second type which

is observed near the granitic intrusion into the country rocks suggesting the migmatite are the

results of intrusive activity in the host rock. Migmatite has resulted in parallel and branching

ramified veins, lenses, lenticles and schliern parallel and across the planar fabric of the host rock.

Mineralogy is nearly same as those of the gneiss/schist with abundance of quartzo-feldspathic

material in the second type. Biotite, muscovite, quartz, plagioclase, K-feldspar, garnet and

opaque minerals are present in the migmatite.

Younger Granitoids: The litho-units of Sela Group are invaded by a system of leucogranitic

rocks throughout the area. These intrusive are medium to coarse grained and occur as sills, dykes,

apophyses, veins, lenses and small bodies mostly trending NW-SE. The granites were dated as of

30 Ma. These younger leucocratic intrusive rocks are divided by (Jamwal et. al. 1996) into

leucogranite, pegmatite veins. Pegmatite cuts across the granite and country rocks and in turn is

itself cut across by quartz-feldspar veins. Granitoids are light coloured, medium to coarse grained

and occur in relatively unreformed state. Minerals present are quartz, sodic plagioclase,

orthoclase, microcline, biotite, muscovite, tourmaline and garnet.

5.1.2 Lumla Formation

The sequence corresponding to the Dirang Formation in the Tethyan Himalaya is referred

to as the Lumla Formation (Tripathi et al . 1979). Resting over the sela Group it is best exposed in

Tawang-Woming La section (Singh 1988). In other areas it may include the Taksing Formation

and the Monigong and Piddi Formation (Singh and De, 1989). It is constituted low grade meta-

sedimentaries comprising of schistose quartzite with bands of biotitegarnetstaurolite schist,

calc-silicate and marble (Kumar, 1997). It is intruded by tourmaline granites of Tertiary age.

Quartzite: Quartzite in general is medium to fine grained and micaceous in nature. It is

composed dominantly of quartz with subordinate amounts of mica especially muscovite.

Generally the rock shows granoblastic texture however mica flakes show strong preferred

orientation providing the rock a banded character along which the rock breaks into parallel slabs.

It occurs as individual litho unit and also as interceded sequence with garnetiferrous mica schists.

Mostly quartzites are schistose in nature and are fractured at few places. However massive and

strong quartzites are also present. Thin layers of carbonaceous matter are also seen withinquartzites at few places.



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Garnetiferrous mica schists: These rocks are dominantly composed of muscovite and biotite

with subordinate amounts of quartz and garnet and minor amount of feldspar. Garnets occur as

porphyroblasts within the rock. Garnetiferrous mica schist also occurs as individual litho unit

and as interbedded sequence with quartzite. Schist in general is close to moderately foliated,

however at places it is quite massive in nature.

Marble: The rock is dominantly composed of calcite with minor amounts of biotite chlorite,

muscovite, sericite, quartz and zoisite. It is granular in character and generally strong in nature.

Leaching effects are commonly observed on the surface.

5.2 GEOLOGY AROUND PROJECT COMPONENTS

The project components are proposed to be constructed within rock types of Sela Group

and Lumla Formation (Fig 5.2). Gneisses with intrusive of leucogranite, pegmatite and

amphibolites are disposed in the eastern part of the project while as rock types of Lumla are

exposed towards western part where part of HRT and underground power house are proposed.

The primary stratification in rock formations S o is defined by colour and compositional

laminations in schistose quartzite of Lumla Formation and in the calc-silicate rocks of the Sela

Group. Regional foliation observed in the schist and the gneiss show a swinging trend. South of

Jung the schist trend E-W with northerly dips while near the bridge on Tawang Chu, the

Foliation trend swings to N-S. The structural elements indicate a regional F 2 fold with an easterly

plunging antiformal axis passing through Jabrang, Shyaro and north of Jang. Apart from this

regional fold, mesoscopic folds of broad open and tight plunging geometry have also been

reported from the area. Based on field evidences collected during geological mapping a thrust has

also been mapped in the area around Lumla.

Geology of main project components is described in subsequent paragraphs.

5.2.1 Barrage site

A barrage has been proposed in the straighter course of river about 600m u/s of

confluence of Tawang Chu and Susum Rong. The river valley at this location is wider.

Generally, the river channel is occupied by riverine deposits comprising of boulders,

cobbles and pebbles in fine to medium sandy matrix. At the proposed axis, rock exposures are



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seen in left bank above EL 1535M beyond the riverine terrace. These rock formations consist of

quartzo-feldspathic gneisses with quartz veins, leucogranite and bands of mica schist which are

strong to very strong and moderately jointed. Right bank is generally occupied by slope wash and

occasional nalla fan deposits. Sporadic outcrops of gneiss are seen at higher elevations above EL

1660M. Keeping in view the overburden deposits a barrage is proposed to be constructed as a

diversion structure.

The barrage area has been well investigated with a back up of geophysical surveys and

drilling. Overburden in the river channel varies from 16-40m along the axis and 35-37m along

the glacis portion. Permeability of overburden is of the order of 10 -2 to 10 -4 cm/sec.

A raft type foundation for barrage is proposed to be constructed on permeable foundation

comprising of boulders, cobbles and pebbles in medium to fine sandy matrix. In situ tests

namely, bearing capacity, modulus of sub-grade reaction and SPT tests have been conducted to

ascertain the foundation properties. Proposed barrage is a relatively small structure and

excavation is limited to overburden only. Since excavation in bedrock is not required, as such no

adverse impact is foreseen.

5.2.2 Head Race Tunnel

In order to harness the head in this stretch of rover a head race tunnel of the project had to

be planned in the right bank keeping in view the international border with Bhutan which is

located on left bank about 15.5km downstream of barrage. Along the proposed tunnel route

Paleoproterozoic rocks of Sela Group and Mesoproterozoic metasedimentaries of Lumla

Formation are exposed. The tunnel route has been investigated with a backup of geological

mapping, drilling, drifting and study of imageries.

The rock formations in general have undergone several phases of deformation resulting

into folding/ warping at several places. Some degree of shearing and fracturation has also

resulted from this deformation. Swing in attitude of foliation is a result of these warps.

About 7 km stretch of HRT i.e. from Intake shall be housed within quartzo feldpathic

gneisses of Sela Group while balance 9 km stretch towards downstream shall be within rock

types of Lumla formation. The rock types of Sela group consist of gneisses which are intruded byleucogranites, pegmatites and amphibolites. These occur as lenses and bands of various shapes



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and sizes. The gneisses are generally, moderately strong to strong and moderately jointed. They

are expected to provide fair to good tunneling media barring few stretches of poor rock mass

where shearing is expected within the rock mass.

The meta-sedimentaries of Lumla formation consists of Quartz-Mica schist and

interbands of quartzite, quartzites, schist and calc-silicates (marble).

Quartz mica schist is garnetiferrous, closely foliated and in general medium strong to

strong in nature. The rock mass as a whole is moderate to close jointed and is expected to provide

fair to good tunneling media with few stretches of poor rock mass in between.

Garnetiferrous mica schist is medium strong to strong, generally closely foliated to

moderately jointed in nature. However at places it is quite massive in nature. Generally schists

are expected to provide fair tunneling media with some stretches of poor media.

Mostly quartzites are schistose in nature, fractured and have undergone high degree of

fracturation. However, massive and strong quartzites are also disposed within the area. Quartzites

are expected to provide fair to poor tunneling media in general.

Strong to very strong, slight to moderately jointed calcsilicate (Marble) may be

encountered along the tunnel route. These calc-silicates are expected to generally provide good

tunnelling media.

Now a 16 Km long tunnel is planned with six intermediate adits. The tunnel layout has

been planned within rock formations. Construction of this tunnel will not have any adverse

impact on the geomorphology of the area as the head race tunnel is deep seated within the hills.

5.2.3 Powerhouse site

In order to harness the maximum potential of the river, the powerhouse has been

proposed near the confluence. An underground powerhouse has been proposed near the

confluence of Nyamjang Chu and Tawang Chu. The ridge housing the powerhouse complex

shows sparse vegetation mostly in the form of bushes and shrubs with intermittent rock outcrops.

Bed rock is generally exposed in this area and occasionally covered by a thin veneer of slopewash.



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By and large, rock formations exposed in the area comprises of interbanded garnetiferrous

quartz mica schist with quartzite and occasional intercalation of gneiss. These rock formations are

generally fresh to slightly weathered, moderate to closely jointed and strong in nature.

Powerhouse area has been investigated with a backup of geological mapping, drilling and

drifting. Powerhouse is suitably located to have sufficient vertical and lateral cover. Moreover

orientation of powerhouse has also been optimized so as to make sufficient angle with average

orientation of major discontinuity sets.

The underground caverns have been planned taking into account the geological

conditions and therefore construction of these caverns is not expected to cause any adverse

environmental impact.

5.2.4 Reservoir

The reservoir of Tawang Hydroelectric Project, Stage-II (FRL at El. 1536 m) will be a

very small water body. It will submerge an area of about 0.06 km 2 only and will extend for a

length of about 800 m along the river in a moderate valley. From about 300m upstream of

barrage axis, the river follows almost NESW course. Overall the terrain is unapproachable

except for a few foot paths. River Tawang Chhu being the master drainage system in this area,

possibility of water escaping from the reservoir of this valley to the adjoining valley does not

exist. No major deposits of economic importance are reported to be present in the reservoir area,

nor is any mining activity seen to be going on in the area. By and large the reservoir will remain

within the existing flood plain of the river and therefore considerable change around the reservoir

periphery is not expected. Further, the reservoir being very small it is not expected to change the

seismic pattern of the area.

5.3 SEISMOTECTONICS AND SEISMICITY

Seismotectonically the area encompassing the proposed project is located in Main

Himalayan Belt in Arunachal Himalaya. Northern part of the terrain is occupied by the Trans

Himalayan Tectogen with late to post tectonic granitoid batholiths. This pocket is followed to the

south in the western part by the ophiolite and accretionary complex of Tsangpo Suture Zone.

However, along this tectono-stratigraphic level, towards east only an incipient development of ophiolite is observed. Further south the Himalayan Belt exposes Proterozoic crystallines,



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Proterozoic folded cover rocks, Palaeozoic sequence and volcanics that have been tectonically

reworked during Himalayan fold thrust movements. Within the Siang window fossiliferous

Cenozoic cover sequence along with basic volcanics is present.

Major structural elements of this region are Tsangpo Suture, the Main Central Thrust

(MCT), Main Boundary Thrust (MBT) and intermittently exposed Foot Hill Thrust (FHT) along

with some subsidiary thrusts and transverse faults (Narula et al. 2000) (Fig 5.3). The crystalline

complexes in the north are overlain by cover rocks of Tethyan shelf sediments. South of this

tectonic domain lies Brahmaputra Basin which is characterized by several sets of neotectonic

faults of which the NE-SW and E-W trending sets are most conspicuous. The central channel of

the river Brahmaputra appears to be controlled at many places by E-W and NE-SW trending fault

systems, majority of which have affected older and younger alluvium surfaces.

Different tectonic domains in this area exhibit different seismicity clusters, trends and

blocks. Parts of Bhutan and Arunachal Himalayas in the west are moderately active with large

earthquake concentrations. Though most of the Himalayan earthquakes are shallow foci (0-40km),

there are a few events with focal depths in the range of 41-70 km. Many of events have either strike

slip or thrust mechanism. In the area east of the proposed project, the seismicity is low and

epicenters are sparsely located. Similarly, the seismotectonic domain forming Brahmaputra Fore

Deep shows more seismic activity in western part as compared to that in the east.

Keeping in view the overall seismicity and seismotectonic set up the area around the

proposed project has been kept in Seismic Zone-V (Fig 5.4) as per Map of India Showing

Seismic Zones (IS: 1893, Part-I-2002).

5.3.1 Earthquake StudiesKeeping the high seismicity of the region in view, Indian Meteorological Department

(IMD) was requested to provide a catalogue of earthquakes recorded in the region bounded by

latitude 24 to 31 N and longitude 89 to 96 E. IMD supplied a brief technical report on seismic

history and seismicity of this area along with a catalogue of earthquake recorded between the

period from August 1828 to September 2004 (Table 5.1). From this catalogue it is seen that the

area has recorded as many as 1238 seismic shocks during this period.

The spatial distribution of the past earthquakes in this region shows that they are mostly



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associated with significant geological and tectonic features such as The Great Himalayan

Boundary fault zone, Eastern Boundary Fault (EBF), Dhubri fault, Mishmi Fault, Lohit Thrust,

Dishang Thrust, Dauki fault, Naga thrust, etc. Being source region of the earthquake, the areas

are exposed to the worst effect of earthquake. Keeping these aspects in view, CWPRS-Pune

carried out studies for evolving site specific seismic design parameters of the Tawang Stage-II

Hydroelectric Project. CWPRS, Pune, has recommended a value of 0.399 for maximum credible

earthquake (MCE) and corresponding value of design based earthquake (DBE) has been

suggested as 0.199 g.

The project components have been planned keeping in view the seismicity of the region

and taking into account the maximum credible earthquake and adequate safety has been taken

with respect to seismicity.

Table 5.1: Earthquake history of the area in 300 km vicinity of the project area

Approx. LocationSl.No

Year

Lat (N) Long (E)

MaximumMagnitude

Epicenterdepth(km), direction

from project

Seismogenic faults

1 1897 91.01 26.01 >8 182 , S26W VIII-VII(MFT)2 1927 91.40 27.34 5 to 6 254 , S19W Transverse Fault3 1930 91.53 25.47 6 to 7 262 , S44W Transverse Fault4 1932, 1956 92.00 26.29 6 to 7 114 , S10E Transverse Fault5 1941 92.46 26.59 6 to 7 117 , S62E MBT6 1941 93.00 26.59 5 to 6 133 , S65E MBT7 1941 93.06 26.46 5 to 6 147 , S58E Transverse Fault8 1946 92.35 26.23 5 to 6 146 , S32E Transverse Fault9 1947 91.43 27.28 5 to 6 12 , N58W MNT

10 1947,48,50 91.56 27.53 5 to 6 41 , N16E Transverse Fault11 1950 92.55 27.27 6 to 7 73 , S88E MCT12 1959 93.00 27.59 5 130 , N66E13 1960 92.40 26.53 5 110 , S54E Transverse Fault

14 1960 92.41 26.47 5 115 , S48E Transverse Fault15 1965 92.20 26.40 5 to 6 104 , S28E Transverse Fault16 1965 92.31 26.40 5 105 , S36E Transverse Fault

17 1966 92.21 27.29 5 61 , S87E MCT18 1966 92.50 27.36 5 to 6 110 , N80E MCT19 1966 92.46 27.35 5 93 , N79E MCT20 1968 92.15 26.47 5 93 , S32E Transverse Fault21 1969 92.31 26.57 5 108, S50E Transverse Fault22 1969 92.26 26.38 5 106 , S31E Transverse Fault23 1969 91.40 26.20 5 132 , S5W Transverse Fault24 1984 92.18 26.59 5 75 , S41E MBT

25 2009 91.50 27.30 6.2 20, SW SE of Tawang26 2009 92.50 26.60 4.9 66, S Assam


Ch5geology&Seismicity Tawang

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