Page 1 of 9

Journal for Studies in Management and Planning

Available at http://edupediapublications.org/journals/index.php/JSMaP/

ISSN: 2395-0463

Volume 04 Issue 01

January 2018

Available online: http://edupediapublications.org/journals/index.php/JSMaP/ P a g e | 18

Tectonic Setting and Major Earthquakes in

India: An Overview

Mr. Sandeep

JRF in Geography

Email: sndpkhkhr7@gmail.com

Abstract: It is likely said India has witnessed a history of earthquake disasters. Therefore

geological data in the form of liquefaction features is needed to extend the historical record beyond

the most recent few centuries. India has a long history of earthquakes which have been recorded in

Tibet and in Northern India and reached up to a magnitude of M = 8.2. This is primarily because

Seismic gaps have been developed along two thirds of the Himalayan these past 5 centuries. When

this data is combined with geodetic convergence rates of approximately 1.8 m/cy, it is observed that

one or more M = 8 earthquakes may be overdue till present day. The reason behind occurrence of

earthquakes in Peninsular India is the consistent stresses induced in the Indian plate flexed by its

collision with Tibet. This makes it a region of abnormally high seismicity in western India appears

to be caused by local convergence across the Rann of Kachch and possibly other rift zones of India.

Most of the scholars agree to the fact that since the plate itself deforms little, this deformation may

be related to incipient plate fragmentation in Sindh or over a larger region of NW India.

Keywords: Earthquake, Natural Calamities, Convergence, Peninsular India, Mitigation.

Introduction: The numerical deformation

data can give us a clear overview of the

earthquake mechanisms in India. It is

noteworthy here that these data, once

analyzed, have required substantial revision

of earlier informed, but speculative,

interpretations of the causal mechanisms of

historic earthquakes. Geodetic data dating as

long as 1819, 1881, 1897 and 1905 is

available and it points out that these

earthquakes have often been not as per the

prediction made in many scholarly articles.

This is certainly a matter of concern for the

geologists as well as the scientists. Moreover,

the conclusions concerning felt reports about

earthquakes in history and prehistory have

limited value in interpreting subsurface

structure. Most of the studies show that faults

have been repeatedly active both on the

subcontinent and within the Himalayan plate

boundary. Furthermore, the analyzation and

study of active faults and liquefaction features

is likely to play an important role in

determining the predictions of earthquake in

the coming decades.

Tectonic Setting of India: The splitting of

Pangea led to the formation of the youngest

mountain ranges, The Himalayas. Due to this,

India is currently penetrating into Asia at a

rate of approximately 45 mm/yr and rotating

slowly anticlockwise. This rotation and

translation results in left lateral transform slip

in Baluchistan at approximately 42 mm/yr

and right lateral slip relative to Asia in the

Page 2 of 9

Journal for Studies in Management and Planning

Available at http://edupediapublications.org/journals/index.php/JSMaP/

ISSN: 2395-0463

Volume 04 Issue 01

January 2018

Available online: http://edupediapublications.org/journals/index.php/JSMaP/ P a g e | 19

Indo-Burman ranges at 55 mm/yr. Because of

complexities in the structural units at its

northern, western and eastern boundaries

these velocities are not directly observable

across any single fault system. Deformation

within Asia reduces India’s convergence with

Tibet to approximately 18 mm/yr, and

because Tibet is extending east-west,

convergence across the Himalaya is

approximately normal to the arc. Arc normal

convergence across the Himalaya results in

the development of potential slip available to

drive large thrust earthquakes beneath the

Himalaya at roughly 1.8 m/cy, hence

earthquakes associated with, say, 6 m of slip

cannot occur before the elapse of an interval

of at least three centuries.

Here it is noteworthy that, the slip across the

150300 km wide plate boundary between

Asia and India in Baluchistan is apparently

partitioned between thrust and strike slip

components. To explain it further, the 1931

Mach Ms = 7.3 earthquake was associated

with 1 m of NW directed reverse slip on a

fault that may have extended entirely through

the crust. It was followed 4 years later by the

Ms = 7.7 strike slip Quetta earthquake on a

subparallel fault less than 150 km NW of the

Mach event. The Mach event slipped in a

sense that effectively unclamped the

subsequent Quetta earthquake. Slip on the

Chaman fault further to the north in

Afghanistan in the past century, and possibly

for a longer period, has been much less than

42 mm/yr according to seismic moment

summation of observed seismicity. Although

this may be the result of minor deformation in

the northern Afghan mountains, or unreported

creep on the Chaman fault, it is quite possible

that the northern Chaman fault system may be

overdue for a large earthquake.

Slip in the Indo-Burman ranges is also accompanied by strike slip and thrust seismicity and

although no recent large earthquakes have occurred on land, the north-south Sagaing fault system is

clearly strike slip and the Indo-Burman ranges to its west the result of distributed east-west

convergence. Near the Andaman Islands slip is partitioned between thrust earthquakes to the west

and beneath islands, and strike slip faulting on the North Andaman fault to their east. GPS

measurements in India reveal that convergence is less than 5 ± 3 mm/yr from Cape Comorin

(Kanyakumari) to the plains south of the Himalaya. Hence the Indian Plate should not be expected

to host frequent seismicity. However, the collision of India has resulted in flexure of the Indian

Plate. The wavelength of this flexure is of the order of 650 km and results in an approximately

450mhigh bulge near the central Indian Plateau, corresponding to the outer rise of an oceanic

collision. Normal faulting earthquakes occur north of the flexural bulge (e.g., possibly on 15 July

1720 near Delhi) and deep reverse faulting occurs beneath its crest (e.g., the M = 6.3 21 May 1997

Jabalpur earthquake). Shallow reverse faulting occurs south of the flexural bulge where the Indian

plate is depressed. This will be further explained by figure 1:

Page 3 of 9

Journal for Studies in Management and Planning

Available at http://edupediapublications.org/journals/index.php/JSMaP/

ISSN: 2395-0463

Volume 04 Issue 01

January 2018

Available online: http://edupediapublications.org/journals/index.php/JSMaP/ P a g e | 19

Figure 1: Depiction of Indian tectonics.

(Source: www.researchgate.net)

From figure 1, we can observe that the plate boundary velocities are indicated in mm/yr. Shading

indicates flexure of India: a 4 km deep trough near the Himalaya and an inferred minor (40 m)

trough in south central India are separated by a bulge that rises approximately 450 m. Tibet is not a

tectonic plate: it extends east-west and converges north-south at approximately 12 mm/yr. At the

crest of the flexural bulge the surface of the Indian plate is in tension and its base is in compression.

Locations and dates of important earthquakes mentioned in the text are shown, with numbers of

fatalities in parenthesis where known. With the exception of the Car Nicobar 1881, Assam 1897 and

Bhuj 2001 events, none of the rupture zones of major earthquakes are known with any certainty.

The estimated rupture zones of pre1800 great earthquakes are shown as unfilled outlines, whereas

more recent events are filled white.

The Indian plate is bent downwards by 46 km beneath the southern edge of the Himalaya attaining

depths of 1820 km beneath the southern edge of Tibet (fig. 1). Stresses within the plate vary from

tensile above the flexed neutral axis to compressional below it. Where no in plane end loading

prevails the position of the neutral axis lies theoretically half way through the thickness of the

elastic plate. Since in plane stresses of the order of 500 bars exist (necessary to maintain the height

of the Tibetan Plateau) this effectively means that the neutral axis rises above the plate south of the