GSI-CHQ-17237
GEOLOGICAL SURVEY OF INDIA
NOTE OK EARTHQUAKES IN RELATION TO THE DAMODAR
VALLEY PROJECT
By
J. B. Auden,
Ex-Superintending Geologist,
Geological Survey of India.
GSI-CHQ-17237
NOTE OK EARTHQUAKES IN RELATION TO THE DAMODAR
VALLEY PROJECT
By
J. B. Auden,
Ex-Superintending Geologist,
Geological Survey of India.
CONTENTS
Paras
Introduction
Structural Location of the Damodar Basin
1
2-6
Incidence of Major Shocks in the Seismic zone to the north
7
Assail Earthquake, 1897
8
Bihar-Nepal Earthquake, 1934
9
Maximum Acceleration to be adopted in design
Literature
10-12
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NOTE OK EARTHQUAKES IN RELATION TO THE DAMODAR
VALLEY PROJECT*
Introduction
This note includes four maps which Illustrate, better than a verbal description, the main points
which can be drawn in connection with the incidence of earthquakes in the area of the Danjodar
Basin. These naps are:Map 1 -
Seismic zones of India based on field studies carried out by the Geological Survey of
India.
Map 2 -
Incidence of recent earthquakes in Northern India.
Map 3 -
Areas involved in certain major earthquakes with epicentres in North Bihar and
Assam.
Map 4 -
Approximate areas in which considerable damage occurred to buildings during the
earthquakes of 1897, 1931, 1934 and 1960.
(Far more data are now available about the incidence of earthquakes in Asia, in particular
from the volume by Gutenberg and Richter entitled "Seismicity of the Earth" (1954). Of particular
value is one of the regional sups on the seismicity of Asia, which is reproduced again as fig. 26.13 of
Richter's "Elementary Seismology" published in 1958).
Structural Location of the Damodar Basin
2.
The basin of the Damodar upstream of ondal (23°35':87°11') is part of Peninsular India,
which is this area consists of ancient crystalline rocks of Archaean age overlain by coal-bearing
Gondwana rocks mainly of Permian age. The coal-bearing beds have been folded and down faulted
into a series of individual basins along a definite east-west alignment.
3.
The folding and faulting of the Gondwana beds was probably accomplished in the Mesozoic
era, for both folds and faults are cut by dia base dikes which are related either to the Jurassic basalts of
the Rajmahal Hills, or to the main outpourings of Eocene (oldest Tertiary) age which occupy 200,000
*
The above short note, which is now to be published in the Symposium, was written 13 years ago without any intention on my part of
subsequent appearance in print. It was a short memorandum prepared for the engineers of the Damodar Valley Project, as the Corporation
was then termed, to meet the needs of the moment and as a background to Information passed geological Survey of India, the note has been
sent to me in England case I wished to make any comment. The note, alight though it is, should remain untouched. Brief comments, made
on specific points have been included in parentheses under the relevant paragraphs : J.B. Auden : 24th May, 1959.
2
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square miles of Deccan Trap in western India. Since the early Tertiary, the Damodar basin has not
been subjected to folding of faulting of orogenic type, but has undergone successive uplifts of a
regional (epeirogenic) nature, with a tilt downwards towards the Gangetic alluvial down warp. The
area is, in fact, geologically stable, aside from slow regional movements with a predominant vertical
component.
(Manifest unconformities within the Gondwana rocks, and below the Deccan traps, indicate
that the greater part of the folding and faulting, followed by erosion, was probably connected with
late-Jurassic to early Cretaceous movements, simultaneous with the formation of the Bay of Bengal,
the eruption of the Rajmahal lavas, and the Lower Cretaceous transgression. On the other hand, the
post-Deccan-trap faulting of the Narbada and Puma valleys, and the post-Eocene faulting seen in the
seismic profiles of the north-central part of the Bengal Basin, demonstrate the persistence of
movements will Into the Tertiary, while the major strike-slip thrust-fault along the southern flank of
the Shi Hong plateau was certainly active, in response to the Himalayan orogenesis, until the and of
the Miocene. The area of the Damodar valley dams appears, however, to have escaped the worst of
the Tertiary faulting and to be reasonably remote from regions involved In the Himalayan
movements.)
4.
The area of seismic instability lies in the Gangetic and Brahmaputra plains to the N.N.W.,
north and north-east, extending from North Bihar, through North Bengal to Assam. Two of the largest
earthquakes of history took place in Assam (1897) and North Bihar (1934). The epicentral region of
the Assam earthquake lay partly on the Shillong Plateau, partly in the plains of the Brahmaputra,
whereas that of the Bihar-Nepal earthquake was between Sitamarhi (26°35':86°29') and Madhubani
(25°56': 86°48'), where the Gangetic alluvium is considered to be of the order of 6,000 to 7,000 feet
thick.
(It is vary probable that a thickness of 6,000 to 7,000 feet for "Gangetie alluvium" is not
unreasonable if the term be used for Pleistocene to Recent sediments. But the total sedimentary
column, including Siwaliks, and Lower Tertiary, very probably exceeds 20,000 feet in thickness in
parts of the Ganga basin. Even greater thicknesses are involved in the Cretaceous to Recent
succession in the north east part of the Bengal Basin. The matter was left open by Dr. D. N. Wadia
and myself in our discussion on pp. 133-136 of Memoir, Geol. Surv. Ind., 73(1939), which dealt with
the Bihar-Nepal Earthquake of 1934, but we favoured a greater depth than that indicated by the
Geodetic Branch of the Survey of India. Geophysical work undertaken since 1950 in north-east IndoPakistan definitely supports the conception of deep basins.)
5.
The relationship between seismic instability and gravity anomalies has not yet been fully
worked out, but there is strong evidence that in the main the seismically unstable areas of India are
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connected with negative anomalies and active down warps. The Shillong Plateau fonts, an exception
to this generalisation. The region of the Damodar basin is one of positive gravity anomalies, and the
seismic zone lies zone 150 miles north of the northern limit of the basin.
(The relationship between areas of seismic instability, active down warps and negative gravity
anomalies, is less confident perhaps than was supposed in 1946. The major earthquakes of 1897 in
Assam and 1819 in the Rann of Katch do not fall into such a scheme, and the environmental
conditions of earthquakes are certainly complex. While it is true, for example, that the zones, of large
negative gravity anomalies along the present island arcs are also son as of shallow earthquake
epicentres, such features do not correspond to the present-day deepest ocean troughs and most recent
down warps. These matters were discussed by the writer on pp. 111-131 of Proc. 38th Indian Science
Congress Part. II, 1961).
6.
The Damodar basin fails the fringe effects of earthquakes which originate in the seismic zone
to the north, but it is not an area which is itself seismically active. As stated above, the faults cutting
and bounding the coal measures are old fractures which have become part of the pattern of the
peninsula and there is no evidence of recent activity along these faults.
Incidence of Major Shocks in the Seismic Zone to the North
7.
1803: No reliable data; epicentre probably in northwest part of North Bihar, known to have
been very severe.
1833: Bihar-Nepal: Data meager: great severity, but covering a smaller area than that of the
great earthquake of 1934.
1897: Assam: extreme severity; felt over an area of 1,750,000 sq. miles.
1931: Dubri: Assam moderate severity felt over an area of 360,000 sq. miles.
1934: Bihar-Nepali: extreme severity; felt over an area of about 1,900,000 sq. miles.
Assam Earthquake, 1897
8.
Probably the most severe shock in populated regions in historical times: Reference Mem.
Geol. Surv. Ind., XXIX 1899.
Distance of epicentral region from the confluence of the Barakar and Damodar rivers was
210-346 miles.
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Oldham places the Damodar basin between isoseismals 8 and 9 on the Rossi-Forel Scale,
though it is possible that this estimate should be stopped down to between isoseismals 7 and
8.
The area of extensive damage to buildings is shown on plate 1 of Oldham's Memoir as
penetrating up the alluvial valley of the Damodar as far as Asansol, and it is probable that
such damage as occurred was mainly on buildings situated on thick alluvium, damage rapidly
diminishing where rock outcrops existed.
The earthquake was heard, but not felt, In the coal mines of the Raniganj coalfield. The only
record of damage in the area of the Damodar basin mentioned in the published account was at
Burdwan, where many houses were cracked.
Bihar-Nepal Earthquake, 1934
9.
Reference: Mem. Geol. Surv. Ind., 1934
Distance of epicentral region from the Barakar-Damodar confluence was 190-250 miles.
The area of the Damodar basin lay between isoseismals 6 and 7 of the Mercalli scale.
The shock was not noticed underground in the numerous collieries In Bengal end Bihar, but
there was a considerable disturbance of the underground circulation of water reported after
the earthquake. An increase in the flow of water, amounting to 50 to 500 percent more than
the normal dry-weather load, was noticed in the deeper mines situated down the dip of the
strata, the increase persisting until the ensuing monsoon. In some cases water appeared from
old fissures which had been dry for years.
The actual record of damage to buildings in the neighbourhood does not Indicate great
severity:at Dhanbad old cracks expanded and new cracks developed
at Asansol and Raniganj several buildings were cracked and parapets fell:
at Burdwan cracks were reported in buildings.
Maximum Acceleration to be adopted in Design
10.
The maximum Intensity of shocks hitherto experienced in the Damodar basin is probably
between Isoseismals 7 and 8 Mercalli Scale. It would presumably be safer to allow for shocks of
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GSI-CHQ-17237
magnitude up to isoseismal 8. Interpreted In terms of acceleration this would, according to Mc. Adie,
approximate to about one tenth. It is probable that an earthquake of high intensity would tend to cause
subsidence of the materials of an earthen dam, in the same manner as the slumping which took place
along the free edges of all depressions in alluvial ground during the Bihar-Nepal earthquake of 1934,
the tendency being for elevations and depressions to approach a common level, [Mem. Geol. Surv.
Ind., 73, pp. 38, 39 (1989),]
11.
It is realised that there is such to be done yet in India in regard to seismological research and
the erection of additional seismographic stations. Several proposals were put up before the 1939-45
was in connection with starting a seismological organisation. This is now under the consideration of
the Geophysical Committee sponsored by the Government of India.
12.
The general conclusions from the available evidence are as follows: (a)
The Damodar basin is part of the stable peninsula and has not undergone major
faulting or folding since the Mesozoic era, although it has subsequently bean
subjected to regional uplift.
(b)
Severe shocks do not originate in the Damodar Basin.
(c)
The seismic tone lies 160 miles to the north, and it is from snacks of very great
intensity originating in this zone that the Damodar Basin feels, the fringe effects.
(d)
The attention of the engineers is called to the increase in water circulation in the
deeper coal mines after the 1934 earthquake.
(e)
The effect of such shocks, originating in the north, on an earthen dam say be to cause
settlement.
(f)
The maximum intensity which should be allowed for is probably isoseismal 8
Mercalli Scale, equivalent roughly to an acceleration of one tenth.
Literature
13.
Mem. Geol. Surv. Ind., XXIV (1899) Assam Earthquake of 1897
Mem. Geol. Surv. Ind., 73 (1939)
Bihar-Nepal Earthquake, with a discussion in chapters
8 & 9 on the geological structure in northern India in
relation to earthquakes.
Earthquakes in India" by W. D.
West.
Presidential Address, Indian Science Congress 1937,
with a similar discussion.
Calcutta, 27th February, 1946
London, 24th May, 1959.
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Comment on Dr. Jaikrishna's Map of the Seismic Zones of India
The epicentral data on this Map appear to be derived largely from Gutanperg and Richter, and
it would appear sound to retain the focal-depth data of the original map. The shock off the Makran
coast of 27.11.1945 had a magnitude of 8.0, and was met less than 5.9 as indicated on Dr. Jaikrishna's
map. This acceleration contours are possibly graded somewhat high, and for north-western IndoPakistan it may be suggested that Map. 3 of F.A.O. Report No. 476 (Rome: February 1966) is a closer
approximation to conditions containing in that region.
Sd/- J. B. Auden.
London, 24.5 .59.
NOTE ADDED IN MAY 1959
The above short note, which Is now to be published Symposium, was written 13 years ago
without any intention of my part of subsequent appearance in print. It was a short memorandum
prepared for the engineers of the Damodar Valley Project, as the Corporation was then termed, to
meet the needs of the moment and as a background to Information pass on to the consultants. Through
the courtesy of Mr. P.C.D. Hazra, Superintending Geologist of my former Department, the Geology
Survey of India, the note has been sent to me in England in case I wished to make any comment. The
note, slight though it is, should remain untouched. The following brief comment may be made on
specific points.
1. Introduction
Far more data are now available about tilt incidences or earthquakes in Asia, in particular
from the volume by Gutenber and Richter entitled "Seismicity of the Earth" (1954). Of particular
value is one of the regional maps on the seismicity of Asia, which is reproduced again as fig. 26-13 of
Richter's "Elementary Seismology" published in 1958.
2. Paragraphs
Manifest unconformities within the Gondwana roars, and below the Deccan traps, indicate
that the greater part of the folding and faulting, followed by erosion, as probably connected with lateJurassic to early Cretaceous movements, simultaneous with the for ration of the fray of Bengal, the
eruption of the Rajmahal lavas, and the Lower cretaceous transgression. On the other hand, the postDeccan-trap faulting of the Narmada and Purna valleys, and the post-Eocene faulting seen in the
seismic profiles of the north-central part of the Bengal Basin, demonstrate the persistence of
movements well into the tertiary. While the major strike-slip thrust-fault along the southern flank of
7
GSI-CHQ-17237
the Shillong plateau as certainly active, in rest to the Himalayan orogenesis, until the end of the
Miocene. The area of the Damodar valley dams appears, however, to be seemed the worst of the
tertiary faulting and to be reasonably remote from regions involved in the Himalayan movements.
3. Paragraph 4
It is very probable that a thickness of 6,000 to 7,000 fast for "Gangetic alluvium" is not
unreasonable agnatic if the term be used for Pleistocene to Recent sediments. But the total
sedimentary column, including Siwaliks, and Lower Tertiary, very probably exceeds 20,000 feet in
thickness in parts of the Ganga basin. Even greater thicknesses are involved in the Cretaceous to
Recent succession in the north-east part of the Bengal Basin. The matter was left open by Dr. D.N.
Wadia and myself in our discussion on pp. 133-135 of Memoir, Geol. Surv. Ind., 73(1939), which
deals with one Bihar-Nepal Earthquake of 1934, but we favoured a greater depth than that indicated
by the Geodetic Branch of the Survey of India. Geophysical work undertaken since 1950 in north-east
Indo-Pakistan definitely supports one conception of deep basins.
4. Paragraph 5
The relationship between areas of seismic instability active downwards and massive gravity
anomalies is less confident perhaps than was supposed in 1946. The major earthquakes of 1897 in
Assam and 1819 in the Rann of Katch do not fall into such a scheme, and the environmental
conditions of earthquakes are certainly complex. While it is true, for example, than the zones of large
negative gravity anomalies along the present island areas are also zones of shallow earthquake
epicenters, such features do not correspond to the present-day deadest ocean trough and most recent
downwarps. These meters were discussed by the writer on pp. 111-131 of Proc. 38th Indian-Science
Congress, Part, II, (1951).
5. Dr. Jaikrishna's map of the seismic ones of India.
The epicentral data on this map appear to be derived largely from Gutenberg and Richter, and
it would appear sound to retain tae focal-depth data of the original map. The smock off the Makran
coast of 27.11.1945 and a magnitude of 8.3, and was not less than 5.9 as indicated on Dr. Jaikrishna's
map. His acceleration contours are possibly grained somewhat high, and for north-western IndoPakistan it may be suggested that map. S of F.A.O. Report No. 476 (Rome: February 1956) is a closer
approximation to conditions obtaining in that region.
Sd/- J.B. Auden
London, 24.5.59.