1930 dhubri earthquake

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Dhubri, Assam,India. 1930 Earthquake

Introduction

Northeastern Region, including Assam is prone to natural disasters like earthquake,floods, landslides, cyclone and occasional drought .The population in the NER of

India- particularly Assam is subjected to perennial floods, landslides andenvironmental degradations. Disasters cause sudden disruption to the normal life of

a society and cause enormous damage to property to a great extent.

Earthquake occurance

Wedge between two plate collision boundaries, the Himalayan in the north and the

Indburman in the east, the Northeastern region is one of the seismically most activeregions of the world .With complex tectonic and geology set up of the region and

intense continental convergence of the northward moving Indian plate at the rate of20+03mm/year can produce earthquakes of magnitudes 8 and above every few

hundred years. Consequently it has been under continual threat from majorearthquakes and the subject being seriously debated in national and international

forums.The two great earthquakes of magnitudes 8.7 in 1897 and 1950 arememorable events in the annals of earthquake history of the world. These

earthquakes have been so intense that the rivers changed their courses, ground

elevations immensely affected. Besides as many as twenty destructive earthquakesof magnitudes 6~7 rocked this region during the past century.

The Impact

Date 3rd July 1930

Epicenter: 3.9 kms NNW of Dabigiri (Meghalaya), India

Latitude: 25.800N

Longitude: 90.200E

Origin Time: 21:03:34.4 UTC / 03:23:34.4 ISTMagnitude: Ms 7.1

A large portion of northeastern India was, during the early hours of the morning

of 3rd July, 1930, affected by seismic activity. Centeringnear the northwestern

end of the Garo hills and adjoining valley of the Brahmaputra river, this earthquakewas attended with disastrous results in northern Bengal and in western Assam, and


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was felt very distinctly over a wide area, extending from Dibrugarh and Manipur in

the east, to Chittagong and Calcutta in the south, to Patna in the west, and beyondthe frontiers of Nepal, Sikkim and Bhutan in the north.

The sensible zone of the earthquake includes widely contrasting types of

topography and geology. The epicentral tract, in the vicinity of the town of Dhubriadjoining the Brahmaputra river, and the areas badly affected to the northwest,

west and south, comprise a portion of the alluvial plain country which is traversedby the lower courses of the Brahmaputra and Ganges rivers and by their numerous

tributaries. To the north, in the outer part of the sensitive zone, rise the outer rangesof Nepal, Darjeeling, Sikkim and Bhutan Himalayas. To the NE and ENE of

Dhubri, the higher reaches of the Brahmaputra river traverse a wide alluvial valley,

narrowing eastward and dotted by a number of prominent hills, whilst the moredistant southeastern areas include the alluvial plains of Mymensingh and Sylhet.

Between these two latter tracts, east of the Brahmaputra, are the jungle-clad ridges

of the Garo hills rising to well over 4,000 feet; these continue eastwards to link upwith the Khasi and Jaintia hills of the Shillong plateau.Fortunately, from a point of view of estimating the intensity of the earthquake

shock, a large portion of the epicentral and adjoining tract is traversed by the

Eastern Bengal Railway line, the stations and railway cantonments along which,being built wholly of brick masonry of a fairly standard type have afforded very

useful data in demarcating the isoseists of the main shock. These populated areas

comprise the alluvial tract lying between the Ganges and Brahmaputra rivers. Tothe south and east of the Brahmaputra, however, within the jungle covered uplands

of the Garo hills, the town of Tura, lying a short distance outside the epicentral

tract, and the still more distant station of Goalpara, are the only places of sufficientsize and type from which the intensity of the shock can be gauged. With the

exception of Rowmari and Manikarchar, where several brick buildings exist,

the villages are mainly constructed of light bamboo or ikra (a reed grown in

the locality) upon which the vibrations of the earths crust, resulting from the

main shock, would have left few recognizable imprints.

In these earlier investigations, seven degrees of intensity lying within their

isoseists, were defined as follows:

1) The first and innermost isoseist includes all places where the destruction of

brick and stone buildings was practically universal.2) Those places where damage to masonry or brick buildings was universal, often

serious, amounting in some cases to destruction.


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3) The third, those places where the earthquake was violent enough to damage all

or nearly all brick buildings.4) Places where the earthquake was universally felt, severe enough to disturb

furniture and loose objects but not severe enough to cause damage, except in a few

instances, to brick buildings.5) The fifth, those places where the earthquake was smart enough to be generally

noticed but nor severe enough to cause any damage.6) All those places where the earthquake was only noticed by a small proportion of

people who happened to be sensitive and being seated or lying down werefavourably situated for observing it.

Damages to the structures, railway station.

All buildings located on made-up ground, in-filled tanks, ditches, etc, suffered

acutely. In several instances, where the structure was founded partly on the naturalalluvium and partly on old excavation that had been refilled with earth, a large

crack occurred along the junction of the infilling and the alluvium, and that portionof the building located on the former subsided to the extent of over a foot.

Amongst the brick-masonry structures, the four walls of the house of Rai

Bahadur Biraj Mohan Dutt suffered partial or total collapse; the tilted roof however

remained supported at certain points by pillars enabling the owner to escape

unhurt. The old rectangular treasury building situated near the river was badlycracked and condemned. A tall conical shaped Observatory located on the riverbank was also badly cracked in the upper portion. Near the center of the town the

two-storey house and compound of Mr. Rabindra Narayan Chaudhuri suffered

considerably; several brick walls and the brick-masonry pillars at the gate-entrancecollapsed. Another two-story house of Mr. Sourindra Narayan Chaudhuri, was

badly fissured, portions of the window and door arches were dislodged, while abrick-masonry partition in the upper story of the building collapsed. Several E-W

cracks along with dislodged bricks were noted in the recently constructed

extension of the Dhubri Charity hospital; two old pakka quarters in the hospital

compound were also badly damaged. The Bara Musjid, a brick building withgalvanized iron roof, suffered partial collapse. The railway station buildings,constructed of somewhat better quality materials, escaped with a few cracks. The

police lines cracked in several places and walls collapsed.


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Of the Semi-pakka structures, the Bar Library, situated on the river bank,

suffered considerable damage; the lower brick portion was badly cracked andpartially collapsed, while the upper split bamboo with plaster was severely

affected, particularly at the river end. The floor of the old buildings of the

Government High School for boys was badly cracked; the ikra superstructure andsupporting posts being in places shattered and shaken out of the vertical. N-S crack

along with partial subsidence occurred in the new nearby school buildings. Severalopen N-S cracks across the floor noticed in a Government Hostel for criminal

tribes. Of several houses situated in Dufferin road, the floor and basal three-footmasonry portions were badly damaged; here houses founded partly on in-filled

tank subsided up to 3 feet, the superstructure being badly damaged. Buildings

situated in Keshugaon road, being founded on an old in-filled ditch, the frontportions resting on the made-up ground had sunk considerably, resulting in large

fissures across the lower pakka portions and distortion of the upper. The plinth and

masonry floor of Dhubri Charity hospital was traversed by a number of WNWtrending cracks.

At Gauripur, about 4 miles west of Dhubri, the railway station was seriously

affected by the main shock, the ground up-heaving in the vicinity of thebookingoffice, resulting in large cracks in the floor and walls of the building. At

Gauripur village a number of buildings were severely damaged. Statesman on11

thOctober, 1930 reports: There are 5 reinforced concrete structures in Gauripur,

of which 4 are 2-storied and one single-story. One, built on a small hillock about

20 years ago, has suffered to some extent, narrow cracks appearing along the iron

posts. All heavy furniture in this building fell down; all electric pendants werebroken and the papering on the walls and decorated ceiling pealed off, but still the

building was not materially damaged. The other four buildings were undamagedthough in one of them a big fissure with sand and water spouting was formed in the

base.

Geology of the Area

The greater portion of the northwestern end of the Garo hills, in the vicinity of the

epicenter of the main Dhubri earthquake, is composed of ancient metamorphicstrata. These continue eastwards into the Shillong plateau and recur in the area eastof Nowgong. These gneissic rocks are overlain by a variety of sediments ranging

from Mesozoic to Tertiary in age. At the southern edge of the plateau thesesediments are often inclined at steep angles and have been affected by numerousfaults and thrusts.


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The low ground around the Brahmaputra river and to the south of the plateau tract,

these beds pass beneath the soft alluvial deposits that spread westwards into theIndo- Gangetic plain. Similar alluvial deposits extend north of the Brahmaputra to

near the foothills of the Himlayas, where the outermost strata include Tertiary and

Gondwana sediments, steeply folded and striking in a general E-W direction. AtDhubri, and higher up this Brahmaputra valley, several inliers of the ancient

metamorphic strata crop out among the recent alluvium.It appears that the Assam plateau topography originated in late Tertiary to sub-

Recent times as a result of earth-movementssharp flexures accompanied byfaulting along its southern and western extremities. With the relative advance of

the Himalayas towards the south, also during the late to post- Tertiary, lines of

fracture were doubtless formed to the north of the present plateau, separating theancient gneisses, from the more recent sediments of the Himalayan foothills. The

low-lying areas immediately to the north, west and south of the Garo hills and the

Shillong plateau are, therefore, in all probability zones of structural weakness,liable to earth-movement.The epicenter of the Dhubri earthquake lies near the junction of the northern and

western of these zones, while the epicenters of certain of the more severe

aftershocks appear to have been located further up the Brahmaputra valley withinthe northern zone of instability.

Seismograph Records

Epicenter:From field observations it has been possible to fix the position of theepicenter of the main earthquake within narrow limits. This position, a few miles

south of Dhubri, is at 25 57 N: 90 00 E. Established on field-evidence alone,

this point agrees quite well with that indicated by seismograph records.

Depth of Focus:Regarding the depth of the focus, little evidence is apparent. Norapid decrease in intensity is observed in the vicinity of the epicenter, the area

included within Isoseists 2 and 3 being of a varying radius of 35 to 50 miles. Thismight suggest a focus of very considerable depth; but the data are indeed very

inconclusive.Foreshock:There appears to be no evidence of accessory shocks preceding the

main Dhubri earthquake. Reports indicate that the disturbance took place suddenlyafter a considerable period of quiescence of seismic activity in the region.Aftershocks:During the 21 hours that succeed the main earthquake, a total of

54 separate shocks were recorded. Almost all of these were experienced at Dhubri;a number were felt at Gauhati, while the one recorded at about 5-49 AM was felt atmuch greater distances from the Dhubri epicenter. On 4 and 5 July 1930, 37 and 34


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shocks respectively were recorded. A large number of these appeared to have

originated near the main earthquake others not registered at Dhubri suggest anorigin higher up the Brahmaputra valley in the vicinity of Gauhati. After 5 July the

number of aftershocks decreased very considerably from 5 shocks/day at the end if

first week to 3 shocks/ day in the final week of July, 1930. This gave a total of 223aftershocks during the month of July of which more than one-half occurred during

the three days that followed the main shock.The shock that occurred about 12-37 on 11th July, 1930 was felt at such distant

places as Calcutta in the south and Manipur in the east. 35 aftershocks were 15recorded in August 1930 followed by 17 during September and only another 4 up

to 2nd July 1931; a total of 294 events were recorded during the first 12 months.

During the year 3rd July 1931 to 2nd July 1932 the monthly total varied usually upto 5, though in January 1932 nine shocks were reported. Several of these appear to

have centered up the Brahmaputra valley to the east of the main epicenter.

A fairly severe quake was experienced over a large area at about 21- 36 on 24thMarch 1932. The total number of shocks reported during the second year was 35.

In August 1932 there appears to have been a revival of seismic activity. A fairlysevere shock occurred at about 11-35 on 1st August, and a still more acute one at


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about 10-10 on the morning of 14th. This latter shock may have originated high up

the Brahmaputra valley in the vicinity of Dibrugarh or Digboi. Two less severeshocks also originating in the same locality occurred later on 14th August. The

total for that month was 10. A second revival of seismic activity occurred on 10th

November, 1932, when 12 minor shocks were reported from Gauhati andneighbouring stations. Others followed, principally around Gauhati, during the

remainder of the month, bringing the monthly total for November up to 25. Thetotal again fell during the next three months but rose again to nine during March

1933. During March to June 1933 majority of the aftershocks appear to haveoriginated near the main Dhubri epicenter. Total number of aftershocks for the

third year following the main disturbance was 68 almost double the number

reported during the second year.

1.Entrance Hall of the

palace,Cooch Bihar

2.Vice presidents

house,Cooche Bihar

3.Barrie Club

4. Monument in new

graveyard,Cherrapunji

5.Mission building,Tura

6.Marble cross,Tura


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Map showing the impact of the earthquake

1930 Dhubri.

Zone V.


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Some photos


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1930 dhubri earthquake

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