Effects of the December 2004 Indian Ocean Tsunami on the Indian Mainland

Effects of the December 2004 Indian
Ocean Tsunami on the Indian Mainland
Alpa Sheth,a… Snigdha Sanyal,b… Arvind Jaiswal,c… and Prathibha Gandhid…
The 26 December 2004 tsunami signi?cantly affected the coastal regions
of southern peninsular India. About 8,835 human lives were lost in the tsunami
in mainland India, with 86 persons reported missing. Two reconnaissance
teams traveled by road to survey the damage across mainland India.
Geographic and topological features affecting tsunami behavior on the
mainland were observed. The housing stock along the coast, as well as bridges
and roads, suffered extensive damage. Structures were damaged by direct
pressure from tsunami waves, and scouring damage was induced by the
receding waves. Many of the affected structures consisted of nonengineered,
poorly constructed houses belonging to the ?shing community.
DOI: 10.1193/1.2208562
MAINLAND AREAS SURVEYED
The Great Sumatra earthquake of 26 December 2004 did not cause shaking-induced
damage to the mainland of India, but the consequent Indian Ocean tsunami had a sig-
ni?cant effect on the southern peninsular region of India Jain et al. 2005 . The tsunami
severely affected the coastal regions of the eastern state of Tamil Nadu, the union terri-
tory of Pondicherry, and the western state of Kerala. Two reconnaissance teams under-
took road trips to survey the damage across mainland India. One team traveled from the
Ernakulam district in Kerala, then continued south along the west coast to the southern-
most tip of mainland India Kanyakumari and up along the east coast to Tuticorin. The
coastal journey was then resumed from Nagapattinam, moved northward, and concluded
at Chennai. The second team traveled from Vishakhapatnam in Andhra Pradesh along
the coast down to Chennai Figure 1 . This paper is based on observations made during
these trips.
SEISMICITY OF THE REGION
The southern peninsular region comprising Kerala and part of Tamil Nadu on the
west coast and the rest of Tamil Nadu, Andhra Pradesh, and Pondicherry on the east
coast is a region of low-to-moderate seismicity. The area lies in the Stable Continental
Region, which is not believed to be exposed to the hazard of strong earthquakes. The
strongest known earthquake in the region M = 6.0 occurred on 8 February 1900 near
Coimbatore and had a maximum intensity of VII. There was an earthquake of magnitude
a Vakil Mehta Sheth Consulting Engineers, Mumbai, India; E-mail: alpa_sheth@vakilmehtasheth.com
b Department of Civil Engineering, Indian Institute of Technology Kanpur, Kanpur, India
c EON Designers Consulting Engineers, Secunderabad, India
d Department of Civil Engineering, Indian Institute of Technology Madras, Chennai, India
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Earthquake Spectra, Volume 22, No. S3, pages S435–S473, June 2006; © 2006, Earthquake Engineering Research Institute

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A. SHETH, S. SANYAL, A. JAISWAL, AND P. GANDHI
Figure 1. Reconnaissance team survey routes covering the mainland.
Map courtesy of
C. V. R. Murty
M = 5.8 on 31 March 1843 in Bhadrachalam, Andhra Pradesh. Earthquakes of magnitude
M = 5.5 1959 and M = 5.2 1967 occurred at Ongole, Andhra Pradesh. Figures 2 and 3
indicate the broad shield sources and tectonic features of the peninsular shield of India
Rao 1970, Reddy 2004 .
In the last decade, the area has experienced earthquakes of magnitude 5.0 and lower.
The most recent signi?cant earthquakes were M = 5.0 2000 and M = 4.8 2001 , both of
which occurred in the same area south of Idukki in central Kerala.
TSUNAMI HISTORY
Prior to 26 December 2004, there was no known record of tsunamis on the southwest
coast of India. The west coast experienced a tsunami due to the M = 8.1 earthquake of 27
November 1945 with an epicenter 100 km from Karachi, Pakistan, but the effects were
felt only up to Karwar, 250 km north of the Kerala border. The southeast coast, however,
has experienced tsunamis earlier. The earliest record dates back to 31 December 1881,
when a tsunami 1 m high was recorded in Chennai. It was caused by an earthquake of
M = 7.9 below Car Nicobar Island. The August 1883 eruption of the Krakatoa volcano in
Indonesia caused 2-m-high tsunami waves in Chennai. On 26 June 1941, an M = 8.1
earthquake occurred in the Andaman archipelago, which triggered a tsunami of about

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EFFECTS OF THE DECEMBER 2004 INDIAN OCEAN TSUNAMI ON THE INDIAN MAINLAND
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Figure 2. Tentative broad shield sources in the peninsular shield for India source: I. Gupta .
1 m in the city of Chennai. While some scientists have estimated deaths of over 3,000
people along the east coast of India in the 1941 tsunami, there are no reliable data on the
number of deaths, if any, due to that tsunami Murty and Ra?q 1991, Bilham 2005 .
GEOLOGY OF COASTAL MAINLAND INDIA
The structure of peninsular India is complex because of the varied geology, faults,
and fractures. More than a third of this area is covered by basaltic ?ows called the Dec-
can Trap. The thickness is 2 – 3 km on the west coast and decreases toward the east. The
rest of the peninsula is covered by Precambrian rocks and sedimentation formation of
later eras Figures 2 and 3, Gupta 2005 .
The soil along the west coast of Kerala and Tamil Nadu is primarily sandy, underlain
by soft clay layers. Further south, away from the coastline, the land slopes steeply up-
ward and is rocky. The coastal strip of southwest Tamil Nadu is rich in minerals. There

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A. SHETH, S. SANYAL, A. JAISWAL, AND P. GANDHI
Figure 3. Major evolutionary units and associated tectonic features in peninsular India source:
I. Gupta .
has been signi?cant dredging in the mineral-rich Kanyakumari coast, and this has led to
a change in the topology of the area by ?attening some areas and making them more
vulnerable to a tsunami.
The east coast has rich alluvial soil in the river deltas and along the coast. The other
predominant soils in this region are clay, loam, and red laterite. Along the Andhra
Pradesh coast, the soil is also rich alluvial with rocky outcrops but, in certain pockets of
the delta areas of Godavari, the soil is deep friable, well-drained sandy loam.
WAVE ARRIVAL TIME
The tsunami waves arrived ?rst on the east coast. Details of the tide gauge levels at
the ports of Kochi, Tuticorin, Chennai, and Vishakhapatnam are shown in Figures 4–7

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EFFECTS OF THE DECEMBER 2004 INDIAN OCEAN TSUNAMI ON THE INDIAN MAINLAND
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Figure 4. Tide gauge data for Kochi Port source: NIO .
NIO 2005 , respectively. As can be seen from the tide gauge data, the tsunami waves
?rst reached Kochi at 11:10 A.M., Tuticorin at 9:57 A.M., and Chennai and Vishakhap-
atnam at 9:05 A.M. all Indian Standard Time .
Most locations experienced 3–5 waves, details of which are described elsewhere in
this paper.
GENERAL FEATURES OF TSUNAMI EFFECTS
The tsunami effects varied greatly across different parts of the coast according to the
number of waves experienced, inundation distance and height of the waves, and density
of the area—as well as topological and geographical features that made some areas more
vulnerable than others Table 1 . The number of lives lost was also in?uenced by the
proximity of habitats to the coastline, exposure to previous disasters, and the local di-
saster management capability. These are discussed in detail in this paper. The affected
areas are discussed in three parts, which are based on their geography:

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A. SHETH, S. SANYAL, A. JAISWAL, AND P. GANDHI
Figure 5. Tide gauge data for Tuticorin Port source: NIO .
•
Southwest coast: this comprises Kerala, which suffered signi?cant damage that im-
pacted the largest number of people of any affected state but suffered relatively lower
loss of life, and the Kanyakumari district of Tamil Nadu, which suffered heavy loss
of life due, to a large extent, to human-created local topographical features.
•
Southeast coast: this comprises the rich alluvial delta region of the Tamil Nadu coast
and Pondicherry, which experienced maximum wave heights and recorded the maxi-
mum loss of life and damage in mainland India.
•
East coast: this comprises Andhra Pradesh, which suffered marginal damage and loss
of life.

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EFFECTS OF THE DECEMBER 2004 INDIAN OCEAN TSUNAMI ON THE INDIAN MAINLAND
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Figure 6. Tide gauge data for Chennai Port source: NIO .
GEOGRAPHIC AND TOPOLOGICAL FEATURES AFFECTING TSUNAMI
BEHAVIOR ON THE MAINLAND
SOUTHWEST COAST OF MAINLAND INDIA
Kerala
The state of Kerala experienced tsunami-related damage in three southern districts,
Ernakulam, Allapuzha, and Kollam Table 2 , due to the diffraction of the waves around
Sri Lanka Murty 2005 . The southernmost district of Thiruvananthpuram, however, es-
caped damage. This was possibly due to the wide turn of the diffracted waves at the pen-
insular tip, thereby missing Thiruvananthpuram.
The coast of Kerala is relatively ?at and practically at sea level. Throughout the
coastal areas of Kerala, and especially in the affected districts, are long stretches of
lakes, lagoons, and ponds connected by a network of canals called “backwaters” kay-
als . The backwater routes date from centuries ago and have long been used for all trans-

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A. SHETH, S. SANYAL, A. JAISWAL, AND P. GANDHI
Figure 7. Tide gauge data for Vishakhapatnam Port source: NIO .
portation needs, in particular for trade in coconut, rubber, rice, and spices. Today, these
waterways link remote villages and islands to the mainland.
Major damage in Kerala occurred in two narrow strips of land bound on the west by
the Arabian Sea and on the east by a network of backwaters.
Ernakulam District
The northern strip comprises the island of Wypeen north of the city of Kochi in the
Ernakulam district. It is about 20 km long and has a maximum width of about 3 km.
Edavanakkad is a prominent ?shing village in Wypeen Island that suffered maximum
damage. Fifty houses were completely destroyed Figure 8 , and 350 houses were dam-
aged in this village, which lost 5 lives. The coast in this area had a seawall along most
parts, with openings in the seawall for the passage of boats. Damage due to the tsunami
was more intense in the areas that were not protected by the seawall. At Edavanakkad,
the seawall was about 100 m from the shoreline and was made of random loose rubble

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EFF
ECTS
OF
THE
Table 1. Tsunami effects in mainland India source: Ministry of Home Affairs
DECEMBER
Water
Coastal
penetra-
Average
Max.
State or
length
tion into
height of
runup
Number of
Population
Dwelling
2004
union
affected
mainland
tsunami wave*
height
Human lives lost,
villages
affected
units lost
territory
km
km
m
m
per district
affected
millions
or damaged
INDIAN
Kerala
250
0.5?1.5
3?5
3.4
131
Kollam
187
1.3
17,381
35
Allapuzha
OCEAN
5
Ernakulam
Tamil Nadu
100
0.2–2.0
3–10
4.5
824
Kanyakumari
376
0.9
128,394
TSUNAMI
west coast
Tamil Nadu
800
0.4–1.5
2–10
5
6,051
Nagapattinam
east coast
612
Cuddalore
ON
128
Kancheepuram
THE
206
Chennai
144
Other
INDIAN
Pondicherry
25
0.2–2
5–10
4
484
Karaikal
33
0.04
10,061
max. at
107
Pondicherry
MAINLAND
Karaikal
Andhra
985
0.2–1.0
4
2.2
27
Krishna
301
0.2
1,557
Pradesh
20
Nellore
35
Prakasham
23
Other
* Based on survivors’ estimates
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A. SHETH, S. SANYAL, A. JAISWAL, AND P. GANDHI
Table 2. Characteristics of tsunami waves in Kerala
Wave
Inunda-
Wave
travel
tion
No. of
Arrival time
height distance
height
Special
Recession of
District
waves
of waves
m
m
m
features
water
Ernakulam
3
First wave at
4
1,000
2.4
Water level Water receded
11:10 A.M.,
rose from
about 150 m into
second wave at
10:30 A.M. sea after ?rst wave;
1:30 P.M.,
when water re-
third wave at
ceded, it took a lot
1:45 P.M.
of sand and
scoured roads.
Allapuzha
3
First wave at
4
1,000
3
—
Water receded
and Kollam
11:30 A.M.,
500 m before ?rst
second wave at
wave.
1:40 P.M.,
third wave at
1:45 P.M.
masonry comprising large boulders, some of which were displaced by the tsunami. The
houses in Edavanakkad were built about 15 m from the seawall. The plinth height was
about 0.6 m from mean sea level.
Allapuzha and Kollam Districts
The other strip most affected in Kerala is a shoestring isthmus south of the city of
Allapuzha about 40 km long and extending from Trikunnapuzha in the Allapuzha dis-
trict to Karunagapalli in the Kollam district. The strip has a maximum width of less than
1 km and is bound by the open coast on the west and Kayanakulam Lake and backwa-
ters on the east. A small opening in the strip connects the lake to the sea. The width of
the land strip is less than 0.5 km at many places. As a result, the tsunami waves lashed
over the entire strip of land, traveled across the backwaters, and rolled onto the opposite
bank.
Two areas that bore the brunt of the tsunami in the region were Arattupuzha in the
Allapuzha district and the Alappad panchayat in the Kollam district Figures 9 and 10 .
These areas are the gatekeepers of the opening where the lake disgorges into the sea. The
villages are densely populated with a density of 2,652 per km2, versus the state average
of 762 per km2 on both sides of the coastal road that barely separates the lake from the
sea. The isthmus has no intermediate bridge connection to the mainland and is con-
nected to it only at the two ends. The area thus has to depend on boats for safe exit in
times of emergency. The largest number of casualties 130 in Kerala was reported from
the densely populated Alappad panchayat including the villages of Cheriya Azhikkal
and Azhikkal . In the village of Arattupuzha in the Allapuzha district, the death toll was
28. The seawall, where it existed, was dislodged and did not exist in many places along

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