18 years ago, we learned what was Tsunami, was it the first time Chennai saw Tsunami? No, Lets see the historic Tsunami

Tsunamis usually are associated with dip-slip type earthquakes rather than with strike-slip type earthquakes and the earthquake depth have to be shallow and not too deep. The earthquakes in the Andaman region are associated mainly with strike-slip type of faulting. It is believed that these events probably occur along the north-south trending West Andaman fault. Upto the 26 December 2004, the earthquake of 26 June 1941 had been the strongest ever recorded in the Andaman and Nicobar Islands, in generating a destructive Tsunami. The 1941 event was the last great earthquake in the Andaman and Nicobar Islands. The 1881 Nicobar Islands earthquake was the only other event of comparable magnitude.
(i). Strike-slip faults indicate rocks are sliding past each other horizontally, with little to no vertical movement. Both the San Andreas and Anatolian Faults are strike-slip. These rarely dont generate Tsunamis.
(ii). Dip-slip Normal faults create space. Two blocks of crust pull apart, stretching the crust into a valley. The Basin and Range Province in North America and the East African Rift Zone are two well-known regions where normal faults are spreading apart Earth’s crust.  These Dip slip types are the ones which generate Tsunami when they are in very high magnitude when happens in shallow depth.
(iii). Dip-slip Reverse faults, also called thrust faults, slide one block of crust on top of another. These faults are commonly found in collisions zones, where tectonic plates push up mountain ranges such as the Himalayas and the Rocky Mountains.
However, Earthquakes with magnitude 8.0 or greater (such at the 1941 and 2004 events) associated with “dip-slip” types of vertical crustal displacements along thrust faults have the potential of generating very destructive tsunamis in the entire Bay of Bengal Region the Andaman Sea and the Indian Ocean. It can be observed that once in every 60 years statistically, there has been Major Tsunami in the India Coast
Now lets the past events which have generated Tsunamis in India. I have compiled this from various authors, NoAA archives and other media sources.  The credits of the articles belong to them as applicable. I have just consolidated the information from various official sources.

April 2, 1762

Date: 2 April 1762 time 5:00 pm
Epicentre: Arakkan Sea (Burma)
Earthquake Magnitude: 8.8
Deaths in India due to Tsunami: 200+

Tsunami wave of 1.83 mts hit Bangladesh and West Bengal coast. The water in the Hoogly River in Kolkata rose by 2 mts. The rise in the water level at Dhaka was so sudden that hundreds of boats capsized and many people were drowned. This is the earliest well-documented tsunami in the Bay of Bengal.

June 16, 1819

Date: 16 June 1819 time 06:15 pm
Epicentre: Rann of Kutch
Earthquake Magnitude: 7.7
Deaths in India due to Tsunami: 1543

The tsunami flooded the Great Rann immediately after the earthquake. The fort at Sindri was destroyed by the earthquake and then partly submerged by the tsunami, “forcing survivors to climb to the top of the ruins. A tsunami from the Arabian Sea surged across the Rann and sand vents in the region were active to a height of 2-3 m.

June 19, 1845

Date: 19 June 1845
Epicentre: Rann of Kutch
Earthquake Magnitude: 6.3
Deaths in India due to Tsunami:  N/A

The sea rolled up the Koree (the eastern) mouth of the Indus, overflowing the country as far westward as the Goongra river (a distance of twenty English miles), northward as far as a little north of Veyre (forty miles from the mouth of the Koree), and eastward to the Sindree Lake. Most of the habitations throughout the district must have been swept away, the best houses in Scinde being built of sun-dried bricks, and whole villages consisting only of huts made of a few crooked poles and reed mats. Of Lak nothing was above water but a Fakeer’s pole (the flagstaff always erected by the tomb of some holy man); and of Veyre and other villages only the remains of a few houses were to be seen.

October 31, 1847

Date: 31 October 1847
Epicentre: Near Nicobar Islands
Depth: N/A
Earthquake Magnitude: 7.9
Deaths in India due to Tsunami: N/A

Tsunami in Little Nicobar and Kondul Island was inundated.

August 19, 1868

Date: 19 August 1868
Epicentre: Near Andaman Islands
Depth: N/A
Earthquake Magnitude: 7.5
Deaths in India due to Tsunami: N/A

Tsunami at Port Blair of 4 mts was reported.

December 31, 1881

Date: 31 December 1881 Time 7:49 am
Epicentre: Near Nicobar Islands
Earthquake Magnitude: 7.9
Deaths in India due to Tsunami: Nil

Entire East coast of India including Andaman & Nicobar coast was affected by tsunami from Sri Lanka to Ganges delta. Tsunami amplitudes:  Nagapattinam 1.22 mts (highest in Indian coast), Port Blair 0.92 mts, Car Nicobar 0.72 mts, Sagar Island 0.30 mts. Madras was first hit by Tsunami in the east coast. The tsunami was recorded by eleven of a series of continuous tide gauges around the Bay of Bengal that had been deployed by the Great Trigonometric Survey of India. The ten gauges on the Indian mainland were synchronised using a telegraph to Madras (Chennai) time, while that at Port Blair was set by a chronometer linked to local time.

Distance from Epicentre:

Car Nicobar – 81
Port Blair – 351 kms
Chennai – 1419 kms
Vishakapattinam – 1415 kms
Pamban – 1456 kms

August 27, 1883

Date: 27 August 1883
Epicentre: Volcano in Indonesia (Krakatau)
Depth: N/A
Earthquake Magnitude: N/A
Deaths in India due to Tsunami: Not known (worldwide 36000)

The tsunami induced by the massive Krakatoa volcanic explosions in Indonesia in August 1883, is the biggest in known history and  killed nearly 36,000 people, also had an impact on the east coast of India. A recent numerical simulation of the tsunami by a research group comprising two scientists from Korea, one from Japan, and one from Russia suggests that the waves should have affected the Andaman and Nicobar islands, the eastern coasts of Sri Lanka and India and parts of the western Indian coast as well, somewhat similar to what has happened in the tsunami of 2004. The results of their simulation appears to match fairly well with the original tide gauge data of the wave heights at various points, which they have been able to retrieve from archival sources. The analysis shows that wthe tsunami waves arrived about 4 hours after the event. The source of the waves was about 2,440 km from the Indian coast. Unofficial accounts have placed the wave height at Madras to be about 2 mts.

Tide-gauges records at many ports in India (Madras and Nagapattinam) show the sea level disturbances. An extraordinary phenomenon of tides was witnessed at Bandra near Bombay (4500 km and 11 h from the Krakatau), the reflux of the tide went to the sea in an abrupt manner and with great impetus, and the fish, not having sufficient time to retire with the waves, remained scattered on the seashore and dry places, and the fishermen, young and old, had a good and very easy task to perform in capturing good-sized and palatable fish, without the least trouble or difficulty, to their hearths’ content, being an extraordinary event never seen or heard of before by the old men; but suddenly the flux came with a great current of water, more swift than horse’s running. The tide was full as before, and this flux and reflux continued two or three times, and at least returned by degrees as usual.

June 26, 1941

Date: 26 June 1941, Time 10:22 pm
Epicentre: Andaman Sea near Middle Andaman Island
Depth: 15.0 km
Earthquake Magnitude: 8.0
Deaths in India due to Tsunami: 3000-5000

The tsunami did hit the east coast of India, damaging masonry structures and property in places like Madras. The number of dead in this event is not known. It is believed that nearly 5,000 people were killed by the tsunami on the east coast of India. Local newspapers are believed to have mistaken the deaths and damage to a storm surge, however, a search of meteorological records does not show any storm surge on that day on the Coromandel Coast. While some believe that there may not have been any dead as the magnitude has probably been overestimated, C.P. Rajendran, a scientist at the Centre for Earth Science Studies (CESS), Thiruvananthapuram, an expert in the seismology of the Andamans, believes that the value may actually be an underestimate. According to him, the rupture length of over 800 km suggests a magnitude higher than what has been calculated on the basis of seismic waves.

The Andaman and Nicobar islands were under Japanese occupation at that time, so data from there was not available. However, according to Rajendran, for some reason, reliable tide gauge data of the east coast for events of that period are also apparently not available with the Survey of India. In fact, no records of the 1941 tsunami seem to have survived, although unofficial accounts put the toll as 3,000 – 5000 dead. the estimated tsunami heights were 1.25 m along the east coast of India such as Madras.

November 28, 1945

Date: 28 November 1945, Time 02:57 am
Epicentre: South South West of Pasni in Balochistan in Makran Coast
Depth: 15.0 km
Earthquake Magnitude: 8.1
Deaths in India due to Tsunami: 30

West coast of India was affected by Tsunami. The sea wave swept the whole of the Arabian sea coast causing casualties as far away as Bombay, and producing noticeable effects at Karwar about 1,000 miles from the epicenter. Bombay recorded 1.98 mts while Karachi recorded 1.37 mts. The tsunami reached as far south as Mumbai. Bombay Harbor, Versova (Andheri), Haji Ali (Mahalaxmi), Juhu (Ville Parle) and Danda (Khar). In Bombay the height of the tsunami was 1.8 meters. Fifteen (15) persons were washed away. According to reports the first wave was observed at 8:15am (local time) on Salsette Island in Mumbai. Five people died at Versova (Andheri, Mumbai), and six more at Haji Ali (Mahalaxmi, Mumbai), Several fishing boats were torn off their moorings at Danda and Juhu. A most remarkable aspect of the 1945 tsunami is that its main waves were significantly delayed (avg 2.5 h) with respect to the earthquake.

Distance from Epicentre:

Kutch – 712 km
Bombay – 1190 km and first wave reached in 2 hrs and 37 mins
Karwar – 1583 km

September 13, 2002

Date: 13 September 2002, Time 01:06 am
Epicentre: East of Cadell Point, North Andaman Island
Depth: 21.0 kms
Earthquake Magnitude: 6.5
Deaths due to Tsunami in India: Nil

A local tsunami damaged several shops at Ariel Bay on Middle Andaman and a lighthouse on East Island. The tsunami was observed on Ross and Smith Islands.

Distance from Epicentre:

Ariel Bay, Andaman – 27 kms,
Smith Islands, Andaman – 65 kms
East Islands, Andaman – 67 kms
Ross Islands, Andaman – 154 kms

December 26, 2004

Date: 26 December 2004, Time 6.29 am IST
Epicentre: North of Aceh, Indonesia
Depth: 10 kms
Earthquake Magnitude: 9.1
Deaths due to Tsunami in India: 16269

A Teletsunami (distant tsunami) is a tsunami that originates from a distant source, defined as more than 1,000 km away or three hours’ travel from the area of interest affected Andhra Pradesh, Tamil Nadu, Kerala, Lakshwadeep, Andaman & Nicobar Islands. The Tsunami heights at various stretches are as follows –

10–12 mts at Malacca (Car Nicobar Island) and at Hut Bay on Little Andaman Island
6.6 mts at Wandoor Beach in South Andaman Island
5.0 mts in coastal districts such as Nagapattinam in Tamil Nadu that were directly across from Sumatra.
4.5 mts at Kanyakumari District
3.4 mts each at Kollam and Ernakulam Districts in Kerala.
2.2 mts in Andhra Pradesh,
1.6 mts in areas in the state of Tamil Nadu that were shielded (Thoothukudi, Pudukottai, Ramanthapuram) by the island of Sri Lanka

Distance from Epicentre:

Nicobar Islands – 465 kms
Chennai – 2024 kms and first wave reached in 3 hrs and 33 mins
Cochin – 2287 kms and first wave reached in 5 hrs and 41 mins

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