Abstract

Gujarat Earthquakes - A Study of 1819 & 2001 Earthquakes


Narender Verma
Research Scholar, Department of Geography
College of Social Science & Humanities,
Mohanlal Sukhadia University
UDAIPUR (Rajasthan)
Phone: +91 294 2432421
E-mail: - vermanaren2003@yahoo.co.in, vermanaren@indiatimes.com


Abstract
The Kachchh Region in the state of Gujarat is seismically an active zone, which has experienced continued tectonic activity since Mesozoic times. Several minor and major earthquakes have occurred in this region. In the past 200 years three major earthquakes have struck the region. These are 1819, Rann of Kachchh Earthquake, 1956 Anjar Earthquake and 2001 Bhuj Earthquake. The Kachchh region forms an important geodynamic part of western continental margin of the Indian Sub continent. It extends for 250 Kms (east- west) and 150 Kms (north -south). Structurally it comprises several faults trending east-west. These include Kachchh Mainland Fault, Nagar Parkar Fault, Banni Fault etc. The region is made up of rocks mainly from Jurassic to Cretaceous Age. The east-west trending faults have witnessed continued earth movement and have been responsible for the tectonic activity in this region. This has not only helped in the evolution of present day landscape but has also accentuated the structural pattern.

The present paper is an attempt to make a comparative study of the 1819 Rann of Kachchh Earthquake and the recent Bhuj Earthquake of 2001. The main aim of this study is to make a comparative analysis in terms of the magnitude of the earthquake, surfacial and subsurfacial changes, affect on life and property, location of the epicenters and the extent of area affected.

The study area lies between 68° 30' E to 71° 30' E longitudes and 23°N to 24°30'N latitudes. The study of 1819 Rann of Kachchh Earthquake is based on the secondary accounts whereas the study of 2001 Bhuj Earthquake is based on various satellite images and remotely sensed data. These have been supplemented with relevant maps of the region and photographs to ascertain the ground truth.

The 1819 Rann of Kachchh Earthquake occurred on 16th June 1819 at 7 P.M. Its impact was felt all over India from Calcutta in the East to Baluchistan Hills in Pakistan in the West and from Kathmandu in Nepal in the North to Pondicherry in the South. The radius of impact was 1600 Kms but the most severely affected area was within 80 Kms radius from the epicenter. It led to complete destruction of Fort Sindri. Ahemdabad lying 140 Kms East also had damaging affects. According to J.M.Murdo approximately1500 to 2000 people were killed and 1500 houses damaged mainly around Bhuj. One of the most important surfacial deformities was the creation of a natural dam 80 Kms long and 6-9 Mts. high called Allah Bund. Tsunamis struck the coastal areas and sand venting caused enormous flooding. The exact magnitude of the earthquake is not known but from various estimates it is stated to be between 7.5-7.7 on Richter Scale.

The Bhuj Earthquake occurred on 26th January 2001 at 8.46 a.m. when the nation was celebrating its Republic Day. The earthquake was felt in the entire Indian Subcontinent. Its epicenter lay at 23°36'N and 70°34'E longitude, 100 Kms NNE of Jamnagar. It was 50 Kms to the southeast of the Allah Bund. The Earthquake measured 7.9 on Richter Scale (U.S.G.S. estimates) and its focus was at a depth of 22 Kms. It affected 21 districts and a population of 1.58 Gores. It caused approx. 30,000 deaths and left 1.66 lakh injured. The earthquake led to severe damage to property worth 2500 crore rupees.

The earthquake led to several surfacial and subsurfacial changes in form of creation of fault lineaments, water surges, surfacial deformities etc. Important faults include a linear fault near Manfra Town and hence called Manfra Fault, Budharmora Fault near the epicenter. Cracks have also been observed in the salt marshes near Dhori Village. Just a day after the earthquake at many places sweet water poured out from below in the areas of salty water but this was a temporary phenomenon. Liquefaction has been recorded at several places. Crater like structures commonly found in volcanic regions was seen near Rapar.

A comparative analysis of both the events brings to light many interesting features. Firstly if we look at the magnitude of the earthquake then their intensity is nearly the same i.e. between 7.5 and 7.9 on the Richter Scale. Secondly the extent of area affected too is similar in extent. Thirdly the epicenter of both earthquakes lie in close vicinity to each other. The epicenter of Bhuj Earthquake lay approx. 50 Kms southeast of 1819 Rann of Kachchh Earthquake. Another interesting feature has been the temporary emergence of sweet water from below in both events. Capt. Mc.Merdo in his letters mentioned emergence of sweet water at many places where it was salty earlier. In case of Bhuj Earthquake it was observed at a location near village of Lodi that ground water continued to bubble even three weeks after the Earthquake which was sweet even though water is salty in this part. In terms of people affected in both cases about 10 percent of the population has been affected finally both the Earthquakes have been probably the result of the compressive stress in the crust due to the ongoing northward collision of India into Eurasia.

From the comparative analysis of both the earthquakes a remarkable similarity can be observed in the mechanism, extent of damage, area affected and surfacial deformities. An earthquake of such remarkable similarity within a span of 182 years in itself includes the vulnerability of the seismic activity. A detailed analysis of the Bhuj Earthquake 2001 can perhaps help us understand the past record of seismic activity and also help in making our preparedness for the future.