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Ahmedabad 20 May 2024
The new book ‘The Rumbling Earth – The Story of Indian Earthquakes’ has been written by renowned seismologist Dr. CP Rajendran. In which Gujarat has been mentioned, after the Himalayas, the Pacific Ocean, the Gujarat region has been described as the most dangerous area for earthquakes. For this, the earthquakes of 1819 and 2001 in Kutch have been studied in depth. The devastating earthquake that occurred 200 years ago in Kutch has been studied in depth with modern equipment for the first time.
66 fault lines
The Geological Survey of India has documented that there are 66 active fault lines. All of these can cause earthquakes. Gujarat is one of them. It includes the Himalayas, Northeast India, Gujarat and Andaman and Nicobar. Earthquakes occur several tens of kilometers below the surface, which are not visible. Modern computational techniques will take us closer to that goal.
The North Kathiawar Fault, South Wagad Fault, Kutch Mainline Fault, Hill Fault, Island Mainfault, Nagarparkar Faultline are located in Kutch, which is vulnerable to earthquakes.
Large earthquakes can alter the course of major rivers. The first major earthquake known historically occurred on June 16, 1819 in the Kutch desert. It has been studied in some detail. What were the findings?
Excavations were carried out in the Kutch region to find remains of past earthquakes. The most important finding was that earthquakes before 1819 were of similar size and physical impact and had a recurrence interval of about 1,000 years. These earthquakes transformed low-lying sea into land. The 1819 Kutch earthquake damaged the Allah Dam and altered the course of the river, which has been physically mapped for the first time. The area has never been surveyed before using modern equipment. This is the first modern study of the 1819 earthquake.
The 2001 Bhuj earthquake was surprising because the region where it occurred had no earthquakes in the historical past. With the 1819 earthquake, which is far from Bhuj, no one expected an earthquake near Bhuj in less than 200 years. The most important outcome of the study was the recognition that there are multiple sources of earthquakes in the Kutch region. The 1819 earthquake and the 1956 Anjar earthquake may have occurred with different recurrence intervals on the order of a few thousand years. The recurrence period of the 1819 source differs from that of the 2001 source near Bhuj.
274 earthquakes
During the last decade, 274 magnitude 4 earthquakes occurred within 300 km of our borders. His research over the last three decades also raises the question whether we are on the verge of another major earthquake.
More tremors in Kutch
On an average, 40 tremors of magnitude 3 to 3.9 occur per year.
Tremors have now become common in Kutch after the 2001 earthquake, with tremors of 3 to 4 magnitudes occurring every month. Earthquakes occur when there is movement between two plates in the earth’s crust.
On January 28, 2024, a 4.0 magnitude tremor hit eastern and western Kutch, with its epicentre 21 km from Bhachau in Kutch. A truck might have passed through there in a 4 magnitude earthquake. Windows can break in an earthquake of 4 to 4.9 magnitude. Frames hanging on walls can fall.
On May 17, 2023, the epicentre of the Kachma 4.2 magnitude earthquake was 39 km northeast of Khavda.
In May 2020, a 4.0 magnitude earthquake was recorded in the South Arabian Sea, 44 km from Mangrol in Saurashtra, according to seismometers.
Dhundalwadi village, 40 km from Vapi on the border of Gujarat and Maharashtra, has experienced more than 2000 earthquakes so far. A few tremors of magnitude 4 hit Vapi-Umargam and Selvas-Daman.
In Kutch in 2015, the Ministry of Earth Sciences conducted 8 projects on fault lines at Kutch University. As per research, 6 earthquake fault lines have been located.
Rapid urbanisation, expansion of built environment and population density amplify the impact of earthquakes leading to greater damage and deaths. Many engineered structures do not pass stability tests during earthquakes and are not designed to mitigate the impact of tremors.
Seismologists
Renowned seismologists Dr CP Rajendran and Dr Kusala Rajendran have taken up the study of earthquakes as their field of research. Their interest was sparked while doing post-doctoral research at the University of Southern California where a mysterious earthquake in 1886 destroyed much of the historic city of Charleston. Returning to India they have focused on the mysteries associated with earthquakes in a country where earthquakes occur every 1-3 days.
This is perhaps the first attempt of its kind to review most of the recent and historical earthquakes in India. There are individual reports and scientific papers on many of these earthquakes, which collect this information.
The largest documented earthquake in history occurred in Northeast India on August 15, 1950. It is called the Assam earthquake.
The 1993 Kilari earthquake was not caused by the Koyna dam in Maharashtra. The dam caused a similar earthquake in 1967 and minor earthquakes keep occurring near the Koyna reservoir. The source of the Kilari earthquake is more than 350 km away from the Koyna reservoir and it will not have any impact on the region.
Don’t build dams
Building large dams in the Himalayan region has many consequences. It is anyway very seismically active and earthquakes are inevitable. The real danger will be from landslides that may break the dams and cause floods. Dams in the Himalayan region have weakened the mountains.
