The Himalayan frontal arc is one of the seismically active regions of the world.

The peninsular shield of India has generated some remarkable earthquakes. The Latur earthquake in the heart of the Indian shield is considered as a typical SCR earthquake.

The largest earthquake induced by an artificial reservoir occurred at Koyna, Maharashtra.

The 1819 Runn of Kutch earthquake (M ~ 8.0) is one of the largest intraplate events that produced a surface scarp about 100 km long.

The Himalayan mountain range is the dramatic outcome of the collision of Indian and Eurasian plates, some 40 million years ago.

The Indian plate is still penetrating deeper at an estimated rate of about 5 cm/year.

The Himalayan collision zone has been marked by intense seismic activity.

Four great earthquakes (1897 Assam,1905 Kangra; 1934 Bihar-Nepal and 1950 Assam) occurred here in a short span of 53 years.

The frequent moderate earthquakes and the infrequent great earthquakes suggest that episodic slippage is continuing.

These ongoing processes also imply that future great earthquakes can be expected in the unruptured parts of the Himalayan front. Major uncertainties remain regarding the recurrence interval of great earthquakes

The Latur earthquake generated a surface rupture that was traceable for about 2 km. The maximum height of the scarp observed near Killari was about one metre. Several geological studies conducted in this deformation zone by various agencies provided valuable information about the seismogenic characyeristics of this important fault zone in the Stable Continental Region (Photo: Kusala Rajendran, CESS )

The Latur (Killari), Maharashtra, earthquake of September 30, 1993 is the most devastating SCR earthquake in the world.Its epicentre was located in a region considered to be aseismic

This earthquake occurred in the typical rural setting of India. The severity of the destruction was compounded by the nature of village settlements. While most of the engineered structures survived the earthquake, the non-engineered ones were totally damaged.

Over 10,000 lives were lost in this earthquake and several villages were destroyed. With a magnitude 6.3 and focal depth less than 10 km, this earthquake is similar to other moderate events in the Australian and Canadian shields.

It is suggested that the repeat time of moderate SCR earthquakes are of the order of hundreds of thousands of years. The recurrence interval at Latur may also be of the same order, and the recorded human history may not document any previous earthquakes. Thus, we have very little information about the earthquake history of such regions and the earthquakes occur as a total surprise.

This event led to several studies, giving a new perspective to seismic hazard assessment in the peninsular India. It also led to strengthening of the seismic network, upgrading several existing facilities

Seismicity associated with the Shivaji Sagar lake formed by the Koyna dam is considered to be a classic example of earthquake activity triggered by reservoirs.

Over hundred cases of reservoir induced seismicity have been reported from all over the world.

Koyna is among the four cases that have generated earthquakes of magnitude >6.0. An earthquake of magnitude 6.3 (1967) and many of magnitude >5.0, have occurred at Koyna.

Seismicity at Koyna shows remarkable correlations with the filling cycles in the reservoir. It is believed that the pore pressure changes induced by the reservoir reduces the strength of the rocks leading to failure along a major fault zone in the vicinity of the dam.

The 1819 and 1956 earthquakes have caused significant damages in the area. Since 1997 CESS had beenstudying the epicentral region around the 1819 earthquake with a view to understand the morphological characteristics of previousdeformation associated with that earthquake and to understand its paleoseismic history. Occurrence of the present earthquake in the region has given an opportunity to study the coseismic deformation and also to compare the effects of the two earthquakes. The CESS team conducted a detailed field investigation in the epicentral area of the Bhuj earthquake and documented major surface effects and liquefaction features generated by the earthquake.

India Meteorological Department (IMD) has located this earthquake at 23.40°N, 70.28°E, using 53 stations forming part of a national grid. The U. S. Geological Survey has used teleseismic data and located it at 23.36°N and 70.34°E. Focus of this earthquake is placed at 24 km by the IMD and 22 km by the USGS. Both these are located north of Bachau, a village that was totally destroyed in this earthquake.

The Bhuj earthquake has also destroyed several historical monuments in the region, dating from 9th century A.D. The Sun Temple at Kotai (11th century A.D.) and the Punvareshwar Temple at Manjal (9th century A.D.) are among the oldest temples that were destroyed. While the Lakhpatji’s Chhatardi (A.D. 1752-61) collapsed completely, Aina Mahal Palace(~ 200 years old) is still standing, with extensive damage. These structures seem to have survived the 1819 and 1956 earthquakes, but the ground shaking was apparently too severe during the recent earthquake. Although the damage was not severe, it is conceivable that the Bhuj earthquake was the largest to have occurred in the close proximity of these structures since 9th century A.D.This earthquake also provided an opportunity to compare the liquefaction features induced by the current earthquake with that of otherearthquakes. Craters observed in the area exposed a major liquefaction event prior to 2001 and we consider this to be due to the 1819 event, based on our previous observationsin several trenches in this area. This event is more dramatic in regions close to the Allah Bund, but small-scale venting episodes prior to 2001 are observed also in the Banni Plains. At this time, most of these craters are wet and the conditions are not ideal for trenching excavations. We plan to take up these at a later stage

(See also)

The 2001 Kutch (Bhuj) earthquake: Coseismic surface features and their significance

Kusala Rajendran* , C. P. Rajendran*, Mahesh Thakkar † and Martitia P. Tuttle ‡
*Centre for Earth Science Studies, P.B. No. 7250, Akkulam, Thiruvananthapuram 695 031, India
† Department of Geology, R.R.Lalan College, Bhuj, 370 001, India
‡ M. Tuttle & Associates, Tibbetts Lane, Georgetown, ME 04548, USA

CURRENT SCIENCE, VOL. 80, NO. 11, 10 JUNE 2001

Seismic zonation map of a country is a guide to the seismic status of a region and its susceptibility to earthquakes

India has been divided into five zones with respect to severity of earthquakes. Of these, Zone V is seismically the most active where     earthquakes of magnitude 8 or more could     occur

Recent strong motion observations around the world have revolutionized thinking on the design of engineering structures, placing emphasis also on the characteristics of the     structures themselves

It should be realized that in the case of     shield type earthquakes, historic data are     insufficient to define zones because recurrence intervals are much longer than  the recorded human history

This may often give a false sense of security. Occurrence of the damaging earthquake at Latur, falling in Zone I is a typical example of     this situation