Isoseismals for the Kutch earthquake of 26th January 2001

Abstract

Damage observed during the Kutch earthquake of 26th January 2001 is classified according to the type of structure. This damage pattern has been used to draw the isoseismal map on the basis of the intensity scale given in IS 1893-2002 which covers only traditional one to two storey houses. Having thus estimated intensities, and observed damage to other types of structures, a new criterion was adopted which is included in this paper. Areas that showed maximum damage to structures have been assigned maximum intensity X.

Surface Level Synthetic Ground Motions for M7.6 2001 Gujarat Earthquake

“…In both towns, many (> 50%) ordinary brick structures, buildings of the large block and prefabricated type, half-timbered structures witnessed total damage. In both towns, many (> 50%) reinforced buildings and well-built wooden structures were destroyed [2]. In the town of Bhachau, even well-built reinforced concrete structures were totally devastated.…”

“…The observations for both towns are consistent with the response spectra derived from synthetic ground motions. Both towns were assigned an MMI intensity level X [2]. Next, ground motions at Rapar and Dhori, two towns located at epicentral distances of 46 km and 49 km are analyzed.…”

“…The predominant form of construction in these towns consisted of low rise unreinforced masonry and reinforced concrete structures, which are susceptible to high-frequency ground motions. In Rapar town, most (> 75%) buildings constructed with infield-stone, clay and unburnt-brick witnessed total damage, while many (> 50%) ordinary brick structures, buildings of the large block and prefabricated type, half-timbered structures witnessed total damage [2]. Also, many (> 50%) reinforced buildings and well-built wooden structures were destroyed.…”

“…The M w 7.6 earthquake which struck Gujarat on 26 January, 2001 was the largest intraplate earthquake in India [1]. The maximum felt intensity was X on the Modified Mercalli Intensity (MMI) scale [2]. The earthquake mechanism was shallow oblique reverse faulting [1] with the epicenter about 9 km southwest of the village of Chobari in the Kutch region of Gujarat, India [3].…”

“…Damage in the epicentral region of the 2001 Gujarat earthquake was not uniform and often inconsistent [10]. Isoseismals for the earthquake [2] for seismic zone 5 show that some towns (e.g., Bhachau, Rapar, Dudhai and Adesar) witnessed complete destruction while other towns (e.g., Nakhatrana, Naliya, Khavda, and Mandvi) witnessed relatively less damage. A relationship between the building typology and ground motion characteristics can aid in understanding the unusual damage pattern in the region.…”