On Better Engineering Preparedness: Lessons from the 1988 Bihar Earthquake

The rather moderate sized (magnitude 6.6) Bihar earthquake of August 21, 1988 demonstrated clearly that the Indian Engineering profession is far from prepared for a larger earthquake. During the author's extensive travel within the areas affected by this earthquake, it became clearer that the engineering community should immediately initiate serious and coordinated efforts to prepare for the possibility of a large earthquake in many parts of India or nearby countries. This paper discusses some such efforts and possible strategies. Suggested strategies for being better prepared include rationalization and implementation of seismic codes, review of actual construction practices, seismic safety evaluation of critical facilities such as dams and refineries, training and preparation of field engineers for handling post-earthquake situations and learning from earthquakes. Introduction An earthquake of magnitude 6.6 occurred close to the India Nepal border on August 21, 1998 at 4:39:11 hours (Indian Standard Time). The epicenter was located in eastern Nepal between Udaipur and Dharan (26.7° N, 86.8° E). The focal depth was estimated to be about 36 miles. Widespread devastation and loss of life was reported. One thousand and four people died (282 in India and 722 in Nepal) and more than 16000 were injured. The affected area consists of mainly the Gangetic alluvial plain of Bihar (India) and Nepal, and the hilly regions of eastern Himalayan ranges. Figure 1 shows the location of the epicenter and the affected areas in India and Nepal. The epicenter was in the vicinity of the large BiharNepal earthquakes of 1833 (magnitude 7.0-7.5) and 1934 (magnitude 8.4). Major damage was observed in 3 distinct areas: the area near the epicenter and the areas around Munger (India) and Bharakpur (near Kathmandu in Nepal). Similar damage was observed in the 1934 earthquake and is due to the peculiar geology of the area (e.g., Richter, 1958; GSI, 1939). During the earthquake, ground fissuring and emission of sandy water were observed at many places in the Darbhanga and Madhubani districts of Bihar, while no signs of liquefaction were seen at Munger. There was significant damage to embankments, railway bridges and buildings in Bihar. In addition, hilly regions of Darjeeling district (in the state of West Bengal) and Sikkim, located far away (approximately 125 miles) from the epicenter, sustained extensive damage, including damage in roads and highway bridges. Despite the tragic loss of life and property caused by the earthquake, it provided an opportunity to learn how to be better prepared for larger earthquakes and how to mitigate the damaging effects of future earthquakes. Through this earthquake, nature conducted a real-life full-scale test on construction practices in India as well as on our post-earthquake performance and ability to respond to earthquakes. During the author's extensive travel in north Bihar, Sikkim, and Darjeeling, many instances were noted where the engineering community could have been much better prepared, and consequently, could have responded much more effectively and efficiently. In this paper, these and other related areas in which we must initiate coordinated efforts to prepare ourselves are discussed. Figure 1: Affected areas of the earthquake Implementation Effects of Seismic Codes The implementation of earthquake resistant design codes continues to be very poor in India. Many instances were noted where not only the private builders but also government organizations do not follow the seismic code provisions. For example, numerous buildings were built by the state engineering departments in Bihar with specified cement/sand mortar in the ratio of 1:8, even for masonry load bearing construction, in towns, which lie in seismic zones IV and V. Many buildings constructed with this mortar mix suffered earthquake damage. The code requires a minimum of 1:6 for such construction. Even in Delhi, India, which lies in zone IV, the code requirement of a lintel band in load-bearing brick masonry buildings is quite often not allowed. The reasons for non-compliance with codes include lack of understanding, undue concern for economy, lack of adequate technical literature on seismic codes, and sometimes lack of clarity in the way the codes are written. As an example of the latter, criteria for traverse reinforcement design for beams of reinforced concrete frame buildings are stated in IS: 4326-1976 (IS: 4326-1976) as: "The web reinforcement in the form of vertical stirrups shall be provided so as to develop the vertical shears resulting from all ultimate vertical loads acting on the beam plus those which can be produced by the plastic moment capacities at the ends of the beam. The spacing of the stirrups shall not exceed d/4 in a length equal to 2d near each end of the beam and d/2 in the remaining length." It is seen that very few design engineers in India understand the intent and spirit of this clause, particularly the first statement which aims at preventing the brittle shear failure preceding the ductile flexural failure. Moreover, the code does not define "plastic moment capacity". More often than not, design engineers follow the second statement on spacing of shear reinforcement and ignore the first statement. Obviously, the codes cannot be reinforced unless the difficulties faced by the design and engineering profession in implementation are removed and the codes are rendered comprehensible. Thus, there is a need to understand, rationalize and implement code provisions on seismic design. To accomplish this, it is suggested that a committee be established on which are actively represented government engineering departments, consulting engineers, builders and contractors, legal experts, the Bureau of Indian standards, and researchers in earthquake resistant design. Once established, this committee must look into the following aspects: