The earthquake hazard assessment study carried out for the proposed nuclear power plant at Jaitapur in Maharashtra has notable flaws, eminent geophysicist Vinod K. Gaur said here on Friday.

Professor Gaur of the Indian Institute of Astrophysics, Bangalore, said the site investigation work had several weaknesses including geotechnical findings with ambiguous implications. The study neglected crucial observations relating to seismicity, he said delivering the 11th C. Karunakaran endowment lecture organised by the Centre for Earth Science Studies (CESS).

“The absence of seismicity in Jaitapur in the past century is erroneously interpreted to infer that no seismicity will occur in the future. The fallacy of this argument lies in the recognition that the same claim could have been made for both the Koyna and Latur regions before they experienced massive earthquakes of magnitude above 6 on the Richter scale.”

Offshore faults

The Jaitapur plant was claimed to have no active faults within five km, ignoring the fact that the National Institute of Oceanography mapped offshore faults that had disturbed recent submarine sediments within three km of the site. “The Vijaydurg fault, a 35-km onshore fault at the base of the Jaitapur terrace, is classified as inactive, yet no seismic evidence is presented to indicate when this fault last slipped. No trenching of the fault was considered necessary and no estimate of the earthquake magnitude that could occur on this fault has been attempted. There has been no attempt to map the offshore extent of the fault.”

Professor Gaur also questioned the claim of immunity of the site to a tsunami. Observing that what appeared a major tsunami occurred in 1524, 100 km north of Jaitapur, possibly caused by offshore faulting or a distant earthquake, he said the study offered no discussion of the potential tsunami threat faced by the plant.

The nuclear establishment had avoided a discussion on seismic safety, he said. “The Nuclear Power Corporation of India has invoked the expert opinion of three notable seismologists to endorse the safety of the Jaitapur site. Seismologists who might have other views on the issue are intimidated and silenced.” He pointed out that U.S. geologist Roger Bilham, who authored a paper on the seismicity of the Jaitapur region, was banned from entering India.

Professor Gaur said it was intriguing that high resolution seismic, palaeoseismic studies and submarine mapping of offshore faults were missing from the investigations aimed at ensuring safe design of the plant. “That a plea is necessary to ask for transparency in scientific analysis of issues crucial to societal well-being is a tragic commentary on the democratic character of a society.”