Washington: Two Indianscientists have stressed the urgent need to update design standards toconstruct adequate and safe industrial facilities, dams, and communitybuildings in earthquake-prone peninsular India.

The seismic hazard associated with some major urban areas,such as Mumbai, is higher than the standard design specification now used tobuild earthquake-resistant structures there, they say in a paper published inthe February issue of the Bulletin of the Seismological Society of America(BSSA).

"The results of this paper imply that the level ofseismic safety of structures designed based on current standards is lower thanits desired level," states co-author Ravi Sinha, Ph.D., professor of civilengineering at Indian Institute of Technology (IIT) in Mumbai.

As earthquakes in stable continental regions lack sufficientunderstanding to prepare local populations for future seismic activity, Sinhaand Kishor Jaiswal, also at IIT, focused their research on peninsular India,which is an old and stable continental plate and home to more than 400 millionpeople, as stable continental regions are areas away from the boundariesbetween tectonic plates but still are threatened by infrequent earthquakes thatcan create strong shaking. Because the large earthquakes are infrequent, theyare difficult to study.

The Central and Eastern United Statesis also considered a stable continental plate and has experienced strongearthquakes.

The 1811-1812 New Madrid, Missouri earthquakes, for example,were of a magnitude greater than 7.

To estimate the devastating consequences of potentialearthquakes, scientists continually re-evaluate hazard assessments for an area.Based on these assessments, governments modify codes for construction ofstructures, such as dams, industrial buildings, and homes. Design codes basedon outdated assessments could increase the risk of heavy damage by seismicactivity.

Sinha and Jaiswal conducted a hazard assessment for theregion that looks at a variety of information regarding seismic activity in theregion, using a probabilistic framework.

The authors noted an apparent increase in seismic activitydue to better seismological instrumentation to record earthquakes. The increasein seismic activity requires a closer consideration of construction standards.

Sinha and Jaiswal explain that their work is useful inspecifying design level for upgrading and retrofitting major structures such asdams and industrial facilities to the desired level of seismic safety.