Many similarities between Gujarat, Mexico quakes
KANPUR, FEB. 4. There are several similarities between the January 26 earthquake in Ahmedabad and the killer earthquake that hit Mexico in 1985, an Indian scientist has said.
As in the case of the Mexico quake, soft soil fillings may be one of the causes behind the massive devastation resulted from last week's earthquake in Ahmedabad, says Prof. Vinay Kumar Gupta of the Indian Institute of Technology (IIT), Kanpur.
Talking to UNI here, Prof. Gupta said reports reaching here from Gujarat indicated certain similarities in the pattern of damages and reasons behind the earthquake in Ahmedabad and Mexico.
He said it was surprising that places like Ahmedabad which were about 300 to 400 km away from the epicentre of the quake had suffered so much devastation.
Prof. Gupta said he was told that earlier, Ahmedabad and surrounding areas had a number of ponds and water holes which were buried under soft soil fillings during the course of time. Several new colonies had come up on these lands with soft soil fillings and this phenomenon, coupled with ``poor quality'' of construction work and suspected violation of seismic code, might be the root cause of the massive loss of lives and property witnessed last week.
Mexico City is also founded on soft fillings of volcanic deposits and was situated about 400 kms from the epicentre of the deadly earthquake in 1985, he said adding that in that earthquake, 10 to 12 storeyed buildings and other structures suffered the maximum damages.
He said he was told by some friends in Ahmedabad that three to four-storeyed buildings in various new colonies of the capital town suffered the maximum damages while localities in the old Ahmedabad township witnessed less devastation.
Elaborating his point, Prof. Gupta said that soft soil fillings facilitates amplification of the motion of seismic waves and in a situation where the natural period of the soft filling and the structures on it were equal, the devastation was the maximum.
Prof. Gupta said that the veracity of his observations could be ascertained if the seismic motion was monitored at various locations in Ahmedabad. This could be done even now as the aftershocks were still occurring.
He said that variation in the motion at different locations would be a confirmation to the above situation and his observation. Practice of sub-seismic zoning and micro-seismic mapping and enforcement of seismic code could accordingly minimise the extent of devastation in situations like those in Mexico and Ahmedabad, Prof. Gupta added.