Wednesday, February 1, 2012

Earthquake studies: Scientists find most vulnerable areas in Vijayawada metropolis

Syed Akbar
Hyderabad: Micro-zonation of earthquake studies in Vijayawada reveal that Gunadala, Bhavanipuram and Kanuru areas will receive the maximum impact and may experience severe damage in case an earthquake of considerable magnitude hits the city.

The soil in these areas is silty clay with high depths of “soil filled up”. This results in high amplification factor (shaking of the ground) leading to the maximum damage in case of a major earthquake.

Researchers at the earthquake engineering research centre of the International Institute of Information Technology, Hyderabad, have found as many as 22 seismic sources in and around Vijayawada that could affect a number of localities in the city. The IIIT-H team comprising M Akhila, S Silpa Chowdary and D Neelima Satyam selected Vijayawada for the earthquake site effect studies, as it is the only major place in the State that falls under earthquake zone III.

The soil amplification factor (SAF) for 14 locations in Vijayawada was calculated to understand and predict the impact of a major earthquake on the city. The SAF varied between 1.55 and 5.01. The higher the SAF the higher is the damage threat. Kanuru recorded the highest SAF of 5.01, followed by the Housing Colony in Bhavanipuram with 4.05, Bank Colony in Gunadala with 3.1, Moghalrajpuram with 2.25, Ryves canal in Gunadala with 2.4 and Ramalingeswaranagar with 1.6. The industrial estate in Kondapalli showed an SAF of 1.85.

The damage will be quite high in areas with SAF above 2.5, moderate in areas with SAF between 2.5 and 2, and low in areas with SAF less than 2.

The geography of Vijayawada with varied lithological (rock) formations and the low water table makes it vulnerable to earthquakes. According to IIIT-H study, the damaging effects associated with soft deposits may lead to local intensity increments. Gunadala and Bhavanipuram are predominantly silty clay while Kanuru and Sethannapet have silty clay and sandy silt soils. Kondapally has equal amounts of silty clay and silty sand. Ramalingeswaranagar has high amounts of clayey sand while the land texture in Moghalrajpuram is predominantly clayey sand, sand silt and rock.

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