What is the name of the zone the region falls under that is moderately vulnerable to earthquakes?
Tiruchirappalli is situated in central south-eastern India, almost at the geographic centre of the state of Tamil Nadu. The Cauvery Delta begins to form 16 kilometres (9.9 mi) west of the city where the river divides into two streams—the Kaveri and the Kollidam—to form the island of Srirangam. By road it is 912 kilometres (567 mi) south of Hyderabad, 322 kilometres (200 mi) south-west of Chennai and 331 kilometres (206 mi) south-east of Bangalore. The topology of Tiruchirappalli is almost flat, with an average elevation of 88 metres (289 ft). A few isolated hillocks rise above the surface, the highest of which is the Rockfort; its estimated age of 3,800 million years makes it one of the oldest rocks in the world. Other prominent hillocks include the Golden Rock, Khajamalai, and one each at Uyyakondan Thirumalai and Thiruverumbur.The two major rivers draining Tiruchirappalli are the Kaveri and its tributary the Kollidam, but the city is also drained by the Uyyakondan Channel, Koraiyar and Kudamuritti river channels. The land immediately surrounding the Kaveri River—which crosses Tiruchirappalli from west to east—consists of deposits of fertile alluvial soil on which crops such as finger millet and maize are cultivated. Further south, the surface is covered by poor-quality black soil. A belt of Cretaceous rock known as the Trichinopoly Group runs to the north-east of the city, and to the south-east there are layers of archaean rocks, granite and gneiss covered by a thin bed of conglomeratic laterite. The region falls under Seismic Zone III, which is moderately vulnerable to earthquakes.
Seismic Zone III