Earthquake & Seismic Zones
Disaster Management · भूकंप और भूकंपीय क्षेत्र · 19 facts
India's Seismic Zonation: BIS (Bureau of Indian Standards) divides India into 4 zones (II, III, IV, V) based on earthquake hazard level.
Zone II (Least hazard): Parts of Peninsular India, Rajasthan; low seismic activity.
Zone III (Moderate hazard): Kerala, Goa, Lakshadweep, remaining parts of Maharashtra, UP, Punjab, Bihar and parts of Gujarat.
Zone IV (High hazard): J&K, Himachal Pradesh, most of Uttarakhand, Delhi, Sikkim, parts of Indo-Gangetic plains, Andaman & Nicobar.
Zone V (Highest hazard): NE states (Assam, Meghalaya, Manipur, Nagaland, Arunachal Pradesh), Kashmir Valley, Andaman Islands, Kutch region of Gujarat.
Richter Scale: Logarithmic scale (1-10); each unit increase = 31.6 times more energy; magnitude 7 = 1000 times more energy than magnitude 5.
Moment Magnitude Scale (Mw): More accurate than Richter Scale for large earthquakes; measures energy released; modern seismology standard.
1950 Assam Earthquake: August 15, 1950; magnitude 8.6; largest recorded earthquake in India; caused massive landslides; Brahmaputra changed course.
2001 Bhuj Earthquake: January 26, 2001; magnitude 7.7; 20,000+ deaths; Gujarat; showed need for earthquake-resistant construction.
1993 Latur Earthquake: September 30, 1993; magnitude 6.2 (surface wave 6.3); 9,748 deaths; Marathwada region, Maharashtra.
2011 Sikkim Earthquake: September 18, 2011; magnitude 6.9; 111 deaths; triggered landslides blocking major roads.
India lies on the boundary of Indian Plate and Eurasian Plate — this collision causes Himalayan seismic activity; Indo-Australian plate pushes north.
Seismograph: Instrument that records earthquake waves; seismogram is the record produced; P waves (primary/compressional) arrive first, S waves (secondary/shear) second.
Epicenter: Point on Earth's surface directly above the focus (hypocenter) of an earthquake; maximum damage usually at epicenter.
Mercalli Scale: Measures intensity (damage/effects) of an earthquake, not energy; scale I to XII; subjective unlike Richter/Mw.
IMD (India Meteorological Department) also monitors seismic activity through its Seismological Monitoring Network; issues alerts.
National Center for Seismology (NCS): Under Ministry of Earth Sciences; monitors and studies earthquakes in India and neighboring regions.
Earthquake early warning system: India has no real-time public alert system yet; Japan and USA have such systems; India is developing one.
Earthquake-resistant building codes: BIS IS 1893 (structural safety), IS 4326 (earthquake-resistant construction); mandatory in Zones IV and V.