Earthquake & Seismic Zones — Set 11

Correct Answer: B. A major NE-SW oriented tectonic lineament associated with large earthquakes in Assam

The Assam Valley Shear Zone is a major tectonic lineament running northeast-southwest through the Brahmaputra valley, associated with some of the large historical earthquakes in Assam. This structure, along with the Indo-Burmese arc and the Eastern Himalayan syntaxis, creates the complex tectonic environment responsible for northeast India's exceptionally high seismicity. Understanding this zone is critical for assessing earthquake risk to Assam's large population in the Brahmaputra valley.

Correct Answer: B. NDMA's School Safety Programme conducts regular earthquake drills and includes earthquake safety in curriculum

NDMA's School Safety Programme conducts regular earthquake drills in schools located in earthquake-prone areas and advocates for inclusion of earthquake safety in the school curriculum. Students are taught the 'Drop, Cover, Hold On' procedure and evacuation routes. NCERT has incorporated disaster management content, including earthquake safety, into school textbooks. This program builds earthquake awareness from an early age, creating a more resilient future generation.

Correct Answer: B. One of India's most seismically active intraplate regions, including the devastating 2001 Bhuj earthquake and earlier 1819 earthquake

The Kutch region of Gujarat is one of India's most seismically active intraplate regions despite being in the stable cratonic interior. The region experienced major earthquakes in 1819 (Allah Bund earthquake, magnitude ~7.8), 1956 (Anjar earthquake), and most devastatingly in 2001 (Bhuj earthquake, magnitude 7.7). The seismicity is associated with the Kutch Mainland Fault and other fault systems in the region. Kutch is classified in Seismic Zone V.

Correct Answer: B. Graphical representation of maximum response of single-degree-of-freedom systems to earthquake ground motion at different periods

The seismic design spectra (response spectra) in IS 1893 graphically represent the maximum response (acceleration, velocity, or displacement) of idealized single-degree-of-freedom structural systems with different natural periods to a specified earthquake ground motion. Engineers use design spectra to determine the earthquake forces acting on buildings of different heights and stiffnesses. The spectra account for soil site conditions, providing different spectra for hard rock, medium soil, and soft soil sites.

Correct Answer: B. Combination of seismic hazard, high building exposure, and vulnerability of old building stock — Delhi in Zone IV with millions of pre-code buildings

Urban seismic risk combines the seismic hazard (Delhi is in Zone IV, close to the active Himalayan zone), exposure (millions of buildings and people in the city), and vulnerability (large proportion of old, non-seismically designed buildings). A major earthquake affecting Delhi could cause catastrophic damage given these combined factors. NDMA has prioritized Delhi's earthquake preparedness including microzonation mapping, school safety programs, and awareness campaigns for the capital region.

Correct Answer: B. Critical role — community members are first responders and can save lives in the crucial first hours before NDRF arrives

Community-based organizations play a critical role as first responders in post-earthquake search and rescue before professional NDRF teams arrive, especially in remote areas where it may take many hours or days for professional rescuers to reach. Community members who have received basic search and rescue training through programs like Aapda Mitra can save lives in the crucial first 24-72 hours after an earthquake. NDMA's community-based DRR programs specifically train community volunteers for this vital first-responder role.

Correct Answer: B. Main Boundary Thrust (MBT) — the Himalayan thrust system

The 1999 Chamoli Earthquake occurred due to seismic activity on the Main Boundary Thrust (MBT) system in the Himalayan fold-thrust belt of Uttarakhand. The MBT is one of the major active fault systems separating different geological units of the Himalayan mountains. This earthquake, similar to other Himalayan events, was associated with the ongoing tectonic collision between the Indian and Eurasian plates that continuously builds the Himalayas.

Correct Answer: B. Multi-channel approach including mass media, school programs, community workshops, and Aapda Mitra training

NDMA uses a multi-channel approach to disseminate earthquake preparedness messages including: mass media campaigns (television, radio, print), school earthquake safety programs, community-level workshops through Aapda Mitra and civil defence volunteers, training for government officials, and publications of guidelines and educational materials. NDMA works with state SDMAs and DDMAs to ensure these messages reach communities in earthquake-prone areas.

Correct Answer: B. Buildings on slopes are prone to landslide-triggered damage; buildings on soft soils face amplified shaking and liquefaction risk

IS 1893 provides specific guidance about the increased risk to buildings located on slopes (due to potential landslide triggering) and on soft soils (due to amplified ground shaking and liquefaction potential). The code requires higher design forces for buildings on soft soils compared to those on hard rock. For buildings on slopes in earthquake-prone areas, additional stability analysis and slope stabilization may be required.

Correct Answer: B. Gujarat — with major earthquakes in 1819 (Allah Bund), 1956 (Anjar), and 2001 (Bhuj)

Gujarat has experienced multiple catastrophic earthquakes demonstrating persistently high seismicity, particularly in the Kutch region: the 1819 Allah Bund earthquake (magnitude ~7.8, killed thousands), the 1956 Anjar earthquake (killed 115), and the devastating 2001 Bhuj earthquake (magnitude 7.7, killed ~20,000). Despite being in the stable interior of the Indian plate, the Kutch region's complex fault system makes it one of India's most earthquake-prone areas, classified in Seismic Zone V.