UPSC Prelims Practice Questions — New seismic hazard spotted in Japan’s 2011 quake

Q1. According to the 2026 study on the 2011 Tōhoku earthquake, by approximately how many millimetres did the entire Japanese archipelago shift eastward as a result of the newly identified ScS-wave-induced ground displacement?

  • A. About 2 mm
  • B. About 6 mm
  • C. About 20 mm
  • D. About 50 mm

Q2. With reference to the ScS waves recently identified as a new seismic hazard after the 2011 Tōhoku earthquake, consider the following statements: 1. They belong to the family of shear (S) waves. 2. They reflect off Earth's solid inner core before returning to the surface. 3. They strike an entire plate boundary nearly simultaneously rather than sequentially. 4. The associated ground displacement was identified using satellite-based GNSS data. Which of the statements given above is/are NOT correct?

  1. They belong to the family of shear (S) waves.
  2. They reflect off Earth's solid inner core before returning to the surface.
  3. They strike an entire plate boundary nearly simultaneously rather than sequentially.
  4. The associated ground displacement was identified using satellite-based GNSS data.
  • A. 2 only
  • B. 1 and 3
  • C. 2 and 4
  • D. 3 only

Q3. In the context of the 2026 finding on Japan's 2011 earthquake, the term 'ScS wave' is best defined as:

  • A. A shear wave that travels from the earthquake source down through the mantle, reflects off the core–mantle boundary, and returns nearly vertically to the surface
  • B. A compressional wave that is refracted through the solid inner core and re-emerges as a shear wave
  • C. A long-period surface wave that travels along the crust–mantle (Moho) discontinuity
  • D. A converted phase produced when a P-wave is transformed into an S-wave at the free surface

Q4. The 2026 research paper that first identified ScS-triggered slip on megathrust interfaces after the 2011 Tōhoku-Oki earthquake as a previously unrecognised source of seismic hazard was published in which one of the following peer-reviewed journals?

  • A. Nature
  • B. Science
  • C. Proceedings of the National Academy of Sciences (PNAS)
  • D. Geophysical Research Letters

Q5. In India, the sole nodal agency of the Union Government for monitoring earthquake activity, maintaining the national seismological network, and disseminating earthquake information is:

  • A. National Centre for Seismology, under the Ministry of Earth Sciences
  • B. National Disaster Management Authority, under the Ministry of Home Affairs
  • C. Geological Survey of India, under the Ministry of Mines
  • D. India Meteorological Department, under the Ministry of Earth Sciences