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<p>We estimated a one-dimensional (1D) crustal velocity structure for Tehri in the Garhwal Himalayas. This estimation was based on the simultaneous inversion of 1643 P-wave and 1559 S-wave phase arrivals from 212 well-located earthquakes. The data were recorded by a 12-station local seismic network operating within the region. The estimated velocity structure consists of six layers up to 18 km depth with P- and S-wave velocities ranging from 5.16 to 6.64 km/s and 2.86 to 4.17 km/s, respectively. The depth of Moho estimated from travel time curves of crustal phases is around 44 km with P- and S-wave velocities, 7.69 and 4.55 km/s, respectively. Using the proposed velocity model, 2124 earthquakes from the study region were relocated. The spatial distribution of events showed that the seismic activity in the Lesser-Himalaya is significantly greater than the activity in the Sub-Himalaya and Higher-Himalaya. Two prominent clusters of seismicity in the Inner Lesser Himalaya are delineated: A northwest–southeast trending cluster following the surface trace of MCT and a horizontal cluster to the northwest of the 1999 Chamoli earthquake. Seismic activity in the region is mainly confined to shallower depths exhibiting an inverted umbrella shape, with a significant reduction in activity observed below 25 km. Additionally, a few sub-Moho earthquakes were also observed in the region.</p>

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One-dimensional crustal velocity structure for Tehri, Garhwal Himalaya and its implications in improved locations of earthquake hypocentres

  • 期刊论文

  • 发表日期：

    2025年3月27日

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  • R Modi,
  • M L Sharma,
  • S Mukhopadhyay

摘要

We estimated a one-dimensional (1D) crustal velocity structure for Tehri in the Garhwal Himalayas. This estimation was based on the simultaneous inversion of 1643 P-wave and 1559 S-wave phase arrivals from 212 well-located earthquakes. The data were recorded by a 12-station local seismic network operating within the region. The estimated velocity structure consists of six layers up to 18 km depth with P- and S-wave velocities ranging from 5.16 to 6.64 km/s and 2.86 to 4.17 km/s, respectively. The depth of Moho estimated from travel time curves of crustal phases is around 44 km with P- and S-wave velocities, 7.69 and 4.55 km/s, respectively. Using the proposed velocity model, 2124 earthquakes from the study region were relocated. The spatial distribution of events showed that the seismic activity in the Lesser-Himalaya is significantly greater than the activity in the Sub-Himalaya and Higher-Himalaya. Two prominent clusters of seismicity in the Inner Lesser Himalaya are delineated: A northwest–southeast trending cluster following the surface trace of MCT and a horizontal cluster to the northwest of the 1999 Chamoli earthquake. Seismic activity in the region is mainly confined to shallower depths exhibiting an inverted umbrella shape, with a significant reduction in activity observed below 25 km. Additionally, a few sub-Moho earthquakes were also observed in the region.