A 3D Crustal Velocity Model for Ground-Motion Simulation in the Northwestern Himalayas: Revisiting the 1905 Kangra Earthquake

In the present study, we have developed a new 3D crustal velocity model for the northwestern part of the Himalayas and the Siwalik basin. The developed model spans a 4° × 4° region between 75.5°–79.5° E and 29.5°–33.5° N and accounts for regional geological heterogeneity. A comprehensive velocity profile dataset of 423 1D velocity–depth profiles from five different crustal investigation studies is used for model development. The study includes an evaluation of different spatial interpolation techniques for developing the crustal velocity model, among which kriging interpolation yielded the best results. Furthermore, the model was validated through comparison with recorded data from the past three Himalayan earthquakes, that is, the 1986 Mw 5.54 Dharamshala earthquake, 2009 Mw 4.7 Uttarkashi earthquake, and 27 March 2020 Mw 4.1 earthquake. In addition, a detailed case study of rupture scenarios for the 1905 Kangra earthquake is performed. A total of 25 simulations are performed, accounting for uncertainty in the source geometry and slip distribution. The results show that several regions within the Siwalik basin exhibit mean peak ground velocity values up to 100 cm/s and mean spectral acceleration values up to 0.2g at periods of 2 and 3 s. The developed 3D velocity model can be used to perform physics-based simulations for scenario earthquakes. Further applications of the developed model include source inversion and multihazard studies for the region.