Physics Based Seismicity Rate Computation For Northeast Himalaya, India

The computation of probable occurrence of future large earthquakes is the prime objective of the present study in the Northeast Himalaya India. For this purpose, the physics based rate-and-state friction law is adopted for forecasting the seismicity rate changes for M_W ≥ 5.0 during the period 2016-2020. The coulomb stress changes (ΔCFF) is consider as a principle component which associated with the earthquake ruptured from the receiver’s fault. The reason behind considering the coulomb stress changes lies on the fact that the seismicity rate increases where the stress increase and decrease where the stress decreases. Here, it has been observed that high ΔCFF values are found widespread along the Main Central Thrust. Moreover, highest b-value is found to be in and around the Sikkim Himalaya. However, the highest background seismicity rate is also obtained in the vicinity of Sikkim and Bhutan with values ranging from 0 to 3.6. Finally, we have considered the consecutive fault parameter (Aσ = 0.05 MPa) for computing the forecast model with variable ΔCFF and heterogeneous b-value. The different value of the constitutive parameter (Aσ = 0.01, 0.02, 0.09, and 0.30 MPa) is adopted to understand the contribution of this parameter in a sudden change of seismicity rate due to stress perturbations. Also, various friction coefficient values (μ' = 0.2, 0.5, 0.6 and 0.8) are considered to find out the variation of seismicity rate changes. Then, CSEP model have been explored to check the consistency between the observed earthquakes and forecasted seismicity rates. The result from the CSEP model approves that the observed earthquakes matches well with the forecasted seismicity rates, thereby showing the consistency and efficiency of our forecast model.