Earth Process Modeling

Earth Process Modeling
The Earth system is a dynamic one at all spatial and temporal scales: dynamics of tectonic plates, core-mantle evolution, surface processes of landscape evolution, hydrological cycle, climate change, etc. etc. Modeling of these complex and interconnected mechanisms is the ultimate challenge for the geoscientist only which will have the potential to predict the future of our earth planet.  Mathematical formulation of any physical process involves various complex equations, which can be solved using different analytical and or numerical techniques to get the desired solutions, which can be analyzed in terms of the physical phenomena. These equations involve various types of operators such as differential, integral, divergence etc. The solution to these differential equations can be solved using the deterministic and stochastic approaches. Deterministic differential equations arise when the parameters are known with certainty, whereas stochastic differential equations are those, which include randomness in their parameters.
Modellingthe Earth system for seismological, thermal, groundwater and tsunamigenic processes are carried out at CSIR-NGRI using mathematical and stochastic tools and integrating the results with the available geological information. It is well established that geophysical properties exhibit non-linear behavior, hence the existing formulation for the geophysical and geological problems is being re-addressed incorporating the non-linear/ stochastic geophysical models to study the Earth system processes and quantify its behaviors.

Tsunami Studies

Andaman-Sumatra subduction zone had produced several large and great earthquakes in the past, some of which have generated destructive tsunamis. Tsunami forecast model is to provide an estimate of wave arrival time, wave height, and inundation area immediately after a tsunami event. Forces caused due to a tsunami on different structures also play an important role; calculation of forces due to tsunami using the wave heights are made acting on any proposed wall constructed between India and Sri-Lanka are calculated. And change in forces with time is also estimated.  Results reveal that the hydrostatic forces acting on the wall structure in the ocean or the sea shall not pose a great threat to the structure, suggesting thatconstruction of such barriers would dissipate the tsunami wave energy resulting in reduced damage to adjoining coastal region.

Numerical solution for shallow subsurface temperature using COMSOL Multiphysics for coupled SAT and Land Surface Temperature along with time dependent recharge
Surface and subsurface thermal profiles for various values of step changes in the recharge, duration of higher recharge rate, and the heat transfer coefficient is studied. Analysis of simulated temperature signals for sudden step decrease in recharge shows slower rise in the surface temperature to the prescribed air temperature. This pattern is seen in distribution of the temperature anomalies with depth. Surface temperatures for a given value of higher recharge decrease after a time period to join the surface temperature anomaly curve for lesser value of recharge. Numerical solution to the one-dimensional advection diffusion equation with exponential increase of air temperature with time in robin type boundary condition is obtained to know the subsurface thermal environment for surface climate change. And the results are studied for various values of parameters represents different scenarios. The results are important in understanding the effect of coupled air and land surface temperatures with mass movement (fluid flow) on the subsurface temperatures.

3-D modeling of pore pressure diffusion beneath Koyna and Warna reservoirs, Western India
The mechanism of reservoir-triggered seismicity is well-understood and explains the earthquake occurrence at different reservoir sites. It can be attributed to the stresses due to water loading and to changes in fluid pressure in pores within the rock matrix. A 3-D fluid flow numerical model is used to investigate the pore pressure diffusion as a cause for continued seismicity in the Koyna–Warna region in western India. It is shown that reservoir water level fluctuations are sufficient to trigger earthquakes at the seismogenic depths in the region. Our numerical model suggests that a vertical fault with hydraulic conductivity in the range 2–6 m/day facilitates the diffusion of pressure at focal depths of earthquakes in the Koyna–Warna region. Also, for triggering of earthquakes a higher vertical conductivity is required for the Warna region than for the Koyna region. A lag of two months period is found between the maximum water level and the significant hydraulic head required to trigger earthquakes at the focal depth using the appropriate hydraulic conductivity for both the reservoirs.