A brief Note compiled by: Prof. Madhav N. Kulkarni, IIT Bombay Since the inception of the Very Long Baseline Interferometry (VLBI) system in 1967, this radio interferometry technique has revolutionised the fields of geodesy, geodynamics and astrometry. With the unprecedented precision and resolution made possible by VLBI various tasks such as geodetic positioning, reference frames interconnect...

The Permanent Scatterers Interferometric SAR technique (PSInSAR) is a method that accurately estimates the near vertical terrain deformation rates, of the order of ∼1 mm year(-1), overcoming the physical and technical restrictions of classic InSAR. In this paper the method is strengthened by creating a robust processing chain, incorporating PSInSAR analysis together with algorithmic adaptations...

Ground penetrating radar (commonly called GPR) is a high resolution electromagnetic technique that is designed primarily to investigate the shallow subsurface of the earth, building materials, and roads and bridges. GPR has been developed over the past thirty years for shallow, high resolution investigations of the subsurface. GPR is a time-depen­ dent geophysical technique that can provide a 3...

Sensitivity analysis of capital investments can be effectively carried out by employing a metamodel approach and experimental designs. Although polynomial regression metamodels are popular and straightforward, they do not consider spatial relationships among the data. Dual kriging is an estimation technique that allows the incorporation of spatial correlation into the interpolation or estimatio...

Geophysical inverse problems typically involve a trade off between data misfit and some prior. Pareto curves trace the optimal trade off between these two competing aims. These curves are commonly used in problems with two-norm priors where they are plotted on a log-log scale and are known as L-curves. For other priors, such as the sparsity-promoting one norm, Pareto curves remain relatively un...

The post-perovskite phase of (Mg,Fe)SiO 3 (PPv) is believed to be the main mineral phase of the Earth's D " layer (2700-2890 km depths). Its properties explain 1-6 numerous geophysical anomalies associated with this layer: e.g., the D " discontinuity 7 , its topography 8 and seismic anisotropy 9. Here, using a novel simulation technique, first-principles metadynamics, we identify a family of lo...

Digital image correlation is a measurement technique that allows one to retrieve displacement fields “separating” two digital images of the same sample at different stages of loading. Because of its remarkable sensitivity, it is not only possible to detect cracks with sub-pixel opening, which would not be visible, but also to provide accurate estimates of stress intensity factors. For this purp...

A data assimilation strategy based on feedback control has been developed for the geophysical sciences— a strategy that uses model output to control the behavior of the dynamical system. Whereas optimal tracking through feedback control had its early history in application to vehicle trajectories in space science, the methodology has been adapted to geophysical dynamics by forcing the trajector...

Recently developed methods for inferring abrupt changes in data series enable such change points in time or space to be identified, and also allow us to estimate noise levels of the observed data. The inferred probability distributions of these parameters provide insights into the capacity of the observed data to constrain the geophysical analysis and hence the magnitudes, and likely sources, o...

Neural networks are increasingly popular in geophysics. Because they are universal approximators, these tools can approximate any continuous function with an arbitrary precision. Hence, they may yield important contributions to finding solutions to a variety of geophysical applications. However, knowledge of many methods and techniques recently developed to increase the performance and to facil...