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In Geophysics, topographic factors are observations that can be directly measured, but they are often ignored to simplify the model. Studying the coseismic deformation caused by earthquakes helps accurately determine the epicenter's parameterization. It provides a reference for the reasonable layout of coseismic observation stations and GNSS observation stations. After the Mw7.8 earthquake in Nepal in 2015, GCMT, USGS, GFZ, CPPT, and other institutions released their epicenter parameter. However, according to their parameters, the coseismic displacements simulated by the spectral-element method are quite different from the GNSS observations. Firstly, this paper inverts the geometric parameters of the seismogenic fault with Nepal's coseismic GNSS displacement. The spectral-element method determines the source's location and depth under the heterogeneous terrain and outputs the source parameters. Among the results of many studies, the surface source is more consistent with the generation mechanism of large earthquakes. Secondly, this paper calculates the fault slip distribution of this earthquake using SDM (Steepest Descent Method) based on GNSS and InSAR data, which is divided into 1500 subfaults, and the moment tensor of each subfault is calculated. This paper investigates the distribution characteristics of the coseismic deformation field of the 2015 Mw 7.8 earthquake in Nepal under three different models. The results show that the influence of topographic factors is ~ 20%, and the influence of heterogeneous factors is ~ 10%. This paper concludes that the influence of topographic factors is much more significant than that of heterogeneous factors, and the influence of both should be addressed in coseismic deformation calculations. [ABSTRACT FROM AUTHOR]

This paper describes the results of an experimental investigation on the coefficient of friction at the interface of a PVC–sand–PVC layer that is utilised as part of a low-cost geotechnical seismic isolation devised to be used in low-income countries. The PVC–sand–PVC configuration consists of two smooth PVC surfaces enclosing a single layer of sand grains, with surface densities between 0.5 kg/m2 and 3 kg/m2, which aim to facilitate relative sliding at friction resistance between 0.15 and 0.30 depending on the design acceleration, by acting like "non-perfectly rounded ball bearings". The latter isolation method has been extensively studied both numerically and experimentally by means of large-scale testing at the shaking table of the EQUALS Earthquake Laboratory of the University of Bristol. However, in the light of the construction of the first building worldwide to be designed and constructed in Nepal with the particular low-cost PVC–sand–PVC sliding interface, it was deemed necessary to reliably assess the mean and dispersion of the coefficient of friction as a function of vertical pressure, sand density and degree of saturation. The results of the tests performed using an improved direct shear apparatus are presented herein using sand samples and PVC sheets that were locally resourced in Nepal to be used in construction. The results indicate that the variation of friction is reasonably low and in any case within the desirable range, irrespectively of the parameters examined, thus establishing confidence to the forthcoming design of the novel isolated building. [ABSTRACT FROM AUTHOR]