Search

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]

Purpose: The scarcity of flat lands in the hilly region forces the construction of buildings on sloping terrain with foundations constructed at different levels. These buildings are inherently vulnerable to earthquakes due to horizontal and vertical irregularities that are extremely hard to avoid because of the nature of the terrain. Compounding on that fact, a large stock of buildings in the hilly region have been constructed without following the earthquake-resistant design provisions, the consequences of which were evident in past seismic events such as the 2011 Sikkim earthquake and the 2015 Nepal earthquake. Methods: The paper aims to assess the explicit and combined effect of seismic design provisions of Indian Standards on the seismic response of a set of Un-Reinforced Masonry (URM) infilled Reinforced Concrete (RC) buildings on a hill with the prevalent configuration observed. 3D analytical models have been considered for the RC frame elements with infill-frame interaction taken into account by diagonal strut elements. Incremental dynamic analyses have been performed for a realistic assessment of key parameters influencing the seismic performance of such buildings. Results: It has been observed that the seismic response parameters in terms of joint displacement and inter-storey drift ratio are higher for buildings designed considering only gravity loads as compared to buildings designed as Special Moment Resisting Frame (SMRF) as per relevant Indian seismic design standards whereas minor variations were observed in the roof acceleration and Peak Storey Acceleration (PSA). It has also been observed that collapse probability at any given seismic hazard level reduces significantly when the Gravity Load Designed (GLD) RC building is designed and detailed as SMRF. It has further been observed that the collapse probability of the GLD RC building can be reduced by more than 40% at the design seismic hazard level if seismic design and ductile detailing provisions are implemented. [ABSTRACT FROM AUTHOR]

We model interseismic plate coupling distribution on the Main Himalayan Thrust (MHT) in Nepal through the inversion of secular GNSS velocity data. To complement previously published data, we compile velocity data from ten additional continuous stations to improve spatial resolution in central and mid-western Nepal. A regional non-planar structural model is adopted to reproduce the MHT fault plane. In general, the coupling pattern seems nearly binary, indicating that transition from full coupling to decoupling is occurring sharply in very narrow zones. In eastern Nepal (> 84.5ºE), plate coupling is very strong from the surface to intermediate depths, including the source region of the 2015 Mw 7.8 Gorkha earthquake. Geodetically estimated slip deficit rates are consistent with the rupture history of great earthquakes in the east revealed by geomorphological observations. In the west (< 83.0ºE), a weakly coupled zone extends laterally at intermediate depths, whereas the coupling in the shallower part remains very strong. Although the slip deficit rate in the west is significantly smaller than that in the east, seismic moment accumulated, since the last complete rupture in 1505 may be capable of generating a future great event. In central Nepal, estimated slip deficit rates are comparable with those in the east, and no great event has been documented over the past several centuries. Thus, the seismic risk may be most urgent in central Nepal. The development of local seismicity and crustal deformation should be carefully monitored. [ABSTRACT FROM AUTHOR]