Probabilistic seismic hazard assessment of Nepal for revision of national building code NBC105 (2020)
Being located in seismically active Himalayan mountain belt, Nepal has been the locus of many devastating earthquakes. The Mw 8.4 Bihar-Nepal earthquake of 1934 AD was the biggest earthquake disaster in Nepal that had highlighted the need of a building seismic design code for safer construction. Though the necessity was realised earlier, Nepal developed its first National Building Code (NBC-105) only in 1994 after the 1988 Mw 6.9Udayapur earthquake in eastern Nepal. In April 2015, central Nepal witnessed the Mw 7.8 Gorkha earthquake, which had epicentre at Barpak village of Gorkha district, about 75 km west of Kathmandu. The ground mtions recorded at soft soil sites in Kathmandu Valley clearly show strong site effect resulting in high energy in long period, i.e. at 3s to 5s. A comparative study has revealed that, at least in Kathmandu Valley, the observed ground motions exceeded the seismic design demand proposed by NBC-105 for some period ranges. Unsurprisingly, the earthquake caused extensive damage to buildings and infrastructures in 14 districts(mostly towards east of the epicentre due to further ruptured directivity effect) and killed 8,970 people. This earthquake also triggered revision of the existing national building code (known as NBC- 105)by the Government of Nepal.A key feature of the revision of NBC-105 has been re-assessment of national seismic hazard by adopting a probabilistic approach. Since the development of NBC-105 in 1994, a large number of studies have been carried on seismo-tectonics, active fault, paleoseismology, seismicity, geodesy etc, which have significantly increased the level of knowledge on seismic sources in the central Himalayas. In addition, after the 2015 Gorkha earthquake, much knowledge is gained on the geometry of the main seismogenic fault, the Main Himalayan Thrust (MHT) also called the Main Frontal Thrust (MFT) at the surface of the Himalayan front. Based on recent researches, in contrast to seismic sources adopted in 1994, a fault source (MHT) and area sources, i.e. northern garbens in Tibet, strike-slip event dominant sources in eastern and western Nepal and a source south of MHT are considered for seismic hazard analysis. As there is no specific Ground Motion Prediction Equation (GMPE) for the Himalayas, based on seismo-tectonics, GMPEs are adopted including Next Generation Attenuation laws. More than two GMPES are used for each source using the logic tree approach. Seismic hazard is computed for 2%, and 10% probability of exceedence in 50 year. In contrast to hazard map of 1994, the zones of relatively higher Peak Ground Acceleration (PGA) i.e. 0.36g to 0.46g are, for 10% probability of exceedence in 50 year, concentrated just above the locked portion of MHT throughout the country. The PGA values gradually decrease towards the north and south of MFT. This pattern of PGA distribution is consistent with the coupling nature of the MHT in the Himalayas.
CitationChamlagain D, Niraula GP, Maskey PN, Bista MK, Tamrakar MR, Gautam BK, Ojha S, Dhakal R, Acharya IP (2020). Probabilistic seismic hazard assessment of Nepal for revision of national building code NBC105. Sendai, Japan: 17th World Conference on Earthquake Engineering (17WCEE). 27/09/2021-02/10/2021.
This citation is automatically generated and may be unreliable. Use as a guide only.
KeywordsSeismic Hazard Assessment; Main Himalayan Thrust (MHT); National Building Code-105; Nepal
ANZSRC Fields of Research40 - Engineering::4005 - Civil engineering::400506 - Earthquake engineering
40 - Engineering::4010 - Engineering practice and education::401001 - Engineering design
RightsAll rights reserved unless otherwise stated
Showing items related by title, author, creator and subject.
Maskey PN; Tamrakar MR; Bista MK; Ojha S; Gautam BK; Acharya I; Chamlagain D; Dhakal, Rajesh (2020)The NBC 105: 2019 Seismic Design of Buildings in Nepal is the revised version of the original code for seismic design first published in 1994. The code has never been reviewed and updated since then till the moment. ...
Maniyar, M.; Khare, R.K.; Dhakal, Rajesh (University of Canterbury. Civil and Natural Resources Engineering, 2009)In this paper, probabilistic seismic performance assessment of a typical non-seismic RC frame building representative of a large inventory of existing buildings in developing countries is conducted. Nonlinear time-history ...
Bradley, Brendon; Cubrinovski, M.; Dhakal, Rajesh; MacRae, G.A (University of Canterbury. Civil and Natural Resources Engineering, 2010)This paper presents the probabilistic seismic performance assessment of an actual bridge-foundation-soil system, the Fitzgerald Avenue twin bridges. A two-dimensional plane strain finite element model of the longitudinal ...