Effects of topographic and geological features on building damage caused by 2015.4.25 Mw7.8 Gorkha earthquake in Nepal: a preliminary investigation report

Abstract

Background: The 2015.4.25 Gorkha earthquake affected about eight million people in Nepal. Most injuries and loss of life were due to building collapse and damage. This work aims to investigate the topographical and geological effects on the severe damage caused by this earthquake. Findings: In one-week field investigation in the earthquake-affected areas, several severely damaged areas with different topographic and geological features were surveyed, as well as the site of Kaligandaki River landslide dam failure. Some general tendency related to the building damage and landslide dam failure was obtained. Conclusions: Through the field investigation, it was found that geological and geomorphological characteristics of a site, combined with the structure feature of the building, such as the short column effect, amplified the seismic vibration and caused severe building collapse and damages, i.e., 1) For buildings on flat area consisting of lacustrine deposit or diluvial deposit, resonance effect might be the main reason, while for the buildings on the top of hills or narrow ridges, topographic effect and sometimes, short column effect should take the main responsibility; 2) For buildings located on the gentle slopes or landslides, the settlement in the infill side caused by the strong seismic vibration can be the main reason; 3) Besides of the building failure on lacustrine deposit, failure patterns in three types of topographic and geological features, i.e., narrow ridges formed by landslides, diluvial deposits and alluvial fans, and landslides, were proposed as the possible mechanism of the building damage caused by the earthquake. For landslide dam failure, it was found that landslide dam could easily breach or collapse, when the landslide-dam-deposits were fine.

The impact of topography on seismic amplification during the 2005 Kashmir earthquake

“…Intensity and duration of seismic-induced ground shaking is mainly determined by earthquake magnitude, depth of hypocenter, distance from the epicenter, medium of the seismic waves, topography and site-specific geology (Kramer, 1996;Wills and Clahan, 2006;Shafique and van der Meijde, 2015;Khan et al, 2017). The influence of the Earth's topography on seismic response has been observed and proven numerically and experimentally (Athanasopoulos et al, 1999;Sepúlveda et al, 2005;Lee et al, 2009a).…”

The impact of topography on seismic amplification during the 2005 Kashmir Earthquake

“…Lee et al (2008). Due to the unavailability of a wave speed model for the area, we assigned constant wave speeds (Vp=2800 m/s, Vs=1500 m/s) and density ρ=2300 kg/m 3 ) in the modelling, representative for upper crustal conditions (Taborda and Roten, 2015;Wang et al, 2016;Makra and Raptakis, 2016).…”

Citizen Disaster Science Education for effective disaster risk reduction in developing countries

“…There were several organizations involved in advocating the DRR, have several programs conducted through government and nongovernmental organizations, even though one study found that the perception and preparedness state for disaster prevention education is not properly placed (Tuladhar et al 2015). The long period dominant ground motion of Gorkha earthquake resulted relatively low damages in low rise buildings (Parajuli and Kiyono 2015), however, several other factors also contributed in structural damage (Sharma et al 2017;Wang et al 2016). Major themes of earthquake safety endorsed by all institutions and media were 'HIDE UNDER THE TABLE or BED' and 'DROP, COVER & HOLD'.…”