Unearthed lessons of 25 April 2015 Gorkha earthquake (M_W 7.8): geotechnical earthquake engineering perspectives

Abstract

Gorkha earthquake (M W 7.8) of 25 April 2015 struck central, eastern and western Nepal and neighbouring areas. Enormous losses during Gorkha earthquake were attributed to collapse of 498,852 buildings, 446 public health facilities and partial damage of 256,697 buildings, 765 health facilities as well as severely affected 2900 cultural and historical sites. Anomalies were in particular observed in terms of localized damage and recurrent damages during 1833, 1934, 1988 and 2015 earthquakes. This paper reports geotechnical earthquake engineering observations noted during field reconnaissance conducted in affected areas. Damage reports from historical as well as recent Gorkha earthquakes are mapped in this paper. To depict lessons, forensic interpretations are presented considering 1833, 1934, 1988 and 2015 earthquakes.

Probabilistic seismic liquefaction hazard assessment of Kathmandu valley, Nepal

“…As the return period of 73 years, none of the borehole locations depicted considerable liquefaction probability ( < 0.05) for any magnitude of earthquake at any depth, and mapping was not done for this return period either. This highlights that at low PGA occurrence during the earthquakes, liquefaction is not expected throughout Kathmandu Valley, which is consistent with the observations during 2011 Sikkim-Nepal border earthquake (Gautam 2017a). Similarly, for 475 years return period, eastern and central areas of Kathmandu Valley depicted higher liquefaction probabilities as shown in Figures 4 and 5.…”

“…Soil liquefaction is getting considerable attention in almost all seismically active regions worldwide. To date, many researchers have used evidence-based, experimental, and analytical assessment of soil liquefaction in many parts of the world (e.g., Singh, Roy, and Jain 2005;Idriss and Boulanger 2006;Cox et al 2013;Gautam, de Magistris, and Fabbrocino 2017;Gautam 2017a;Bray et al 2014;Verdugo and Gonz alez 2015;Cetin et al 2004;Kramer and Mayfield 2007;among others).…”

Mapping surface motion parameters and liquefaction susceptibility in Tribhuvan International Airport, Nepal

“…Details regarding ground motion and field observations during Gorkha seismic sequence are reported by several researches (e.g. Angster et al 2015;Parameswaran et al 2015;Ahmad & Singh 2016;Gautam & Chaulagain 2016;Gautam et al 2016aGautam et al , 2016bRai et al 2016;Gautam 2017aGautam , 2017bRupakhety et al 2017). Recent studies highlight the possibility of major earthquakes in Nepal Himalaya (e.g.…”

“…Soil liquefaction can be detrimental in terms of damage aggravation in building infrastructures and lifelines as observed during 2015 Gorkha earthquake (e.g. Angster et al 2015;Gautam & Chaulagain 2016;Gautam 2017b). During 1964 Alaska earthquake (M w 9.2), 1964 Niigata earthquake (M w 7.6) and 1989 Loma Prieta earthquake (M w 6.9), soil liquefaction was one of the major causes of destruction.…”

“…Several strong to major earthquakes have highlighted damage concentration in Kathmandu Valley even in case of far-field events like the 1833, 1934 and 2015 events. Strong to major earthquakes like the 1934 Bihar-Nepal (M w 8.1) and 1988 Udaypur (M w 6.8) and 2015 Gorkha (M w 7.8) depicted that damage would occur particularly in alluvial soft soil deposits recurrently in case of Kathmandu Valley (Rana 1935;Fujiwara et al 1989;Gautam et al 2016aGautam et al , 2016bGautam & Chaulagain 2016;Gautam 2017aGautam , 2017b. In addition to this, major urban centres, critical facilities and residential areas are situated in these formations, so future earthquakes may also affect the same areas severely.…”