Damage assessment within the Kathmandu valley’s World Heritage Monument Zones after 2015 Gorkha Earthquake

Kathmandu, the capital city of Nepal experienced a cultural catastrophe in the aftermath of the 2015 Gorkha Earthquake (Mw=7.8) which destroyed hundreds of historical and cultural monuments. Five out of the seven mountain zones within Kathmandu’s UNESCO World Heritage Sites suffered damage ranging from the complete collapse of several temples near Hanumandhoka’s Durbar Square to partial damage at Changu Narayan. This study presents the results of reconnaissance surveys conducted in December 2017 and June 2018 within the Pashupati and Changu Narayan monument zones investigating the plausible causes of damage incurred. Geotechnical assessment of soils reveals the presence of gravelly sand at Pashupati and clayey silt at Changu Narayan. The soil-water retention characteristics and strength parameters of these soil were also obtained in the laboratory. Evidence of rotation and differential settlements in the foundations of the ancient structures was not observed suggesting that soil liquefaction had not taken place at these locations. Structural damage patterns observed at these sites indicated a lack of periodic maintenance and low bending and shear stiffness of the masonry walls of the temples. This study suggests engineering interventions and monitoring systems that could safeguard these structures in the event of future earthquakes.