Dynamic Characterization of High Plinths of Temples in the Kathmandu Valley Using Microtremors

ABSTRACT

The 2015 Gorkha earthquake damaged many unreinforced masonry buildings in the UNESCO World Heritage Sites of Kathmandu Valley, such as Kathmandu, Patan, and Bhaktapur. But there were a few multi-tiered temples, with high plinths, that survived the recent earthquake. The temples with a massive high plinth have shown better seismic performance both in past historical earthquakes as well as in the recent 2015 earthquake. In this paper, the results of a reconnaissance survey conducted to assess the seismic effect on the high plinth caused by the 2015 Gorkha earthquake is presented first. Extensive field investigation of excavation works indicates the bulky volume of the traditional construction materials were used to build the high plinth with distinct construction techniques. Second, the dynamic properties of high plinths of nine Nepalese temples measured from microtremor data are presented. The damage assessment shows that the 2015 Gorkha earthquake had minor effects on the plinths. The predominant frequencies obtained at the ground points nearby the temples vary from 0.44–1.32 Hz and predominant frequencies obtained from the H/V spectral ratio ranged 2.88–12.70 Hz. Damping ratios obtained vary from 2.01–8.50%. 1-D wave propagation shows that the plinth act as damping agent.

KEYWORDS:

• Pagoda temples
• high plinth
• damage assessment
• microtremor
• natural period
• damping ratio

Acknowledgments

The authors would like to express sincere gratitude to Professor Dr. Netra Prakash Bhandary, Graduate School of Science and Engineering, Ehime University, Japan, for his kind consent to use the microtremor instrument.