Use of Ambient Vibration Methods for Post-Earthquake Geotechnical Reconnaissance in Kathmandu, Nepal


Abstract eng:
The Canadian Association of Earthquake Engineering sent a seven member team to Kathmandu, Nepal, following the 2015 M7.8 Gorkha earthquake. The M7.8 Gorkha earthquake of 25 April 2015 resulted in ~8800 fatalities and structural damage of ~600,000 buildings. A set of five small Tromino seismographs were brought to Nepal to obtain a crude reconnaissance of potential earthquake site response across Kathmandu. Individual sensor measurements were conducted in several locations across Kathmandu – in locations of minimal to heavy structural damage. Microtremor horizontal-to-vertical spectral ratios (MHVSR) are computed for each individual measurement to obtain an estimate of site period (fundamental frequency) of the subsurface soils. Three groupings of MHVSR response are observed: (1) moderate-to-high amplification at distinct frequencies occurs in locations of heavy structural damage or collapse, (2) low, broad amplification is observed in locations with minimal structural damage, and (3) moderate amplification at high frequencies is observed atop topographic hills and/or rock sites. All five Tromino sensors were also deployed, together as an array, in select locations of Kathmandu for measurement of surface wave dispersion. This paper presents application of surface seismic field techniques for postearthquake geotechnical reconnaissance purposes in Kathmandu, Nepal.

Contributors:
Conference Title:
Conference Title:
16th World Conference on Earthquake Engineering
Conference Venue:
Santiago (CL)
Conference Dates:
2017-01-09 / 2017-01-13
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 Record created 2017-01-18, last modified 2017-01-18


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