The SAFER geodatabase for the Kathmandu Valley: Geotechnical and geological variability

Charlotte El Gilder,Raffaele De Risi,Paul J Vardanega,Rama Mohan Pokhrel,Anastasios Sextos,Prem Nath Maskey,Flavia De Luca,Maximilian J Werner,Domniki Asimaki

doi:10.1177/8755293019899952

Abstract

The Kathmandu Valley is within a seismically active region with only few recorded strong-motion data. Geophysical information in the Valley is also sparse. In addition, the absence of an open database which compiles in situ geophysical tests, borehole records, and geotechnical laboratory data is affecting the advancement of knowledge in the region. This article presents SAFER/GEO-591 database, named after the Engineering and Physical Science Research Council (EPSRC)-funded project Seismic Safety and Resilience of Schools in Nepal (SAFER). SAFER/GEO-591 contains data from groundwater wells and boreholes originally commissioned for research and commercial purposes. This work describes (1) the quality assessment and harmonization process conducted on the dataset, (2) the variation of shear-wave velocity ( VS) measurements and geotechnical parameters with depth and elevation in the Valley, (3) the current understanding of the Valley sediment/bedrock topography, and finally (4) new geological cross sections. A companion article presents an updated VS30map across the Valley based on the contributions of this article. The database can be downloaded from the University of Bristol repository via DOI: https://doi.org/10.5523/bris.3gjcvx51lnpuv269xsa1yrb0rw

Highlights

The Kathmandu Valley and surrounding region has experienced recurring destructive earthquakes: the first recorded circa 1255 CE (e.g. Paudyal et al, 2012, 2013) and later 2015 Mw 7.8 Gorkha earthquake (e.g. Goda et al, 2015)
It is expected that the sediment/bedrock boundary is very steep sided beneath the sediment surface and the hydrological modeling undertaken to date does not characterize this well; these results proved more realistic than when using other interpolation methods, such as Kriging
This article presents a geodatabase for the Kathmandu Valley SAFER/GEO-591

Summary

Introduction

The Kathmandu Valley and surrounding region has experienced recurring destructive earthquakes: the first recorded circa 1255 CE (e.g. Paudyal et al, 2012, 2013) and later 2015 Mw 7.8 Gorkha earthquake (e.g. Goda et al, 2015). The Kathmandu Valley and surrounding region has experienced recurring destructive earthquakes: the first recorded circa 1255 CE The Valley is an intermontane tectonic basin with a base defined by the Main Central Thrust (MCT) formed within the Lesser Himalayas by crustal shortening (Stocklin, 1980). This basin is filled with thick semi-consolidated sediments transported primarily by the Proto-Bagmati River derived from metamorphosed sedimentary sequences surrounding the Valley (Sakai, 2001).

Objectives

Findings

Conclusion