Summary The objective of this study is to find an efficient way to measure bedrock depth and geotechnical parameters through the estimation of shear wave velocity, Vs. The Norwegian Geo Test Sites (NGTS) initiative aims to establish five national test sites as field laboratory for testing innovative soil investigation and foundation methods. We have measured ambient seismic noise data as well as Multichannel Analysis of Surface Waves (MASW) data at two NGTS sites, Onsøy and Halden. The results of the shear-wave inversions are compared with ground-truth measurements from the two well-characterized sites. The results obtained with the passive seismic test and the MASW active test are quite similar despite the fact the passive method requires less time and equipment in the field.
Recently, the development of international standard on geophysical techniques has been discussed in ISO (International Organization for Standardization) / TC 182 (Geotechnics) / WG 9 (Geotechnical aspects of geophysical methods). In the WG 9, an international standard providing specifications of equipment and survey procedure of array measurement of microtremors which is one of the non-destructive testing methods with an array of sensors deployed on the ground surface, and data analysis of array records of microtremors (e.g. EAGE [2014]; Foti et al. [2017]) has been developing. The standard is intended for use by administrators of infrastructure facilities, building constructors, house builders, consultants, academia, and public/private research institutions to measure and evaluate soil structure and geotechnical site characteristics, with a view to contributing to various engineering fields. The international standard "array measurement of microtremors to estimate shear wave velocity profile" focuses on the array measurement of microtremors using vertical ground vibration to estimate an S-wave velocity profile by processing microtremor records as fundamental mode of Rayleigh waves. The document specifies requirements for equipment, survey procedure, data analysis, and reporting of array measurement of microtremors. This paper reports the outline of the international standard "array measurement of microtremors to estimate shear wave velocity profile" under development.
Heavy damage was observed in Muzaffarabad, Pakistan due to the 2005 Kashmir earthquake, especially on terraces with thick well compacted gravel deposits and along the terrace rims. We evaluated the damage distribution visually from Ikonos satellite images. In an effort to contribute to the restoration of Muzaffarabad city and its future urban and infrastructure development, we investigated the area's geomorphology and measured microtremors at some 20 locations. The four terraces in the city consist of well compacted gravel deposits and our microtremor results indicate slightly higher amplification values and lower fundamental frequencies on the thicker deposits in the South-East of the city, where damage was very severe. We hope our study will be a good complement to JICA's (Japan International Cooperation Agency) Master plan for the city's reconstruction.
