Development of international standard ISO 24057 on the array microtremor survey

<p>　Recently, an array microtremor survey which is one of the non-destructive geophysical methods has been widely applied in Japan and overseas, to estimate the S-wave velocity profile of the subsurface structure. To improve the quality of data and reduce the variability of results that depend on the measurers and analysts, there are guidelines independently established by institutions and research groups in Japan, Europe, and US. At the same time, institutions and research groups in Japan and Europe are conducting international blind predictions for the array microtremor survey, to verify the estimation accuracy of the S-wave velocity profile and the variability of results estimated by the array microtremor survey. Although the array microtremor survey has been widely applied in Japan and overseas, there is no internationally common guideline on the array microtremor survey. Therefore, it is important to establish the international common guideline on equipment specifications and survey procedures for the array measurement of microtremor, and the data analysis. First, in this commentary, we outline the development process of international standards on the array microtremor survey in the international and domestic deliberation activities of ISO/TC 182 (Geotechnics). We, second, explain the scope and basic requirements of an international standard for the array microtremor survey. The developed international standard ISO 24057:2022 "Geotechnics - Array measurement of microtremors to estimate shear wave velocity profile" is a new international common guideline. Therefore, by complying with the basic requirements for array measurements of microtremors and the data analysis in 24057:2022, it is expected the quality of data will be improved and the variability of results will be reduced.</p>