Spatial correlation models of VS30 values: A case study of the Tehran region

Abstract

The average shear wave velocity of the top 30 m of soil profile (VS30) is considered as an indicator of local-site effects in seismic hazard assessment (SHA) studies. Previous research works have demonstrated that in addition to actual VS30 values, their spatial correlation characteristics have considerable effects on the estimated values of earthquake intensity measurements, particularly when the seismic risk assessment of spatially distributed assets and infrastructure networks is of interest. Tehran city, in addition to its proximity to several faults, is situated on a variety of sedimentary textures and encompasses a large number of residential buildings and infrastructure networks. The current study utilizes advanced spatial statistics methods and investigates the spatial correlation characteristics of the random field of VS30 values in Tehran. Moreover, by employing a more comprehensive database of VS30 values measured using geoseismic approaches and using eight spatial interpolation methods, a new estimated VS30 map of Tehran city is provided. The geological formations of the study area are also investigated considering the distribution of sample points with different VS30 values. The findings of the current research can be utilized in spatially correlated SHA studies in the Tehran region and can be viewed as a step towards filling the data gap required for seismic risk assessment studies in this region. Moreover, by identifying the local variations in site classes, the findings of the current study can be used for further detailing of geological formations.