An empirical relationship between seismic bedrock depth and fundamental frequency for Değirmendere (Kocaeli-Turkey)

Abstract

Sediments’ thickness is one of the important parameters in seismic hazard assessment. This study aims to establish a new empirical relationship to determine the overburden layer thickness on seismic bedrock by using a relationship between the fundamental frequencies obtained from microtremor measurements and seismic bedrock depth obtained from microgravity measurements and subsequently produce an approximate seismic bedrock depth distribution map for the study area. In this context, ambient noise analyses were performed to estimate the fundamental frequency of the ground. Within this scope, noise measurements at 43 points were established in the study area. Determined fundamental frequencies and seismic bedrock depths obtained by microgravity measurements were iteratively processed to calculate the best-fitting exponential function for the empirical depth–frequency relation. This relation was established as $$m = 338.2 \cdot f_{0}^{ - 0.6558}$$ (m is seismic bedrock depth, f 0 is fundamental frequency) for the study area.