Seismic bedrock depth represents one of the crucial steps in site response analysis as the input seismic ground motion is propagated from the bedrock level through soil profile column to estimate surface ground motion. In the last two decades, several studies estimated bedrock depth using microtremor horizontal-to-vertical-spectral ratio fundamental (resonance) frequency and known (mostly boreholes) bedrock depth in different regions through power-law regression. In this study, seismic bedrock (H₈₀₀—depth of the bedrock formation identified by shear wave velocity V_S ≥ 800 m/s) is estimated using H/V forward modelling routine in which shear wave velocity profile from geophysical measurements was used as an initial soil model. Based on geological, geophysical and microtremor data, empirical relationships between average shear wave velocity in top 30 m, resonance frequency and bedrock depth are derived. Given evaluation of sedimentary thicknesses showed to be within the range of published studies for similar geological and site characteristics if the errors between different methods, approaches and site parameters are considered. The main limitation to validate proposed relationships is the lack of realistic deep borehole data like in similar studies. Further work is required that should include deep data from borehole drilling, seismic refraction and reflection or vertical electrical sounding. The intention is that presented regressions between resonance frequency, bedrock depth and V_S30 would be implemented into nonlinear site amplification model and further development towards Ground Motion Prediction Equations for Croatia.

地震基岩深度代表现场响应分析中的关键步骤之一，因为输入地震地震动从基岩水平传播到土壤剖面柱，以估算地表地面运动。在过去的二十年中，有几项研究使用微震水平/垂直频谱比的基波（共振）频率和不同区域的已知（主要是钻孔）基岩深度，通过幂律回归来估算基岩深度。在这项研究中，地震基岩（H _800-通过剪切波速V _S确定的基岩形成深度 ≥800 m / s）是使用H / V前向建模程序估算的，其中将来自地球物理测量的剪切波速度剖面用作初始土壤模型。根据地质，地球物理和微震数据，推导出30 m以内的平均剪切波速度，共振频率与基岩深度之间的经验关系。如果考虑到不同方法，方法和场地参数之间的误差，则对沉积厚度的评估表明在相似地质和场地特征的已发表研究范围内。验证提议的关系的主要局限性是缺乏类似研究中的实际深井数据。需要做进一步的工作，其中应包括来自钻孔，地震折射和反射或垂直电测深的数据。V _{S 30}将被应用到非线性场地放大模型中，并进一步发展为克罗地亚的地面运动预测方程。