Analysis and modeling of earthquake strong-motion site effects on Icelandic arrays for earthquake engineering applications

• Main Author: Rahpeyma, sahar
• Other Authors: Benedikt Halldórsson, Umhverfis- og byggingarverkfræðideild (HÍ), Faculty of Civil and Environmental Engineering (UI), Verkfræði- og náttúruvísindasvið (HÍ), School of Engineering and Natural Sciences (UI), Háskóli Íslands, University of Iceland
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: University of Iceland, School of Engineering and Natural Sciences, Faculty of Civil and Environmental Engineering 2018
• Subjects: Site-effect; Bayesian Hierarchical Model; Arrays; Jarðskjálftaverkfræði; Jarðskjálftamælingar; Bayesísk tölfræði; Líkön; Doktorsritgerðir; Hveragerði; Tjörnes; Húsavík; Iceland
• Online Access: https://hdl.handle.net/20.500.11815/987

A comprehensive site-effect investigation framework was developed and applied to earthquake strong-motion data collected on small-aperture urban arrays, the ICEARRAY I in Hveragerði in the South Iceland Seismic Zone and ICEARRAY II in Húsavík in the Tjörnes Fracture Zone in the north, where considerable variations over short distances in ground motion amplitudes have routinely been observed. Through the Horizontal-to-Vertical Spectral Ratio and Standard Spectral Ratio methods the amplification levels were shown to remain relatively low on lava rock, but predominant frequencies of resonance were found that vary systematically and correlate with the local soil structure and geological units. For stations on lava-rock characterized by one or more velocity reversals due to softer sedimentary layers at depth, modeling the soil structure as a two-degree-of-freedom dynamic system captures the observed predominant frequencies. For non-reversal sites, an inversion procedure for the velocity profile based on Bayesian statistical theory was developed. Furthermore, a versatile Bayesian Hierarchical Model (BHM) was developed and applied to peak ground acceleration data, quantifying the contribution of earthquake source, wave propagation and local geological effects to PGA variations. This study thus improves the modeling of site effects in Iceland, quantifies the variabilities of physical parameters of the subsoil through a Bayesian inversion technique, and through the new BHM shows that for ICEARRAY I the earthquake effect dominates the variability while for ICEARRAY II, the site effects are dominating. The results of this study thus facilitate our understanding of local ground motions and have practical implications for urban planning and seismic hazard assessment. Í þessu verkefni voru staðbundin mögnunaráhrif efstu jarðlaga á jarðskjálftabylgjur greind með jarðskjálfta- og jarðsuðsgögnum frá ICEARRAY hröðunarmælafylkingunum í Hveragerði og á Húsavík, en þær einkennast af umtalsverðum breytileika á einkennum og umfangi ...