Seismic hazard

We perform complete seismic hazard studies to provide earthquake design data for a large variety of projects. Our experience includes strategic buildings, offshore platforms, deepwater pipelines, subsea facilities, wind farms, LNG terminals, ports, infrastructure projects and nuclear power plants. We assess seismic hazard by applying the classic probabilistic approach developed by Cornell (1968) and its continuous refinements to keep up with the most recent developments from the scientific community. RINA also provides studies on induced seismicity, a phenomenon often associated with mining, construction of large dams as well as hydrocarbon exploitation and carbon storage projects, to complete the offering of seismic hazard assessment. 

The results of PSHA are given in terms of: 

- Hazard curves 

- Uniform Hazard Spectra (UHS) 

- Peak Ground Acceleration (PGA) and Peak Ground Velocity (PGV) 

- Seismic hazard maps 

- Deaggregation of hazard 

While the Probabilistic Seismic Hazard Analysis (PSHA) is employed to define the earthquake motion at the seismic bedrock regardless of the structural type and ground type, the Site-Specific Response Analysis (SSRA) is the most powerful tool to obtain the design earthquake motion at the ground surface or at the foundation of a structure. 

We implement 1D non-linear SSRA in the time-domain to model the influence of the shallow sediments, which act as a filter on the earthquake ground-motion, causing amplification/de-amplification of the seismic waves propagating from the earthquake source. The non-linear approach provides reliable and accurate results, especially for high-intensity input motions. The higher computational efforts required by this approach are well-balanced by the expertise of RINA’s team of geotechnical and seismic engineers, who combine their technical capabilities to ensure that the highest-quality results are delivered to Clients.  

Results of SSRA are usually provided as technical report and digital data, in terms of: 

- acceleration and displacement time series at the surface and/or at the desired depth along the soil profile 

- spectral amplification factors based on the dynamic response of local soil conditions 

- acceleration design response spectra 

SSRA results are validated through sensitivity analysis of the parameters that govern the soil response to guarantee the reliability and robustness of the outputs. We work in close collaboration with Clients to meet their needs and solve problems in the most effective way, providing full assistance on the interpretation of the results delivered. 

Liquefaction poses major challenges to the geotechnical design of foundations and buried pipes. Soil liquefaction occurs when the effective stress of soil is reduced to nearly zero, causing a subsequent fluid like behavior which may be exhibited by saturated soils under cyclic loading. Such loadings can result from horizontal ground shaking during an earthquake, or from wave pressure on the sea floor during storms. 

RINA is well suited to provide assessment on this complex phenomenon thanks to our highly qualified team of geotechnical and seismic specialists. According to the project needs, this service can be performed at different levels of detail, including either deterministic or probabilistic methods. 

Stress-based methods are usually employed to assess the factor of safety against liquefaction, defined as the ratio between the Cyclic Resistance Ratio (CRR) and the Cyclic Stress Ratio (CSR). The most reliable way to derive the CSR is from the Site-Specific Response Analysis (SSRA), while CRR can be assessed through CPT data correlations and cyclic laboratory testing measurements. 

While PSHA addresses earthquake induced ground shaking, Probabilistic Fault Displacement Hazard Assessment (PFDHA) considers the impact of the permanent surface deformation, such as fault displacement at the site. During this site-specific analysis the active and capable faults contributing to the overall hazard at the site are identified, and the hazard is modelled considering both primary and secondary faulting at or near the site. The key parameters controlling the hazard variability in terms of annual probability of exceedance are investigated, and the uncertainties are accounted for in logic-tree approach. 

We have expertise of applying PFDHA to various types of sites at different kinds of fault structures worldwide. Being a relatively novel approach, we follow closely the scientific developments of the methodology in order to follow the current state-of-practice. 

PFDHA consists of: 

- Identifying the seismic sources impacting the site 

- Defining the probability and slip parameters of surface rupturing 

- Calculating the hazard at the site given in terms of annual frequency of exceeding a selected displacement level following the state-of-practice of PFDHA. 

A tsunami is one of the most powerful and destructive natural forces that can be generated in all the world's oceans, inland seas, and in any large body of water. Each of these regions of the world has its own cycle of frequency to generate tsunami. 

Tsunami are huge waves triggered by large earthquakes, volcanic processes, submarine and/or onshore landslides. Earthquakes and subduction mega-earthquakes are the primary cause of the largest tsunamis. Before reaching the nearshore and onshore areas, the height of the tsunami waves is influenced by the shape of the seafloor and the bays as well as that of the coastlines.  

After the last mega-thrust subduction earthquakes which caused the most destructive tsunami events of the last century (e.g., 1960 Chile, 2004 Indian Ocean, and 2011 Tohoku), the research on the tsunami hazard accelerated globally. Tsunami Hazard Assessment can be performed by applying either deterministic or probabilistic methodologies. Following the PSHA approach, Probabilistic Tsunami Hazard Assessment (PTHA) aims to estimate the possibility of a tsunami occurrence in a target location, quantifying the probability of exceedance of tsunami intensities in a defined time-window. The results offer a probabilistic simulation of the tsunami wave height on the site location, the inland potential inundation, and the runup wave characteristics.