Seismic Hazard Assessment

Name of the provider (company name or main contact name), or FIRE IN ID ? George Kaviris, National and Kapodistrian University of Athens

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Scope, rationale, context: general description. Precise here if this technology is currently use (eg. company name or contact info) Estimation of seismic hazard is seismic prone areas and for critical infrastructure (e.g. bridges, national roads, pipelines). These studies can be provided as a service. Seimic hazard assessment is based on scientific methods and tools that are applied worldwide and accepted by the scientific community

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The first step towards reliable seismic hazard assessment is the compilation of the earthquake catalogue that will be utilized. For that purpose, a detailed seismological study has to be compiled. Sources of both historical and instrumental seismicity are used. Following, the completeness of the earthquake catalogue is examined.
Both the probabilistic and the deterministic seismic hazard assessment require the assignment of a ground motion prediction equation (GMPE). GMPEs are probabilistic relations between earthquake characteristics, distances and site conditions. In other words, GMPEs are statistical models used to predict the ground shaking in terms of ground motion parameters. GMPEs are a powerful tool for engineering seismology and earthquake engineering and are widely used to assess seismic hazard. .
Probabilistic Seismic Hazard Assessment (PSHA) is performed with two independent methodologies. The first, zone-free, adopts the extreme values method and requires only an earthquake catalogue and one GMPE per ground motion parameter (PGA, PGV and PGD). The second, apart from the above, also requires the inclusion of seismogenic sources. Both methods are applied for certain return periods:
• 475 years (90% probability of not being exceeded in 50 years), the return period adopted in National Building Codes
• 950 years (90% probability of not being exceeded in 100 years) that represents the Safe Shutdown Earthquake (SSE)
• 1950 years (95% probability of not being exceeded in 100 years) that represents the Maximum Design Earthquake (MDE)
The extreme values distribution was founded by Gumbel in 1939 and has extensively been applied to seismic hazard studies. Catalogue completeness causes less severe problems when maximum values are used. The maximum values approach is useful in aseismic design, where the knowledge of either the maximum dynamic load that might be applied on a structure in its life expectancy period, or the most probable reoccurrence period of such a load at that site is essential. The results of all seismic hazard parameters (Mmax, PGA, PGV and PGD) fare will be presented with maps and iso-contour lines.
The second PSHA methodology that is applied incorporates sesimotectonic models which combine seismicity and the basic tectonic elements. The main objective of any modeling effort is the determination of a distribution law for the parameter of interest i.e. PGA, PGV and PGD, in terms of time intervals and area. Thus, the methodology presently applied in estimating seismic hazard, includes the following stages: (i) Definition of the seismic zones. (ii) Assumption of a certain stochastic process in time for earthquake occurrence. (iii) Determination of the relation between number of earthquakes and magnitude for each zone. (iv) GMPE assignment per seismic hazard (PGA, PGV and PGD) parameter. (v) Determination of the seismic hazard. The results of the seismic hazard parameters (PGA, PGV and PGD) are presented with maps and iso-contour lines.
Results obtained by the two independent methodologies are compared.

Deterministic Seismic Hazard Assessment (DSHA) refers to the computation of synthetic time histories of ground motion. The simulation of the strong ground motion is performed through an empirical method where time and frequency features of the motion are represented through the physical spectrum, extending the spectral moment’s theory to the nonstationary case by summing Fourier series with time-dependent coefficients. The simulated time histories fit the recorded accelerograms in terms of ground-motion amplitude measures, such as peak acceleration, peak velocity and peak displacement. The main advantage of the method that is applied consists in correlating the simulation parameters with earthquake magnitude, source distance and soil conditions.

TRL of the proposed solution - Innovation stage (if applicable) 9: System Test, Launch & Operations

Expected/scheduled future developments

Use of algorithms to perform hybrid seismic hazard assessment regarding low, intermediate and high frequencies to be applied for both residential buildings and critical infrastructures.

Generic comments

The proposed solution is a service