Engineering Seismology

Knowledge Deepening / Consolidation

The course is also offered to exchange programme students.

1) Understanding the role and contain of Engineering Seismology, which is the boundary between Seismology and Civil Engineering. The target is to provide all the necessary information about the ground strong motion, which are necessary to design a technical construction, resistant to possible strong earthquakes in an area. 2) Understanding the importance of the information derived from the study of the seismicity of an area where a technical project is to be constructed. Measures describing the level of seismicity of an area. 3) Understanding the factors that affect strong seismic motion. The importance of the source, of the path and of the site conditions in the impact of earthquakes on constructions. 4) Understanding the importance of PGA and PGV 5) Learning the procedure to produce isoseismal maps of a strong earthquake. Globally used intensity scales – relations connecting them. 6) Comprehending the relationship between intensity and magnitude – relationships describing the attenuation of intensities. 7) Learning how to assess an area's seismic hazard and understand its measures. 8) Understanding how technical constructions respond to strong ground motion. Basic principles of Earthquake Engineering. 9) Learning how to conduct a microzonation study.

1. INTRODUCTION – SEISMICITY MEASURES Seismology and society – strongest earthquakes globally and during the 20th century - Economic consequences of earthquakes. Most destructive earthquakes in Greece. Earthquake prediction. Early warning systems. Quantitative measurement of seismicity. Magnitude distribution of earthquakes (Gutenberg-Richter). The importance of b parameter for estimating the seismicity level. 2. GROUND MOTION MEASURES Accelerographs – accelerometers. Factors defining the strong motion (focus, magnitude, path, site). PGD, PGV, PGA. Duration and energy characteristics of strong motion. 3. ATTENUATION RELATIONSHIPS Seismic waves attenuation – Elastic medium: Geometric dispersion – anelastic attenuation – quality factor Q. Velocity and acceleration spectra – attenuation models, use in seismic hazard assessment. Use of GMPEs in seismic codes. Effect of path and local site effects. 4. SITE EFFECTS Definitions. Methods to evaluate site effects. a) Experimental – empirical: ambient noise (Kanai 1956), Spectral ratios over a reference station (SSR). Horizontal over vertical spectral ratio (HVSR). Coda waves technic b) Theoretical: simple models, analysis of ground response (1D or 2D). 5. MACROSEISMIC EFFECTS Macroseismic observations – macroseismic intensity. Isoseismal maps. Isotropic and anisotropic radiation. Relations connecting intensity with magnitude and distance for Greek earthquakes. Near real time shake maps after strong earthquakes. Epicenter and magnitude estimation based on macroseismic observations of historical earthquakes. 6. SEISMIC HAZARD Seismic hazard measurements: Maximum expected values of intensity, magnitude, PGA and PGV. Maximum and dominant values of expected ground motion. Probabilistic and deterministric methods of seismic hazard assessment. 7. STRUCTURES RESPONSE Structure motion equation (single degree of freedom oscillator). Technical structure parameters (oscillation period, damping factor and plasticity index). Elastic and inelastic response spectrum. Design ground motions. Seismic response and design spectra. Structured pseudospectra. Hellenic Seismic Code. Dynamic and static seismic response estimation. Soil classification. Seismic zones. 8. MICROZONATION STUDIES Detailed assessment of ground response for an area. Evaluation of required variables for earthquake planning. Calculation and representation of various parameters distribution at sub-zones of the study area. Seismic hazard scenarios. Composition of microzonation studies. Structure and contain of exercises The exercises will include a step-by-step preparation of a technical report on a seismic hazard study in an area where significant construction is planned (e.g. dam, power plant, etc.) Collection of seismological information of the study area, compilation of a homogeneous earthquake catalog, study of its completeness and determination of seismicity parameters (mean return period for different magnitudes and time intervals, maximum expected magnitude for different time windows, probability of exceedance of magnitude for several time periods). Use of accelerograms to estimate PGA and the corresponding period, as well as the duration of the ground acceleration for values above a certain threshold. Estimates of PGD, PGV and PGA at various distances from the epicenter of a design earthquake Attenuation relations - ground spectral displacement for different values of period, attenuation factor, epicentral distance and earthquake magnitude. Use of ambient noise to estimate predominant period and fundamental frequency Use of ambient noise to estimate Vs30 (and/or Vs20 etc.) through inversion of HVSR. Use of macroseismic observations to create isoseismal maps and surface motion map. Plot of intensity attenuation vs epicentral distance with/without anelastic attenuation coefficient. Convert macroseismic intensities to PGA in order to create shake maps (in the absence of strong motion data) by using various relationships from the literature. Comparison with real data from accelerograms. Probabilistic Seismic Hazard Assessment Deterministic Seismic Hazard Assessment. Combination of probabilistic and deterministic method for the study of an extreme seismic scenario. Use accelerograms and PGA to define absolute and normalized seismic response spectra at surface for several attenuation values. Use of all the above to conduct the final technical report.

Strong motion, site effects, anelastic attenuation, seismic hazard, macroseismic effects, microzonation studies.

17-12-2021