Why study this topic? The challenges
Engineering seismology is the field linking seismologists to engineers. Seismology studies how earthquakes happen, while earthquake engineering studies how structures respond to them. Norman Abrahamson, one of the most renowned scientists in this field, has been known to say that ‘Engineers do not design for earthquakes; they design for ground motions’. Indeed, engineers do not design our society’s buildings and infrastructures to withstand a given earthquake that may occur dozens or even hundreds of kilometres away, but rather to withstand a given (strong) ground motion applied at foundation level. Engineering seismology uses seismic data recorded at permanent and temporary accelerometric networks and other infrastructures, as well as theoretical and numerical tools and methods, in order to estimate the characteristics of the expected ground shaking that will determine the response of the building stock at a given region under seismic excitation.
Ground motion at a given site is affected by the seismic source (the magnitude and rupture mechanism of the event), the path travelled by the seismic waves from the source (a.k.a. focus or hypocentre) to the site where the structure of interest lies, and the underground characteristics of the site itself (layering, material properties of the soils and rock formations present). The ground shaking caused by any given earthquake cannot be reduced, generally speaking, nor can it be predicted in an absolute manner. However, some of its characteristics (maximum intensity, duration, frequency content) can be estimated, and based on such predictions, the load-bearing elements of a structure can be designed so as to exhibit the required strength and serviceability during an earthquake in order to avoid casualties. Thus, advances in seismic hazard research can lead to the reduction of seismic risk and societal losses, and to the improvement of future seismic design codes.
Our key research activities
- Ground motion attenuation and variability
- Site response, effect of local soil conditions (empirical estimation, numerical simulation)
- Defining reference motion and bedrock conditions, high-frequency phenomena
- Seismic hazard estimation and quantification of uncertainties for critical facilities and infrastructures
- Synthetic ground motions (stochastic methods, Green’s functions)
Our operational activity, infrastructure and services
- Developing and maintaining NOA’s permanent strong-motion network
- Installing special accelerometric arrays for structural monitoring of modern and historical structures
- Providing strong-motion data, ShakeMaps and significant-earthquake reports
- Seismic hazard assessment and microzonation studies
- Using macroseismic and strong-motion data for educational purposes
- NOA is a founding member of the European organisation EFEHR (European Facilities for Earthquake Hazard and Risk)