The modelling of intraplate seismic hazard based on displacement

The fundamental relationship between the long period components of the earthquake ground motion and the seismic moment has resulted in the maximum displacement demand to be expressed as a function of the maximum credible earthquake (MCE) and the site-source distance. Interestingly, the effect of the crustal waveguide has resulted in very moderate attenuation of medium and long period waves beyond a critical distance of 70 kilometers in Eastern North America. Consequently, the critical Moment Magnitude (M) and Distance (R) combination can be reasonably assumed to be M=MCE and R=70km. The displacement response spectrum associated with this M-R combination is defined herein as the characteristic displacement response spectrum. The effect of resonance in a flexible soil layer has been accounted for using the recently developed hand calculation procedure which is known as the 'Frame Analogy Soil Amplification' (FASA) procedure. Predictions from the FASA procedure have been found to be in excellent agreement with large number of simulations using program SHAKE and limited measurements from an instrumented borehole. The displacement predictive model described in this paper is essentially generic in nature, and is therefore particularly suitable for seismic design codification in intraplate regions where indigenous earthquake record are typically lacking making the development of reliable empirical models difficult. The model subject to further modifications and development has excellent potential for worldwide application