Development of Ontario ShakeMaps

A methodology to generate simple, reliable ShakeMaps showing earthquake ground shaking in Southern Ontario is developed using the near-real-time data from Ontario POLARIS (Portable Observatories for Lithospheric Analysis and Research Investigating Seismicity) stations. ShakeMaps have been implemented in California and the western United States (Wald et al, 1999b), but this is the first ShakeMap development in eastern North America. The eastern ground motion characteristics and sparse network pose new challenges for ShakeMap development in this region.; The ground motion parameters selected to display in the near-real-time ShakeMaps include peak ground acceleration (PGA), peak velocity (PGV), Pseudo-acceleration (PSA) amplitude at periods of 0.1s, 0.3s and 1.0s, and an instrumentally derived felt-intensity. The ground motion values are plotted on a map and contour lines are added to show areas of equally-strong shaking.; In the ShakeMaps, PGA, PGV, and PSA values are assigned to map grid points by using a combination of the recorded ground motions and values estimated using the empirical relations developed in Chapter 6. Intensity values are estimated from the peak ground velocity using relations developed in Chapter 5, where the intensity is a qualitative measure of the strength of shaking and damage based on the Modified Mercalli scale.; A grid of site amplification factors to account for the appropriate level of soil amplification is incorporated, by using interpolations of currently-available site conditions. The site classification is based primarily on the average shear-wave velocity of the top 30 meters (Vs30) wherever possible. Since shear-wave velocity measurements are not available for most grid points, I assume Vs30 =500 m/s for sites with unknown properties.; An important component of ShakeMap is its potential use as a rapid earthquake warning system. ShakeMap sends email notifications to subscribers immediately (within 3 minutes) following an earthquake, giving information on motions experienced at specific sites of interest, such as nuclear power plant sites. Near-real time ShakeMaps are automatically produced and posted within 7 minutes at (http://www.shakemap.carleton.ca). This development is a significant step forward in the development of near-real-time seismic information relevant to post-earthquake rapid warning systems in Canada.