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Author : Atkinson, G.M.; Kaka, S.I.; and Soh, S.L.
Date : 2004.
Title : Development of Ontario ShakeMaps.
Publication : Eos Transactions. Joint Assembly of the CGU, AGU, SEG and EEGS, Montreal, Canada, May 17-21, 2004.
Issue : 85(17):
Page(s) : S24A-01.
Abstract
We have developed automated procedures to produce "ShakeMaps" in near-real-time for earthquakes in southern and central Ontario. ShakeMaps are maps that show the intensity of ground shaking at locations throughout the region, for purposes of providing rapid public, planning and emergency response information in the immediate aftermath of local and regional earthquakes. The Ontario ShakeMap program continually accesses real-time data from seismographic stations of the POLARIS (Portable Observatories for Lithospheric Analysis and Research Investigating Seismicity) and CNSN (Canadian National Seismographic Network) arrays. When an earthquake is detected, ShakeMap uses the data to find the centroid location and magnitude of the event. The centroid is a geographic location near the largest recorded ground motion, from which the ground motion appears to radiate (based on the pattern of observed amplitudes in the region). The centroid magnitude is the earthquake magnitude that best explains the observed ground motions, given the centroid location and regional ground motion relations. A modified version of the regional ground motion relation of Atkinson and Boore (1995), giving peak ground velocity (PGV) as a function of magnitude and distance, is used in the determination of the centroid's location and magnitude. ShakeMap uses a combination of computed ground motions that are based on the centroid and the regional PGV ground-motion relation, along with the actual measured ground motions at all stations, to create a contour map of PGV. The PGV map is also translated into a map of felt intensity/damage, using a relationship between PGV and Modified Mercalli Intensity. The maps are still under development, as improvements are required in the following aspects: (i) determination of site response factors throughout the region; (ii) development of improved predictive relations for PGV from earthquake magnitude and distance; and (iii) implementation of maps for other ground motion parameters including peak ground acceleration (PGA) and response spectra (PSA(f)). The prototype ShakeMaps can be viewed as they are generated at http://www.shakemap.carleton.ca. Implementing ShakeMap is a significant step forward in the development of near-real-time seismic information, particularly for nuclear utilities and other critical services that must provide timely information on all felt events.
Bibliography of Canadian Geomorphology