Horizontal-to-vertical ground motion relations at short distances for four hard-rock sites in Eastern Canada and implications for seismic hazard assessment

Horizontal-to-vertical (H/V) ground-motion relations were determined for four long-running, three-component broadband seismograph stations situated on hard rock in eastern Canada. We focused our attention on earthquakes of magnitude 2.5 and greater at close range (<200 km) to each station because most earthquake damage results from nearby earthquakes. An H/V value of approximately 2 is the general average for eastern Canada, although there are some differences from station to station. H/V in general increases with increasing frequency. There is little or no systematic variation in H/V as a function of either distance or magnitude. The H/V ratios obtained in this study are somewhat higher than previously published values. Much of the difference appears to be due to the use of different definitions of H rather than to differences in the data sets and/or methods of data processing and analysis. These results raise questions regarding the best definition for H for use in hazard assessment.