Abstract

A set of maps have been constructed which estimate the hazard of seismic ground shaking in the Puget Sound, Washington, area as measured by the peak ground acceleration (PGA). The average PGA in this region for which there is a 5 per cent chance of exceedence in 50 yr is approximately 30 per cent of g. PGAs on the map vary from a low of 20 per cent of g to a maximum of near 60 per cent of g. The effects of local seismicity patterns, type of soil, and subsurface geology are all included, and all contribute significantly to the variation of expected PGA across Puget Sound. The predicted PGAs are slightly larger than or comparable to the PGAs experienced in magnitude 6.5 and 7.2 earthquakes in this century, and the average PGA is consistent with work by previous investigators. The hazard estimates are controlled by earthquakes in the magnitude 4.5 to 7.0 range and are largely independent of the rate of occurrence of earthquakes outside of that range.

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