ABSTRACT

We introduce an enhancement to our Monte Carlo software for performing probabilistic seismic hazard analysis (EqHaz), which enables a smoothed‐seismicity option, similar in concept to that used by the U.S. Geological Survey in its national seismic hazard mapping. Under the smoothed‐seismicity option, the EqHaz catalog simulator uses the geometry and seismicity parameters of the areal sources, along with the catalog of recorded earthquakes and their associated magnitude‐completeness data, to mimic the clustering trends seen in historic seismicity catalogs. We use an example application from the western Canada sedimentary basin to show that in cases when clustering of events is pronounced, a 2% in 50 yr ground‐motion amplitudes for the smoothed‐seismicity option may be up to an order of magnitude higher (or lower) in some locations than would be estimated under the uniform‐seismicity approach. If the stationarity of clustering is unknown, hazard assessment should weight the ground motions from the two approaches, according to the perceived likelihood that each approach will represent future seismicity trends.

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