Abstract

Seismic‐hazard assessment for earthquakes with long recurrence intervals requires long earthquake records. Historical records for seismic damage can complement instrumental earthquake records, which is particularly useful for low‐seismicity regions. Uncertainty in epicenters and magnitudes, however, hinders the full use of historical earthquake records. A probabilistic method to determine the epicenters of historical events is presented. The epicenters of historical events are determined probabilistically considering the nature of seismicity such that the spatial distribution of seismicity is nearly stationary with time in a constant tectonic environment. The probabilities for historical events to have occurred at given locations can be calculated using an instrumental seismicity density function and a distance‐dependent weighting function. A location is selected randomly from a set of candidate source locations, of which probabilities are greater than a given prescribed value. The epicentral seismic intensity for the determined source location is calculated using an intensity–distance relationship. The magnitude is determined using an intensity–magnitude relationship. The method is verified with analysis of seismic intensity data for earthquakes in California. The method is applied to an ∼1900 year long Korean historical seismic record, and the magnitudes of historical earthquakes are estimated. The Gutenberg–Richter b values for the historical events are determined to be 0.73. It is observed that the northwestern and southern peninsula, and the southeastern offshore region have high seismic‐hazard potentials.

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