Estimating Real Seismicity Rates from Nonhomogeneously Recorded Earthquake Catalogs

Abstract Accurate estimation of seismic activity using epidemic-type aftershock sequence (ETAS) models for small earthquakes is complicated by the incompleteness of the aftershock catalog immediately following frequent large earthquakes. For example, in conventional aftershock analysis using the ETAS model, the earthquakes immediately following the mainshock, including the mainshock, are used only as a history, and the estimate is based on data for subsequent segments above the lower magnitude limit where detection completeness can be guaranteed. However, the high activity in the missing interval itself contains important clues to the physical structure associated with the immediate aftershocks. In this article, I consider all detected seismic data, even if incomplete. I try to estimate the detection probability of each earthquake in the catalog and show how to estimate the real underlying activity of the ETAS and nonstationary ETAS models.