A new 1649–1884 catalog of destructive earthquakes near Tokyo and implications for the long-term seismic process



[1] In order to assess the long-term character of seismicity near Tokyo, we construct an intensity-based catalog of damaging earthquakes that struck the greater Tokyo area between 1649 and 1884. Models for 15 historical earthquakes are developed using calibrated intensity attenuation relations that quantitatively convey uncertainties in event location and magnitude, as well as their covariance. The historical catalog is most likely complete for earthquakes M ≥ 6.7; the largest earthquake in the catalog is the 1703 M ∼ 8.2 Genroku event. Seismicity rates from 80 years of instrumental records, which include the 1923 M = 7.9 Kanto shock, as well as interevent times estimated from the past ∼7000 years of paleoseismic data, are combined with the historical catalog to define a frequency-magnitude distribution for 4.5 ≤ M ≤ 8.2, which is well described by a truncated Gutenberg-Richter relation with a b value of 0.96 and a maximum magnitude of 8.4. Large uncertainties associated with the intensity-based catalog are propagated by a Monte Carlo simulation to estimations of the scalar moment rate. The resulting best estimate of moment rate during 1649–2003 is 1.35 × 1026 dyn cm yr−1 with considerable uncertainty at the 1σ level: (−0.11, + 0.20) × 1026 dyn cm yr−1. Comparison with geodetic models of the interseismic deformation indicates that the geodetic moment accumulation and likely moment release rate are roughly balanced over the catalog period. This balance suggests that the extended catalog is representative of long-term seismic processes near Tokyo and so can be used to assess earthquake probabilities. The resulting Poisson (or time-averaged) 30-year probability for M ≥ 7.9 earthquakes is 7–11%.