5:30 PM - 5:45 PM
[J05-2-04] Reciprocal relationship between seismically estimated slip rates and geodetically estimated slip-deficit rates at plate interfaces: Physical interpretation and logical consequence
Repeating earthquakes, the sequence of stress accumulation and release at isolated small asperities on a plate interface, can be regarded as a renewal process in statistics. From such a point of view, we modeled a sequence of repeating earthquakes and developed an objective Bayesian method to estimate the space-time distribution of interplate slip rates from the recurrence intervals of repeating earthquakes. Appling this method to the complete data set of repeating earthquakes in northeast Japan for 18 years before the 2011 Tohoku-oki earthquake, we revealed spatiotemporal variations of interplate slip rates (Nomura et al, GJI 208, 2017). For a seismically calm period (1996-2000), we compared the average slip-rate distribution estimated from repeating earthquake data with the average slip-deficit-rate distribution estimated from GPS array data (Hashimoto et al., GJI 189, 2012), and found good reciprocal relationship between their spatial patterns. What we can estimate from repeating earthquake data is the background slip rates for small asperities. On the other hand, what we can estimate from GPS array data is the slip-deficit rates of underlying large asperities. So, the sum of the slip rate and the slip-deficit rates should be equal to a plate convergence rate, but the actually estimated slip rates are a bit small to satisfy the above postulation. This may be responsible for the empirical relation between recurrence intervals and magnitudes of repeating earthquakes (Nadeau & Johnson, BSSA 88, 1998), which scales the amplitude of slip rates. If we use a theoretical relation instead of the empirical one, the above postulation, which suggests a hierarchic structure of asperities, is well satisfied.