Abstract
Similar earthquakes that occur in approximately the same location have the potential to reveal the spatio-temporal changes in aseismic slip along plate boundaries. Here we identify similar earthquakes with moderate magnitudes that occurred worldwide between 1989 and 2016 by using seismograms recorded by the Japanese dense seismic network. The slip rate along the plate boundaries estimated from similar earthquakes increased rapidly following M > 8 megathrust ruptures and then gradually decayed over periods of ~10 years, which correlates with after-slip progressing around the source areas. More than 30 years after large megathrust earthquakes, the slip rate begins to show a gradual increase. This gradual increase in slip rate after the decay may be due to an increase in stress levels that accumulate during tectonic loading. The spatio-temporal characteristics of inter-plate aseismic slip can be used to provide a valuable framework for understanding the long-term evolution of slip-rate during megathrust earthquake cycles.
Highlights
Similar earthquakes that occur in approximately the same location have the potential to reveal the spatio-temporal changes in aseismic slip along plate boundaries
We identified numerous similar earthquakes that occurred along subducting plate boundaries, including the Andaman–Sumatra–Java, the Solomon–Vanuatu–Tonga, and Japan–Kuril–Kamchatka–Aleutian subduction zones
Based on the spatio-temporal evolutions of similar earthquakes that occurred during the analysis period, we demonstrate that interplate similar earthquake sequences occurred more frequently after megathrust earthquakes
Summary
Similar earthquakes that occur in approximately the same location have the potential to reveal the spatio-temporal changes in aseismic slip along plate boundaries. Seismic observations made over several decades in Japan have shown that many similar earthquake sequences in the subducting plates are caused by repeated slips in small patches surrounded by creeping aseismic regions along with the plate boundary[3,4,5] These sequences are referred to as repeating earthquakes due to the recurring nature of seismic energy release, and they yield information on the spatio-temporal evolution of fault slip rate (i.e., creeping rate). We detected moderate-sized similar earthquakes around the world by calculating the cross-correlation coefficients of bandpass-filtered seismograms recorded by the Japanese dense seismic network Based on these data, we investigated the spatial distributions and temporal characteristics of inter-plate aseismic slip at a number of subduction zones around the world
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