Abstract
We review previous numerical simulations of interaction between fault segments on a plate interface based on a friction law, comparing combined events with single events on the amount of coseismic and preseismic slip. We find out the characteristics of combined event: (i) In case of multiple fault segments nearby enough to have short delay time of rupturing, coseismic slip is increased nearly in proportion to the size of combined fault segment while preseismic slip is almost the same as single event. (ii) In case of those distant enough to have long delay time of rupturing, seismic moment magnitude is almost the same as single event while preseismic slip is significantly increased by several tens percents. We discuss several combined earthquakes in Sumatra with short-term and long-term delay times and the possibility of megathrust earthquakes following the 2011 off the Pacific Coast of Tohoku Earthquake occurring off Kanto and off Sanriku with long-term delay time in the near future. We point out that seafloor observation of crustal deformation and seismicity off Kanto, Sanriku and Tokachi is necessary to enhance the detection ability of preseismic changes.
