Non-technical summary: This study was designed to re-examine the seismic hazards in the Tokyo region based on new data and new ideas concerning the nature and significance of various postseismic deformation mechanisms. Postseismic deformation represents the continued movements as crust re-adjusts to the enormous stresses associated with the earthquake. It typically involves flow of rock deep beneath the Earth's crust which is too hot and malleable to sustain large stresses for a long time period. Using idealized properties of the material one can predict with computer models how the material will relax with time. The model has been in development for 13 years and validated by comparing with independent computer programs which accomplish the same task. The new data used for the study originates from the Geographical Survey Institute and is essential to improving the understanding of postseismic deformation in the Kanto region.

In the study, the group analyzed data that measure deformation in the years after the 1923 kanto earthquake and found that previous ideas regarding postseismic deformation were not accurate. Deep flow of mantle rock is important under part of Japan for driving continued crustal deformation after the 1923 earthquake, but slip on the Philippine Sea - Japan plate interface at surprisingly shallow levels appears necessary to account for much of the observed deformation. This result may bear on the overall question of "asseismic slip" to fill in the gaps that are apparently not filled by seismic slip (that associated with earthquakes). This is important because the gap left by the 1923 earthquake would imply much current seismic potential along oceanward parts of the plate interface were it not filled by such aseismic slip events.

Future work for the Kanto region will be to investigate the continuing debate on just exactly where along the tectonic plate boundaries is stress building, by focusing on parameters such as interseismic stress accumulation.