How Steady is Interseismic Crustal Deformation in Northeast Japan? Evidence From an Integrated Analysis of Centennial Geodetic Data

We analyze conventional horizontal geodetic data (triangulation and trilateration) and GPS data from 1890 to 2009 in NE Japan to investigate interseismic deformation over a centennial time scale and to determine if a previously reported decadal strain rate decrease preceding the 2011 Tohoku-oki earthquake had started prior to the beginning of GPS observations. Analysis of conventional geodetic data shows that the maximum shear strain rate was relatively constant from 1894 to 1984 within one standard deviation, and it is comparable to observations during the GPS era. The conventional geodetic data does not support extrapolation of the strain rate deceleration prior to the 2011 Tohoku-oki earthquake to epochs before the beginning of GPS observations in the mid-1990s. Our favored interpretation suggests a transient increase in strain rate followed by a return to the long-term rate prior to the 2011 earthquake. However, poor temporal resolution and uncertainties in the conventional geodetic data allow for other interpretations, including the possibility of multiple decadal transients during the interseismic period prior to the 1990s. Integration of our results with observations of vertical deformation and physical modeling of mechanical processes at the subduction zone is essential to better understand the tectonic as well as seismological implications of the observations.

Automated summary

This study analyzed conventional horizontal geodetic data and GPS data from 1890 to 2009 in NE Japan to investigate interseismic deformation over a centennial time scale. The results show that the conventional geodetic data and observations during the GPS era are comparable, suggesting that the deceleration of strain rate before the 2011 Tohoku-oki earthquake did not start prior to the beginning of GPS observations in the mid-1990s. Further research is needed to integrate these results with observations of vertical deformation and physical modeling for a better understanding of the tectonic and seismological implications.