Abstract
The second order triangulation had been performed in the South Kanto district during 1883-1885. The area around Tokyo Bay was resurveyed during 1899-1900. We do not know the reason why the resurvey was made in the area. The third order trianguration was performed in 1902 around the area of the west part of Tokyo Bay. We calculated preseismic horizontal strain from these observations during the period from 1884 to 1900 preceding the 1923 Kanto earthquake. The summary of the result is as follows. The minor principal axis of the strain is almost parallel to the Sagami Trough. The polarity of the strain axes reversed at the coseismic movement and returned to the preseismic one during postseismic movement. The preseismic strain velocity is much larger than the one in the steady state stage.
