Central Japan is situated on the inflection point of the bow‐shaped Japanese islands. Numerous NW‐SE trending active faults, arranged in parallel at intervals of 20 to 80 km are found in this area. These active faults are more than 30 km long with shattered zones from 30 to 300 m wide. Several active faults constitute a given block boundary, which serves as the dividing line for one of the four blocks that make up central Japan. The block boundaries require careful study since numerous historical earth‐quakes have occurred along these lines. Offset measurements of basement rocks, created during the Quaternary period due to left‐lateral faulting, amount to 1 to 7 km. Gravity lineaments, which link points of sudden change and saddles of Bouguer anomalies, are clearly found along the block boundaries. The NW‐SE trending active faults appearing on the ground surface are associated with motions of the block boundaries. Block rotational movement, caused by left‐lateral faulting, plays an important role in the crustal deformation of central Japan. Rotational angles of the blocks calculated from the amount of displacement of basement rocks, initiated during the Quaternary period, are estimated to be 3° to 7° in a clo