2002 Volume 2002 Issue 22 Pages 83-98
The recent activities of the Kokura-higashi Fault, northeast Kyushu is investigated on the basis of the interpretations of aerial photographs, field surveys, leveling of topographic profiles and trenching surveys.
The Kokura-higashi Fault extends with a NNE-SSW trend for about 17km and the fault tra c e is straight. The vertical component is upthrown on the west side: about 3m on the L surface younger than 25ka, and 5-10m on the H surface older than 140-150ka. These fluvial terrace surfaces show cumulative vertical offsets. The fault plane dips steeply westward and the striations are plunging to the south at an angle of 10-30°. The Kokura-higashi Fault has repeatedly moved in the late Quaternary with predominantly right-lateral movement. The average slip rate of the fault is over 0.1 m/ky (class B).
The most recent faulting occurred around the early BC 2ndcentury. The timing of the penultimate faulting event is ca.10,000yBP. If the average recurrence interval is over 9,000yrs, it is not likely that the fault will generate a large earthquake in the near future. The ground surface might be vertically dislocated about 1.7m by reverse slip associated with the past faulting. The net-slip should be several times as large as the reverse slip, taking the right-lateral movement into account.
