The Kamogawa Garben striking W-E across the southern part of the Boso Peninsula is bounded of the northern marginal fault and the southern marginal fault. We examined the Holocene activity of these faults,
(1) The northern marginal fault of Kamogawa Gaeben has no evidence of faulting since about 6,000yrs B. P..
(2) The southern marginal fault of Kamogawa Gaeben has been active in the mean rates of vertical displacement of 0.2∼0.6mm/years in Holocene time. At least three faulting events are recognized and vertical slip of single event is 1.1∼1.4m. The mean recurrence interval is estimated to be 2,000∼3,000 years. The last faulting event occured before 1703 AD∼2,850 B. P..