Abstract
This paper introduces characteristics of observed offshore waves by two sets of GPS buoy system at the Northern Pacific Coast of Japan from April to September in 2007. Very few lack of data appeared during the term, including in the very rough sea conditions caused by typhoon attacks. Offshore GPS buoys observed much bigger significant wave heights in both normal and abnormal sea states than the shallower seabed wave gauges, due to the topographical sheltering effects by peninsulas, meaning that deep-sea wave observation is necessary in order to obtain offshore wave conditions.
