This research is to utilize the high-quality tsunami tide-gauge records for earthquakes as far back as 1850 to extend earthquake history for active seismic zones near continents backwards beyond the time of good modern seismic records, only about 30 years. Among the outstanding problems in seismology are temporal variation of seismic activity and its effects on global changes in strain, variable rupture mode of great earthquakes, slip distribution on a fault plane, especially beneath the accretionary wedge in subduction zones, and anomalous tsunamigenic earthquakes of presumably non-fault origin. This research proposes to conduct quantitative analysis of tsunami data to improve our knowledge of these processes. This work has direct application to the National Earthquake Hazard Reduction Program.