Abstract
Rokko formula is a discriminant function for risk assessment of slope failures by earthquake. There are three problems to apply the formula for real time anticipation : too narrow target range of PGA (peak ground acceleration), lack of PGA data, and too long calculation time. We developed modified Rokko formula, estimation method of PGA from JMA (Japan Meteorological Agency) seismic intensity scale, and calculation method using precomputed histogram of real-time-independent part. We applied the methods to past earthquakes using shake maps (estimated seismic intensity distribution data) by JMA, and compared the results with slope failure positions by air photo interpretation. The results were appropriate in the interpretation area except narrow steep-slope-strips, but the system sometimes anticipated higher risk at the outside of the interpretation area. The difference was mainly caused by lack of seismometer near the epicenter.
