Examination of the correlation between tectonic landforms and shallow subsurface structural datasets for the estimation of seismic source faults

Estimation of the magnitudes of future earthquakes produced by faults is critical in seismic hazard assessment, especially for faults that are short in extent compared with the thickness of the seismogenic layers of the upper crust. A new seismogenic fault model for earthquake size estimation was constructed by combining (a) new assessments of the precise location and distribution of active faults from aerial photograph analysis and (b) estimations of subsurface structures from geological, gravity, and seismicity datasets. The integrated results of (1) tectonic landforms determined from aerial photographs, (2) geologic data showing the distribution of geologic faults, (3) Bouguer gravity anomaly data over wavelengths of 4–200 km, and (4) seismicity data were superimposed on geographic information system (GIS) data around the nuclear power plants in Japan. The results indicate the possible occurrence of large earthquakes, because the lengths of the subsurface earthquake faults were estimated to be longer than the length of the surface faults if subsurface structures were included.