Hazards from Surface Faulting in Earthquakes

Abstract

Well-known earthquakes accompanied by surface faults since the 1891 Nobi earthquake are reviewed, and hazards from faulting are summarized. Morphology of the hazards as the offset of ground, grabens, mole tracks, tension cracks en echelon, gentle flexure or wavy swelling of land surface are described. Several examples of distribution of damage relative to faults shows that in earthquakes of M 7.0 to 7.5 the width of the endangered area where totally collapsed houses would exceed 30% would be 5.5 to 7.5 km in mountaineous regions and some ten kilometers in alluvial plains. Dimensions and other features of faults are investigated and the region at risk due-to faulting is discussed. The horizontal displacement is predominant in most earthquake faults in Japan. Plural faults generally move in an earthquake, and a belt 0.4 to 3 km wide on both sides of a postulated fault as well as conjugated faults crossed by the latter are at risk.