The Northridge, California, earthquake of 1994: fire ignition by strong shaking

Abstract The Northridge earthquake contributed unprecedented detail and quality of data on strong ground motion and on its effects on man-made structures. About 110 fires have been attributed directly to the effects of this earthquake. Two hypotheses for the principal causative agents leading to fire ignition were examined: differential motion and strains in the soil, and inertial forces. The fire-ignition frequency is described with respect to: (1) simple measures of strain in the soil (via density of water pipe breaks, n ), (2) occurrence of severely damaged buildings (via density of red-tagged buildings, N ), (3) site intensity of shaking, ( I MM ), and (4) inertial forces (via peak horizontal ground velocity, v m ). It is shown that the rate of fires (per unit area) ignited by earthquake shaking can be predicted by several empirical equations of comparable accuracy and in terms of common scaling parameters of strong ground motion.