The January 17, 1995 Kobe Earthquake.
On the first anniversary of the moment magnitude (MW) 6.7 1994 Northridge Earthquake, Kobe, Japan was struck by an MW6.9 earthquake. Both earthquakes struck in the pre-dawn hours, both ruptured beneath densely populated areas, and both caused horrible damage. Yet in Kobe there were many more deaths, financial losses dwarfed those in Northridge, and the amount of destroyed building stock and infrastructure was far worse in Kobe than in Northridge. .
The reasons for these differences are many, but it would be incorrect to issue a blanket condemnation of current Japanese seismic engineering practice. While engineered structures did fail due to design flaws, they were predominantly older structures built before the current Japanese building code became effective; or they frequently failed due to problems revealed to be deficiencies in California design practices by the Northridge Earthquake. Japanese seismic engineering expertise has justifiably been considered among the best in the world, and a careful examination of the damage in Kobe does not change that conclusion. .
Despite differences in design and construction practices, the same general principles frequently came into play: highway collapses were often primarily due to insufficient lateral ties in the concrete columns, nonductile concrete frame buildings did much worse than ductile design, shear walls typically helped to lessen catastrophic damage, and soft soils resulted in greater damage to the structures constructed on them. .
The most important lesson in both earthquakes is that the knowledge to significantly improve structures to resist earthquake damage and thereby avoid most of the deaths and financial losses exists; what is lacking is a consistent willingness to marshall the resources necessary to put that knowledge to work on the scale necessary to prevent disasters. It is an odd paradox, for time and time again it is demonstrated that it usually costs less to prepare for earthquakes in advance than to repair the damage afterwards.
