In 1939 the Garrison Act applied Field Act Standards to existing school buildings . The first real world test of the Field Act took place in the 1940 Imperial Valley earthquake . This earthquake was magnitude 6.9 ( larger than the Long Beach earthquake ) but the 16 post Field Act school buildings subjected to intense shaking suffered damage that was less than 1 % of their valuation . Older pre Field Act structures in contrast suffered damaged equal to 29 % of their valuation
1940 Imperial Valley earthquake
1940 El Centro earthquake
Field Act