Not surprisingly, California was the birthplace of seismic regulations for buildings in the U.S. In the wake of the 1906 earthquake, many scientists and engineers agreed that "San Francisco would have been safer had there been more engineering design, supervision and [honest] building practice in the city’s making." These men banded together and, a month after the disaster, founded the Structural Association of San Francisco, which later would become the Structural Engineers Association of California (SEAOC).
Based on their assessment of the damage, the group concluded that wooden buildings could withstand an earthquake of the magnitude of the 1906 tremor – if they were well secured to their foundations and incorporated "appropriate internal bracing." Unreinforced masonry structures, on the other hand, had not fared well; while the handful of reinforced concrete structures and steel framed buildings had done the best, surviving with relatively little structural damage.
And yet surprisingly, no direct mention was made of earthquakes in subsequent buildings codes as San Francisco was rebuilt, although the city did incorporate a wind load requirement for lateral forces of 30 pounds per square foot (psf) in the belief that "any buildings that could withstand such pressure would have survived the earthquake" (the wind load would later be reduced to 20 psf in 1910 and then to 15 psf in 1920). New ordinances were passed that approved the use of reinforced concrete, which local brickmakers and the bricklayers’ union had previously blocked. Steel framing was made a requirement in any new brick construction.
More progress toward seismic design, however, was effectively thwarted by city politicians and businessmen who were fearful of the economic fallout from the disaster. With the Southern Pacific Railroad Company taking the lead, this interest group launched a public relations campaign that placed the blame for the destruction on the fire rather than on the earthquake in order "to assure easterners that investment in California enterprises would continue to be good business." Major developments in earthquake–resistant building codes would have to wait until after the Santa Barbara earthquake of 1925 — a 6.3 magnitude quake that caused widespread structural damage and led to the adoption by that city of earthquake provisions in its municipal code, the first city in California to do so.