The Great San Francisco Earthquake & Fires of 1906
A City Crumbles
San Francisco was destined to see its buildings collapse because it was built near a fault line and was poorly constructed. Certain buildings experienced significantly more damage because of surface instability, not because of structural weaknesses. Wood frame homes, when well constructed, readily absorbed the earthquake shocks. However, many of these frame homes suffered, oftentimes from their poorly constructed chimneys that toppled and destroyed the residences. Many of the city's brick buildings were of inferior quality and prone to crumbling. Many of these same brick buildings were also built with floors and roofs that were improperly anchored to the building walls, allowing roofs to cave in, crushing the brick walls in the process and shooting bricks onto the sidewalks and streets.
Stone buildings without steel frames showed the same poor craftsmanship with their weak connections between the stone walls and interior floors. Steel-framed structures fared the best as these buildings' steel beams had greater elasticity, allowing the buildings to sway without distorting their form; however not all of the steel–framed buildings remained unscathed. Much of the most horrendous earthquake destruction occurred on the made land South of Market, but there were many structures on more solid soil that also experienced significant damage.
A City Landscape Transformed
San Francisco streets were a bizarre sight following the earthquake. In areas built on made land, formerly flat, straight streets were contorted. The buckled streets looked as if they had been in motion, rolling like waves until the earthquake subsided. These undulating streets were not evidence of earthquake waves, but were caused through a compression and shifting of the fill used to create made land.
It is believed that the earthquake tremors shifted the debris and sand that had been used to fill in the old South of Market marshes, causing the earth to sink and rise. Upturned paving stones and bowed rail and trolley tracks illustrate areas of compression where patches of earth were pushed together by the quake's tremors. In many other locations, however, stretching, not compression, was evident in the large snaking fissures that split streets into two or three sections.