The San Francisco Fault: The Earth And The Earth

On the 18th of April in 1906, the lives of many San Francisco residents changed in a split second. Most of the city was either sound asleep or getting ready for another normal day (or so they thought), when the disastrous natural disaster struck. At around 5:12 a.m., the Golden City was jolted awake by a monstrous earthquake that would soon go down in the record books. With a Richter magnitude rating of 7.9, this earthquake was not only felt in the San Francisco Bay area, but also all the way from southern Oregon to south of Los Angeles and inland as far as central Nevada.

As the massive tectonic plates that make up the earth’s outer crust slowly collide, grind together, or pull apart, the rocks on either side of a fault stretch to absorb

The major fracture in the earth’s crust extends northwestward through southern and northern California for roughly 810 miles. According to the theory of plate tectonics, the San Andreas forms the tectonic boundary between the Pacific Plate and the North American Plate. Geologists describe the fault as right-lateral strike-slip, which means that the Pacific side of the fault is slowly moving horizontally northward, usually by an inch or two per year. Such movements deep in the earth produces earthquakes-and such movements along the San Andreas Fault have produced most of the largest earthquakes in American

In 1906, not only was earthquake research in the United States falling behind compared to Japan and Europe, the technology in building and city design was nothing like how it is today. The wake-up call issued by the earthquake made geologists undertake massive research in the affected area. Their investigation shows that the damage to buildings by the earthquake was strongly related to both the design and construction of the structure and the local geology – the type of soil or rock on which it was built. It was revealed that the earthquake did the most harm on the soft soil areas of San Francisco, as the buildings that lay on these areas experienced a much greater amount of shaking and tremors, compared to the buildings that lay on the hard rock beds. Based on the assessment of the damage, it was concluded that wooden buildings could withstand an earthquake of the same magnitude of the 1906 tremor – if they were well secured to their foundation, combined with the right internal bracing. Unreinforced masonry structures, on the other hand, would not do so well. The handful of reinforced concrete buildings and steel framed structures would do the best, surviving with generally very little structural damage. However, as San Francisco was being rebuilt, the building code changed very little in the aftermath of the natural disaster. It wasn’t until the 1925