San Francisco: Living on borrowed time?

Disaster struck San Francisco on on October 17, 1989. In this image, firemen search for occupants in a heavily-damaged building in the Marina District of the city, one of the areas hardest hit by an earthquake estimated at 7.0. The so-called Loma Prieta earthquake lasted between 10 and 15 seconds - striking during the World Series between two local teams, the San Francisco Giants and the Oakland A's coincidentally - leaving 63 people dead and more than 3,700 people injured.

San Francisco and Oakland were rocked after a section of the San Andreas fault located around Santa Cruz, Calif., ruptured over a 45 kilometer stretch. The force of the temblor reminded the country - and even San Francisco old timers - about the risks of building in an earthquake zone. And while it may have been the first such quake in most Americans' memories, it had antecedents going back to the 19th century. After the recent tragedy in Japan, is complacency still an option? If past is prologue, the answer may be one we won't like very much.

San Francisco after the earthquake of 1868

Bancroft Library, University of California

On October 21, 1868, San Francisco was rocked by an earthquake with a magnitude of 7.0. At the time, about 260,000 people lived in the Bay Area. The earthquake, felt throughout the northern part of the state and Nevada, left five people dead and 30 injured. Damage was estimated at $300,000.

Following the quake, one conclusion reached by engineers was to avoid erecting buildings on land reclaimed from San Francisco bay. Unfortunately, that concern was quickly forgotten as the city rapidly rebuilt - with tragic results in 1906.

Flour mill & warehouse, Hayward, Calif. after the 1868 earthquake

The Bancroft Library, University of California

The next day, the San Francisco Morning Call recounted how the city "was visited by the most severe earthquake" residents had ever experienced.

"The great shock commenced at 7:53 A.M. and continued nearly one minute, being the longest ever known in this region. The oscillations were from east to west, and were very violent. Men, women, and children rushed into the streets--some in a state of semi-nudity--and all in the wildest state of excitement. Many acted as if they though the Day of Judgment had come. for a time the excitement was intense, and the panic was general."

You can read the entire dispatch here.

Harper's Weekly, 1868

Virtual Museum of the City of San Francisco

Since 1800, 21 earthquakes with a magnitude of 6.0 or greater have hit San Francisco area (Six of them have registered between 6.5 and 7.0.)

Hayward, California after the 1868 quake

The Hayward Fault runs through the San Francisco suburb of Hayward, California. During the 1868 earthquake, the southern end of the fault ruptured, sending seismic shock waves throughout the region.

Active traces of the Hayward Fault

Periodic movements in the Hayward Fault have jolted the region for decades. According to the USGS, scientists consider the fault to be a tectonic time bomb, one likely to generate earthquakes in the 7.0 range.

Fire during 1906 San Francisco earthquake

California State Library, Stanley Mosk Library and Courts Building

The 1906 San Francisco earthquake is estimated to have been in the 7.8 range (and possibly even larger.) Like the Loma Prieta earthquake of 1989, the San Andreas Fault was responsible for the 1906 temblor. More than 3,000 people died due to a combination of the earthquake and resulting fire. At the time, the area had a population of 400,000 people.

Deep cracks left by the 1906 quake

San Francisco after the 1906 earthquake. The image shows a fissure in the road at Eighteenth and Folsom streets.

Building left destroyed by 1906 earthquake

Ruins left after the fire and earthquake of 1906. This picture was taken downtown near Sacramento and Montgomery.

San Andreas Fault

This photograph taken 1908 shows the surface rupture along the San Andreas fault near Point Reyes Station, north of San Francisco.

The fault represents the classic boundary between the North American and Pacific Plates.

A 1908 photograph of a pushed up shoal in the marsh flats along the west shore of Tomales Bay. Eyewitnesses in the area said that the 1906 earthquake generated tsunamis more than 6 feet high along bay.

More than 40 people died after the two-level Cypress Street Viaduct of Interstate 880 in Oakland collapsed during the 1989 earthquake. Although the structure had been retrofitted 12 years earlier - the viaduct was built on what had been marshland - it collapsed after soil liquefaction occurred.

The San Francisco bay area sits along major fault lines and thus runs the risk of suffering devastating consequences should it ever get hit by a monster-sized earthquake. But the problem isn't necessarily that earthquakes are increasing in frequency or size. In fact, says Colin Stark, Lamont Associate Research Professor at the Lamont-Doherty Earth Observatory of Columbia University, the problem is that we prefer to keep believing the dice will fall in our favor and so we keep building. "Megacities across the world continue to grow, and many are along major faults. Most of these faults have not generated giant earthquakes in recent memory, but historical and geological records, supported by abundant geophysical data, show they do so every few hundred years," he wrote in an op-ed piece for CNN.com.