The ‘Great Shake’ – The San Francisco earthquake – 1906

Over a century later, seismology is still learning from San Francisco’s 1906 ‘Great Shake’. The more we understand, the greater the disaster seems. In less than a minute the earth ruptured at a speed of 13,300 kph (8,300 mph) towards the north, and 10,080 kph (6,300 mph) towards the south, cracking open 477 km (296 mi) of the northern San Andreas fault from outside San Juan Bautista to the fault’s triple junction at Cape Mendocino. The ninth biggest city in the USA collapsed. Its 400,000 residents woke at 05:12 buried in the rubble of their boom town, and with the flames of thousands of overturned cooking stoves already catching hold.

The water and gas mains had fractured and the fire chief had been killed. Lacking means and leadership, people already stunned and often badly injured could only watch the city bum. Many newer buildings were damaged but still standing when the fiercest tremors stopped; but nothing could resist the fire, especially since it was encouraged by unscrupulous people whose insurance covered fire but not earthquake. San Francisco burned for three days. The fire trebled the earthquake damage: 28,000 buildings were destroyed across some 500 city blocks, leaving 225,000 people homeless. In some places groups were isolated by fire against the shore.

Two days after the first shock, the USS Chicago evacuated 20,000 victims by sea. Back in the heart of the conflagration police and soldiers shot around 500 looters. Afterwards, the blackened skeletons of City Hall and other symbols of San Francisco’s prosperity left little to the imagination.

Exhaustive analysis of the 1906 earthquake and fire has gradually revealed how the city fathers played down the casualties. With the opportunity to create a new San Francisco in their own, modern image, it’s hard to blame them.

When was The ‘Great Shake’: April 18 1906

Where was The ‘Great Shake’: San Francisco, California, USA

What was The ‘Great Shake’ death toll: US Army relief operations in 1906 reported 498 deaths in San Francisco, 64 in Santa Rosa, and 102 around San Jose. More accurate, recent figures suggest at least 3,000 died and tens of thousands were injured or burned. The earthquake was the first large natural disaster to be recorded by photography, which greatly helped the research that led to Reid’s 1910 formulation of the ‘elastic-rebound’ theory that remains the best model of why earthquakes happen. The discovery of plate tectonics 50 years later only confirmed in detail what he had hypothesized.

You should know: The ‘Great Shake’ was assessed in 1935 (when the scale was invented) as 8.3 on the Richter scale. On the more recent and accurate ‘moment magnitude’ scale it is measured as 7.8 or 7.9. The combined damage of the earthquake and fire was estimated at $400 million in 1906 dollars, which translates to about $9 billion today.

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