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The Great San Francisco Earthquake (and Fire)

Earthquakes aren't caused by weather., and earthquakes don't do anything with the weather. So why am I writing about one? Well, I was getting bored looking for something to write about on this week's article, and the weather does play a bit of a role in it.


April 17, 1906 at 5:12 am, resident of the San Francisco Bay area had a VERY rude awakening. It was the foreshock to the main quake that happened about 20-30 seconds later. The big one lasted about a minute. But that 1 minute changed a lot of lives. It was felt from southern Oregon, all the way to south of Los Angeles.


The quake measured a very strong 7.9 magnitude. Over 3000 people died, making it the deadliest earthquake in America, by far. Also it's California's deadliest natural disaster.

It was widely thought the epicenter was near the town of Olema, but more modern technology has shown the epicenter may have been just off shore of CA. The occurrence of a small local tsunami (3 inches) is a plus for an off shore quake.


The Modified Mercalli Intensity Scale showed damage up to a level XI, which is extreme.

As bad as the damage from the quake was, the fires that followed were much worse. Experts thank that upwards of 90% of the destruction caused was from fires. Within three days, over 30 fires, caused by ruptured gas mains, destroyed approximately 25,000 buildings on 490 city blocks. The fires cost an estimated $350 million at the time (equivalent to $8.08 billion in 2021)

The little role the weather played, was that there was an east wind that persisted and this helped spread the fires to more and more areas. The fires lasted for 4 long days.


Some of the fires were started when San Francisco Fire Department firefighters, untrained in the use of dynamite, attempted to demolish buildings to create firebreaks. The dynamited buildings often caught fire.


Most of the destruction in the city was attributed to the fires, since widespread practice by insurers was to indemnify San Francisco properties from fire but not from earthquake damage. Some property owners deliberately set fire to damaged properties to claim them on their insurance.


Over 20,000 people were displaced by the disaster, so the army built 5610 'relief houses' Ren was $2 a month and were available until rebuilding was completer. The peak population of the area was 16,448, with most moving out by 1907. The little cottages were about 720 sq ft and cost $100 to build.

Most of the homes were destroyed, but a few survived. In 2006 one was sold for a whopping $600,000!


So not much weather this week, but still a very big part of our history.


Thanks for reading guys and gals, have a great week!

Article published on April 17, 2023 by Greg Dixon

HLEW Weather Rewind



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