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1906 San Francisco earthquake intensity map, as applied to the area in 2003. The earthquake of 18th April 1906 had a magnitude of around 7.9. The quake itself, and the subsequent fires, led to the deaths of over 3000 people, and some 300,000 out of the city's 400,000 inhabitants were left homeless. This intensity map is based on current knowledge of the earthquake's strength and source, and of the surrounding rock types. The quake was due to a slip in the San Andreas fault (thick black line). Shaking intensity is colour-coded, from red (extreme) through orange (severe) and yellow (strong) to green (moderate). This map was made in the run-up to the centenary of the event, to help model what damage would be likely to occur in this heavily-populated area in future quakes. San Francisco occupies the southern peninsula enclosing the bay. (KEYSTONE/SCIENCE PHOTO LIBRARY/CHR 366 US GEOLOGICAL SURVEY/SCIENCE PHOTO LIBRARY) === ===