San Francisco was hit with a big earthquake at 5:12 am April 18, 1906. In some places the earth moved sideways 20 feet in 4 seconds. This is just over 3 miles per hour but heavy things like buildings cannot move that fast without damage. If you were outside you would be OK but an estimate 3000 people were killed in San Francisco and several hundred in other other towns. Look at the second picture. It was taken high above the city but there were no airplanes or balloons in San Francisco at that time. How was this picture taken? This earthquake was about 8 on the earthquake scale so it was big. Vancouver has had earthquakes this big in the past so we should be prepared. How do they know how big earthquakes were in the past?
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