A thoroughly rewarding explanation of earthquakes built around the famous San Andreas fault, which runs the length of California.
Science writer Dvorak emphasizes that it was barely 50 years ago when scientists agreed that earthquakes were not the result of exploding underground gases, volcanism or a wrinkling of the Earth’s surface as it slowly cooled. Much of their enlightenment occurred in California, and the author turns up half a dozen intrepid, eccentric and largely unknown geologists (Grove Gilbert, Andrew Lawson, Charles Richter, Harry Fielding Reid) whose insights began to converge after the devastating 1906 San Francisco earthquake. In the massive studies that followed, scientists could not fail to notice the long San Andreas fault, a crack in the Earth’s surface soon found to extend the entire length of the state. No one doubted that movement along this fault had occurred during the quake since roads, pipes, rails and fences that crossed the line had shifted as much as 20 feet and always in the same direction. This was considered an effect, not a cause of the quake, and the few perceptive observers who disagreed were dismissed. It’s a rule of science that facts mean little in the absence of a good theory to explain them. This finally arrived in the 1960s with plate tectonics, which asserted that vast, floating segments of the Earth’s crust are creeping horizontally past each other. One segment often sticks fast against its neighbor; pressure builds over decades until it breaks loose, producing one or a series of quakes. “[T]he San Andreas Fault and its many subsidiary faults are slowly tearing California apart,” writes the author, “so that much of what is California today will be transformed into a collection of islands that are destined to be rafted northward across the Pacific.”
Although almost entirely focused on California, this is a fine popular primer on the subject, lucidly written and no more technical than necessary.