The name of the San Andreas Fault precedes itself like, well, an immense and unavoidable rift in the earth’s surface. Running some 1,300 kilometres through the US state of California and reaching a depth of 15 to 20 kilometres, the San Andreas forms the tectonic boundary between the Pacific and North American Plates. Yet because of its vast size, it’s difficult to grasp this giant geological feature; except, that is, when you look at it from above.
The reason the San Andreas Fault is so famous – or perhaps infamous – is because of the major earthquakes for which it has been responsible. Names like the great 1906 San Francisco Earthquake, which left 3,000 dead, or 1989’s Loma Prieta earthquake, which killed 63, leave some trembling at the thought of the next big one. Worrying, a study suggests that the fault is set for just such a super quake of magnitude 7.0 or over, with the risk rising faster than was previously believed.
View along the fault where it cuts along the base of the Temblor Mountains.
The San Andreas fault’s momentous historic earthquakes have together caused hundreds of kilometres of breaks in the earth’s surface. One of the longest and most active faults in North America, the San Andreas was nevertheless only identified in 1895 by Berkeley geology professor Andrew Lawson. After the fateful 1906 San Francisco earthquake, it was Lawson too who realised that the fault extended into Southern California through locations like the magnificent Carrizo Plain.