Writing on the Walls
I have spent my entire career studying earthquakes, most of that time living in—and traveling around—California. I thus regard my home state as both a gigantic geologic jigsaw puzzle to be investigated and a vast outdoor playground to be enjoyed.
Sometimes the different facets of my appreciation come together, as they did recently when I set out to write a tour guide to California's myriad geological faults. Along the way I found myself following an idea that sprang into my head seemingly from nowhere but that, once it entered my mind, sparkled and danced and grew. It started with a simple realization: that California's most spectacular petroglyph sites tend to coincide with the state's most spectacular earthquake and volcano sites.
Such a connection is scarcely without precedent. Even before geologists had come to appreciate fully the earthquake potential of the Pacific Northwest, legends and oral histories of native tribes there were known to be suggestive of earthquake and tsunami activity. Ruth Ludwin, a seismologist at the University of Washington, has studied these stories at great length, in some cases using them to corroborate recent geologic inferences about great earthquakes that took place before written records began to be kept.
In contrast, earthquake motifs do not figure prominently in the lore of Californian tribes. This absence might seem odd to modern residents, who can't help but talk about earthquakes that have just happened. Not surprisingly, Californians these days do much of that talking over the Internet.