| It's been a hundred years since the
last big one in California, the 1906 San Francisco earthquake, which helped give
birth to modem earthquake science. A century later, we have a highly successful
theory, called plate tectonics, that explains why 1906-type earthquakes happen--
along with why continents drift, mountains rise, and volcanoes line the Pacific
Rim. Plate tectonics may be one of the signature triumphs of the human mind,
geology's answer to biology's theory of evolution. There's the broader question: Are there clear patterns, rules, and regularities in earthquakes, or are they inherently random and chaotic? Maybe, as Berkeley seismologist Robert Nadeau says, "A lot of the randomness is just lack of knowledge." But any look at a seismic map shows that faults don't follow neat and orderly lines across the landscape. There are places, such as southern California, where they look like a shattered windshield. All that cracked, unstable crust seethes with stress. When one fault lurches, it can dump stress on other faults. UCLA seismologist David Jackson, a leader of the chaos camp, says the field of earthquake science is "waking up to complexity." This regular versus chaotic debate isn't some esoteric academic squabble. Earthquakes kill people. They level cities. The tsunami of December 26, 2004, spawned by a giant earthquake, annihilated more than 220,000 lives. One of the world's largest economies, Japan, rests nervously atop a seismically rambunctious intersection of tectonic plates. A major earthquake on one of the faults hidden underneath Los Angeles could kill ten thousand people. A tsunami could smash the Pacific Northwest. Even New York City could be rocked by a temblor. Yet at the moment, earthquake prediction remains a matter of myth, of fabulations in which birds and snakes and fish and bunny rabbits somehow sniff out the coming calamity. What scientists can do right now is make good maps of fault zones and figure out which ones are probably due for a rupture. And they can make forecasts. A forecast might say that, over a certain number of years, there's a certain likelihood of a certain magnitude earthquake in a given spot. And that you should bolt your house to its foundation and lash the water heater to the wall. Turning forecasts into predictions-- "a magnitude 7 earthquake is expected here three days from now" --may be impossible, but scientists are doing everything they can to solve the mysteries of earthquakes. They break rocks in laboratories, studying how stone behaves under stress. They hike through ghost forests where dead trees tell of long-ago tsunamis. They make maps of precarious, balanced rocks m see where the ground has shaken in the past, and how hard. They dig trenches across faults, searching for the active trace. They have wired up fault zones with so many sensors it's as though the Earth is a patient in intensive care. Surely, we tell ourselves--trying hard to be persuasive--there must be some way to impose order and decorum on all that slippery ground. |