The Forces Underlying the Fury
The economic cost of natural disasters in the United States has averaged as much as $1 billion a week since 1989and is expected to rise, according to a 1999 NSF-supported study. Because natural disasters can have such brutal consequences, it's easy to think of them in terms of human misery that, somehow, must be mitigated. But society cannot mitigate what it does not understand. Natural disasters are, after all, a part of nature, and though human activities can influence the impact of extreme events, researchers must first learn as much as possible about the basic physical forces underlying the fury. At NSF, most of the research into natural disasters and their mitigation takes place within the Directorate for Geosciences, the Directorate for Engineering, and the Directorate for Social, Behavioral, and Economic Sciences.
Almost from its inception, NSF has been a critical player in the global effort to understand and cope with earthquakes and volcanoes. NSF funded a series of explorations during 1957-58dubbed the International Geophysical Yearand again in the 1960s. These explorations confirmed a wild idea that scientists had begun to suspect was true: the Earth's seafloors, rather than being congruous like the rind of a melon, were actually disparate pieces that, at least in some places, were slowly moving away from each other. These findings pushed geophysicists toward the modern theory of plate tectonics. Researchers now know that the upper part of Earth's crust is broken up into a number of rigid plates, and that these plates float atop soft-solid rock kept in a molten state by an unimaginably hot inner core. As the plates drift, they not only separate but also collide and slide past each other, forming valleys and mountain ranges. Occasionally, some of the molten rock breaks throughand a volcano is born. When two plates grind past each other, the shuddering friction generates earthquakes.
Of the one million or so earthquakes that rattle the planet each year, only a fewabout one each weekare large enough to grab our attention. Predicting when and where the next "big one" will take place is still far from a certainty. Short-term forecasts are sometimes pegged to swarms of smaller quakes that may signal mounting stress at a fault. Or a sudden change in underground water temperature or composition may be significant: this type of signal led to the successful evacuation of a million people before a major earthquake near the city of Haicheng, China, in 1975the first earthquake to be scientifically foretold.
NSF-funded researchers are making headway on the difficult question of earthquake prediction by narrowing their focus to specific regions of the world. Because the behavior of seismic waves is so strongly affected by the different kinds of soil and geological structures through which the waves must travel, the effects of an earthquake can vary widely from place to place, even along the same fault. A soft-soil area such as a lakebed, for example, will shake more than a rocky hill. Knowing this, scientists and engineers at the NSF-sponsored Southern California Earthquake Center in Los Angeles have reassessed the consequences of earthquakes along faults in the surrounding region. The scientists were able to simulate the anticipated effects of future local quakes by using sophisticated computer models of the Los Angeles basin that accounted for fault geometry and motion, sediment composition, and other factors that can reflect, prolong, or amplify quaking motion. Such modeling, supplemented with data from new digital seismic recorders capable of sensing a broad range of actual earthquake vibrations, can help researchers and residents of quake-prone areas to anticipateat least in a general waywhen and where the next big temblor will hit and what damage may result.
Even as local efforts to understand earthquake activity improve, scientists are finding new ways to take another look at the big picture. In June 1999, NSF-funded researchers joined an international team headed to the east coast of Japan to establish long-term seafloor observatories in one of the world's busiest earthquake zones: the so-called Japan Trench, where two of Earth's biggest tectonic plates are colliding. The international team of scientists drilled holes about one kilometer deep into the ocean floor along the trench, which itself is two kilometers underwater. They then installed instruments at the bottom of these boreholes to monitor the amount of seismic activity there. Robotically controlled vehicles similar to those used to investigate the sunken Titanic will periodically travel to and from the seafloor observatories and help provide scientists with long-term observations of one of the planet's most active quake regions.
Another way that NSF is helping researchers gather data close to the moment of seismic activity is through its funding of the Earthquake Engineering Research Institute (EERI) in Oakland, California. Besides encouraging regular communication among engineers, geoscientists, architects, planners, public officials, and social scientists concerned about natural disasters, EERI quickly assembles and deploys teams of researchers on fact-finding missions in the wake of earthquakesanywhere in the worldsoon after they occur.