British Dictionary definitions for earthquake earthquake noun a sudden release of energy in the earth's crust or upper mantle, usually caused by movement along a fault plane or by volcanic activity and resulting in the generation of seismic waves which can be destructiveRelated adjective: Earthquakes are caused by the release of built-up stress within rocks along geologic faults or by the movement of magma in volcanic areas. They are usually followed by aftershocks.
But every so often, it slows down. Gain a millisecond here, lose a millisecond there. Last week at the annual meeting of the Geological Society of America here, two geophysicists argued that these minute changes could be enough to influence the timing of major earthquakes—and potentially help forecast them.
Usefully, the spike, which adds two to five more quakes than typical, happens well after the slow-down begins. Most seismologists agree that earthquake prediction is a minefield. And so far, Bilham and Bendick have only fuzzy, hard-to-test ideas about what might cause the pattern they found.
But the finding is too provocative to ignore, other researchers say. The research started as a search for synchrony in earthquake timing. Individual oscillators, be they fireflies, heart muscles, or metronomes, can end up vibrating in synchrony as a result of some kind of cross-talk—or some common influence.
She and Bilham dove into the data, using the only complete earthquake catalog for the past years: First, major quakes appeared to cluster in time—although not in space.
And second, the number of large earthquakes seemed to peak at year intervals. The earthquakes could be somehow talking to each other, or an external force could be nudging the earth into rupture. Exploring such global forces, the researchers eventually discovered the match with the length of day.
Although weather patterns such as El Nino can drive day length to vary back and forth by a millisecond over a year or more, a periodic, decades-long fluctuation of several milliseconds—in particular, its point of peak slow down about every three decades or so—lined up with the quake trend perfectly.
Researchers think slight changes in the flow of the molten iron of the outer core may be responsible for both effects. Just what happens is uncertain—perhaps a bit of the molten outer core sticks to the mantle above. That might change the flow of the liquid metal, altering the magnetic field, and transfer enough momentum between the mantle and the core to affect day length.
But they should, Bilham said during his talk here. At the equator, Earth spins meters per second. Beginning next year, Earth should expect five more major earthquakes a year than average—between 17 to 20 quakes, compared with the anomalously low four so far this year. If the pattern holds, it will put a new spin on earthquake forecasting.NASA Kids is an excellent site for "kids" of all ages and provides an abundance of information, images, and interesting things to do on astronomy and the space sciences.
We usually only learn about the magnitude of an earthquake and the location of the epicenter. This infographic explains how ground waves and depth define the magnitude on the Richter Scale and the.
Science Desk - Earthquakes - Discovery Education. Earthquake early warning systems can give people crucial seconds to move to safety—but only if they send the message in time.
Now, scientists working on such systems have discovered that the. Non-quantitative and carefully illustrated, unique in both organization and approach, this three-books-in-one book introduces the scientific, historical, and personal safety aspects of earthquakes.
Significantly broad in perspective on the subject, this book provides the basic scientific facts about earthquakes, explaining how the study of earthquakes has progressed through time, offering. Earthquake Science Center web site.
U.S. Department of the Interior | U.S. Geological Survey Page URL: attheheels.com Page Contact Information: shaefner.