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A new theory may solve the mystery of why the New Madrid fault, which lies in the middle of the continent and not along a tectonic plate boundary, produces large earthquakes such as the ones that shook the eastern United States in 1811 and 1812.

This December marks the bicentennial of the New Madrid earthquakes of 1811-12, which are the biggest earthquakes known to have occurred in the central US. Now, based on the earthquake record in China, a researcher says that mid-continent earthquakes tend to move among fault systems, so the next big earthquake in the central US may actually occur someplace else other than along the New Madrid faults.

When small earthquakes shake the central US, citizens often fear the rumbles are signs a big earthquake is coming. Fortunately, a new study instead shows that most of these earthquakes are aftershocks of big earthquakes (magnitude 7) in the New Madrid seismic zone that struck the Midwest almost 200 years ago. Aftershocks go on until the fault recovers, which takes much longer in the middle of a continent.

As the relative speed of the plates around a fault increases, is there a corresponding increase in the number of earthquakes produced along the fault? According to a new study, the answer depends upon the type of tectonic boundary. On certain types of boundary, the efficiency of earthquake production actually depends on the fault slip rate.

The "signature of synchronicity" of large earthquakes -- clusters of ruptures of several faults followed by periods of quiescence -- found in the paleoseismic record also reflects the common observation that large earthquakes can trigger other large earthquakes on nearby faults. Researchers are examining the mechanism by which the seismic cycles of nearby faults become synchronized.

Geophysicists have developed a new theory to explain the global motions of tectonic plates on the earth's surface. The new theory extends the theory of plate tectonics -- a kinematic description of plate motion without reference to the forces behind it -- with a dynamical theory that provides a physical explanation for both the motions of tectonic plates as well as motion of plate boundaries.

University of Oklahoma researchers are working with Chinese colleagues to better understand intraplate earthquakes -- those occurring far from a tectonic plate boundary -- in an effort to minimize the loss of life and property in both China and Oklahoma.

(University of Arizona) Some slow-moving faults may help protect against destructive earthquakes, suggests new research. Until now, geologists thought when the crack between two pieces of the Earth's crust was at a very gentle slope, there was no movement along that particular fault line. Now two University of Arizona geoscientists have found that such a low-angle normal fault in Italy is moving slowly and steadily.

Scientists have found a way to monitor the strength of geologic faults deep in the Earth. This finding could prove to be a boon for earthquake prediction by pinpointing those faults that are likely to fail and produce earthquakes. Until now, scientists had no method for detecting changes in fault strength, which is not measurable at the Earth's surface.