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Why do earthquakes stop?
February 06, 2008The underlying structure of a fault determines whether an earthquake rupture will jump from one fault to another, magnifying its size and potential devastation. Understanding why some earthquakes terminate along a fault, while others jump or step-over a gap to another fault, is essential to forecasting the seismic hazard of complex fault systems, such as the San Andreas Fault.
In a paper published in this issue of BSSA, author David Oglesby of University of California at Riverside suggests that the pattern of stress at the end of the primary fault can strongly affect an earthquake's ability to jump to a secondary fault. He suggests that a smooth, gradual decrease in stress along a rupture results in slower rupture deceleration, less strain, less generation of seismic waves, and lowers the likelihood that the earthquake will jump to another fault.
In contrast, a stress pattern that terminates suddenly leads to abrupt rupture termination, higher strain, more seismic radiation, and a higher likelihood of the rupture jumping to a secondary fault. The results of this numerical study illustrate the importance of the slip gradient and the acceleration of the rupture front in determining the probability of a rupture jumping from one fault segment to another.
Seismological Society of America
Seismological Society of America
Earthquakes Current Events and Earthquakes News RSSAfrican Desert Rift Confirmed as New Ocean in the Making
In 2005, a gigantic, 35-mile-long rift broke open the desert ground in Ethiopia. At the time, some geologists believed the rift was the beginning of a new ocean as two parts of the African continent pulled apart, but the claim was controversial.
New Celestial Map Gives Directions for GPS
Many of us have been rescued from unfamiliar territory by directions from a Global Positioning System (GPS) navigator. GPS satellites send signals to a receiver in your GPS navigator, which calculates your position based on the location of the satellites and your distance from them.
Tsunami waves reasonably likely to strike Israel
"There is a likely chance of tsunami waves reaching the shores of Israel," says Dr. Beverly Goodman of the Leon H. Charney School of Marine Sciences at the University of Haifa following an encompassing geo-archaeological study at the port of Caesarea. "Tsunami events in the Mediterranean do occur less frequently than in the Pacific Ocean, but our findings reveal a moderate rate of recurrence," she says.
Seismic Noise Unearths Lost Hurricanes
Seismologists have found a new way to piece together the history of hurricanes in the North Atlantic - by looking back through records of the planet's seismic noise. It's an entirely new way to tap into the rich trove of seismic records, and the strategy might help establish a link between global warming and the frequency or intensity of hurricanes.
Tsunami evacuation buildings: another way to save lives in the Pacific Northwest
Some time soon, a powerful earthquake will trigger a massive tsunami that will flood the Pacific Northwest, destroying homes and threatening the lives of tens of thousands of people, says Yumei Wang, a geotechnical engineer at the Oregon Department of Geology and Mineral Industries in Portland.
Satellite data look behind the scenes of deadly earthquake
Using satellite radar data and GPS measurements, Chinese researchers have explained the exceptional geological events leading to the 2008 Wenchuan Earthquake that killed nearly 90 000 people in China's Sichuan Province.
Radio waves 'see' through walls
University of Utah engineers showed that a wireless network of radio transmitters can track people moving behind solid walls. The system could help police, firefighters and others nab intruders, and rescue hostages, fire victims and elderly people who fall in their homes. It also might help retail marketing and border control.
Scientists measure the rate of ascent of volcanic magma
Plinian volcanic eruptions are notoriously destructive. These very powerful eruptions often occur after long periods of quiescence and are preceded by relatively short periods of seismic restiveness.
San Andreas affected by 2004 Sumatran quake
U.S. seismologists have found evidence that the massive 2004 earthquake that triggered killer tsunamis throughout the Indian Ocean weakened at least a portion of California's famed San Andreas Fault.
Unlocking the secrets of the seafloor: The future of scientific ocean drilling
Close to 600 scientists from 21 countries met Sept. 23 - 25 2009 in Bremen, Germany, to outline major scientific targets for a new and ambitious ocean drilling research program.
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