Laura M. Wallace et al., GNS Science, Lower Hutt 5040, New Zealand. Posted online 23 July 2012; doi: 10.1130/G33373.1.
Faults that accommodate subduction of one tectonic plate beneath another produce the largest and most destructive earthquakes and tsunamis on Earth -- such as the March 2011 M9.0 earthquake and tsunami in northern Japan. The increasing use of GPS techniques to measure deformation of tectonic plates at subduction zones has revealed that in some cases the subducting and overriding plates are locked or "coupled" together between large earthquakes due to friction along the fault, while other subduction plate boundaries tend to creep aseismically. Using GPS data from subduction zones in southwest Japan, New Zealand, and Vanuatu to document the degree of fault locking versus fault creep, Laura M. Wallace and colleagues show that a lateral change from aseismic creep to deep locking also correlates with a change in the tectonic behavior of the overriding plate from rifting to contraction. To explain this observation, they suggest that interactions between fluid pressure and the tectonic stress regime within the overriding plate may influence the degree of locking versus creep on the subduction interface fault. This new hypothesis may help to explain why some subduction zones lock up and produce great megathrust earthquakes while others do not.
Thickness of the chemical weathering zone and implications for erosional and climatic drivers of weathering and for carbon-cycle feedbacks
A. Joshua West, Dept. of Earth Sciences, University of Southern California, 3651 Trousdale Parkway, Los Angeles, California 90089, USA. Posted online 23 July 2012; doi: 10.1130/G33041.1.
The thin veneer at Earth's surface, known as the Critical Zone, plays host to a range of chemical reactions that are critical for generating and sustaining the resources that support life and shape the natura
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Geological Society of America