Noda et al. simulate how an earthquake ruptures when a small fragile zone is embedded within a larger, less slip-prone region. They find that both of the hypothesized mechanisms can occur, but which takes place depends on the size of the fragile patch compared to the size of the nucleation region required to trigger the whole fault. They find that if the whole fragile patch is smaller than the nucleation size required to trigger big earthquakes, then only small earthquakes will come from the fragile patch. Large earthquakes could still occur if there is a large slip in the tough region away from the fragile zone. If the fragile patch is bigger than the nucleation size of the big earthquake, then small earthquakes will cascade up into large ones. If the fragile patch and the nucleation size are comparable, then both types of large earthquakes will occur over time.
Source: Journal of Geophysical Research-Solid Earth, doi:10.1002/jgrb.50211, 2013 http://onlinelibrary.wiley.com/doi/10.1002/jgrb.50211/abstract
Title: Large nucleation before large earthquakes is sometimes skipped due to cascade-upImplications from a rate and state simulation of faults with hierarchical asperities
Authors: Hiroyuki Noda and Takane Hori: Institute for Research on Earth Evolution, Japan Agency for Marine-Earth Science and Technology, Yokohama, Kanagawa, Japan;
Masao Nakatani: Earthquake Research Institute, The University of Tokyo, Tokyo, Japan.
3. Evaluating solutions to the faint young Sun problem
During the Archean eon, between about 3.8 billion years ago and 2.5 billion years ago, the Sun was about 20 to 25 percent fainter than it is today. With less sunlight
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