How weak are rocks?
The strength of rocks is a key parameter for understanding the dynamics of the lithosphere, from single earthquakes to long-term plate tectonics. While strength of rocks is well understood under laboratory conditions, it is not yet well understood in nature, where weakening processes reduce the actual strength of rocks. Both field observations and mechanical concepts indicate that strength of rocks can be almost negligible, allowing failure at stresses that are only a fraction of the stress in rock deformation experiments. However, it remains unclear how common weak rocks are when considering the entire rock volume. Here I present quantitative estimates for the lower limit of rock strength obtained from stress changes in great subduction earthquakes. The data shows that rock strength can be almost negligible within the upper 60 km of the lithosphere, even though only for a small fraction of the entire rock volume. Implications of the low rock strength for short-term and long-term deformation processes are discussed.
https://www.munich-geocenter.org/events/seminars/frontiers-in-earth-sciences-34/folgt-4
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How weak are rocks?
Abstract
The strength of rocks is a key parameter for understanding the dynamics of the lithosphere, from single earthquakes to long-term plate tectonics. While strength of rocks is well understood under laboratory conditions, it is not yet well understood in nature, where weakening processes reduce the actual strength of rocks. Both field observations and mechanical concepts indicate that strength of rocks can be almost negligible, allowing failure at stresses that are only a fraction of the stress in rock deformation experiments. However, it remains unclear how common weak rocks are when considering the entire rock volume. Here I present quantitative estimates for the lower limit of rock strength obtained from stress changes in great subduction earthquakes. The data shows that rock strength can be almost negligible within the upper 60 km of the lithosphere, even though only for a small fraction of the entire rock volume. Implications of the low rock strength for short-term and long-term deformation processes are discussed.
