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This Mw=5.2 earthquake occurred at mantle depth beneath southern Tibet and belongs to a class of rare earthquakes first described by Chen et al. (JGR, 1981). These mantle earthquakes tend to have T-axes oriented East-West and therefore represent similar strains as the much more common earthquakes in the shallow crust.
This Mw=5.2 earthquake occurred at mantle depth beneath southern Tibet and belongs to a class of rare earthquakes first described by Chen et al. (JGR, 1981). These mantle earthquakes tend to have T-axes oriented East-West and therefore represent similar strains as the much more common earthquakes in the shallow crust.
Starting in 1994, an increase in the rate of moment release is seen in the cumulative moment calculated from earthquakes in the CMT catalog. The more rapid moment release is seen to be caused exclusively by a few large earthquakes. The rate of moment release for smaller earthquakes remains nearly constant.
The relative frequency of occurrence for small relative to big earthquakes can be examined using the Harvard CMT catalog. The typical b-value in a traditional Gutenberg-Richter magnitude-frequency graph is 1.0. Given the relationship between seismic moment and magnitude, this corresponds to a B-value of 2/3, relating the log(number of earthquakes) with the log(seismic moment). The figure shows that this relationship is quite appropriate for shallow earthquakes in the CMT catalog.
