It has been argued that power-law time-to-failure fits for cumulative Benioff strain and an evolution in size-frequency statistics in the lead-up to large earthquakes is evidence that the crust behaves as a Critical Point (CP) system. If so, intermediate-term earthquake prediction is possible. However, this hypothesis has not been proven. If the crust does behave as a CP system, stress correlation lengths should grow in the lead-up to large events and drop sharply once these occur. However, this evolution in stress correlation lengths cannot be observed directly. Here, we show using the lattice solid model to describe discontinuous elasto-dynamic systems subjected to shear and compression, that it is for possible correlation lengths to exhibit CP-type evolution. This provides the first direct evidence that systems with realistic elasto-dynamics may behave as CP systems, and hence supports the Critical Point hypothesis for earthquakes.
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