Estimates of Lithospheric Failure Cycle Parameters from Regional Earthquake Catalogues

Abstract—Based on the generalized frequency–magnitude relation for earthquakes, the failure cycle parameters are estimated from regional seismic catalogues for zones with different typical tectonic regimes: subduction zones and shear fault zones. The Kamchatka and Japan catalogues are used for the subduction zones. The estimates for the shear fault zones are based on the data for the San-Andreas Fault presented in the Northern California Earthquake Catalog, the data for the North Anatolian fault presented in the earthquake catalogue for Greece, and the data for the Zagros shear zone presented in the catalogue for Iran. Distribution maps are constructed for the failure cycle duration and for parameter \(q\) characterizing the dependence of the duration of the failure cycle on the size of the fractured area. It is shown that on average for each region, the \(q\) values are close to zero, indicating that the probability of failure for structural elements of the medium does not depend on their size and that the strength and stress distributions by size of inhomogeneities are, on average, consistent with each other. The intraregional spatial variations of parameter \(q\) exceed the statistical error of the estimates, which can be interpreted as evidence for the existence of variations in the distribution of stresses by size of inhomogeneities. The intensities of these variations estimated under Zhurkov’s kinetic concept of fracture of solids are comparable to the stresses released by earthquakes. The statistical range of regional variations in the duration of the failure cycle is about two orders of magnitude; the durations are inversely proportional to the region-mean velocities of relative plate motions along the fault zones. This indicates that the durations of the failure cycle are mainly determined by the velocities of tectonic deformations. The significant scatter in the failure cycle duration values within regions testifies to the substantially heterogeneous intraregional distribution of the strain rates and strength, which is consistent with up-to-date notions of the hierarchical nature of a geological medium and mosaicity of the stress field.