Dynamic stress field of a kinematic earthquake source model with k-squared slip distribution

Source models such as the k -squared stochastic source model with k -dependent rise time are able to reproduce source complexity commonly observed in earthquake slip inversions. An analysis of the dynamic stress field associated with the slip history prescribed in these kinematic models can indicate possible inconsistencies with physics of faulting. The static stress drop, the strength excess, the breakdown stress drop and critical slip weakening distance D _c distributions are determined in this study for the kinematic k -squared source model with k -dependent rise time. Several studied k -squared models are found to be consistent with the slip weakening friction law along a substantial part of the fault. A new quantity, the stress delay, is introduced to map areas where the yielding criterion of the slip weakening friction is violated. Hisada's slip velocity function is found to be more consistent with the source dynamics than Boxcar, Brune's and Dirac's slip velocity functions. Constant rupture velocities close to the Rayleigh velocity are inconsistent with the k -squared model, because they break the yielding criterion of the slip weakening friction law. The bimodal character of D _c / D _tot frequency–magnitude distribution was found. D _c approaches the final slip D _tot near the edge of both the fault and asperity. We emphasize that both filtering and smoothing routinely applied in slip inversions may have a strong effect on the space–time pattern of the inferred stress field, leading potentially to an oversimplified view of earthquake source dynamics.     

The IASPEI procedure for the evaluation of earthquake precursors

Full scientific evaluation of proposed earthquake precursors for earthquake prediction is a problem because independent testing is difficult or impossible. To approach this difficulty, and to assess the current state of the art of earthquake prediction research, IASPEI has devised a peer-review procedure for precursor evaluation. The procedure does not consider predictions of impending earthquakes, but evaluates case histories of proposed precursors for past events according to stated validation criteria, which are specified in terms of guidelines concerning the hypothesized physical model, data quality, anomaly definition, the rules of association of precursor with earthquake, and statistical significance. So far, five precursors have been placed on a preliminary list of significant earthquake precursors, although none has satisfied the validation criteria well enough to ensure that their placement is permanent. Exclusion of a precursor from the list does not mean it is useless, but further work is required if it is to become convincing. The main objectives in producing the list are to establish a consensus on the criteria which a precursor must satisfy to be recognized as validated, and to find case histories which satisfy these criteria. Further nominations of precursor candidates are requested for evaluation by the IASPEI procedure.     

Reply to comment by A. Douglas on 'Systematic determination of earthquake rupture directivity and fault planes from analysis of long-period P-wave spectra'

We respond to the comments by Douglas regarding our earlier paper by emphasizing that our automated method was intended to distinguish between the primary and auxiliary fault planes in earthquake focal mechanisms and does not always produce reliable results for rupture velocity and rupture length.