Structural analysis of hypocentral distribution of an earthquake sequence using anisotropic wavelets: Method and application

[1] Spatial organization of earthquake sequences is investigated to localize active rupture planes and to reconstruct the geometry of the inferred rupture zone. We have developed a new approach, the Normalized Optimized Anisotropic Wavelet Coefficient (NOAWC) method, to extract from a set of hypocenters the active ruptures planes. Our approach permits the detection of organized structures within a plane regardless of its size, location, shape anisotropy, and orientation. It includes the determination of a system of three perpendicular sections, minimizing the effects of projections of the hypocenters, and intrinsically accounts for uncertainty in the location of the seismic events. The accuracy and the effectiveness of the NOAWC procedure are illustrated on both synthetic and real data. An application to the M = 5.1 Arudy (French Pyrenees) aftershock sequence shows how a combination of the possible mathematically reconstructed geometries can be combined with the available fault plane solutions and geomorphological markers to determine the active rupture planes and to propose and validate a local tectonic model. This new multitool approach lends itself to quantitative and computer-assisted analyses of large data sets.