A procedure to resolve areas of different source mechanism when using the method of composite nodal plane solution

The composite nodal plane solution method fails when it is applied to a region where the events have different source mechanism in different areas. Presented here is a systematic procedure to delimit those areas and find their particular source mechanism. In its first step, the method consists of a graphical analysis of the regional distribution of P first motion data of all events as recorded at each station. From that analysis, it is possible to identify small areas where the events have the same source mechanism. In a second step, those elemental areas are expanded into adjacent areas with compatible P data until they cover the whole seismic region under study. The method resolves the source mechanism in each area and allows the identification of anomalous ones.