The benefit of the RCMT technique for smaller magnitudes is clear considering that, for this time period, the number of moment tensors is more than tripled with respect to what was achieved by the standard, global analysis. The map also shows, in blue, RCMTs for some older events. The map shows 73 solutions, in red, in the 2-year period, with magnitude between 4.5 and 5.5, which had not been previously analyzed on a global scale. Provided that they cover a fair azimuthal range, as few as 3 stations at distances of the order of 100's of kilometers proved to be sufficient. The RCMT procedure contributed valuable information for the timely study of the complex process of stress transfer to different fault segments that marked the unusual time evolution of the sequence.
Labels indicate month and day of occurrence of events.
The radii of the focal spheres are proportional to the moment magnitude. Compressional quandrants are shaded in different colors to distinguish between 1997 and 1998 events. Being based on a modification of the CMT scheme, our RCMT solutions have similar characters and, for earthquakes whose size allows both to be computed, the two procedures yield compatible and very similar results, as shown in Figure 4. Note that, for each event, the two solutions shown have been computed with different sets of stations, at different distance ranges, and modelling different parts of the seismogram. The level of agreement is also significant as an empirical estimate of stability to possible bias in the data or due to simplifying assumptions in the theory.