Source geometry of historical events retrieved by synthetic isoseismals

The possibility of computing complete synthetic signals for laterally homogeneous structural models in an exact, efficient and computationally rapid way allows an investigation of the effects of given source and structural models on the macroseismic field. Synthetic isoseismals are computed by first adding vectorially, in the horizontal plane, the SH-wave and P-SV-wave displacement fields. The maximum zero-to-peak value of displacement is then calculated at points distributed in space in such a way that it is easy to contour the isolines automatically. This methodology, developed mainly in the point-source approximation and used to investigate the macroseismic field of some instrumentally recorded earthquakes, can also be applied to historical events.