The damage areas from historical records are not gathered by scientists and are usually biased by uneven population density. So the magnitudes and locations are not very accurate, as stated earlier. As mentioned in the footnotes of Table 5, there are doubts on the correct rupture size from global relations between magnitude and rupture length.
From both reasons, given here, a model was calculated that uses the same seismic moment of the events, but cuts the fault length to 50% while doubling the co-seismic displacement. It will be termed "short rupture model". One side-effect of this change is an increase of the stress level by a factor 2.5, as the moment release is concentrated to a smaller area. The background stress field amplitude was increased accordingly, because - as described above - this field is adjusted to the average stress change of the strongest event. It is important to note that the increase in stress level does not change the stress pattern of the initial stress field; as we are not looking for specific stress amplitudes but for stress concentrations, the change in level is not important.
The resulting pre-seismic stress level is expected to be smoother than before due to the concentration of stress release to high stress areas.
For comparison with the models above, some results obtained in the "short rupture model" are given in Figures 32 through 34.
The pre-event stress level now varies between 6.5 and 7.4 MPa for the main shocks (for more details cf. Figure 34). It is more stable than the level in the previous models, if relative values are compared. For most events, the initial stress level is considerably higher than the background. Only for two main shocks it is near the background (1706 and 1896a) and only for two strong aftershocks it is below (1896b and d). The differences to the previous model are not very large, but a further improvement of the "improved model" could be achieved in using shorter rupture planes. Concerning the extension to a layered crustal structure with an inelastic substratum to include post-seismic relaxation processes, these models will be addressed as soon as the elastic ones are finished. A new code has been prepared for this, much faster, more accurate, and capable of including even more layers than the existing code. The extension of the computer programme for the superposition of stress fields with the new code has already begun. The results will not only be compared to those from the purely elastic models, but also to continuous GPS crustal deformation data, as soon as these are available.
