indicated by the reference number 2 that the region of the seismic resource is reduced or converged on the range within the specific region after the term indicated by the reference number 9 after aug 7 1999 the graph indicated by the reference number 6 indicates the tendency of minus values before and after the term indicated by the reference number 8 especially the characteristics of the graph indicated by the reference number 6 are not the same for fig1 if the seismic source which was identified after the proper time was set as the first spatial base the characteristics indicated by the reference number 2 u2032 for the spatial characteristics of the seismic source indicated by ssrqr 1 i indicated the tendency of reducing or a specific area from june 11 indicated by the reference number 8 u2032 the number of the seismic events for the calculation period is 8 even if other conditions are defined as the same not shown in figures by setting the limit of depth as 40 to 0 km on the calculation condition of fig1 to 13 the characteristic having the minus values or the tendency of time sequence different apparently from the term before the term indicated by the reference number 8 of the graph indicated by the reference number 6 and dd 1 i in the same term after august 1 is not changed in fig1 the.