The spatiotemporal stress states in the aftershock region of the 2005 West Off Fukuoka Prefecture Earthquake are examined via an analysis of the b values and focal mechanism solutions. The aftershocks are aligned roughly NW–SE, with the southeastern part of the aftershock region believed to correspond to the Kego Fault, which extends beneath the Fukuoka metropolitan area. This study reveals depth-dependent b values in the focal region, where the b values (b = 0.7–1.4) are generally higher above the mainshock depth (9.5 km) and lower (b = 0.5–1.0) at greater depths. The shallower region possesses a significant temporal increase in b values, whereas a lateral b value heterogeneity is observed in the deeper region. The b values (b ~ 1.0) near the mainshock are relatively high, whereas the northwestern and southeastern edges of the deep region have lower b values (b = 0.5–0.7). On the other hand, many of the focal mechanisms for the \(M\ge 3.5\) events are located in the low b value area of the deep region. The stress tensor inversion results reveal a change in stress state from strike-slip to strike-slip/normal faulting. These findings imply that the stress state remains high and/or slightly decreased in the northwestern and southeastern parts of the deep region. These results and the findings of previous research on this earthquake sequence suggest that the likelihood of future large earthquakes along the southeastern part of the aftershock region should be considered relatively high.

通过对b值的分析和震源机制解，研究了2005年福冈西部西部地震余震地区的时空应力状态。余震大致呈NW-SE走向，余震区的东南部被认为与Kego断层相对应，Kego断层在福冈市区下方延伸。这项研究揭示了在震源区中与深度有关的b值，其中b值（b  = 0.7-1.4）通常高于主震深度（9.5 km），而 在较大深度处较低（b = 0.5-1.0）。较浅的区域在b值上具有明显的时间增加，而横向b在较深的区域观察到值异质性。的b值（b  〜1.0）主震附近相对较高，而深区域的西北和东南部边缘具有较低的b值（b  = 0.5-0.7）。在另一方面，许多震源机制为\（M \ GE 3.5 \）事件被位于低b深部区域的价值区域。应力张量反演结果揭示了应力状态从走滑到走滑/正断层的变化。这些发现表明，在深部地区的西北和东南部，应力状态仍然很高和/或略有下降。这些结果和先前对该地震序列研究的发现表明，应将余震地区东南部未来发生大地震的可能性考虑为相对较高。