Stress State Inferred from b Value and Focal Mechanism Distributions in the Aftershock Area of the 2005 West Off Fukuoka Prefecture Earthquake

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