Table 1. Stress tensor inversion results using aftershock first-motion polarities and the regional stress tensor derived from the fault plane solutions of large events which occurred between 1943 and 1999. The locations of the clusters labeled with capital letters A–G are shown in Fig. 1. The total number of aftershocks in a cluster, the number of events used to determine the local stress tensors, and the total number of polarities in these clusters are also given. σ1, σ2, and σ3 denote the maximum, intermediate, and minimum principal compressive stress axes, while ϕ and δ show the azimuth and plunge of these axes in degree, respectively. The plunge is measured from horizontal. R is the ratio of the principal stress amplitudes defined as R = (σ2 - σ1)/(σ3 - σ1), where σ1 ≥ σ2 ≥ σ3. Min and Max are the minimum and maximum number of polarity misfits in the clusters obtained for a 5δ grid search.