(a) Inverted slip distribution obtained under a weak constraint given by a standard deviation of 30% of the initial slip, and (b) the same under a strong constraint given by a standard deviation of 7% of the initial slip. The arrows indicate the slip vectors. The thick arrow indicates the direction of motion of the Pacific plate relative to the North American plate. The contours denote the depths of plate interface at 20-km intervals. S indicates the variance of weighted residuals, and Mw the moment magnitude.