emphasis lines

Lines drawn in a burst pattern, radiating outward from a part of the image to which the artist wants to draw attention. They cause the area surrounded by the lines to stand out more in the viewer's eye.

These are not the same as speed lines, which indicate motion; emphasis lines indicate focus, rather than motion.

A similar technique used in filmography is to focus the camera toward a specific part of the shot (sometimes off-center) while allowing other parts of the image to become unfocused, thus drawing extra attention to the focused area.

The Japanese word / Pixiv tag is 集中線 (Shuuchuusen)