Fig. 4.

Displacement vector map (at peak strain) and plots of circumferential Green strain versus time for all sectors before (a–b) and after (c–d) spatial smoothing of the displacement vectors. Asterisk* notes focal artifact of the displacement field before smoothing that results in an abnormally high circumferential strain. Red arrow notes artifactual increase in circumferential strain before $t_{12}$ in (b). Both artifacts improve following smoothing with $v_{\mathrm{s}\mathrm{p}}=2$.