Figure 3: The migration of the VLP inclination vector (blue line) measured during the eruption (grey band in Fig. 2a) is compared with the residual magma volume in the upper cylindrical reservoir (black line) by assuming the measured effusion rate and with the discharge model (equation (1)) controlled by the drainage of magma stored above the vent (red line).

The inset shows the remarkably good (R2=0.93) correlation between the level of magma h(t) in the reservoir and the seismic source dip.