Changes in tilt show a diurnal pattern comprising low tilt changes during the velocity peak itself, followed by two periods of high tilt changes (in the afternoon during the velocity decline, and overnight, during the small velocity increase), a short period of low tilt change in the early morning, and finally an intermediate level of tilt change as the temperature warmed during the morning.
Water pressure, tilt changes, and case stress data from an in situ probe embedded in the till, alongside surface melt from 2008 to 2010 are shown in Fig. 3a, with the winter of 2008/2009 shown in Fig. 3b.
A most promising approach would involve laser altimetry and gravitational field observations from an orbiting spacecraft combined with monitoring of tidally-induced gravity and tilt changes at the surface.
On the other hand, for a small, the displacement and tilt changes increase with time, being proportional to t′1.5.
For this reason, it is important to be able to detect precursor phenomena other than imminent seismic activity and tilt changes.
However, after the beginning of February, tilt changes accompanied by BH-type earthquake swarms were often observed for about 60 hours before the events (Fig. 11).
During the 2001 and 2013 swarm activity, tilt changes of 1 5 μrad were also observed by the tiltmeters in the caldera.
The use of broadband seismograms may be a promising way to deduce tilt changes at particular points (e.g., Aoyama and Oshima, 2008).
In fact, tilt changes prior to the sub-Plinian eruptions of Shinmoe-dake were indicated by data from a broadband seismogram positioned about 1 km from the crater of Shinmoe-dake (Maehara et al., 2012).
On the other hand, after the beginning of February, tilt changes accompanying BH-type earthquake swarms were often observed up to 60 hours prior to the individual eruption events.
Immediately before the eruption, volcanic tremor and tilt changes were recorded at 11 41 and 11 45, respectively, at the JMA stations at Tanohara, 2 km SE of the summit (Japan Meteorological Agency 2014).
