MOESM1 of Infrasonic wave accompanying a crack opening during the 2015 Hakone eruption

Additional file 1. Photographs near the vents (Owakudani) taken using a time-lapse camera before and during the rapid tilt change

MOESM2 of Infrasonic wave accompanying a crack opening during the 2015 Hakone eruption

Additional file 2. Calibration test for the microphone at the OWD station

MOESM3 of Infrasonic wave accompanying a crack opening during the 2015 Hakone eruption

Additional file 3. Shift in the peaks and node of the seismic-infrasonic correlation resulting from background seismic oscillation

MOESM4 of Infrasonic wave accompanying a crack opening during the 2015 Hakone eruption

Additional file 4. Strain changes using the open crack model estimated by InSAR data

Additional file 1 of Harmonic tremor from the deep part of Hakone volcano

Additional file 1: Figure S1. Particle motions on the horizontal plane during the main volcanic tremor (03:25–03:45). (a) The vertical waveform at the N.ASGH stations. Red trajectories in (b) and (c) show the particle motions of velocity waveform on the horizontal plane at each station during the period of harmonic tremor as indicated by the red and yellow rectangles in (a), respectively. Figure S2. Particle motions on the radial–vertical plane during the main volcanic tremor (03:25–03:45). (a) The vertical waveform at N.ASGH stations. Red trajectories in (b) and (c) show particle motions of the velocity waveform on the radial–vertical plane at each station during the period of harmonic tremor during the periods indicated by the red and yellow rectangles in (a), respectively. The radial direction of each trajectory is eastward as shown in the inset of (c). Note that the particle motion in N.ASGH on the radial–vertical plane is not shown owing to the differences in the natural frequency of the horizontal and vertical seismometers. Figure S3. Record section of the tectonic earthquake (35.44010°N, 139.10108°E, depth = 28.46 km, local magnitude = 2.5) that occurred 10 km horizontally NNE from the epicenter of the volcanic tremor. (a) Record section 100 km from N.ASGH station along to N–S section. Zero second on the time axis corresponds to the origin time (09/06/2015 12:52:25 JST). (b) Station distribution. The stations used in this record section are the same as that shown in Figures 2a and 2c. The yellow star shows the epicenter of the tectonic earthquake. Figure S4. Results of the envelope correlation method assuming the P wave velocity structure. The meaning of (a)–(c) is the same as in Figure 4 in the main text

MOESM1 of Precursory tilt changes associated with a phreatic eruption of the Hakone volcano and the corresponding source model

Additional file 1. Comparison of synthetic apparent tilt motions calculated using four time functions. Examples of the time functions of source expansion are shown in the left panel. F1 [Eq. (2)] was used in this study with the time constant T set to 45 s. F2 is an exponential relaxation function represented by 1 − exp(−t/T) with T set as 45 s. F3 and F4 are smoothed ramp functions (0.5 × (1.0 + tanh((4.0 × t)/Tr))) with the rise time Tr set to 60 and 120 s, respectively. The right panel shows the apparent tilt motions calculated using the functions in the left panel. The NS component of tilt change observed at KZR is indicated by the orange line

MOESM2 of Precursory tilt changes associated with a phreatic eruption of the Hakone volcano and the corresponding source model

Additional file 2. The map represents surface slope gradation. The location of the best-fit model (red rectangle), the eruption center (red circle), and tilt observation stations (white triangles) are shown in the map. Yellow arrows indicate the locations of old fissures

MOESM2 of Analyzing the continuous volcanic tremors detected during the 2015 phreatic eruption of the Hakone volcano

Additional file 2. Temporal changes in amplitude ratios during volcanic tremor. This file shows the temporal changes in the amplitude ratios among the stations near the vents

MOESM1 of Resistivity characterisation of Hakone volcano, Central Japan, by three-dimensional magnetotelluric inversion

Additional file 1. Epicentral distributions of swarm activities in 2001, 2009, 2011, 2013 and 2015; and vertical cross sections of the obtained resistivity structure overlain by the hypocentres of such swarm epochs