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Table 2 Parameters of best-fit source models (August 2014–August 2016)

From: Precursory ground deformation of the 2018 phreatic eruption on Iwo-Yama volcano, revealed by four-dimensional joint analysis of airborne and spaceborne InSAR

Parameters

Okada model

Mogi model

Yang model

Residual [cm]1

0.814

0.797

0.788

Latitude [deg]

31.9463966

31.9468

31.946895

Longitude [deg]

130.8530366

130.8529

130.8531273

Depth [m]

149 [134/161]

118 [109/128]

100 [94/128]

Length [m]

103 [65/139]

–

–

Width [m]

34 [17/73]

–

–

Major axis a [m]

–

–

11 [6/17]

b/a [m/m]2

–

–

0.67 [0.60/0.95]

Dip [deg]3

0 (fixed)

–

68 [8/83]

Strike [deg]4

0 (fixed)

–

245 [116/302]

Opening [m]

1.71 [0.43/1.95]

–

–

ΔP/μ [Pa/Pa]5

–

–

2.23 [0.52/9.33]

Volume change [m3]

5988

4342 [3557/5207]

8325

  1. Square brackets show 2.5 and 97.5 percentiles of posterior probability density functions of the parameters
  2. 1Residual is defined as: \(\sqrt {\frac{{\mathop \sum \nolimits_{\varvec{i}}^{\varvec{N}} \left( {{\mathbf{Obs}}\left( \varvec{i} \right) - {\mathbf{Cal}}\left( \varvec{i} \right)} \right)^{2} }}{\varvec{N}}} ,\) where Obs is the observed displacement, Cal is calculated displacement, i is the pixel index, and N is the number of pixels used for the calculation
  3. 2Ratio of minor axis b to major axis a
  4. 3Dip angle δ is defined as δ = 0° if the ellipsoid is horizontal and δ = 90° if it is vertical
  5. 4Strike is defined as clockwise from the north
  6. 5ΔP/μ corresponds to ratio of pressure change (ΔP) to host rock rigidity (μ)
  7. 6Position of the southwest corner of the horizontal crack