Additional supporting information may be found in the online version of this article.

text01.docxWord 2007 document131KDetailed description of the gravity survey and gravity data reduction procedures used.
text02.docxWord 2007 document136KDetailed description of the gravity inversion routine and parameters used (density contrasts and regional gravity signals).
text03.docxWord 2007 document127KFurther discussion on the volume and density contrast calculations used in plotting the data in Figure 3 in the main text.
text04.docxWord 2007 document90KDescription of the analysis of synthetic data carried out in order to show that the inversion routine used is capable of resolving between rooted and rootless anomalous bodies.
fs01application/unknown2084KInversion modeling results for a wide range of the models carried out. The location of the vertical cross sections is indicated in minimum ±300 −25 km. Ticks in cross sections are every 10 km. Vertical exaggeration on vertical sections is ×2. Columns highlighted in green correspond to the preferred models.
fs02application/unknown718K(a) Bouguer Anomaly for each benchmark using a reduction density of 2270 kg m−3. This original data has been interpolated for the Bouguer anomaly shown in Fig. 1b of the main manuscript. (b) Best fit “regional” first-order polynomial for a Free configuration and a density contrast of ±150 kg m−3. (c) The “local” anomaly inverted to produce the anomalous bodies shown in Figure 2a of the main manuscript. This same local anomaly is inverted using the Bottom Free setup.
fs03application/unknown1220KHorizontal cross sections through the gravity inversion models (left) Bottom Free ±150 kg m−3 and (right) Free ±150 kg m−3, at sea level, −5, −10 −15, and −20 km bsl (below sea level). The negative anomalous bodies are the blue polygons, the Neogene calderas the black lines, gravity benchmarks are black dots, and color fringes correspond to the 18 years of stacked InSAR data presented by Fialko and Pearse [2012]. The top left box shows the residual of the inversion at each benchmark for both models.
fs04application/unknown662KInversion of synthetic models. (a) Artificial structure built to which a regional first-order polynomial and white noise have been added. (b) Inversion results using a Free configuration and (c) using a Bottom Free configuration with domain depth maximum at 30 km bsl. The wiggly green lines indicate the Neogene caldera rims while the green straight lines indicate the position of the cross sections shown. (d) Histogram of model residuals and (e) distance-normalized autocorrelation between resulting inversion residuals for the Free model (Figure S4b).
fs05application/unknown736K(a) Top, inversion residuals for the Bottom Free configuration and a density contrast of ±150 kg m−3 at each benchmark. Bottom left is a histogram with the distribution of the residuals and bottom right the distance-normalized autocorrelation between residual values. (b) Similar model residuals, for the Free configuration and a density contrast of ±150 kg m−3.
fs06.docxWord 2007 document131KGraph of density contrast change with temperature.
readme.docxWord 2007 document122KSupporting Information

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