November 2021: Craig Miller

Cones, calderas and fields (volcanic and potential). Imaging the volcano factory.

Craig Miller

Nov 18 at 2pm PM


Interpretation and inversion of potential field data offer the abiity to image in high resolution shallow and mid crustal structures, including those caused by magmatism and volcanism. Here I present examples from three volcanic regions in Chile and New Zealand. At Laguna del Maule Volcanic Field, Chile, gravity inversion reveals a low density body at 2 km depth, interpreted by use of thermodynamic models as a high silica rhyolite magma with a free volatile content. At Okataina Volcanic Center, interpretation and inversion of new and existing terrestrial, lake and airborne gravity and magnetic data reveals the evolution of the caldera through repeated episodes of eruption, collapse and infill. At Mt. Ruapehu, New Zealand, inversion of helimag data in conjunction with interpretation of hyperspectral imaging maps the distribution of surface alteration and its volumetric extent with implications for probability of future large scale flank collapse. All models presented rely on the SimPEG inversion framework which is and continues to be a critical tool for my work.


Craig Miller is a senior volcano geophysicist at GNS Science New Zealand specialising in imaging volcano, magmatic and hydrothermal systems using potential field geophysical methods, such as gravity, magnetics and resistivity. Through inverse and forward models these data are turned into images of the Earth’s crust to locate features of interest. He has a broad background in geosciences having worked in mineral exploration, volcano monitoring and geothermal assessment.