July 30 — Aug 5

This week in SimPEG…

Craig Miller, Seogi Kang and Dom Fournier had their paper: Distribution of vapour and condensate in a hydrothermal system: Insights from self-potential inversion at Mount Tongariro, New Zealand, accepted this week!

Volcanologists routinely sample fluids from springs and vents on volcanoes to determine that volcano’s state of unrest. Prior to the 2012 Te Maari eruptions at Mt Tongariro, New Zealand, changes in water and gas chemistry that preceded the eruption, were found at only a few of the vents and springs sampled, despite evidence for a large hydrothermal system, thought to connect them. We wanted to understand why chemical changes in the water and gas weren’t observed more widely on the volcano, and if it was related to the pattern of underground water movement. Water moving within a rock generates a small electrical charge, measurable on the surface as a voltage. We mapped voltage variations around the hydrothermal system at Mt Tongariro, and developed new 3D computer software to simulate the subsurface water movement. We found varying degrees of water and steam within the hydrothermal system that is likely controlled by the rock’s ability to allow water movement. Importantly, we found no connectivity between individual springs and vents on the volcano, explaining observations of geographically isolated changes in water and gas chemistry prior to the eruptions. This has important implications for how geochemical monitoring of similar multivent volcanoes is undertaken.

Notebooks used to generate the results are available at: https://github.com/simpeg-research/miller2018_Tongariro_SP_inversion.

At the meeting last week…

Dom Fournier led the meeting on OcTree meshes and utilities for generating meshes.