Magma Depletion: A Swiss cheese alternative for vent distribution in volcanic fields
Melody Whitehead , Mark Bebbington, Gabor Kereszturi
Affiliations: Volcanic Risk Solutions, School of Agriculture and Environment, Massey University, Palmerston North, Aotearoa-New Zealand
Presentation type: Poster
Presentation time: Thursday 16:30 - 18:30, Room Poster Hall
Poster Board Number: 2
Programme No: 3.7.9
Abstract
For small volume eruptions, such as those common for volcanic fields, the location of an eruptive vent controls the hazards, their intensities, and ultimately the impact of the eruption. An eruption through water can result in a highly explosive phreatomagmatic eruption, as opposed to an eruption driven only by magmatic volatiles. We look here at long-term probabilistic assessments, the outputs of which inform evacuation plans, the (re)location of vital infrastructure, and inform the placement of early-warning monitoring equipment. Current estimates of future vent locations are based on point-process methods with probability surfaces built from spatial patterns, clusters, and/or lineaments identified from previous vent locations. These all assume that locations with more past-vents are more likely to produce future-vents. We provide here an alternative (but not necessarily better) hypothesis of magma depletion, i.e., that after an eruption, the magma source at depth is depleted in this area, causing holes or dips to appear in a probability surface. More formally: H0: The location of future eruptions is inversely proportional to past vent locations. We present the maths, and code around how to produce various Swiss cheese estimates, and then set out to try and disprove our null hypothesis, all using the exemplar of the Auckland Volcanic Field, Aotearoa-New Zealand.