111-7 Modeling Changes in Magma Body Source Parameters During Episodic Lava Fountaining in the Ongoing Halema‘uma‘u Eruption at Kīlauea, Island of Hawai‘i using GPS Data

Session: Using Near Surface Geophysics to Investigate Geological Problems (Posters)

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On December 23rd, 2024, the ongoing eruption in Halema‘uma‘u crater began with lava fountains reaching heights of almost 100 m. At the time of this writing, there have been over 29 episodes of fountaining that have been growing taller, reaching heights of approximately 365 m during episode 28. The increasing fountain heights and erupted volume raises the question: where is all of this magma coming from? If the Halema‘uma‘u reservoir is being sampled, is it the entire magma body or only the shallowest portion? If only the top of the magma body is being sampled, it may be that the modeled depth and location would likely be shallow and near the vents. Conversely, if the entire body is being sampled, the modeled depth and location might be deeper and closer to the location posited for the Halema‘uma‘u reservoir. 

To test this, cm-level epoch-by-epoch positions were calculated for stations in the permanent GPS network managed by the Hawaiian Volcano Observatory.  Surface deformation measurements were calculated for 11 episodes of the eruption using the Track module of GAMIT/GLOBK. Then, the calculated GPS positions and the McTigue (1987) model for deformation of a spherical void in an elastic half-space were used with the Bayesian inversion algorithm of the Versatile Modeling of Deformation package in Python, to find the posterior parameter distribution including the location, depth, and radius of the source. 

After finding the parameter distributions and the most likely parameter values, it is clear that most of the episodes are sampling the Halema‘uma‘u reservoir at about a depth of 2 km. Some episodes, however, could sample depths as shallow as 0.5 km (considering uncertainty). The modeled depths for episodes 10, 13, 14, and 15 begin at about a depth of 1.25 km and deepen to about 2.5 km. The modeled locations of the magma bodies during this period shift from the caldera center, where the Halema‘uma‘u reservoir is posited to be, to the southwest, ending due west of the vents. There is a similar westward motion with episodes 22, 23, and 24, but the modeled depths and latitudinal motion are not as well constrained. Generally, there is a weak negative relationship between modeled depth and time, implying an inverse relationship with erupted volume. 

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

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