Post‐2018 Caldera Collapse Re‐Inflation Uniquely Constrains Kīlauea's Magmatic System

Abstract

The supply, storage, and subsurface transport of magma are some of the most fundamental, yet least understood volcanic processes (Poland et al., 2014). These processes, along with eruptive dynamics, are modulated by the geometry and nature of the pathways connecting magmatic reservoirs (Keating et al., 2008). The geometry and dimensions of individual pathways can be constrained by inverting surface deformation with continuum mechanics based models (e.g., Owen et al., 2000;Montagna & Gonnermann, 2013). However, with multiple reservoirs and a network of magmatic pathways, estimating the dimensions of each pathway directly from deformation can be challenging. Because magma flux is proportional to the hydraulic conductivity of the pathway, and pressure change in a reservoir depends on magma flux, time dependent deformation associated with each reservoir may reveal the connectivity of a multi-reservoir system (e.g., Bato et al., 2018;Le Mével et al., 2016;Reverso et al., 2014). Here we demonstrate that, physics-based models, coupled with Bayesian inversion, can synthesize multi-reservoir conceptual models with geodetic measurements to quantitatively constrain the hydraulic connectivity of magmatic systems.Despite decades of research, the nature of Kīlauea's summit reservoirs and their connectivity to the East Rift Zone remains enigmatic (we reserve "East Rift Zone" for the geographic location and "ERZ" for the reservoir active in the observation period). Efforts to interpret summit deformation in terms of simple reservoir models yielded diverse reservoir locations and geometries (e.g., Baker & Amelung, 2012;Fiske & Kinoshita, 1969). Although modeled reservoirs cluster into two groups -a shallow Halema'uma'u (HMM) and a deeper South Caldera (SC) reservoir (e.g., Cervelli & Miklius, 2003;Poland et al., 2014), it has been suggested that the summit system represents a single irregularly shaped reservoir (Dieterich & Decker, 1975;Ryan, 1988). This ambiguity arises because deformation signals associated with these reservoirs are almost always of the same sign. The configuration of magmatic pathways connecting Kīlauea's summit reservoirs and ERZ is also elusive. Cervelli and Miklius (2003) argue that an "Γ shaped" pathway connecting the deeper SC reservoir to the shallower HMM reservoir, and then to ERZ, is required to explain the drainage Abstract From August 2018 to May 2019, Kīlauea's summit exhibited unique, simultaneous, inflation and deflation, apparent in both GPS time series and cumulative InSAR displacement maps. This deformation pattern provides clear evidence that the Halema'uma'u (HMM) and South Caldera (SC) reservoirs are distinct. Post-collapse inflation of the East Rift Zone (ERZ), as captured by InSAR, indicates concurrent magma transfer from the summit reservoirs to the ERZ. We present a physics-based model that couples pressure-driven flow between these magma reservoirs to simulate time dependent summit deformation. We take a two-step approach to quantitatively constrain Kīlauea's magmatic plumbing system. ...

Could Kı̄lauea's 2020 Post Caldera‐Forming Eruption Have Been Anticipated?

“…We estimated the pressure history within the summit reservoirs, assumed ellipsoidal (Cervelli, 2013), by least squares, fixing the reservoir geometry of Wang et al (2021). We use all summit GPS stations, except CALS, which is on the down-dropped block.…”

“…This result does not account for uncertainty in HMM volume, which directly trades off with inferred pressure change. To account for this, we resampled the posterior distribution of chamber geometry (e.g., aspect ratio, location) from Wang et al (2021) and HMM volume from Anderson et al (2019). We subtracted the increase in caldera volume (0.8 km 3 ) from the HMM volume, but limited the minimum to the minimum in the pre-collapse distribution (0.45 km 3 ).…”

Integration of DInSAR Time Series and GNSS Data for Continuous Volcanic Deformation Monitoring and Eruption Early Warning Applications

“…The 2018 event at Kilauea volcano was the largest caldera collapse and most effusive volcanic eruption in Hawaii within the past 200 years [26,[48][49][50][51]. Combining high-quality geodetic datasets, such as DInSAR and GNSS, resulted in detailed observations and precise measurements regarding the development and evolution of volcanic events.…”

“…Furthermore, our results extend further evidence of the 62 summit collapse events between May 16 and August 2, reported by HVO. Another study by [50] used raw GNSS and DInSAR measurements from Hawaii as input for multi-reservoir conceptual models to quantitatively constrain the hydraulic connectivity between magmatic systems. By exploiting high-quality geodetic data, they learned that the Halema'uma'u magmatic reservoir is distinct from the South Caldera reservoir and that the ERZ is being fed simultaneously by both chambers.…”

“…This interaction between the two volcanic systems has been studied before [46][47][48][49] and provides further evidence of upper mantle links and magma transportation. On 30 April 2018, the Pu'u ' Ō' ō eruptive vent collapsed [48][49][50], and on May 4, a Mw 6.9 earthquake occurred on the south flank of Kilauea, initiating the 2018 volcanic eruption. Our integrated results from 5 May 2018 (Figure 5d) recorded the 43 cm southeast ground rupture of the earthquake.…”