Insights into Fault Friction and Caldera Collapse from the 2018 Kilauea eruption

Paul Segall, & Kyle Anderson

Published August 11, 2021, SCEC Contribution #11274, 2021 SCEC Annual Meeting Poster #137 (PDF)

The 2018 eruption of Kilauea volcano, Hawai`i, caused 62 repeatable collapse events in which the caldera dropped several meters, accompanied by Mw 4.7-5.4 Very Long Period (VLP) earthquakes. Collapses were exceptionally well recorded by GPS and tilt instruments, including GPS receivers on the down-dropped caldera block(s). These data provide unique constraints on the caldera collapse process and can also be interpreted as in-situ kilometer-scale friction experiments. Analysis of collapse induced deformations constrains the geometry of the ring-fault system and the volume and compressibility of the underlying magma reservoir.

We developed a lumped parameter model of a roof block collapsing into a magma reservoir. Pressure at the piston base and shear stress on its margin, governed by rate and state friction, balance its weight. Downward motion of the piston compresses the underlying magma, driving flow to the eruption vents. Collapse transfers weight of the caldera block to the underlying magma reservoir, sustaining the eruption. We identify initial conditions and material and magma-system parameters that lead to episodic caldera collapse, revealing that small differences in the elevation of eruptive vents can lead to major differences in eruption volume and duration. Most historical basaltic caldera collapses were, at least in part, episodic -- implying that the conditions for stick-slip derived here are commonly met in nature.

Monte Carlo estimation of the system parameters using data from the last 32 collapse events, when the ring-fault geometry was fully developed, validates laboratory friction parameters at the kilometer scale, including the magnitude of steady-state velocity weakening. The absence of accelerating pre-collapse deformation constrains the slip weakening distance, dc to be less than 10 mm, potentially much less. Our results support the use of laboratory friction laws and parameters for modeling earthquakes.

Details available at: Segall, P., Anderson, K. Repeating caldera collapse events constrain fault friction at the kilometer scale. Proceedings of the National Academy of Sciences of the United States of America 2021; 118 (30) DOI 10.1073/pnas.2101469118

Citation
Segall, P., & Anderson, K. (2021, 08). Insights into Fault Friction and Caldera Collapse from the 2018 Kilauea eruption. Poster Presentation at 2021 SCEC Annual Meeting.

Related Projects & Working Groups
Fault and Rupture Mechanics (FARM)