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Physics-based model reconciles caldera collapse induced static and dynamic ground motion: application to Kīlauea 2018
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  • Taiyi Wang,
  • Katherine Coppess,
  • Paul Segall,
  • Eric M Dunham,
  • William L. Ellsworth
Taiyi Wang
Stanford University

Corresponding Author:[email protected]

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Katherine Coppess
Stanford University
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Paul Segall
Stanford University
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Eric M Dunham
Stanford University
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William L. Ellsworth
Stanford University
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Abstract

Inflationary deformation and very long period (VLP) earthquakes frequently accompany basaltic caldera collapses, yet current interpretations do not reflect physically consistent mechanisms. We present a lumped parameter model accounting for caldera block/magma momentum change, magma chamber pressurization, and ring fault shear stress drop. The effect of pressurizing a spheroidal chamber is represented as a tri-axial expansion source, and the combined caldera block/magma momentum change as a vertical single force. The model is applied to Kīlauea 2018 caldera collapse events, accurately predicting near field static/dynamic ground motions. In addition to the tri-axial expansion source, the single force contributes significantly to the VLP waveforms. For an average collapse event with fully developed ring fault, Bayesian inversion constrains ring fault stress drop to ~0.4 MPa and the pressure increase to ~1.7 MPa. That the predictions fit both geodetic and seismic observations confirms that the model captures the dominant caldera collapse mechanisms.
28 Apr 2022Published in Geophysical Research Letters volume 49 issue 8. 10.1029/2021GL097440