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Abstract Liu et al. (2022,https://doi.org/10.1029/2021GL093691) used Rayleigh waves extracted from the cross‐correlation of ambient noise recorded by two stations to monitor the seismic velocity variations associated with the 2018 Kı̄lauea eruption. However, their study ignored the fact that the tremors on the Island of Hawai'i were dominated by a source at the Kı̄lauea summit before the eruption. Close inspection of the waveforms of the station pair PAUD‐STCD shows a simple, mistakenly identified wave traveling direction in Liu et al. (2022,https://doi.org/10.1029/2021GL093691). A correct wave traveling direction agrees with the noise source model, where the dominant tremor source should be at the Kı̄lauea summit. Because of the drastic change in the tremor source after the eruption, the cross‐correlation of the tremor records may reflect predominantly changes in the source rather than in the medium properties between the two stations.
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P Waves Emerged From Ambient Noise Cross‐Correlation Post the 2018 Kı̄lauea Eruption Revealing Middle Crust Velocity Discontinuities Beneath the Island of Hawai'i
Abstract Empirical Green Functions (EGFs) obtained from ambient noise cross‐correlation are important for imaging and monitoring underground structures. The EGFs on the Island of Hawai'i in different years are similar at low frequencies (0.1–0.4 Hz), but very different at high frequencies (0.4–1.0 Hz): Only the EGFs after the 2018 Kı̄lauea eruption show clear P waves. Grid search reveals a strong noise source near the Kı̄lauea summit before the eruption, which contaminated the EGFs but became silent after the eruption. Modeling of the P waves identifies the direct arrival and post‐critical reflections from two velocity discontinuities at 4.7 and 7.2 km depth beneath the island, which we interpret as the base of volcanic edifices and deposits and the boundary between basaltic dikes and gabbros, respectively. The P waves in EGFs could provide valuable high‐resolution constraints for monitoring deep magmatic changes and imaging the volcano structures.
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- Award ID(s):
- 1949620
- PAR ID:
- 10371911
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Geophysical Research Letters
- Volume:
- 49
- Issue:
- 16
- ISSN:
- 0094-8276
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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