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- Title
Time Varying Crustal Anisotropy at Whakaari/White Island Volcano.
- Authors
Mengesha, D. Y.; Savage, M. K.; Jolly, A. D.; Ebinger, C. J.
- Abstract
Whakaari/White Island has been the most active New Zealand volcano in the 21st century, producing small phreatic and phreatomagmatic eruptions, which are hard to predict. The most recent eruption occurred in 2019, tragically claiming the lives of 22 individuals and causing numerous injuries. We employed shear‐wave splitting analyses to investigate variations in anisotropy between 2018 and 2020, during quiescence, unrest, and the eruption. We examined spatial and temporal variations in 3,499 shear‐wave splitting and 2,656 Vp/Vs ratio measurements. Comparing shear‐wave splitting parameters from similar earthquake paths across different times indicates that the observed temporal changes are unlikely to result from variations in earthquake paths through media with spatial variability. Instead, these changes may stem from variations in anisotropy over time, likely caused by changes in crack alignment due to stress or varying fluid content. Plain Language Summary: The most active volcano in New Zealand, known as Whakaari/White Island, has recently experienced numerous minor eruptions, which are hard to predict. The most recent eruption occurred in 2019, tragically claiming the lives of 22 individuals and causing multiple injuries. This study examines the stress field and characteristics of cracks within various parts of the volcano, during the period between 2018 and 2020. We used a method called shear‐wave splitting, which examines the alignment of cracks by measuring the speed of seismic waves in different orientations, and another method that measures the ratio of the speed of two different types of waves traveling through the medium (Vp/Vs). Our analysis revealed that both shear‐wave splitting and Vp/Vs changed over time in response to the variations in magmatic activity. This suggests that crack alignment, content, or numbers change in response to the stresses induced by magmatic activity at various depths within the volcano over time. Key Points: Background fast orientations were concentrated parallel to the crater wall at both measurement stationsSeismic waves that follow similar paths to the stations result in different fast orientations pre‐ and post‐eruptionVp/Vs ratio can provide valuable insights into the nature and evolution of seismic anisotropy in the Earth's interior
- Subjects
NEW Zealand; SEISMIC anisotropy; SEISMIC waves; INTERNAL structure of the Earth; SEISMIC wave velocity; VOLCANOES; VOLCANIC eruptions; EARTHQUAKES; ISLANDS
- Publication
Geophysical Research Letters, 2024, Vol 51, Issue 11, p1
- ISSN
0094-8276
- Publication type
Article
- DOI
10.1029/2023GL106473