[S01P-01] フンガ・トンガ＝フンガ・ハアパイ火山における2022年噴火前・中・後のイベント検出と大規模噴火の運動学的モデリング
On 15 January 2022, the Hunga Tonga-Hunga Ha'apai volcano erupted, devastating Tonga and nearby regions. The event produced atmospheric waves and tsunami that traveled worldwide. Additionally, the eruptions generated a series of seismic events. Monitoring these seismic events can offer insights into the magmatic and deformation processes before, during, and after the eruption. However, near-field observations of the Hunga Tonga-Hunga Ha'apai volcano are limited due to its remote oceanic location. Furthermore, seismic signals resulting from volcanic activities often lack clear high-frequency body waves, making it challenging to effectively monitor volcanic events using standard detection algorithms.
We use global broadband seismic records and the Automated Event Location Using a Mesh of Arrays (AELUMA) method to investigate seismic events related to the Hunga Tonga-Hunga Ha'apai eruption. Our procedure has successfully detected and located non-regular earthquake sources using regional arrays, such as the USArray and NIED F-net. Using global data improves the array azimuthal coverage and detection sensitivity for unconventional seismic sources. We analyze Rayleigh waves recorded at ~1924 broadband seismic stations from the FDSN and F-net networks between 2021-11-01 and 2022-07-01, resulting in ~979 triad subarrays. We bandpass filter the data at 20–50 s period band to focus on seismic sources that can produce intermediate period surface waves. We detect a total of 902 reliable seismic events at the volcano during the eight-month study period. Notably, 162 seismic events were previously undetected and are not registered in the ISC catalog. We plan to further explore the connections between the seismic activity and the volcanic eruptions, including the seismicity preceding the main eruptions and the post-eruption seismic activity.
We also investigate the source mechanisms of the most energetic eruption series, which occurred from 2022-01-15T04:14:45 to 2022-01-15T04:22:45. We use the three components of broadband teleseismic data and a frequency-domain inversion method. The source models include both a moment tensor and a single force component, accounting for possible volumetric deformation as well as mass movement. We identify at least four distinct sub-events during the first 480 s from the origin time. These sub-events are characterized by the dominant isotropic component moment tensors and vertical single forces. We confirm the robustness of the results with a bootstrapping uncertainty exercise. Our results indicate that neither the moment tensors nor the single forces on their own can adequately explain the data, suggesting a complex interplay of explosions, implosions, and mass movements.
We use global broadband seismic records and the Automated Event Location Using a Mesh of Arrays (AELUMA) method to investigate seismic events related to the Hunga Tonga-Hunga Ha'apai eruption. Our procedure has successfully detected and located non-regular earthquake sources using regional arrays, such as the USArray and NIED F-net. Using global data improves the array azimuthal coverage and detection sensitivity for unconventional seismic sources. We analyze Rayleigh waves recorded at ~1924 broadband seismic stations from the FDSN and F-net networks between 2021-11-01 and 2022-07-01, resulting in ~979 triad subarrays. We bandpass filter the data at 20–50 s period band to focus on seismic sources that can produce intermediate period surface waves. We detect a total of 902 reliable seismic events at the volcano during the eight-month study period. Notably, 162 seismic events were previously undetected and are not registered in the ISC catalog. We plan to further explore the connections between the seismic activity and the volcanic eruptions, including the seismicity preceding the main eruptions and the post-eruption seismic activity.
We also investigate the source mechanisms of the most energetic eruption series, which occurred from 2022-01-15T04:14:45 to 2022-01-15T04:22:45. We use the three components of broadband teleseismic data and a frequency-domain inversion method. The source models include both a moment tensor and a single force component, accounting for possible volumetric deformation as well as mass movement. We identify at least four distinct sub-events during the first 480 s from the origin time. These sub-events are characterized by the dominant isotropic component moment tensors and vertical single forces. We confirm the robustness of the results with a bootstrapping uncertainty exercise. Our results indicate that neither the moment tensors nor the single forces on their own can adequately explain the data, suggesting a complex interplay of explosions, implosions, and mass movements.