09:30 〜 09:45
[SVC30-03] Ground deformation before and after the Mauna Loa 2022 eruption and its relationship to the decollement activity
キーワード：火山性地殻変動、GNSS、デコルマ、ダイク貫入
Mauna Loa, the largest volcano on Earth, is located on the Island of Hawaii and erupted in 2022. Mauna Loa's volcanic structural features consist of a summit caldera and two rift zones: the Northeast Rift Zone (NERZ) and Southwest Rift Zone (SWRZ). The 2022 eruption occurred in the NERZ a few hours after the eruption in the summit caldera. The decollement fault, a boundary between the volcanic body and the oceanic crust, is located about 10 km below the surface to the northwest and southeast of Mauna Loa. The decollement on the southeast side has experienced a shear slip of 6-33 cm/yr since 2002 (Varugu and Amelung, 2021). This shear slip and intrusion into the rift have been interacting with each other through stress transfer (Walter and Amelung., 2006). On the other hand, the decollement on the northwest side has not been active since 2002.
Previous studies of ground deformation before the 2022 eruption have revealed significant inflationary ground deformation from 2014 to 2020 through the GNSS (Global Navigation Satellite System) and InSAR (Interferometric Synthetic Aperture Radar) measurements (Varugu and Amelung, 2021). In addition, there are few previous studies on post-eruptive crustal deformation. In this study, we calculate ground deformation before and after the 2022 eruption using GNSS measurements and modeled the observation. Our goal is to understand the subsurface magma behavior before and after the eruption and investigate how the 2022 eruption affected the interior of the Mauna Loa volcano.
We employed daily GNSS positions processed and released by the University of Nevada Reno (Blewitt et al., 2018). The ground deformation analysis software pydeform (Munekane et al., 2016) is used to model the observation. The model assumes the inflation of a spherical source, the opening of a dike beneath the summit caldera, and the slip of a decollement fault located southeast of the summit, consistent with previous studies.
Our modeling shows that both the depth of the spherical pressure source and the dike became shallower after the eruption. Additionally, the slip rate of the decollement fault, which was about 38 cm/yr during the year before the eruption, decreased significantly to 0.1 cm/yr after the eruption, indicating that the slip of the decollement fault had almost stopped.
We hypothesized that the stress change by the eruption stopped the slip on the decollement fault. Therefore, we calculated the Coulomb stress change around the decollement fault due to dike intrusions into NERZ during the 2022 eruption using Coulomb 3.3 (Toda et al., 2011). The results indicate that the eruption decreased the Coulomb stress on the decollement by approximately −0.6 bar. Therefore, we interpret that the eruption stopped the slip on the decollement. In addition, seismic activity around the decollement fault (Wilding and Ross, 2024) also decreased after the eruption, further supporting our hypothesis.
Previous studies of ground deformation before the 2022 eruption have revealed significant inflationary ground deformation from 2014 to 2020 through the GNSS (Global Navigation Satellite System) and InSAR (Interferometric Synthetic Aperture Radar) measurements (Varugu and Amelung, 2021). In addition, there are few previous studies on post-eruptive crustal deformation. In this study, we calculate ground deformation before and after the 2022 eruption using GNSS measurements and modeled the observation. Our goal is to understand the subsurface magma behavior before and after the eruption and investigate how the 2022 eruption affected the interior of the Mauna Loa volcano.
We employed daily GNSS positions processed and released by the University of Nevada Reno (Blewitt et al., 2018). The ground deformation analysis software pydeform (Munekane et al., 2016) is used to model the observation. The model assumes the inflation of a spherical source, the opening of a dike beneath the summit caldera, and the slip of a decollement fault located southeast of the summit, consistent with previous studies.
Our modeling shows that both the depth of the spherical pressure source and the dike became shallower after the eruption. Additionally, the slip rate of the decollement fault, which was about 38 cm/yr during the year before the eruption, decreased significantly to 0.1 cm/yr after the eruption, indicating that the slip of the decollement fault had almost stopped.
We hypothesized that the stress change by the eruption stopped the slip on the decollement fault. Therefore, we calculated the Coulomb stress change around the decollement fault due to dike intrusions into NERZ during the 2022 eruption using Coulomb 3.3 (Toda et al., 2011). The results indicate that the eruption decreased the Coulomb stress on the decollement by approximately −0.6 bar. Therefore, we interpret that the eruption stopped the slip on the decollement. In addition, seismic activity around the decollement fault (Wilding and Ross, 2024) also decreased after the eruption, further supporting our hypothesis.