The Relationship Between a 2022-2023 Magmatic Intrusion at Aniakchak Caldera and the 2021 m8.2 Chignik Earthquake, Alaska
A sequence of earthquakes at Aniakchak Caldera (AC), Alaska, began in October 2022 and was accompanied by rapid ground deformation, first observed in February 2023. AC is located only ~160 km from the epicenter of the July 2021 M8.2 Chignik megathrust earthquake, for which co-seismic fault slip >6 m has been modeled; the observed immediate rapid postseismic afterslip slowed in early 2022. This spatio-temporal relationship, especially if considering down-dip afterslip, motivates us to ask whether the Chignik earthquake and its postseismic deformation contributed to the unrest episode at AC, and why the neighboring Veniaminof Caldera, with an eruption in April 2021, has shown no or only very recent (Dec 2023-Jan 2024 deep-long period events) unrest? This is in line with global statistical analyses (e.g., Nishimura, 2021), which suggest that eruption likelihood doubles within 5 years for volcanoes within 200 km of M>7.5 earthquakes.
Our L-band interferograms spanning 2022-2023 resolve >60 cm LOS shortening inside the Aniakchak caldera and GNSS installed in summer 2023 recorded the stop of deformation in September 2023. We can explain the deformation with a shallow spheroidal inflation source centered under AC at ~2.8 km depth with a volume change of about ~28 Mm3. Static normal stress (tensile) increased at both calderas after the Chignik event (0.1-0.3 MPa), suggesting unclamping, which is favorable for magma ascent / bubble formation. While AC earthquakes relocated with a revised velocity model show that DLP events started a few weeks after the Chignik earthquake, eventually culminating into shallow volcano tectonic earthquakes, the full catalog spanning 1997-2023 contains sequences of DLP events without large earthquakes, providing only a weak first order link between the earthquake and volcanic unrest. Here, we explore connections between the earthquake and the magmatic unrest through modeling of time-delayed magmatic processes such as bubble formation and magma migration. We furthermore investigate the impact of postseismic deformation and related additional tensile stress increase on these processes.
Session: Multidisciplinary Approaches for Volcanic Eruption Forecasting [Poster Session]
Type: Poster
Room: Exhibit Hall
Date: 5/2/2024
Presentation Time: 08:00 AM (local time)
Presenting Author: Ronni Grapenthin
Student Presenter: No
Additional Authors
Ronni Grapenthin Presenting Author Corresponding Author rgrapenthin@alaska.edu University of Alaska Fairbanks |
Revathy Parameswaran rmparameswaran@alaska.edu University of Alaska Fairbanks |
Mario Angarita mfangaritasr@alaska.edu University of Alaska Fairbanks |
Tara Shreve tlshreve@alaska.edu University of Alaska Fairbanks |
Yitian Cheng ycheng4@alaska.edu University of Alaska Fairbanks |
John Power jpower@usgs.gov U.S. Geological Survey |
Zechao Zhuo zhuozech@msu.edu Michigan State University |
Taryn Lopez tmlopez@alaska.edu University of Alaska Fairbanks |
Julie Elliott ellio372@msu.edu Michigan State University |
Jeffrey T Freymueller freymuel@msu.edu Michigan State University, East Lansing, Michigan, United States |
The Relationship Between a 2022-2023 Magmatic Intrusion at Aniakchak Caldera and the 2021 m8.2 Chignik Earthquake, Alaska
Category
Multidisciplinary Aproaches for Volcanic Eruption Forecasting
Description