Date of Award
2023
Document Type
Open Access Master's Thesis
Degree Name
Master of Science in Geophysics (MS)
Administrative Home Department
Department of Geological and Mining Engineering and Sciences
Advisor 1
Gregory P. Waite
Committee Member 1
Luke Bowman
Committee Member 2
Simon Carn
Abstract
The 2018 Kīlauea volcano eruption and incremental caldera collapse was accompanied by more than 60,000 seismic events cataloged by the Hawaiian Volcano Observatory as well as 62 caldera collapse events that occurred roughly once per day. The majority of seismicity occurred on the eastern side of the caldera between daily collapses. However, the majority of caldera subsidence occurred to the west. To understand the collapse mechanics behind this variance in subsidence and seismicity across the caldera region, repetitive waveforms and source properties can be studied.
Repeating seismic events suggest a common source that is not moving or destroyed. At Kīlauea, clusters of repeating events can indicate source processes throughout collapse cycles. REDPy, a repeating earthquake detector tool for Python, cross correlates seismic events to determine repetition. Events are separated into families or listed as orphans if no matches are found. We used data from HVO network stations surrounding Kīlauea’s summit. Possible events were identified using an STA/LTA trigger algorithm with a long-time average trigger of 8 seconds, a short-time average trigger of 1 second, and a trigger on/off range of 1-2.5. A minimum correlation coefficient of 0.7 was used to group over 167,000 recognized events from April 29th to August 2nd into nearly 6,000 families. Of these families, 697 were chosen as ‘clusters of interest’ for including >100 events or persisting for 7 days or more. P-wave first-motions were manually picked for waveforms associated with clusters of interest, these clusters were then located using P-wave arrival times, and focal mechanisms were modeled for viable events to learn more about their source processes and relationship to collapse mechanics.
Dilatational first motions dominate our catalog and focal mechanism models have mismatched station polarities indicative of non-double-couple sources. In fact, focal spheres show evidence of reverse motion on ring faults, which is the opposite sense of slip associated with the large, daily caldera collapse events. This change in slip direction suggests that much of the microseismicity results from shortening within the down dropped caldera and rebound in areas adjacent to the caldera.
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.
Recommended Citation
Metts, Isabella S., "AN INVESTIGATION OF MICROSEISMICITY DURING THE 2018 KILAUEA CALDERA COLLAPSE", Open Access Master's Thesis, Michigan Technological University, 2023.