Temporal Velocity Variations Associated with the 2018 Kilauea Summit Collapse based on Temporary Dense Geophone Arrays
Abstract
During the 2018 Kilauea eruption, lava erupted in the Lower East Rift Zone (LERZ) from a series of newly opened fissures more than 30 km from the summit. The magma is thought to be supplied from the reservoir beneath the summit through an underground dike structure. Between late May and early August in 2018, a persistent vent, referred to as fissure 8, becomes the principle source of erupting lava. Once it was established, variations in effusion rate at fissure 8 were observed in the LERZ following the nearly daily M5.2-5.4 collapse events occurring at the summit. This suggests a hydraulic connection between the two ends of the magmatic system, with increases in effusion due to reservoir pressurization by the down-dropping summit system. Monitoring seismic velocity variations in response to the collapse events provides insight to the dynamics of stress variation and magma movement.
In this study, we employ seismic noise coda wave interferometry to investigate the temporal velocity variations (dv/v). We deployed a dense nodal geophone array at Kilauea from mid-June through mid-July 2018, when effusion was localized around fissure 8 and summit collapse events were somewhat regular. We observed 25 of the ~M5 collapse events and evaluated the statistical significance of dv/v changes associated with these events. Across the dike within the LERZ, a clear co-seismic/co-collapsing rapid dv/v reduction followed by an exponential recovery is observed. A maximum velocity drop of -0.27±0.03% is observed immediately above the presumed dike structure, which is likely most susceptible to structural weakening. Adjacent to fissure 8, a gradual velocity increase with 0.18±0.05% maximum amplitude is observed ~2-3 hours after the collapse. We interpret this as the surge of magma influx within the dike in response to summit reservoir pressurization. At the summit, a gradual dv/v increase is also observed with 0.34±0.08% maximum amplitude which peaks ~4 hours after the collapse. This velocity increase at the summit may be related to the logarithmic relaxation process of rock healing/crack closing in response to the instantaneous pressurization of the system at the time of collapse.- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.V43C0203W
- Keywords:
-
- 8419 Volcano monitoring;
- VOLCANOLOGY;
- 8439 Physics and chemistry of magma bodies;
- VOLCANOLOGY;
- 8440 Calderas;
- VOLCANOLOGY;
- 8488 Volcanic hazards and risks;
- VOLCANOLOGY