How Did the 2018 Kilauea Eruption Affect the Volcano’s Submarine South Flank? Preliminary Results From an Ocean Bottom Seismometer Deployment Offshore Kilauea

Date: 4/26/2019

Time: 09:30 AM

Room: Puget Sound

The south flank of Kilauea moves to the southeast as a consequence of gravitational and magmatic stresses. This motion is punctuated by episodic slow or seismic slip events on the decollement or shallow thrust faults underlying the island, generating extension in the East Rift Zone. On May 4 2018, following injection of magma into the Lower East Rift Zone (LERZ), a M6.9 earthquake occurred beneath the south flank. Aftershocks were recorded along the western and southern boundaries of the submarine flank in areas that had not previously experienced significant seismicity. These epicenters suggest a broad change in the flank stress field, triggered by the LERZ intrusion, the M6.9 earthquake, or a combination thereof. This has implications for seismic, landslide, and tsunami hazards associated with slip of the submarine flank.

In July 2018, we deployed a network of 12 short-period ocean-bottom seismometers (OBSs) on the Kilauea submarine south flank; data were recovered from 10. Recording was continuous until recovery in mid-September 2018, spanning the termination of the active eruption. The objectives of the project were threefold: (1) to record aftershocks of the M6.9 event, determine faults that slipped, and identify phases traveling within the decollement, (2) to better constrain the locations of earthquakes occurring beneath and within the south flank to identify other active structures and associated changes in the stress state, and (3) to capture acoustic signals associated with the active ocean entry to better understand the delivery and downslope transport of eruptive products.

Preliminary analysis suggests that many more earthquakes occurred offshore than were detected by the land-based seismic network. The OBS data allow substantially improved hypocentral constraint for offshore earthquakes. Many submarine landslides were recorded, and the relative strength of the acoustic signals allows us to constrain their source locations.

Presenting Author: Jacqueline Caplan-Auerbach

Authors