(BIVN) – Kīlauea and Mauna Loa volcanoes are not erupting. 

The USGS Volcano Alert level for Kīlauea is ADVISORY, while earthquake activity remains low relative to periods before recent intrusions or eruptions. The USGS Volcano Alert level for Mauna Loa is NORMAL, and seismicity has remained at low levels over the past month.

This week’s Volcano Watch article, written by U.S. Geological Survey Hawaiian Volcano Observatory scientists and affiliates, details the seismic network used to monitor the volcanoes:

The Island of Hawai‘i is one of the most seismically active regions in the world. In the last five years, an average of 600-1200 earthquakes per week have been detected by the USGS Hawaiian Volcano Observatory (HVO). This regular rumble of activity across the island can be used to our advantage to assess the hazards that Kīlauea and Mauna Loa volcanoes represent.

The permanent HVO seismic network consists of nearly 100 stations located across the island. HVO scientists use these stations to monitor the location and character of seismic activity, paying particular attention to signals that might herald migrating magma or potential eruptive activity.

USGS: “Distribution of permanent seismic stations and previously deployed seismic nodes in southern half of the Island of Hawai‘i. Shaded regions display the total footprint that nodal deployments this spring and summer will occupy.”

As seismic signals move through the ground, they are affected by the structure of the subsurface that they travel through. The presence of magma or fault zones below the ground surface can change how the seismic signals move through these regions. Scientists can take advantage of these altered signals, which are recorded on seismometers at the surface, to create images of where magma is located below.

Using data from only the permanent HVO seismometers provides us with fuzzy pictures of underlying magma storage. As the number of seismometers at the surface is increased, more of the seismic waves traveling through regions of magma storage are recorded. This yields a crisper picture of where magma is located; how big that region of magma storage is; and how it might connect to the surface. The higher resolution the image of magma storage is, the better our understanding of the volcanic hazard a particular volcano represents.

To move beyond the fuzzy images of magma storage at Kīlauea and Mauna Loa volcanoes created in past studies using only permanent seismic stations on the Island of Hawai‘i, HVO has purchased a pool of lightweight, portable seismometers that can be easily deployed to target regions of interest. HVO’s seismic nodes were purchased as part of the USGS Additional Supplemental Appropriations for Disaster Relief Act of 2019 (H.R. 2157).

In the summer of 2022, these 80 seismic nodes were deployed across the Pāhala region to understand the cause for swarms of deep seismic activity experienced below. Specifically, HVO and collaborators at the University of Hawai‘i at Mānoa are testing the hypothesis that magma stored 15–25 miles (24–40 km) below this area migrates laterally through the subsurface (potentially to Kīlauea and Mauna Loa), causing the observed high earthquake rates.

USGS: “A Hawaiian Volcano Observatory scientist uses a compass to check the orientation of a seismic node (blue) that was deployed on Kīlauea’s summit caldera floor on April 17, 2023. The station is one of 1,800 that will collect data for the next two months. The data will be analyzed to outline where the base of Kīlauea contacts the underlying ocean floor, the location of major faults and fault blocks, where bodies of magma are stored beneath the surface of Kīlauea, and how those bodies connect to the rift zones.” (USGS image by M. Patrick)

In the summer of 2023, HVO scientists and collaborators at the University of Miami and Rensselaer Polytechnic Institute deployed 1800 seismic nodes (both HVO’s nodes and nodes borrowed from the EarthScope Consortium’s instrument pool) across Kīlauea summit. The focus of this experiment is to understand where magma is stored beneath Kīlauea’s summit and how it migrates to the surface before eruptions.

Currently, HVO and collaborators at ETH Zürich, a public research university, are finalizing locations for about 300 nodes to be deployed in the summer of 2024 across the East Rift Zone of Kīlauea. This deployment will collect data near the 2018 Kīlauea eruption site, focusing on understanding how much magma is distributed across the East Rift Zone and how it connects to Kīlauea’s summit magma reservoir.

Finally, HVO and collaborators at the University of Miami will put out another 50 seismic nodes across Mauna Loa’s summit and rift zones in summer 2024 to gain a greater understanding of how much magma is stored in these regions and how they might be connected to the surface.

Results from all of these seismic node experiments will be interpreted together to form a cohesive view of magma storage below the most active volcanoes on the Island of Hawai‘i. We hope to determine how much magma is possibly stored deep beneath Pāhala and whether it connects to Kīlauea and/or Mauna Loa. At Kīlauea and Mauna Loa, we will determine how much magma is stored beneath the summits and rift zones and the potential pathways to the surface. By better understanding the magma storage regions and their connections, we can better asses the hazards posed by these volcanoes.