Volcano Watch: Upgrades below the surface  : Maui Now

by US Geological Survey Hawaiian Volcano Observatory scientists and affiliates. Today’s article is by Research Corporation of the University of Hawai’i technician Miki Warren.  

Technicians at the USGS Hawaiian Volcano Observatory are constantly engineering, building, deploying, maintaining, troubleshooting, or upgrading equipment and instruments that we use to monitor Hawaiʻi’s active volcanoes. This week’s “Volcano Watch” article focuses on the installation process of newly upgraded seismometers that are used to detect and locate earthquakes.

After the 2018 lower East Rift Zone eruption and summit collapse of Kīlauea, Congress allocated funding to HVO via the Additional Supplemental Appropriations for Disaster Relief Act of 2019 (H.R. 2157). Part of the funding was used to restore monitoring stations damaged or lost during the 2018 Kīlauea events. Part of the funding was also used improve or update other existing volcano monitoring sites around the Island of Hawaiʻi. 

Many of the sites that were restored, or improved and upgraded, are seismic stations. While some of the seismic stations were disrupted during 2018, others were in need of improvement in data quality or transmission reliability.  These factors are important for being able to accurately locate earthquakes and determine their magnitude, which in turn helps us to understand volcanic processes and associated hazards. 

To help improve data quality, shallow boreholes are being drilled that will house new instruments and allow them to be thermally insulated. These new seismometers have both broadband and strong motion capabilities, and the seismic data quality is proving to be excellent. 

The new boreholes, which are about 7 in (17 cm) in diameter and 5 feet (1.5 meters) deep also have a smaller footprint than older seismic site designs. Each drilled borehole takes about a week to complete before installing the new seismometer. The work is always done with permission from the landowners or land managing agency.

To effectively drill the borehole, the drilling frame is bolted to the ground surface and continually leveled at four points. A small amount of water is pumped through the drill bit to provide both cooling and lubrication of the bit during the drilling process. The drill is powered by a 5000-watt generator and operated by a USGS technician. 

The drill bit may go through layers of both pāhoehoe and ʻaʻā, so it is a very slow and careful process. Once the full depth is achieved, the hole is lined with silica sand that will help to stabilize and thermally insulate the new instrument that is placed at the base of the hole. 

The instrument is then completely covered with the silica sand and topped with a surface borehole cover. A conduit containing the instrument cables runs along the surface for about 15 feet (4.5 meters) to an electronics box and solar setup that will power the station. Data is then transmitted via radio to one of the hub stations and from there to the observatory, where it can be analyzed by a seismologist. 

Once the drilling is complete and the new instrument is installed, it will run concurrently with the existing seismometer (if it is still operational) for a minimum of six months to verify the data. Eventually, the existing seismometer is removed. 

With over 200 active seismic, geodetic, geochemical, and geologic instrumental sites on the Island of Hawaiʻi alone, there’s rarely any down time for HVO field engineering technicians. Their work maintaining, upgrading, and installing new stations located in remote areas allows us to monitor Hawaii’s active volcanoes. 

Volcano Activity Updates

Kīlauea is not erupting. Its USGS Volcano Alert level is ADVISORY. 

Earthquake activity in Kīlauea summit region remained low over the past week, while summit tilt shows continuing inflation. Unrest over the past several months has fluctuated and eruptive activity could occur in the near future with little or no warning. The most recent sulfur dioxide (SO₂) emission rate for the summit—approximately 80 tonnes per day—was measured on December 28. No unusual activity has been noted along the rift zones. 

Mauna Loa is not erupting. Its USGS Volcano Alert Level is at NORMAL. 

Webcams show no signs of activity on Mauna Loa. Summit seismicity has remained at low levels over the past month. Ground deformation indicates continuing slow inflation as magma replenishes the reservoir system following the 2022 eruption. SO₂ emission rates are at background levels. 

One earthquake was reported felt in the Hawaiian Islands during the past week: a M3.0 earthquake 4 km (2 mi) SW of Pāhala at 31 km (19 mi) depth on Jan. 15 at 10:39 p.m. HST.

HVO continues to closely monitor Kīlauea and Mauna Loa.

Visit HVO’s website for past Volcano Watch articles, Kīlauea and Mauna Loa updates, volcano photos, maps, recent earthquake information, and more. Email questions to [email protected].