GPS World

Tag: volcanic eruption

  • USGS upgrading Hawaiian geodetic network to monitor volcanoes

    USGS upgrading Hawaiian geodetic network to monitor volcanoes

    The Hawaiian Volcano Observatory (HVO) of the U.S. Geological Survey has been working to rebuild its geodesic monitoring network after lava consumed several GNSS stations in 2018.

    The work began following the 2018 Kīlauea lower East Rift Zone eruption and summit collapse, with funding from the Additional Supplemental Appropriations for Disaster Relief Act of 2019 (H.R. 2157).

    Teams are rebuilding and improving HVO’s geodetic monitoring network to better detect, assess and respond to volcanic hazards related to Hawaiian volcanoes. The main geodetic datasets used by HVO scientists to measure surface deformation (ground movements) are GNSS, tilt and satellite radar (InSAR) imagery.

    HVO’s geodetic network includes more than 70 GNSS stations and 15 tiltmeters on the Island of Hawai’i that continuously record and transmit data. These instruments require routine maintenance, must be upgraded periodically due to age, and must be replaced if destroyed by volcanic activity such as in 2018.

    Network upgrades include replacing out-of-date instruments and improving HVO’s network of near real-time monitoring instruments at critical areas on Kīlauea’s summit and rift zones to support early detection of magma movement and associated hazards.

    Lava takes out stations

    In 2018, lava flows destroyed three GNSS stations in the lower East Rift Zone. Another three GNSS stations were destroyed in the caldera collapses at Kīlauea’s summit.

    HVO staff rapidly deployed new GNSS stations at nearby locations to allow for continued monitoring during the eruption. These rapidly deployed sites included GNSS smart antennas mounted on surveys tripods — a setup typically only used for temporary deployments of several days to weeks.

    Many of these rapidly deployed sites were decommissioned and removed after 2018. However, 13 of them are still being used for critical monitoring and remain on temporary tripods. These sites will be upgraded and hardened using engineered fixed monuments and masts. New sites will also be installed to replace sites destroyed in 2018.

    A temporary GNSS monitoring site in the Kīlauea caldera was part of the rapid response to the December 2020 Halema‘uma‘u eruption. The site will be upgraded into a continuously operating reference station with state-of-the-art instrumentation and a hardened antenna mast. (Photo: USGS/A.P Ellis)
    A temporary GNSS monitoring site in the Kīlauea caldera was part of the rapid response to the December 2020 Halema‘uma‘u eruption. The site will be upgraded into a continuously operating reference station with state-of-the-art instrumentation and a hardened antenna mast. (Photo: USGS/A.P Ellis)

    Emergency monitoring ongoing

    GNSS receivers acquired by supplemental funds already have supported emergency monitoring of active eruptions and other volcano-related activity. Data from these instruments help HVO detect volcanic activity and inform partners at Hawai’i Volcanoes National Park (HAVO), Hawai’i County Civil Defense (HCCD) and Hawai’i Emergency Management Agency (HI EMA).

    For example, HVO rapidly deployed three new semi-continuous GNSS stations in response to the December 2020 Kīlauea eruption. These stations gave scientists a more complete view of magma returning to Kīlauea’s summit.

    Similarly, HVO deployed rapid-response GNSS equipment at two pre-existing benchmarks during the Kīlauea south caldera intrusion event in August 2021, allowing scientists to track the migration of magma from the south caldera to farther south. New instruments give HVO a more detailed understanding of and ability to monitor Kīlauea’s volcanic processes.

    HVO’s geodesy program plays a critical role in monitoring Hawaiian volcanoes. HVO’s updated geodetic network ensures that scientists can monitor changes in the shape of volcanoes, respond to eruptions, and understand magma storage and movement underground.

    “Thanks to supplemental funding, HVO is in the best position ever to leverage our state-of-the-art geodetic network to gain insights into the active volcanoes in Hawai’i, assess their hazards, issue warnings, and advance scientific understanding to reduce the impacts of volcanic eruptions,” stated Volcano Watch, HVO’s weekly newsletter.

  • GNSS shows how volcanic eruptions cause ionospheric disruptions

    GNSS shows how volcanic eruptions cause ionospheric disruptions

    On Jan. 15, Hunga-Tonga-Hunga-Ha’apai, an uninhabited volcanic island on the Tongan archipelago in the South Pacific Ocean, erupted with spectacular force, churning ocean waters halfway across the globe.

    GNSS engineers also detected its effects hundreds of miles above, in the ionosphere. The GNSS community is now moving from such after-the-fact detection to real-time monitoring using NASA’s Global Differential GPS (GDGPS) system, according to a team with the Tracking Systems and Application Section at NASA’s Jet Propulsion Laboratory (JPL) in Southern California.

    “We monitored, in real time, four GNSS satellite constellations from numerous stations around the world using the GDGPS network. In particular, the three stations closest to the volcano, in Samoa, Fiji and Tahiti,” said postdoctoral associate Leo Martire. “We could see extremely high and strong signals in the ionosphere, which is very unusual. As a function of radial distance from the eruption, the first detected ionospheric perturbation likely originated directly from the explosion. Then we see patterns propagating at increasing distances at different radial propagation speeds.”

    Monitoring such events adds information to the catalog of signals from natural hazards, pointed out Siddharth Krishnamoorthy, a research technologist who manages JPL’s GUARDIAN near-real-time tsunami warning system, currently under development. “That is useful because, in the future, if you want to be able to spot natural hazards and issue alerts, you need to know what the signal looks like. There have been reports of a tsunami in Tonga due to this event, so we will look at potential tsunami-induced signatures in the ionosphere. We are trying to get to a place where we pick up a signal like this and we are able to say, ‘This is a tsunami propagating at this speed and in this direction.’”

    Chart: Jet Propulsion Laboratory
    Chart: Jet Propulsion Laboratory

    Before being detected in the ionosphere, signals from natural hazards must travel all the way from the surface. For tsunamis, this usually takes more than 10 to 20 minutes, but the volcanic eruption only took a couple of minutes to reach the ionosphere because it shot straight up. “We do not know yet, based on observations, how exactly different events on the surface caused by natural hazards couple with the atmosphere,” said research technologist Panagiotis Vergados. “Every event is unique in its spectral properties.”

    The event did not affect the quality of GDGPS’s GNSS positions or orbits, because dual-frequency measurements remove significant ionospheric effects. “Instead of looking at the direct effects on the position of our available reference stations, which is what our traditional real-time monitoring does and which was basically negligible, imagine the links from each of those stations to a dozen or more satellites,” said Larry Romans, GDGPS chief technologist. “Every time one of those many links pierces the ionosphere, we can monitor that signal for ripples as waves go by. So, this is an incredibly powerful method for seeing disturbances, just in terms of the density of data. It is very complementary to position-based natural-hazards monitoring because the data is much richer.”

    In addition to volcanoes and tsunamis, several other natural events, such as earthquakes and very large thunderstorms, also produce these effects. “These natural forcings cause large-scale, low-frequency pressure perturbations that tend to travel up and be visible in the ionosphere,” Krishnamoorthy said. “There are also perturbations of the ionosphere due to events from outside the Earth, such as solar flares or bolide impacts.”

    Many of these perturbations start from the troposphere, which ranges between 10 km and 15 km in altitude — including hurricanes, which overshoot gravity waves all the way to the ionosphere, and thermal tides that have been observed to go all the way up to 600 km, said Vergados. “There are also geomagnetic storms and sub-storms that, during electron precipitation, can change the ionization of the ionosphere. So, the coupling can happen from either below or above or simultaneously, and then the effect can be dramatically enhanced.”

    Most of the perturbations that come from below are of a pressure nature — that is, they start out as mechanical waves — while most of those that come from above are electromagnetic. “Aside from nuclear explosions, very large chemical ones, such as the 2020 Beirut explosion, also cause a signature on the ionosphere because they create very large pressure waves,” Krishnamoorthy said.

    Photo: Tonga Meteorological Services, Government of Tonga
    Photo: Tonga Meteorological Services, Government of Tonga