New hazard tracking technology uses GPS signals to look for waves in the Pacific Ring of Fire. GUARDIAN’s long-term goal is to improve early warning systems. Tsunamis caused by earthquakes, underwater volcanoes, and other Earth-shaking forces can devastate coastal communities. When it comes to early warning, every second counts. Scientists at NASA’s Jet Propulsion Laboratory are testing a new approach to detecting the ocean’s deadliest waves from far out in the atmosphere.

An experimental monitoring system called GUARDIAN (GNSS Upper Atmospheric Real-time Disaster Information and Alert Network) uses data from GPS clusters and other orbiting satellites orbiting our planet. Collectively, these clusters are known as Global Navigation Satellite Systems or GNSS. Radio signals reach hundreds of scientific ground stations around the world, and data is processed by JPL’s Global Differential GPS (GDGPS) network, which improves real-time positioning accuracy to within a few inches (about 10 centimeters).

The new system examines signals for clues that a tsunami is occurring somewhere on Earth. How does it work? During a tsunami, many square miles of the ocean’s surface can rise and fall almost simultaneously, displacing a significant amount of air above them. The displaced air spreads in all directions in the form of low-frequency sound and gravitational waves. Within a few minutes, these vibrations reach the highest layer of the atmosphere, the electrically charged ionosphere, which is heated by the Sun. The subsequent collision of pressure waves with charged particles may slightly distort signals from nearby navigation satellites.

Leo Martir, a JPL scientist who developed GUARDIAN, noted that while navigators often try to correct for such ionospheric disturbances, scientists can use them as a life-saving alarm bell. “Instead of fixing this as a bug, we use it as data to look for natural hazards,” Martyr said.

The fastest tracking tool of its kind

Martir, who co-chairs a working group at the UN’s International GNSS Committee examining the use of navigation satellite systems to develop early warning strategies, said the technology is still developing. Currently, GUARDIAN’s near real-time data needs to be interpreted by experts trained in tsunami detection. But it’s already one of the fastest tracking tools of its kind: within 10 minutes it can create a sort of picture of the roar of a tsunami that reaches the ionosphere. And it could potentially provide up to an hour of warning, depending on the distance from the shore of the tsunami’s source.

“We think GUARDIAN will one day complement existing land and ocean instruments such as seismometers, buoys and tide gauges that are very efficient but do not systematically cover the open ocean,” says Siddharth Krishnamurthy, who is also a member of the development team. JPL. Scientists affiliated with the NASA Disasters program now use ground-based instruments on GNSS stations to detect tsunamis more quickly.

“When there is a large earthquake near the ocean, we want to know quickly the magnitude and characteristics of the earthquake to understand the probability of a tsunami occurring, and we want to know if it really caused a tsunami,” said Gerald Bawden. Earth Surface and Interior scientist” at NASA headquarters in Washington. “Today there are two ways to tell if a tsunami has occurred before it reaches shore: NOAA’s DART buoys and GNSS ionospheric observations. There are a limited number of buoys and they are very expensive, so systems like GUARDIAN can complement existing warning systems.”

The GUARDIAN team is currently focused on the geologically active Pacific Ring of Fire. According to a historical database maintained by the National Oceanic and Atmospheric Administration (NOAA), about 78% of the more than 750 confirmed tsunamis between 1900 and 2015 occurred in the region. GUARDIAN is currently observing just over half of the area of ​​interest in the Pacific Ocean.

The GUARDIAN team is developing a site that will allow experts to examine the state of the ionosphere in near real time by examining the links of individual satellite stations in the GNSS network. Users can access data from approximately 90 stations around the Pacific Ring of Fire and detect signals of interest within minutes of the event. The team aims to expand the scope and refine the system so that it can automatically flag tsunamis and other hazards, including volcanic eruptions and earthquakes.