Tsunamis Can Now Be Detected through their Atmospheric Rumble by NASA Researchers

New hazard monitoring technology uses GPS signals to go surf fishing in the Pacific Ring of Fire. GUARDIAN’s long-term goal is to strengthen early warning systems.

Due to earthquakes, undersea volcanoes, and other land-shaking forces, tsunamis can devastate coastal communities. When it comes to giving advance warning, every second counts. Scientists at NASA’s Jet Propulsion Laboratory are testing a new method for detecting the ocean’s deadliest waves – from the far reaches of the atmosphere.

Called the GUARDIAN (GNSS Upper Atmospheric Real-time Information and Alert Network) experimental observational system, it draws data from constellations of the Global Positioning System (GPS) and other wayfinding satellites orbiting our planet. Collectively, these collections are known as Global Navigation Satellite Systems, or GNSS. Their radio signals are transmitted to hundreds of science ground stations around the world, and that data is broken down by JPL’s Global Differential GPS (GDGPS) network, which improves real-time positioning accuracy down to a few inches (about 10 centimeters).

The new system filters signals for evidence of a tsunami occurring somewhere on Earth. How it works? During a tsunami, many square miles of ocean surface can rise and fall in unison, displacing a large amount of air above it. Displaced air propagates in all directions in the form of low-frequency gravitational and sound waves. Within several minutes, these vibrations reach the upper layer of the atmosphere: the electrically charged ionosphere cooked by the sun. The collision of pressure waves with charged particles can slightly distort signals from nearby navigation satellites.

While navigation instruments typically seek to correct such ionospheric disturbances, scientists can use them as a life-saving wake-up call, noted Léo Martire, the JPL scientist who developed GUARDIAN. “Instead of correcting this as an error, we use it as data to find natural hazards,” said Martyr.

The fastest monitoring tool of its kind

The technology is still in its maturation stage, which is exploring the use of navigational satellite systems to enhance early warning strategies, said Martire, who co-chairs a task force within the United Nations’ International Commission on GNSS. Currently, GUARDIAN’s output must be interpreted in near real time by experts trained to identify signs of a tsunami. But it is indeed one of the fastest monitoring tools of its kind: within 10 minutes It can produce a kind of snapshot of the rumbling tsunami reaching the ionosphere. And they can provide up to an hour of warning, depending on the distance of the tsunami source from shore.

“We envision that GUARDIAN will one day complement land- and ocean-based instruments such as seismometers, buoys and tide gauges, which are highly effective but lack regular coverage of the open ocean,” says Siddharth Krishnamurthy, who is also part of the JPL development team. Scientists affiliated with NASA’s disaster program are currently using ground-based instruments at GNSS stations to detect tsunamis faster.

Gerald Bauden said: “When there is a large earthquake near the ocean, we want to quickly know the magnitude and characteristics of the earthquake to understand the probability of a tsunami, and we want to know whether a tsunami is actually generated or not.” , Earth Surface and Interior Program Scientist at NASA Headquarters in Washington.

“Today there are two ways to tell if a tsunami originated before it makes landfall—NOAA’s DART floats and GNSS-ionosphere observations. There are a limited number of floats and they are very expensive, so systems like GUARDIAN have the ability to supplement existing warning systems.

For now, the GUARDIAN team is focused on the geologically active Pacific Ring of Fire. About 78% of the more than 750 confirmed tsunamis between 1900 and 2015 occurred in this region, according to a historical database maintained by the National Oceanic and Atmospheric Administration (NOAA). GUARDIAN currently monitors just over half of the Pacific region of interest.

The GUARDIAN team is developing a website to allow experts to explore the state of the ionosphere in near real time by studying the correlations of individual space stations on the GNSS network. Users can access data from about 90 stations around the Pacific Ring of Fire and detect signals of interest within minutes of an event occurring. The team aims to expand coverage and improve the system to the point where it can automatically report tsunamis and other hazards, including volcanic eruptions and earthquakes.