Scientists look to the sky to predict tsunamis with new method
A new approach lets scientists detect tsunamis faster by showing them how the extreme phenomenon disturbs a part of Earth’s atmosphere.
Called Variometric Approach for Real-time Ionosphere Observation, or VARION, the new approach was developed by scientists from Sapienza University in Rome, Italy, and NASA’s Jet Propulsion Laboratory in Pasadena, California. Using observations from GPS and other global navigation satellite systems (GNSS), VARION detects, in real time, disturbances in Earth’s ionosphere associated with a tsunami, according to a press release.
The ionosphere is the layer of Earth’s atmosphere located from about 50 to 621 miles (80 to 1,000 kilometres) above Earth’s surface. It is ionised by solar and cosmic radiation and is best known for the aurora borealis (northern lights) and aurora australis (southern lights). When a tsunami forms and moves across the ocean, the crests and troughs of its waves compress and extend the air above them, creating motions in the atmosphere known as internal gravity waves.
The undulations of internal gravity waves are amplified as they travel upward into an atmosphere that becomes thinner with altitude. When the waves reach an altitude of between 186 to 217 miles (300 to 350 kilometres), they cause detectable changes in the density of electrons in the ionosphere. These changes can be measured when GNSS signals, such as those of GPS, travel through these tsunami-induced disturbances.
VARION could be included in design studies for timely tsunami detection systems that use data from a variety of sources, including seismometers, buoys, GNSS receivers and ocean-bottom pressure sensors.
Scientists explain that once an earthquake is detected in a specific location, a system could begin processing real-time measurements of the distribution of electrons in the ionosphere from multiple ground stations located near the quake’s epicentre, searching for changes that may be correlated with the expected formation of a tsunami. The measurements would be collected and processed by a central processing facility to provide risk assessments and maps for individual earthquake events.
“We expect to show it is feasible to use ionospheric measurements to detect tsunamis before they impact populated areas. This approach will add additional information to existing systems, complementing other approaches. Other hazards may also be targeted using real-time ionospheric observations, including volcanic eruptions or meteorites,” Attila Komjathy from the Ionospheric and Atmospheric Remote Sensing Group at JPL said.
One of the main focus areas at NASA is observing the ionosphere, and how terrestrial weather below it interfaces with space above. By early 2018, the agency will launch two new missions to observe the ionosphere – the Ionospheric Connection Explorer and the Global-scale Observations of the Limb and Disk.