ITEC

Tsunamis cause dramatic numbers of casualties, massive economic losses and extensive destruction of coastal environments. The giant tsunami that occurred in 2011 in Japan devastated a thousand km of the Japanese coastline, claimed almost 20 000 lives, and induced more than 200 billion dollars of economic losses. Yet, even though the 2011 Japanese tsunami was one of the largest ever recorded on Earth, with wave heights up to 40 m, the forecasting systems operating in real-time failed to predict its magnitude. Eight years later, even with all the data now available on the earthquake and tsunami (seismological, geodetic, tsunami gauge data, etc.), the scientific community is still unable to accurately reproduce the actual height of the 2011 tsunami before it reached the coast.

One major reason for our current inability to model and monitor tsunamis properly is that oceans, where the tsunamis occur and propagate, are rarely instrumented, for obvious reasons: there is no emerged site on which to install permanent instrument networks.

In this project, we propose to counter this problem by developing a new technology to monitor tsunamis from Space, based on the Global Navigation Satellite System (GNSS). Indeed, scientists have demonstrated in recent decades that the vertical motions produced by tsunami waves are powerful enough to create atmospheric vibrations that propagate all the way from the ocean surface up to the ionosphere, 300 kilometers up in the atmosphere, where they form a specific physical imprint. Even small tsunamis with waves only a few centimeters high imprint the ionosphere. Because the ionospheric tsunami imprint is a variation in the atmosphere electron content, it can be detected with existing GNSS networks, and thus detected all over the world, including oceans. The GNSS signals are then tracked from land with permanent or portable geodetic stations.

Our project is underway, and for the first phase we are developing the theoretical and software framework. With our US partner, we are consolidating our modeling package, IonoSeis, dedicated to the modeling of the very first ionospheric signal coming from the tsunami initiation zone (PhD work in progress). We will then design and test a GNSS-based tsunamimeter: it will be lightweight, low-power consuming, and multi-GNSS based (i.e., tracking not only GPS but also Galileo and other constellations). We anticipate that this new “instrument” will forge the way to an efficient and low-cost tsunami early-warning system.