(Web Desk) - Researchers from the University of Tokyo have developed an unmanned aerial vehicle (UAV) that can make high-precision, real-time seafloor measurements and communicate them to satellites to provide early warnings for earthquakes and tsunamis.
The Nankai Trough, off the coast of Japan’s Honshu island, lies in a megathrust earthquake zone. Megathrust earthquakes occur along the faults found between the boundaries of tectonic plates. They are the most powerful earthquakes on Earth.
There is a 70% chance a potentially devastating magnitude 8 or 9 earthquake will occur in this zone within the next 30 years.
In March, the Japanese Government’s Central Disaster Management Council released estimates that a worst-case scenario earthquake in the Nankai Trough could lead to 2.35 million buildings destroyed and a death toll of 298,000.
An earthquake that big would likely also trigger a tsunami, which would cause further devastation. So, there is a need for accurate, frequent and real-time seafloor measurements.
Seafloor measurements, which can detect earthquakes, are currently observed through the Global Navigation Satellite System-Acoustic (GNSS-A). Transponder stations on the seafloor collect the measurements and communicate them to satellites, usually via ships.
However, there are several economic and physical factors that limit how frequently observations can be made using ships. The authors of the study were inspired to construct a more effective measuring technique.
Published in Earth and Space Science, the team designed an unmanned, seaplane-type drone which takes the place of a ship to feed the satellites information.
“We conducted initial experiments in a water tank,” says lead author of the study, Yuto Yoshizumi, “and found that the proposed system can detect distances to an accuracy within 2.1 cm.”
The research team also performed a series of at-sea tests off the coast of Japan under optimal sea conditions. Throughout these tests, the UAV was able to conduct frequent observations that were verified as accurate.
“The results were hugely encouraging,” says senior author Yusuke Yokota.
During the at-sea trials, the seaplane moved across the surface of the ocean at a speed of 6km/hr to prevent bubbles from disrupting the acoustic signal.
“These seafloor positioning measurements are the first ever achieved using a UAV,” says Yokota.
“We attained a horizontal root mean square error of approximately 1–2 cm, which is easily comparable to that of existing vessel-based systems.”
Accurate, real-time seafloor measurements are crucial for saving lives as they provide early warnings for earthquakes and tsunamis. The UAV-based GNSS-A system can provide this in a short period of time under optimal conditions.