New research methods could help us find flight MH370

Motivated by a desire to help find Malaysia Airlines flight MH370, which is believed to have crashed into the southern Indian Ocean in March 2014, we proposed a way of working out where objects hit the surface of the ocean using underwater acoustic waves.

Unfortunately this didn’t lead to finding the plane. However, our research into these waves has moved on since we first proposed the idea in 2017, and we have now been able to identify two locations where the aeroplane could have impacted with the ocean, as well as an alternative route that the plane may have taken.

When you drop a pebble in a lake, water waves are generated from the location of the impact, while sound waves create the splashing noise you hear. Another type of wave is generated inside the water too: hydroacoustic. Similar to a sound wave, hydroacoustic waves move much faster through the denser water than they would through air – 1,500 meters per second (m/s) compared to 340m/s.

Similarly, when a large object, such as a meteorite or aeroplane, impacts violently at the surface of an ocean, it generates large surface waves, and a family of sound waves that come from a sudden change in pressure known as acoustic-gravity waves. These can travel thousands of kilometers through the water, carrying vital information on the source of the impact, before dissipating.

In our last study we looked at acoustic-gravity waves picked up by hydrophone (underwater microphone) stations in the Indian Ocean, to narrow down where flight MH370 may have impacted the ocean to two points. But now we have found another factor that may prove crucial for pinning down the location of the impact: sea floor elasticity (flexibility).

When acoustic-gravity waves start traveling through the the sea floor their propagation speed boosts to over 3,500 m/s, from the 1,500m/s they would have been traveling at through the water. Previous analysis considered the sea floor to be rigid, which would not allow the radiating waves to move through it. However, if the elasticity of the sea floor is taken into account then the waves will travel at this enhanced speed.

Rethinking impact

The acoustic-gravity waves that we analyzed for both this and our previous study came from two hydroacoustic stations (each of which has three underwater microphones called hydrophones), which were active at the time when MH370 went missing, on March 7-8, 2014. The first, HA01, is off Cape Leeuwin, Western Australia, while the second, known as HA08s, is at Diego Garcia, which is part of the Chagos Archipelago.