This is unreal and beyond cool. Instead of measuring seismic tremors, it measures, indirectly, the displacement of the ocean surface. Far from the shore, tsunami waves are very long and very low - so they would appear as the whole surface of the ocean going up and down.
That motion pushes air upwards, resulting in a wave reaching high up through the atmosphere, eventually hitting (!) the ionosphere. I didn't even know acoustic waves would propagate through ionised gas!
Finally, this ionosphere disturbance affects GPS signal reception, and can be measured via ground receiver stations.
The upside of this is that it measures, indirectly, motion of the sea, i.e. actual tsunami activity, rather than monitoring directly the potential causes thereof.
It is crazy to me that it works though!
porridgeraisin 2 hours ago [-]
Is this how it's measured? Just to see if I got it right:
The atmosphere directly above the tsunami will have a different TEC (total electron count) pattern due to the upward acoustic waves created by the tsunami waves. This patch of atmosphere may or may not be in the line of sight of your many GPS receivers, to some satellite. Those for which it is in the line of sight will show a disturbance. Others won't. You can now cross-compare to "triangulate" where the tsunami waves are.
chatmasta 2 hours ago [-]
The article notes that the tech successfully notified researchers 20 minutes after the initial quake. What the article _doesn’t_ note is how often the researchers get these notifications.
I wonder what the false positive rate is like for this technology.
radarsat1 1 hours ago [-]
The article mentions gravity waves, I thought these were not possible to detect except from massive events like black hole mergers. Am I getting concepts mixed up?
thatcherc 1 hours ago [-]
Yup, slight mix-up. Gravity waves are waves in the ocean and atmosphere (or other fluid bodies) where Earth's gravity is the restoring forces that causes wave propagation. Gravitational waves are the waves in spacetime caused by powerful astronomical events like black hole mergers.
Latitude7973 1 hours ago [-]
I am not 100% sure, but I think the article is referring to gravity waves in a meteorological context, whereby layers of the atmosphere are displaced and "splosh" around on a large scale. This is as opposed to a gravitational wave which is what you are thinking of.
That motion pushes air upwards, resulting in a wave reaching high up through the atmosphere, eventually hitting (!) the ionosphere. I didn't even know acoustic waves would propagate through ionised gas!
Finally, this ionosphere disturbance affects GPS signal reception, and can be measured via ground receiver stations.
The upside of this is that it measures, indirectly, motion of the sea, i.e. actual tsunami activity, rather than monitoring directly the potential causes thereof.
It is crazy to me that it works though!
The atmosphere directly above the tsunami will have a different TEC (total electron count) pattern due to the upward acoustic waves created by the tsunami waves. This patch of atmosphere may or may not be in the line of sight of your many GPS receivers, to some satellite. Those for which it is in the line of sight will show a disturbance. Others won't. You can now cross-compare to "triangulate" where the tsunami waves are.
I wonder what the false positive rate is like for this technology.
https://en.wikipedia.org/wiki/Gravity_wave