Nasa's Guardian Tsunami Detection Tech Catches Wave in Real Time

Posted4 months agoActive4 months ago

geox

157 points

25 comments

jpl.nasa.govResearchstory

calmpositive

Debate

40/100

Tsunami DetectionNasa TechnologyEarly Warning Systems

Key topics

Tsunami Detection

Nasa Technology

Early Warning Systems

NASA's GUARDIAN technology successfully detected a tsunami wave in real-time, sparking discussion about its potential, limitations, and implications for disaster prevention, as well as concerns about NASA's budget and the need for expert interpretation.

Snapshot generated from the HN discussion

Discussion Activity

Active discussion

First comment

Peak period

60-66h

Avg / period

8.3

Comment distribution25 data points

Loading chart...

Based on 25 loaded comments

Key moments

01Story posted
Sep 12, 2025 at 5:25 PM EDT
4 months ago
Step 01
02First comment
Sep 15, 2025 at 5:34 AM EDT
3d after posting
Step 02
03Peak activity
18 comments in 60-66h
Hottest window of the conversation
Step 03
04Latest activity
Sep 16, 2025 at 2:23 AM EDT
4 months ago
Step 04

Generating AI Summary...

Analyzing up to 500 comments to identify key contributors and discussion patterns

Discussion (25 comments)

Showing 25 comments

rich_sasha

4 months ago

3 replies

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

4 months ago

2 replies

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.

DarkSucker

4 months ago

1 reply

As I read the article. The tsunami wave (water) displaces air at the surface and creates a sound wave, and gravity waves, that travels to the upper atmosphere. These waves then interact with electrons in the upper atmosphere.

JumpCrisscross

4 months ago

> and gravity waves, that travels to the upper atmosphere

You spoke correctly. But to further clarify, these are gravity waves, not gravitational waves.

Geo_ge

4 months ago

You've got exactly the right idea, except "cross compare" is underselling it :)

Here's a previous thread on this topic[0].

For each (receiver, satellite) pair, you can calculate the TEC along the signal propagation path by comparing the time of flight of two carrier waves (e.g. L1 and L2)[1].

By fusing the data from each line of sight together you can get a rough, real time, 3D (4D) model of the ionosphere. Then, you have a separate problem of identifying ionospheric anomalies in the model and relating them to phenomena like earthquakes.

[0] https://news.ycombinator.com/item?id=42441772 [1] https://news.ycombinator.com/item?id=42471052

atonse

4 months ago

To me this is a wonderful example of the power of mathematics and science to go well beyond our normal intuition of how the world around us works works (which was the normal way things were done until only a few hundred years ago).

The fact that we are able to measure things globally indirectly and accurately based on our understanding of physics, hypotheses we make, and then apply those experiments is very cool.

Never mind the marvel of GPS that we've just taken for granted for decades...

jjk166

4 months ago

I wonder if someone theorized that tsunamis were detectable by this method or whether someone trying to debug these disturbances figured out what they were caused by. Not sure which is more impressive.

chatmasta

4 months ago

2 replies

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.

throwway120385

4 months ago

1 reply

I'd rather have a false positive than a false negative. In the FP case I have to get to high ground and hang out until there's an all clear. In the false negative I have to run uphill from an advancing wave.

nsxwolf

4 months ago

2 replies

People stop responding to warnings when the false positive rate is high.

chatmasta

4 months ago

1 reply

Right. If the system generates hundreds of alerts per day, and one of them was right one time, that’s not very useful no matter how cautious you want to be.

jjk166

4 months ago

But it's still preferable to the one that didn't alert you the one time it really needed to.

A test with a high false positive rate can be combined with other tests to give a better picture. A wave detection plus a seismic event is a lot more compelling than either on their own, so long as non-seismic "tsunami" detections and non-tsunami causing seismic events tend to be independent events.

A false negative on the other hand at best might be dismissed if you have enough other evidence, but more than likely will make you stop looking at more data. A zero false negative rate is likely unachievable, and the perfect is the enemy of the good enough, but false negatives are a much worse issue to deal with than false positives.

Aspos

4 months ago

For context: number of earthquakes which potentially may generate tsunamis is measured in hundreds per year across the planet. Number of potential tsunami events for any given "coast" is measured in single digits per year. In the hottest areas it is tens of events per year.

goodcanadian

4 months ago

1 reply

I don't think we know, yet. The system was only in place a day before the earthquake. The fact that it worked is a nice smoke test, but tells us nothing about false positives nor false negatives.

chatmasta

4 months ago

We could know the false positive rate, if it’s been generating a bunch of these alerts but only recently happened to be right.

radarsat1

4 months ago

2 replies

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

4 months ago

1 reply

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.

BurningFrog

4 months ago

3 replies

I don't think I understand. Aren't all ocean waves caused by/dependent on gravity?

magicalhippo

4 months ago

Sure, all the water in the ocean is affected by gravity.

However, there are many different types of waves in physics, usually described by some form of wave equation[1]. And for some of those, body forces[2] like gravity doesn't play a direct role.

A relevant example is acoustic waves[3], which are the propagation of changes in pressure. In that case, the only thing gravity is doing is confining the water to a single body through which the acoustic wave can propagate, it doesn't affect the propagation otherwise as such.

[1]: https://en.wikipedia.org/wiki/Wave_equation

[2]: https://en.wikipedia.org/wiki/Body_force

[3]: https://en.wikipedia.org/wiki/Acoustic_wave_equation

pluto_modadic

4 months ago

wind, boats, whales, current interference/interfaces, cthlulu rolling over...

marcosdumay

4 months ago

There are pressure waves in the ocean too.

Latitude7973

4 months 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.

https://en.wikipedia.org/wiki/Gravity_wave

mhb

4 months ago

1 reply

Near-real-time outputs from GUARDIAN must be interpreted by experts trained to identify the signs of tsunamis.

Hmm. Sort of giving stock market fundamental analysis.

Aspos

4 months ago

This data augments USGS earthquake data and tsunami simulation data, so it is far better than "fundamental analysis". I am guessing it will not take long to train a simple neural network to do the job.

zzzeek

4 months ago

meanwhile current and former NASA employees are outside, today, protesting damaging budget and employment cuts by the federal government which will end or jeopardize many NASA programs:

https://www.space.com/space-exploration/nasa-employees-plan-...

this is the bigger story for the moment

View full discussion on Hacker News

ID: 45226938Type: storyLast synced: 11/20/2025, 6:48:47 PM

Want the full context?

Jump to the original sources

Read the primary article or dive into the live Hacker News thread when you're ready.

Open link View on HN