Deterrence

[Cyrano]

No more low intensity seismic shocks in Pak in the past couple of months ?

[Amber G.]

The frequency’s the same as before — nothing unusual. They’ve just dropped out of the news cycle because there’s no real significance to report (as have been posted a few times here in details).

[Tanaji]

https://www.ndtv.com/world-news/china-c ... s-10966774

No idea about the veracity of this claim as the US may just be trying to do unglee and in all likelihood doing the same thing or sub critical tests.

From the article:

"China has conducted nuclear explosive tests, including preparing for tests with designated yields in the hundreds of tons... China has used decoupling - a method to decrease the effectiveness of seismic monitoring - to hide its activities from the world.

From AI:

Overview of Nuclear Testing by Decoupling
Decoupling is a method used in nuclear testing to reduce the seismic signals generated by an explosion. This technique allows a country to conduct a nuclear test while minimizing detection by monitoring systems.
How Decoupling Works
Mechanism
Underground Cavities: A nuclear device is detonated in a large, deeply buried cavity. This setup absorbs much of the explosive energy, which reduces the seismic waves that escape into the Earth.
Seismic Wave Reduction: The energy from the explosion increases gas pressure in the cavity, which can significantly muffle the seismic signals. This makes it harder for monitoring stations to detect the test.

How is this any different from how India tested or any underground nuclear test?

[Lisa]

The American need to involve ALL nuclear powers in Nuclear Arms Limitation talks is the driver for all current noise.

[Amber G.]

Decoupling isn’t magic stealth. It can reduce seismic signals by maybe 10–50× for very low-yield shots, not make “hundreds of tons” invisible. Even a well-decoupled test at that scale should show up on regional/CTBTO seismic networks, and usually radionuclide stations too.

India’s tests weren’t decoupled and were detected immediately — so comparing the two actually weakens the claim.

Subcritical tests are a different beast altogether (zero yield, legal under CTBT, done by everyone including the US).

My take: Without public seismic or xenon data, this looks more like political signaling than a demonstrated nuclear test.

[Tanaji]

AmberG : is it possible to provide a brief semi technical explanation of what is decoupling and how it differs from an underground test?

The AI explanation is either vague or wrong…

[Amber G.]

AmberG : is it possible to provide a brief semi technical explanation of what is decoupling and how it differs from an underground test?

The AI explanation is either vague or wrong…

Yes, may be important technical distinction being blurred there.

Decoupling is fairly known concept - detonating a device in a large underground cavity reduces seismic coupling to surrounding rock. In ideal conditions, it can suppress seismic amplitudes by roughly a factor of 10–70, depending on geology and cavity size. (Decoupling involves detonating a device in a large underground cavity. The air or empty space inside the cavity acts as a cushion, ensuring the pressure on the surrounding rock walls remains below its elastic limit)

But It does not eliminate seismic signals. ( “Decoupling” isn’t invisibility cloak)

- It works best only for very low-yield tests (tens of tons TNT equivalent).

It requires large, carefully engineered cavities, which themselves leave observable signatures (tunneling, spoil piles, etc).

Most importantly for “hundreds of tons” yield, even a well-decoupled test would still be detectable by regional and teleseismic networks, especially with today’s IMS density.

So the phrase “hide its activities from the world” physics wise does not make sense.
---
India’s 1974 and 1998 tests were fully coupled underground tests, not decoupled cavity shots. produced clear seismic signals, detected internationally within minutes.
--
Subcritical tests are a red herring herent they produce zero nuclear yield by definition. (They are conducted by the US, Russia, China--including at Nevada and Lop Nur - are not prohibited under the CTBT.

If the activity were subcritical, seismic signature (and radio nuclei tests) will be a little different from nuclear explosion.
Calling it a “nuclear explosive test” would be technically incorrect.

-- What I think-
- No nuclear test — claim is political signaling (most likely).

(or Subcritical experiments being rhetorically upgraded.

(or Very low-yield hydronuclear experiment (borderline, still hard to hide). or Hundreds-of-tons decoupled test — least consistent with available evidence)

In short -
Decoupling is real, but it doesn’t make nuclear tests invisible — especially not at “hundreds of tons.”
India’s underground tests were fully detectable and fundamentally different.
Without open seismic or radionuclide data, the claim remains political, not scientific.