US–Indian space mission maps extreme subsidence in Mexico City

3 days ago (phys.org)

Like the article hints at, some of the particular strengths of this new measurement:

- frequent revisit, so can track even sub-monthly changes

- the L-band radar is at a wavelength (24cm) that penetrates vegetation canopy, removing a confounder from the measurement

- excellent spatial resolution that is relevant to urban scenes

The data volume is exceptionally high and required a lot of engineering effort. All radars are demanding, but this one was a new high-water mark.

(https://www.earthdata.nasa.gov/news/now-that-nisar-launched-...)

I wouldn't trust that graphic at the top of the article to be very accurate. It has an obvious acquisition footprint that was not resolved in processing. Those WNW-ESE stripes should've been resolved before publishing by ground-truthing the stripes using benchmarks established inside the mapped area so that the end result wouldn't suggest higher/lower subsidence along tracks than seen on parallel offset from tracks. That's just sloppy.

The striping can have multiple sources so they need to study why there is an obvious footprint and then make the appropriate corrections.

So, perhaps a dumb question, but the article mentions that 14 steps have been added to the base of the Angel of Independence monument, and the Wikipedia article mentions the same things:

> Originally, nine steps led to the base, but due to the sinking of the ground, an ongoing problem in Mexico City, fourteen more steps have been added.

So why didn't the monument itself also sink? Does it have piles going down to bedrock or something?

The amount of subsidence is quite dramatic, up to 25 cm per year!

What are the practical consequences of this today, and what is being done to remedy this?

  • Just as a fun fact, here are some images of the extent of subsidence (due to groundwater pumping for agriculture) in the California Central Valley: https://www.usgs.gov/centers/land-subsidence-in-california/m...

    Note in particular the last one, which is a classic. Roads, buildings, and all underground infrastructure is affected. As well as anyone else who uses that groundwater, as well as future users - because come groundwater reservoirs do not recover, the compaction is permanent.

  • > What are the practical consequences of this today

    Infrastructure degradation. Think overpass collapses or metro rail lines being misaligned.

    > what is being done to remedy this

    Not enough. CDMX faces the issue of multiple political entities with varying power making management difficult.

    A lot of the subsidence happens in informal settlements [0] due to a mixture of political populism (no one would dare demolish an informal settlement and piss off voters).

    Beijing used to have a similar issue, but a mixture of hukou, mass evictions, and mass demolitions helped alleviate the issue.

    [0] - https://penniur.upenn.edu/uploads/media/02_Gutierrez.pdf

    • We can also see it play out in other countries, that had solar water pumping for the last ten years, like afghanistan. In the end stage- its water wars with neighbours like Pakistan or Iran.

Cloudflare: verification rejected. Accessing from Japan.

Thank you very much, Cloudlare.

"Objective:

NISAR is the first of its kind mission, jointly developed by ISRO and NASA. It is an L and S-band, global, microwave imaging mission, with capability to acquire fully polarimetric and interferometric data.

The unique dual-band Synthetic Aperture Radar of NISAR employs advanced, novel SweepSAR technique, which provides high resolution and large swath imagery. NISAR will image the global land and ice-covered surfaces, including islands, sea-ice and selected oceans every 12 days.

NISAR mission’s primary objectives are to study land & ice deformation, land ecosystems, and oceanic regions in areas of common interest to the US and Indian science communities.

NISAR mission will help to measure the woody biomass and its changes track changes in the extent of active crops understand the changes in wetlands’ extent map Greenland’s & Antarctica’s ice sheets, dynamics of sea ice and mountain glaciers characterize land surface deformation related to seismicity, volcanism, landslides, and subsidence & uplift associated with changes in subsurface aquifers, hydrocarbon reservoirs, etc.

Spacecraft Configuration

The Spacecraft is built around ISRO’s I-3K Structure. It carries two major Payloads viz., L & S- Band Synthetic Aperture Radar (SAR).

The S-band Radar system, data handling & high- speed downlink system, the spacecraft and the launch system are developed by ISRO. The L-band Radar system, high speed downlink system, the Solid-State Recorder, GPS receiver, the 9m Boom hoisting the 12m reflector are delivered by NASA.

Further, ISRO takes care of the satellite commanding and operations, NASA will provide the orbit maneuver plan and RADAR operations plan.

NISAR mission will be aided with ground station support of both ISRO and NASA for downloading of the acquired images, which after the necessary processing will be disseminated to the user community

The data acquired through S-band and L-band SAR from a single platform will help the scientists to understand the changes happening to Planet Earth."

https://www.isro.gov.in/Mission_GSLVF16_NISAR_Home.html

The way that this article is written reads like American propaganda. This is already being done, and has been done for a long time, including at the same or better temporal and spatial resolution. NISAR is genuinely cool, do I don't know why they felt the need to write this way. The new capabilities are mainly being able to do this in highly vegetated areas. In urban areas, like mexico city, this is literally 'intro to SAR' stuff.

Excessive groundwater extraction and urban development could be reasons for this. But these are common practice in almost all of the modern world, so why is this only showing up in Mexico City.

There must be other contributing factors too.

  • You can see evidence of subsidence in the rest of the developed world as well: SAR interferometry is sensitive enough to pick up the minimal amount of building movement from building Crossrail in London. It's just this article focuses on Mexico City, where it's dramatic

  • Mexico city was built on top a dried lake. It is really fascinating stuff, I would highly recommend to look it up. Ancient farming technology, floating islands, any nerd is gonna love it.

I really can't believe that an issue discovered in 1925 still isn't solved. A kind of issue which wont take a Nobel prize to be solved. This is sad.

I get that the article is primarily about the satellite capabilities, but it's rather annoying it doesn't mention what the future impact of the subsidence might be.

  • I think that it’s quite responsible not to speculate on something they’re not an expert on.

    It’s exactly the sort of news bite that catastrophists glom onto.

    This is responsible journalism.

    • > I think that it’s quite responsible not to speculate on something they’re not an expert on.

      "Recent satellite maps show Mexico City getting closer to hell at alarming rate"

  • Nor does it say how much subsidence the satellite documented.

    • There's this under the picture.

      > New data from NISAR shows where Mexico City and its environs subsided by up to a few centimeters per month (shown in blue) between Oct. 25, 2025, and Jan. 17, 2026

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In parts of Central Valley CA, there's been over 30 ft / 9m of subsidence from ground water extraction over several decades. (30 cm/y) Lone pipes and drains that previously sat at ground level tower over the land.

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  • Have you visited Mexico City? Your view of Mexico is likely colored by media (particularly social media) and the on-the-ground reality can be quite different.

    While it’s not the best run place, it is perfectly capable of large scale infra projects and state capacity and capability is pretty well developed.

  • Tu entendimiento está tan equivocado que no veo ni siquiera por dónde comenzar a debatirlo, quizás si primero sacas tu cabeza de tu trasero y empiezas a conocer el mundo sería un primer buen paso.

  • The wealthy parts of Mexican cities are substantially more well-managed and upscale than the poor parts of American cities.

    Of course, on average Mexico is poorer, has a lower GDP per capita, and so on. But the level of ignorance among Americans is astonishing sometimes.

    • Yeah that's "the government and people part", it's talking about the average. Of course the rich enclaves in Mexico are doing better than the average, you can find that in many places on the planet that are on average terrible places to live. But taking that into account makes it harder to crow about the ignorance of Americans, as it's so historically fun to do.

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