Inverted deformations and DEM error over mines

[Bo Lee]

Dear all,

I am analysing several surface mines using ISCE2 and MintPy, and I am encountering results that are opposite to what I expect.

I am seeing positive deformation values over mining areas and negative deformation values over dumping areas. This is also visible in the DEM error using both GLO-30 and SRTM 1sec DEMs, where the values inside the mining area are positive and the values at the dumping areas are negative.

At the Hail Creek mine in Australia, some areas make sense in terms of surface deformations, but the DEM error still looks inverted. However, over the Ekibastuz mine in Kazakhstan, I get almost completely opposite results to what I expect.

I have included images of my results, my configs and location information. I would greatly appreciate any feedback or help on why I am getting these inverted results.

Best,

Bo

[Bo Lee]

I run ISCE2 with the following settings:
stackSentinel.py -s ./slc/ -d ./dem/demLat_*.dem.wgs84 -b 'S N W E' -a ./aux/ -o ./orbits -c 5 -useGPU -z 3 -r 9 -f 0.5

[Stuart Edwards]

This may be a result of elastic rebound due to stress relief in the mined area.  I've seen the same thing in mines and large road cuts.  Conversely in the waste areas there is increased stress that causes elastic compression after any upward signal that is indicating material placement is complete.  Dewatering has a similar effect due to increases in effective stress that then causes elastic compression.  Interesting stuff! Probably never see it without InSAR.

Stu

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[Bo Lee]

Okay, that's very interesting! I'm not too familiar with these underlying geological processes, so this is new to me. I only wonder how these rebound and compression signals could exceed the large changes caused by mining and material dumping. Could it be that S-1's C-band is more suited to picking up these smaller, more linear changes?

On Tuesday, July 8, 2025 at 5:08:03 PM UTC+2 Bo Lee wrote:

[Stuart Edwards]

Usually I see some gross dislocations in the time series for ongoing or recent earth moving operations (cut or fill). InSAR isn't really suitable for quantifying those large 'movements'.  So the (visco-elastic) rebound and compression signals are probably going to show up in parts of the mine where not much human activity is taking place over some reasonably extended period of time - maybe 4 or 5 revisit periods - to observe a reliable trend.  And, yes it's a function of what S-1 does best - detect slowly developing ground deformation.

Stu

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[Gabriela Quintana Sánchez]

What was your time period and how many combinations did you used?

[Bo Lee]

Hi Gabriela, I used a 7-year period from 2018-2025 for the Hail Creek mine and a 2-year period from 2019-2021 for the Ekibastuz mine. For both, I used networks with 5 connections per acquisition.

On Tuesday, July 8, 2025 at 5:08:03 PM UTC+2 Bo Lee wrote:

[Gabriela Quintana Sánchez]

You calculated de and du?

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Gabriela Quintana Sánchez

[Bo Lee]

No, not for these sites. I'm working on that now, would you expect the results to change that drastically?

[Gabriela Quintana Sánchez]

Right! 🤔 Then, I guess that the positive deformation likely is caused by rebound or ground relaxation after material extraction. When material is removed, the surrounding ground may adjust upward due to stress release.

The negative deformation in dumping areas may be due to loading effects from deposited waste material, which compress the underlying ground over time. May also reflect settlement of loose material as it consolidates under its own weight.

On the other hand, the positive DEM errors suggest the DEMs were acquired after material removal, so their elevation values are higher than the current ground surface. This aligns with the positive deformation if the DEM was generated post-mining but before rebound occurred.

The negative DEM errors in dumping areas, iIndicates the DEMs were acquired before dumping, so their elevation values are lower than the current (raised) ground surface due to accumulated waste material. I don't know if what I said is correct!

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Gabriela Quintana Sánchez