Question about subsidence / uplift post-unwraping results (Earthquake)

Microwave Toolbox
1

Hello everyone,

I’d like to ask you a question.

I have the following image as an example of a paper study on an earthquake by experts from China:

unw

Why when the step is performed after an unwrapping in the same event, for example, earthquake, in Dsc mode it is indicated as subsidence and in Asc mode as uplift, being that it is for the same event? shouldn’t it be both subsidence or both uplift? Understanding that it is an end result.

Thanks for any reply,

Cheers!

2

I see to potential reasons:

  1. Displacement is always calculated relative to the master image. Ideally, both ascending and descending analyses were performed using the earlier image as the master.
  2. The measurements are displacements in line-of-sight (LOS), that means along the line between of the earth’s surface and the sensor (incidence angle between 25 and 45 degrees). So it is possible that pixels move away from the satellite descending and towards the satellite in ascending modes --> both towards the coast.

Please share the link to the study so we can see if it is 1 or 2.

3

Hello Abraun,

Thank you very much for your answer. This is the download link:

Thank you!

4

as we see, they present LOS displacement with each stack having the first image as master. So any movement towards the coast is

  • movement towards the sensor in ascending mode
  • movement away from the sensor in descending mode

these movements are resolved to vertical displacement in figure 4 (f)

1 Like
5

Thank you very much for the reply! but in the case that I cannot determine the vertical displacement (LOS Asc + LOS Dsc) which one should be used? Figure A or Figure B? Or should it be both to be representative?

Thanks for any reply.

6

both are correct in the way that they describe how the surface has changed with respect to the acquisition geometry.
So it depends on your case what pattern you observe and what is the LOS in range direction.