Project aim

Show that pygeofetch can take one of the world's fastest-sinking cities from raw Sentinel-1 search to a deformation map, and report the result together with its weaknesses.

  • 67SLC scenes
  • 2,211 → 78Pairs → valid interferograms
  • −35.5 cm/yrStrongest velocity (2nd pct.)
  • 17Disconnected SBAS networks
Illustrative map for Mexico City Land Subsidence Illustrative graphic

Overview

Mexico City is a reference case for land subsidence, with a published peak of −39.1 cm/yr (Cigna & Tapete, 2021). Using only pygeofetch, the project searched and downloaded 67 Sentinel-1 SLC scenes, reduced 2,211 candidate pairs to 78 valid interferograms, and recovered vertical velocities between −35.5 and −2.9 cm/yr (2nd–98th percentile).

The challenge

The aim was not only to produce a map but to test the tool honestly. Interferogram networks can be fragmented by gaps and baseline limits, which weakens the inversion even when the map looks convincing. Reporting that openly matters more than a clean picture.

Data & inputs

  • 67 Sentinel-1 SLC scenes
  • ERA5
  • IONEX
  • Precise orbits

Approach

  1. 01

    Search & download

    67 Sentinel-1 SLC scenes were searched and downloaded through pygeofetch's federated search.

  2. 02

    Pair selection

    2,211 candidate pairs were reduced to 78 valid interferograms; pygeofetch's preflight check guards AOI coverage, network connectivity and baselines.

  3. 03

    InSAR chain

    Orbit-based coregistration with ESD, phase removal, ERA5 tropospheric and IONEX ionospheric correction, then SNAPHU unwrapping.

  4. 04

    SBAS inversion

    The network was inverted to vertical velocities and compared against the peer-reviewed reference.

Results

Recovered vertical velocities of −35.5 to −2.9 cm/yr are directionally consistent with the published −39.1 cm/yr peak. The same chain has since been applied to the 2021 Piton de la Fournaise eruption and the 2016 Amatrice earthquake.

Validation

Compared against Cigna & Tapete (2021), the peer-reviewed reference for Mexico City subsidence.

Status & caveats

The interferogram stack fragments into 17 disconnected SBAS networks, so this result is not presented as a validated replication. It is a directional check of the toolchain.