Ground subsidence and earth fissures in the Phoenix basin
Groundwater pumping since the 1940s caused widespread land subsidence and earth fissures in the alluvial basins of south-central Arizona, including the Phoenix metropolitan area. The Arizona Department of Water Resources operates an InSAR-based land subsidence monitoring program across the affected basins.
Source: USGS Circular 1182 — Land Subsidence in the United States
What is documented here
The alluvial basins of south-central Arizona — including the Phoenix metropolitan area — subside because groundwater pumping compacts the basin fill. The process started in the 1940s, and the most affected areas show several meters of cumulative subsidence. The distinctive hazard in Arizona is the earth fissure: a ground crack, sometimes kilometers long, that opens near basin edges where subsidence is uneven. Fissures damage roads, canals, utilities, and foundations. They can open or reactivate years after they first form.
The state takes this seriously: the Arizona Department of Water Resources runs a dedicated land subsidence monitoring program with satellite radar, and the Arizona Geological Survey maps known fissure zones. Those public programs operate at basin scale. The earth-fissure maps show where fissures were found — not what the ground under a specific parcel does today.
Arid, sparsely vegetated terrain is close to ideal for radar interferometry — bare desert ground and structures hold radar coherence well. That makes a screening-grade, site-specific movement history unusually reliable in this region — for a development parcel near a mapped fissure zone, a canal reach, or a distribution facility on basin fill.
What the satellite archive holds here
The public Sentinel-1 radar archive, sampled at a representative point in this region. These numbers describe measurement availability — how often the satellites pass, and over what period — not ground movement. We compute movement per site, after the feasibility check.
- Radar acquisitions
- 136
- Revisit
- ~12 days
- Observed span
- 2022-01 → 2026-06
- Satellite tracks
- 3
Coverage stats as of 2026-07-14 · full Sentinel-1 archive extends back to 2015
What satellite radar can — and cannot — tell you
It can
- — Reconstruct a millimeter-scale movement history for stable radar reflectors (rooftops, pavement, rock, bare ground) on a specific site, from archive data
- — Show if the movement slows, stays steady, or accelerates — the trend shape that matters for decisions
- — Give you a dated record of what the ground did before a purchase, a design, or a dispute
It cannot
- — Measure surfaces that change between passes: dense vegetation, active construction, water
- — Replace geotechnical instrumentation, borings, or engineering judgment — it shows you where to look, not how to design
- — Tell you why the ground moves — it documents that it moves and how fast, as an input to the engineer who determines why
The honest economics: a commissioned InSAR study typically costs $10,000–30,000 and takes weeks. A self-serve report on one site costs $749, one time. The feasibility check before it is free — if the satellites cannot measure the site reliably, you pay nothing, and we say so.
Common questions
What are earth fissures and why does Arizona have them?
Earth fissures are ground cracks that form where groundwater-driven subsidence is uneven, typically near basin edges or buried bedrock highs. South-central Arizona's deep alluvial basins and long pumping history make it one of the few places in the US where fissures are a mapped, named hazard.
Does Arizona already monitor subsidence?
Yes — the Arizona Department of Water Resources runs an InSAR-based monitoring program at basin scale, and the Arizona Geological Survey maps earth fissure zones. Site-specific screening complements those programs: it answers what the ground under one particular site did, at parcel resolution.
Is desert terrain good or bad for satellite radar measurement?
Good — among the best on Earth. Radar interferometry depends on a ground surface that stays recognizable between satellite passes, and arid, sparsely vegetated terrain preserves that signal well. Feasibility scores in this region are typically high.
Check a site in the Arizona region
Draw your site, and you get a free feasibility report from the Sentinel-1 radar archive in about one minute. It tells you how many passes cover the site, how often, over what period — and if the satellites can measure it at all. If they cannot, the report says so.
Check your site freeTelluric readings come from satellite radar and are screening-grade: use them to decide where to inspect. They do not replace geotechnical instrumentation or engineering judgment. Read the methodology.