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Is it earthquake damage or soil movement in my Oklahoma home?

Reviewed by Preston, Oklahoma foundation repair consultant ยท Updated 2026-10-14

In short: Earthquake damage appears at a specific moment, tied to a recorded event with enough shaking at the address. Expansive clay damage builds over months or years, changes with the seasons and matches the shape the foundation has been bent into. Comparing the earthquake record, the shaking intensity and an elevation survey of the house is the usual way to separate the two.

Why does this question come up in Oklahoma?

Oklahoma has had far more earthquakes since 2009 than before 1, and much of the state has expansive clay soil that moves with moisture 6. Both can crack drywall, brick and slabs, so homeowners and insurers often need to know which one did it. Background on the earthquakes is on the induced seismicity page.

What does each cause tend to look like?

Evidence Points toward an earthquake Points toward soil movement
Timing Damage first noticed right after an event listed in the earthquake catalog 3 Builds gradually; changes with seasonal or short-term moisture swings 6
Shaking at the address Intensity reports show meaningful shaking (around MMI VI or more for minor damage) 12 Little or no shaking reported nearby
Progression Damage tied to one event Progresses from cracks to sticking doors and sloping floors 5
Shape of the house Damage not explained by floor elevations Elevations show a center-lift or edge-lift shape 56
Neighborhood Similar damage reported over a wide area after the same event 2 Linked to drainage, leaking pipes, trees or irrigation 6

Shaking intensity

Intensity, measured on the Modified Mercalli (MMI) scale, describes how strongly shaking was felt at a location. The Oklahoma Geological Survey describes MMI VI as minor damage such as falling plaster and a few cracks; MMI VII, reached in the 2011 Prague earthquake, involves more significant damage 17. Central U.S. earthquakes are felt over areas more than ten times larger than similar West Coast quakes, so a distant event can still be felt 4.

Soil movement patterns

Uneven moisture under a slab bends it into a center-lift or edge-lift shape 5. Center lift is associated with long-term moisture gain, while edge lift and edge drop come from seasonal or short-term changes 6. Common causes include poor drainage, leaking pipes, trees, irrigation and wet or dry periods 6. See heave vs settlement and cracks that open and close seasonally.

What are the typical documentation steps?

  1. Pull the earthquake record. The OGS catalog lists date, location and magnitude for Oklahoma events 3; Did You Feel It? maps reported shaking 2.
  2. Establish when damage was first seen. Dated photos help place it before or after a specific quake.
  3. Survey floor elevations and map cracks against them; see elevation surveys and the distress pattern library.
  4. Record soil, drainage, trees and past repairs, the common drivers of moisture-related movement 6.

The OGS has noted that the 2016 USGS hazard report does not address cumulative damage from multiple small-to-moderate earthquakes over time 1, so the effect of repeated small quakes on a specific house is not captured by that assessment. For how engineers use field documentation, see working with engineers.

Free, plain-English answers. It asks a few questions and walks you to the repair that fits.

Common questions

Can a small earthquake crack my foundation?

Damage generally starts around intensity VI on the Modified Mercalli scale, described as minor damage such as some falling plaster and a few cracks.

How do I know how hard the ground shook at my house?

The USGS Did You Feel It? system maps shaking reported by people for each earthquake, and the Oklahoma Geological Survey publishes catalogs with the date, location and magnitude of Oklahoma events.

What does foundation damage from clay soil look like?

Soil-related damage usually builds over time: cracks in walls and foundations, then sticking doors and sloping floors. It follows the shape the slab has been bent into, such as edges dropping or the center rising.

Do earthquake hazard estimates account for damage from many small quakes?

Not fully. The Oklahoma Geological Survey noted that the 2016 USGS hazard model for Oklahoma did not address cumulative damage from multiple small-to-moderate earthquakes over time.

Sources

  1. Statement on USGS Hazard Assessment for Sites with Induced Seismicity Oklahoma Geological Survey
  2. Did You Feel It? (DYFI) U.S. Geological Survey
  3. Earthquake Catalogs Oklahoma Geological Survey
  4. Fact Sheet: Pawnee Earthquake, September 3, 2016 Oklahoma Geological Survey
  5. Residential House Foundations on Expansive Soils in Changing Climates HUD Office of Policy Development and Research (Cityscape, Vol. 25 No. 1)
  6. Expansive Soils (The Mystery) STRUCTURE magazine
  7. Information (Top Ten Oklahoma Earthquakes) Oklahoma Geological Survey

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