Earthquake-caused soil liquefaction risks in Washington State

liquefaction risk map of downtown Olympia
This map of downtown Olympia shows areas of susceptibility to ground liquefaction (red areas are at highest risk; orange is low-to-moderate riskSmall blue icons show where liquefaction (blue squares), structural damage (triangles), lateral ground spreading (stars) ground cracking (lightning bolts), landslides (circles) or toppled chimneys occurred in the 2001 earthquake. Map: DNR

A July 16 in-depth report heard on the Seattle-based NPR affiliate KPLU-FM and nationally examines the efforts of Washington and other Northwest states to map soil liquefaction susceptibility. Soil liquefaction is a potentially dangerous outcome of strong earthquakes. It occurs when water-saturated sand, silt, or (sometimes) gravels are shaken so violently in an earthquake that the soil loses strength and water is pushed toward the surface. The ground can become like quicksand, causing highways and sidewalks to buckle, and buildings to shift or even collapse.

Download DNR’s liquefaction susceptibility maps for any county in Washington State. Or view mapped liquefaction susceptibility and other geologic risk areas on the Washington State Geologic Information Portal.

How we developed the maps
Following the Nisqually earthquake of 2001 near Olympia, DNR was awarded a grant by the Federal Emergency Management Agency and Washington Emergency Management Division to develop earthquake hazard maps for every county in the state. Local and state government agencies, school districts and anyone else can use these maps to update their hazard mitigation plans. Local governments also use these maps to delineate geologically hazardous areas under the Growth Management Act. 

Here’s a blog about the mapping effort.

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