The polygons in this dataset provide information regarding relative liquefaction potential across Washington State. Liquefaction is a natural phenomenon in which saturated, sandy soils lose their strength and behave as a liquid. Liquefaction is caused by severe ground shaking during earthquake events. The polygons in this dataset represent National Earthquake Reduction Program (NEHRP) site class, which provides a general guide to areas where earthquake shaking will be the strongest and where the potential damage to buildings and other structures may be elevated because of soil effects. Please note that it is only a general guide, and does not incorporate other factors affecting the actual severity of ground shaking, such as earthquake size or the distance of the area in question from the earthquake's focus.

Polygons are classified as having 'very low' to 'high' relative liquefaction susceptibility. Areas underlain by bedrock or peat are mapped separately, as these earth materials are not liquefiable, although peat deposits may be subject to permanent ground deformation caused by earthquake shaking and require site-specific analysis under the International Building Code. Water and ice are also separately designated. Liquefaction susceptibility is assigned based on criteria described in: Palmer, Stephen P.; Magsino, Sammantha L.; Bilderback, Eric L.; Poelstra, James L.; Folger, Derek S.; Niggemann, Rebecca A., 2007, Liquefaction susceptibility and site class maps of Washington State, by county: Washington Division of Geology and Earth Resources Open File Report 2004-20, 78 plates, with 45 p. text.

The polygons in this dataset provide information regarding relative liquefaction potential across Washington State. Liquefaction is a natural phenomenon in which saturated, sandy soils lose their strength and behave as a liquid. Liquefaction is caused by severe ground shaking during earthquake events. The polygons in this dataset represent National Earthquake Reduction Program (NEHRP) site class, which provides a general guide to areas where earthquake shaking will be the strongest and where the potential damage to buildings and other structures may be elevated because of soil effects. Please note that it is only a general guide, and does not incorporate other factors affecting the actual severity of ground shaking, such as earthquake size or the distance of the area in question from the earthquake's focus.

Polygons are classified as having 'very low' to 'high' relative liquefaction susceptibility. Areas underlain by bedrock or peat are mapped separately, as these earth materials are not liquefiable, although peat deposits may be subject to permanent ground deformation caused by earthquake shaking and require site-specific analysis under the International Building Code. Water and ice are also separately designated. Liquefaction susceptibility is assigned based on criteria described in: Palmer, Stephen P.; Magsino, Sammantha L.; Bilderback, Eric L.; Poelstra, James L.; Folger, Derek S.; Niggemann, Rebecca A., 2007, Liquefaction susceptibility and site class maps of Washington State, by county: Washington Division of Geology and Earth Resources Open File Report 2004-20, 78 plates, with 45 p. text.