Impacted Populations in Liquefaction Zones in Memphis, Tennessee

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Seismic activity caused by earthquakes can cause catastrophic damage to infrastructure. One such method is the process of liquefaction, the phenomena of strong sediment becoming weak by seismic waves. This causes the soil to no longer be able to physically support the buildings placed on top of its foundation. Historically, the New Madrid Seismic Zone has had multiple earthquakes along the Mississippi Delta near Shelby County. Its principal city, Memphis, has a population estimated at about 650,000 people (US Census 2016). Within this region, there is a 25 – 40% chance that magnitude 6.0 or higher events will occur in the next 50 years (Rix et al. 2006).

Although there have been numerous studies on the New Madrid Seismic Zone, little has been done on potential damage to infrastructure from liquefaction at the city scale. Because of this, it is important to determine how much it would affect the Memphis population. Specifically, we would like to know what population groups are most susceptible to liquefaction. We hypothesize that the most affected groups are low-income residents and minority groups.

City of Memphis and Shelby County

The most susceptible liquefaction zones were overlaid with block groups to determine areas most affected. The demographic groups that were studied were total population, median income, and race (percent white).

Total Population

Median Income

Race Demographics - Percent White

Based on the GIS data, I rejected the hypothesis, as there is no evidence that lower income residents and minorities are more likely to live in areas susceptible to liquefaction. Instead, other factors, such as proximity to downtown and walkability, appeared to have a larger influence on where people lived. With more time, this study could be conducted on the parcel level for increased accuracy.