Top Earthquake Risk Cities in the U.S. -- A - L
Since rankings tend to vary from site to site and year to year, but the highest earthquake risk cities tend to remain in the rankings, the cities are listed in alphabetical order. In the A through L we'll look at Anchorage, Charleston, Dallas, Honolulu, and Los Angeles.
For reference, here's the USGS earthquake hazard map.
California usually takes the headlines for earthquakes in the U.S., but Alaska has the highest earthquake risk.
It’s not uncommon to hear about a large earthquake in Alaska. However, since the population density is extremely low, few people are affected, making the event not very newsworthy.
Anchorage has a population of around 300,000. While not as large as some of the other cities mentioned, if an earthquake were to strike the city, considerable damage, injuries, and even fatalities would occur. Most of the negative effects may not come from the earthquake itself but as the result of an earthquake-caused tsunami.
Recent studies of the seafloor off the coast of Alaska, an area called the Shumagin Gap, indicates a subduction zone, with a detached section, similar to the one that caused the 2011 Tōhoku earthquake and tsunami (Alaska at Risk of a Massive Earthquake and Tsunami Similar to Devastating 2011 Japan Event).
Charleston, South Carolina
If you look at the USGS earthquake hazard map, Charleston has a high risk for having a damaging earthquake within 50 years. As one of 16 states that has experienced a magnitude 6.0 or greater earthquake, South Carolina has “a relatively high likelihood” of another damaging quake ('We are the bull's eye').
Charleston was struck by an estimated magnitude 7.0 earthquake in 1886, but evidence is difficult to find. The local faults—the Middleton Place-Summerville Seismic Zone—are buried under thick layers of sand and sediment, which keep the fault lines hidden, unlike the San Andreas Fault, where much of it can be seen on the surface. The seismologists know the faults are there, but it’s harder to determine which are moving and at what rate.
As mentioned in Chapter 7, and evidenced by the 1886 earthquake, Charleston is within the target zone that has the potential for large earthquakes.
While it’s unlikely a true “Big One” will strike, the risk of a damaging earthquake in the Dallas-Fort Worth area is between 2 to 5 percent. With over 6.8 million people in the Dallas-Fort Worth-Arlington area, a lot of people would be at risk if an earthquake were to strike.
For now, the earthquakes are still in the lower-magnitude range, although these can still cause cracks in buildings and knock things over. However, as Rob Williams, the USGS coordinator for the earthquake program in central and eastern United States, stated, “The more small earthquakes you have, the more of a chance [there is] of having a bigger one” (Risk of quakes on the rise in Oklahoma, North Texas).
In July 2019, researchers at the University of Texas at Austin released a study that includes a map of more than 250 faults in the Dallas-Fort Worth area. Together, the faults total more than 1,800 miles of length under the region. The study found the faults to be stable, if left alone, but they are sensitive to changes.
Furthermore, a big part of the increasing seismicity risk in the region comes from induced earthquake risk. As oil and gas operations increased from 2008 to 2015, the seismic activity in the region also went up. As wastewater injection has slowed since 2015, seismic activity has significantly reduced.
The study found that because the fault system is sensitive and can potentially produce earthquakes, any future increase in deep wastewater disposal needs to be managed better.
Being a volcanic hotspot, Hawaii is a top earthquake risk. With the largest population of the islands, Honolulu is the highest risk.
An 1868 magnitude 7.9 earthquake in Honolulu killed 77 people with the resulting tsunami and landslide. With today’s much larger population, a quake of that magnitude poses a greater threat. Since 1868, seven earthquakes of magnitude 6.1 and larger have hit the islands, including a 6.9 that struck in May 2018.
Los Angeles, California
With the nearby San Andreas Fault, stories and movies about the “Big One” laying waste to Southern California are a common theme. While the possibility of California dropping into the ocean may seem like science fiction, the USGS gives the Los Angeles area a 67% probability of at least one magnitude 6.7 or larger earthquake happening by 2037.
Expanding the area beyond Los Angeles, the probability of a magnitude 6.7 earthquake striking Southern California is 97% for that same time period. A magnitude 7.0 earthquake is an 82% probability. Even a magnitude 7.5 has a 37% chance of hitting the region (Forecasting California’s Earthquakes—What Can We Expect in the Next 30 Years?, 2008).
The magnitude 7.1 earthquake on July 5, 2019, certainly fits into the probability, and it has refueled anxieties and fears about a Big One on the San Andreas Fault.