2014 Update To The USGS Seismic Risk Map
Note: September is National Preparedness Month. Follow this year’s campaign on Twitter by searching for the #NatlPrep #BeReady or #PrepMonth hashtags.
This month, as part of #NPM22, I’ll be rerunning some updated preparedness essays, along with some new ones.
#16,994
In 2006 the USGS calculated that earthquakes posed a significant risk to 75 million Americans living in 39 States. Since then, populations have changed and/or shifted and ongoing research has uncovered new seismic risks (see USGS: Updated U.S. Seismic Risk Hazard Maps), providing geologists with a better understanding of the extent of ground shaking from these quakes.
A new study, published in 2015 in the journal Earthquake Spectra, nearly doubled – to 143 million - the number of Americans who live or work in areas susceptible to potentially damaging ground shaking.
The New Madrid Seismic Zone (NMSZ), the Pacific Northwest (Cascadia fault), coastal South Carolina, Alaska and Hawaii, and even New York City and parts of New England are at risk of seeing significant seismic activity.
But of course, due to popular culture, everyone's first thought is California.
In 2019 the SSA (Seismological Society of America) held their annual meeting, and a study was presented that concludes that California's recent lack of major quakes has no precedent in the past 1000 years.
The Current Unlikely Earthquake Hiatus at California’s Transform Boundary Paleoseismic Sites
Glenn P. Biasi, Katherine M. Scharer
Seismological Research Letters (2019) 90 (3): 1168-1176.
https://doi.org/10.1785/0220180244
ABSTRACT
Paleoseismic and historical earthquake records used to quantify earthquake recurrence rates can also be used to test the likelihood of seismically quiescent periods. At principal paleoseismic sites in California on the San Andreas, San Jacinto, Elsinore, and Hayward faults, no ground‐rupturing earthquake has occurred in the last 100 yr, yet this interval is about three times the average interearthquake period for the ensemble of sites.
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California, they announced, has been in an earthquake drought for the past 100 years. One, that the SSA warns, is unlikely to continue. In a news release they wrote:
They agree that the next 100 years of California earthquakes along these faults could be a busy one. “If our work is correct,” Scharer and Biasi note, the next century isn’t going to be like the last one, but could more like the century that ended in 1918.”
Earthquakes aren't the only seismic hazard in California, or the United States, as there are nearly a dozen `very high risk' volcanoes in the continental US (4 in Washington, 4 in Oregon & 3 in California), along dozens of `lesser' threats. While earthquake damage is generally localized, volcanic eruptions can affect property and populations thousands of miles away.
When you add in that the Gulf and Atlantic coastlines are susceptible to tsunamis generated from distant earthquakes (see East Coast Tsunami Threats), then there is better than a 50-50 chance that you live in an area that is at risk of some seismically induced disaster.
While the `big one' in California (see Dr. Lucy Jones: `Imagine America Without Los Angeles’) is perhaps the most anticipated major disaster of all time, there are other areas in the continental United States equally ripe for a big quake.
FEMA and the U.S. government conducted a huge drill six years ago (see FEMA: Cascadia Rising 2016) involving 20,000 people from both the United States and Canada, in order to prepare for a catastrophic M9.0 quake & tsunami off the Pacific coast.
And in 2011 – during the bicentennial of the four great New Madrid earthquakes of 1811-12 – FEMA and other federal agencies mounted the largest National Level Exercise (NLE) to that date, revolving around a catastrophic earthquake occurring in the New Madrid Seismic Zone (NMSZ) that would involve eight Central U.S. States.
In recent years Oklahoma has see a huge upsurge in seismic activity (see M5.6 Quake In Northern Oklahoma), while northern Alabama, Georgia, Tennessee, Texas, Utah - and even New York City and parts of New England - can experience infrequent, but strong temblors (see USGS: Eastern Earthquakes - Rare But Powerful).
Perhaps least appreciated is the seismic history of South Carolina, which in 1886 was struck by an (Est. 7.3-7.6 magnitude) quake that devastated much of Charleston, South Carolina. Shaking was felt as far north as Boston, south to Cuba, and west as far as New Orleans.
An earthquake of that size today, in the same area, it is estimated would produce:
- 45,000 injuries
- 9,000 hospitalizations
- 900 fatalities
- 200,000 displaced or homeless persons
- 20 billion dollars in Damage
Imagine an M8.0 New Madrid quake collapsing major bridges that cross the Mississippi river, buckling the Midwest's railroad tracks and interstate highways, and taking out the dozens of critical natural gas pipelines that snake through that region.
A quake of that size could impact the transportation of food, the delivery of energy (power, gas, coal, etc.), the national power grid, and the nation's economy in ways we can only partially imagine.
While we can't prevent the next big quake from happening, we can prepare for it.
Working to improve earthquake awareness, preparation, and safety is Shakeout.org, which promotes yearly earthquake drills and education around the country (see A Whole Lotta Shakeouts Going On).
The third Thursday in October (Oct 20th in 2022) is International Shakeout Day, when dozens of states and countries practice earthquake safety. If you live in or near one of these seismically active areas, I strongly would urge you, your family, and your employees take part in these yearly drills.
But after the shaking stops, you'll have to find ways to cope with the aftermath.
While the government will send help, you could find yourself pretty much on your own for several days and living in less than comfortable conditions for weeks.For starters - and as a bare minimum - every household should have a disaster plan, a good first aid kit (and the knowledge to use it), an emergency battery operated NWS weather radio, and emergency supplies to last a minimum of 72 hours during a disaster.
While 72 hours is an admirable start, I wouldn't feel comfortable with it. Here in the United States many agencies and organizations recommend that households work towards having a 10-to-14 day supply of food, water, and emergency supplies on hand.
As the (above) graphic illustrates (see #NatlPrep: FEMA National Household Preparedness Survey), while we've seen some improvement over past few years, Americans still have a long way to go if we are to cultivate a culture of preparedness.
For more on earthquake preparedness, both here in the United States, and around the world, you may wish to revisit:
