How bad will a Hayward Fault earthquake actually be, and what you can do to protect yourself

By David Jacobson, Temblor

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hayward fault earthquake shaking
This figure from the HayWired report shows the distribution of shaking caused by a Hayward Fault earthquake. What is evident in this figure is how the entire region is exposed to varying levels of shaking. Because of this, damage is estimated to far exceed $100 billion.

 

Last week the USGS released the second volume of the HayWired report, a scenario M=7.0 earthquake along the Hayward Fault. This volume focused on the impacts of the earthquake, which includes the estimated losses. Within this volume, two losses stood out, an estimated $82 billion in property and direct business losses, and up to $30 billion in fire damage. While $112 billion in losses sounds extreme, it pales in comparison to the $170 billion in direct damage the company CoreLogic projects.

There is no question that a large Hayward Fault earthquake will be devastating for the region. As it snakes through the East Bay, it cuts under properties, utility lines, and other important infrastructure. Because of this, some scientists describe it as a “tectonic time bomb.” However, until it happens we don’t know exactly how bad it will be. Therefore, having multiple estimates allows us to get a greater overall picture of what we should be prepared for, and also where we may be lacking in protection.

 

USGS and CoreLogic fire costs differ by a factor of 15

Under close examination of the loss estimates from both the USGS and CoreLogic, there are several differences that illustrate both the uncertainty of what could happen, and how a Hayward Fault earthquake could be much worse than what was outlined in HayWired. For example, the USGS states that the HayWired mainshock will trigger over 400 fires, leading to $30 billion in losses. CoreLogic on the other hand only gives $2 billion in fire losses. While it is true that fires wreaked havoc following the 1906 San Francisco Earthquake, CoreLogic states that large fires following earthquakes are rare and that commercial construction tends to be made of fire-resistant materials. Because of this, they chose to go with an average fire-following loss estimate.

san-francisco-earthquake-fire
Following the 1906 San Francisco earthquake fires ripped through the city. In calculating estimates for how much fire damage would be caused by a Hayward Fault earthquake, the USGS and CoreLogic used differing interpretations of this event to forecast what will likely happen in a future Bay Area earthquake.

 

In contrast, the USGS, used the 1906 fire as a reason why there are likely to be significant fire losses after a Hayward Fault earthquake. Additionally, they cite past fires in the Bay Area, and attribute hight winds to the potential rapid spread throughout the region. While both sides have their own methodologies for determining these losses, what is emphasized is that there is great error associated with these scientific models. Having said that, regardless of how damage is caused, a Hayward Fault earthquake will impact the region for decades.

Haywired fire losses
This figure from the HayWired report shows the estimated losses from fires following a Hayward Fault earthquake. While the USGS estimates that there could be as much as $30 billion in fire losses, CoreLogic only estimates $2 billion.

 

USGS and CoreLogic damage costs differ by a factor of 3

Another startling number is that while the USGS estimates that the HayWired mainshock will produce $56 billion in direct building and contents damage, CoreLogic says there will be $140 billion in direct damage. Couple this with an additional $30 billion in losses from aftershocks, fires, and sprinkler leakage, and you get $170 billion in total losses, 20% of the regional GDP. Such a large discrepancy highlights how vulnerable the region could be following a large earthquake. For comparison, in the devastating earthquakes in Christchurch, New Zealand, which began on September 4, 2010 and lasted through December 2011, damage accounted for 25% of the regional GDP. More than seven years on, much of the city is still in repair, and it will likely never be the same.

However, in Christchurch, things were different, the majority of residents had help. In New Zealand, 90% of homeowners have earthquake insurance. While it is a tiered system, this meant that almost everyone received some financial help. In a HayWired earthquake, this will not be the case, as CoreLogic estimates that less than 8% of residential losses will be insured. This means that most Bay Area residents will be forced to cover their losses completely out of pocket. Such glaring numbers highlights the need for people to protect themselves from natural disasters. Whether this is through retrofitting or insurance is up to the individual, but what is extremely evident from these numbers is that a Hayward Fault earthquake may be much worse than what was outlined. However, this should not be seen as a doom and gloom scenario. Just like the HayWired report emphasized that losses are not set in stone, neither are these numbers. With proper preparedness, potential losses can be brought down and the region can recover faster following a large earthquake

 

References
Detweiler, S.T., and Wein, A.M., eds., 2018, The HayWired earthquake scenario—Engineering implications: U.S. Geological Survey Scientific Investigations Report 2017–5013–I–Q, 429 p., https://doi.org/10.3133/sir20175013v2.

Charles Scawthorn, Fire following the HayWired scenario mainshock, in Detweiler, S.T., and Wein, A.M., eds., 2018, The HayWired earthquake scenario—Engineering implications: U.S. Geological Survey Scientific Investigations Report 2017–5013–I–Q, pp. 367-400.

Financial Implications of the HayWired Scenario, CoreLogic, April 2018 Link

  • Keith Porter

    The HayWired rollout had been a little thin on giving credit where credit is due, so the reader of Temblor’s blog should know that HayWired shaking loss estimates were prepared by Hope Seligson, using an updating building stock prepared by Doug Bausch, and a shakemap prepared by by Brad Aagaard and a dozen other seismologists. Dr. Charles Scawthorn prepared the HayWired fire following earthquake losses, and Tom Larsen (and one other person whose identity I’ve forgotten) prepared CoreLogic’s loss estimates. An extraordinarily large number of external experts peer reviewed the HayWired study; it is almost certainly the most heavily peer reviewed scenario ever, as well as the richest in fundamental engineering research and new knowledge.