Global Courant 2023-04-30 17:00:46
SAN FRANCISCO —
The projected annual cost of earthquake damage for California is rising sharply amid a rise in property values and a better understanding of how soft soils can lead to greater damage during shaking.
California is expected to lose an average of $9.6 billion a year in earthquake damage, the new estimates show. That’s a 157% increase from the last estimate, in 2017, when the price tag was $3.7 billion a year, according to a new report of the US Geological Survey and the Federal Emergency Management Agency.
“In any given year, a major earthquake hits … you can easily expect a loss of $100 billion,” USGS research structural engineer Kishor Jaiswal, the report’s lead investigator, told The Times.
The totals underline how much the value of older buildings has risen in recent years, yet they remain vulnerable to major damage or collapse in the next major earthquake.
It’s also a sobering reminder of the seismic toll that awaits California. After the state’s other major earthquakes—the 1906 in San Francisco, 1933 in Long Beach, 1989 in the greater San Francisco Bay Area, and 1994 in Northridge—cities took years, if not decades, to recover, at a huge cost. to be made. not only paid for by governments and insurers, but also by individuals who have never been healed.
According to the new report Los Angeles and Orange counties share the highest price tag of any metropolitan area in the nation, with a combined expected average annual loss of $3.3 billion per year. In second place is the San Francisco-Oakland-Berkeley metro areawith an expected loss of $1.8 billion per year.
The seismic price tag for California is about 65% of the country’s annual earthquake cost, which is $14.7 billion per year.
Projected annual average earthquake losses in other parts of California include $1.3 billion for Riverside and San Bernardino counties$917 million for the San Jose-Sunnyvale-Santa Clara metro area$285 million for it County of San Diego and $220 million for it Ventur County.
Assuming the annual earthquake loss projection remains the same, California is expected to lose $288 billion over three decades from earthquake damage. Such a figure is consistent with recent earthquake scenarios, such as a magnitude 7.8 earthquake on the southern San Andreas Fault or a magnitude 7 earthquake on the Hayward Fault.
Of that total, the five counties of Southern California — LA, Orange, Riverside, San Bernardino and Ventura counties — would lose nearly $150 billion. And the nine-county San Francisco Bay Area would lose about $90 billion.
“It’s a sobering reminder of why we need to prepare for those rare but large earthquakes, as only one major event can overshadow the cost of the more frequent but smaller ones,” USGS director David Applegate said in a statement.
The report’s authors calculated an “annual” earthquake loss to calculate the cost of earthquake damage on an annual basis.
It’s similar to how auto insurers calculate the premium people pay annually: People may get into a collision once every few years, but insurers calculate an annual bill for drivers that takes into account the annual average expected cost of future collisions. How much the annual car insurance premium will be can vary depending on factors such as the driver’s age, accident history, and the type of vehicle being driven.
The magnitude 6.7 earthquake that struck Northridge in 1994 caused a whopping $20 billion in damage and more than $40 billion in economic loss, “making it the costliest earthquake disaster in U.S. history,” the agency said. Geological survey of California.
And the damage from that quake centered in the San Fernando Valley suburbs pales in comparison to the destruction a major quake centered under older neighborhoods, such as in downtown LA, would cause.
The magnitude of the 1994 earthquake was relatively moderate. In contrast, a magnitude 7.8 earthquake would produce 45 times more energy, and such a quake has not struck Southern California since 1857 and Northern California since 1906.
The last earthquake with a magnitude of 7.8 on the Richter scale occurred in February, resulting in strong tremors in Turkey and Syria. More than 50,000 people died.
A significant portion of California buildings constructed in the 20th century are vulnerable to earthquake or collapse damage. Adapting them now would make cities much more resilient – keeping people alive, keeping homes intact and workplaces and neighborhoods functional.
The state’s rise in property values could allow some owners to use the equity they’ve built up to fund retrofits, experts say. A retrofit can now cost much less than repairing extensive damage after an earthquake, which can destroy a building to the point where it may need to be replaced.
Some California cities have required property owners to retrofit certain types of vulnerable buildings. A Los Angeles law passed in 2015 requiring apartment buildings with flimsy first floors — often used for carports — to be reinforced has resulted in retrofits of more than 8,700 out of 12,400. That’s one completion rate of 70%. An analysis estimated that at least $1.3 billion was spent on those retrofits.
FEMA and state officials have worked to make grants available for retrofits. Homeowners in select zip codes in Los Angeles, Pasadena, San Francisco, Oakland, and Berkeley can apply retrofit grants of up to $13,000 through the end of May to reinforce “soft houses,” where a top-heavy living space is built over a garage vulnerable to collapse in an earthquake.
“This study reinforces the nation’s need to be proactive in protecting communities from threats such as earthquakes,” FEMA deputy administrator Erik Hooks said in a statement. “This includes adopting the latest seismic building codes and investing in earthquake resistance projects.”
But many other California cities have not acted to demand retrofits. And even in LA, city officials have yet to address the potential seismic risk of older steel-framed high-rises built before the 1994 Northridge earthquake. The USGS has said it is plausible that five steel-frame buildings in Southern California could collapse in a hypothetical magnitude 7.8 earthquake on the San Andreas Fault, and 10 could be so damaged that it would no longer be safe to occupy them.
Some cities lag far behind. Much of the Inland Empire, which includes Riverside and San Bernardino counties, still has many older brick buildings that have not been retrofitted—one of the most risky structures in an earthquake. They can collapse, killing not only the occupants of the buildings, but also raining projectiles onto nearby sidewalks, parking lots and roads, flinging the remains of brick walls away with such force that they can crush cars and buses.
In the 1989 magnitude 6.9 Loma Prieta earthquake, a brick wall in San Francisco fell into a parking lot, crushing cars; five people died. And in a magnitude 6.3 earthquake that struck Christchurch, New Zealand in 2011, falling stones rained on Red bus No. 702which killed eight people, including the driver.
The number of people that need to be housed after a major earthquake can be enormous. The study estimated that an earthquake so large that it had a 1 in 250 chance of happening in any given year could cause more than 200,000 people to need short-term shelter in California. In an earthquake so large as to have a 1 in 1,000 chance in any given year, more than 700,000 people would need short-term shelter.
Cars were crushed by a brick wall that collapsed near 5th and Townsend streets in San Francisco during the 1989 Loma Prieta earthquake.
(CE Meyer / US Geological Survey)
The latest study also paints a more realistic picture of expected damage in places like LA and the San Francisco Bay Area, where many buildings sit atop basins that amplify ground movement during an earthquake, Jaiswal said. Such shaking can result in a worse outcome for tall buildings that sit on top of basins compared to buildings built directly on bedrock.
“If you have a deep basin, with sediments lying on top of the hard rock, those ground movements are amplified,” Jaiswal said.
Compared to previous models, the latest report accounts for softer soil and basin conditions locally, which has contributed to the increase in projected damage costs for places like LA and the Bay Area.
Other areas with an increase in earthquake hazard from the previous model include the Salt Lake City area and much of the island of Hawaii, the Maui Valley, and the south shore of Oahu.
The Seattle area had an estimated annual earthquake loss of $781 million; the Portland, Oregon area, $403 million; the Salt Lake City area, $174 million; the Memphis, Tennessee, area, $131 million; and the New York City area, $49 million.
The fact that earthquake risk exists in areas of the eastern US may come as a surprise, but such earthquakes can happen. a magnitude 5.8 earthquake near Mineral, Va.caused $200 million to $300 million in damage in 2011 and made $15 million in repairs to the Washington Monument.
Other damaging earthquakes in the eastern US that have been recorded include one of Cape Ann, Mass.in 1755, estimated at magnitude 5.9, resulting in damage to the Boston waterfront; an estimated earthquake with a magnitude of 4.5 near Petersburg, Va., in 1774, which pushed houses off their foundations and was felt by Thomas Jefferson; and an estimate magnitude 7 earthquake near Charleston, SC, in 1886 that killed 60 people, according to the USGS.
There were three major earthquakes in the early 19th century Seismic Zone of New Madrid, around the area along the Mississippi River where Tennessee, Kentucky, Illinois, Missouri, and Arkansas meet. The largest earthquakes were a magnitude 7.5 in December 1811, a magnitude 7.3 in January 1812, and a magnitude 7.5 in February 1812.
“Earthquakes are a national problem,” the USGS said in a statement.
New York City has a small chance of a damaging earthquake, but an earthquake that does occur could still cause significant damage due to the density of the city and the age of the buildings, the city government said. disaster management agency. A major risk to New York City is a large number of older brick buildings that have not been retrofitted.
