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Sunken coastline and higher flooding risks: Scientists chart a worst-quake scenario

A coastal area.
The Samoa Peninsula in Eureka, Calif., on Sept. 2, 2022.
(Myung J. Chun / Los Angeles Times)

Good morning. Here’s what you need to know to start your day.

A worst-quake scenario

The Cascadia subduction zone might not be on the minds of most Californians, but it was for more than a dozen geologists and other scientists in a recent study analyzing flood risks along the Pacific coast.

Sea-level rise is the typical focus of such studies, but the authors focused on another hazard that experts say is a matter of when, not if: a megaquake.

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According to the study, when the next magnitude 8-plus temblor occurs along the Cascadia subduction zone, which stretches from Northern California up to Canada’s Vancouver Island, it could cause sudden subsidence (aka land sinking) of 1.6 to 6.6 feet, dramatically heightening flood risk.

“Earthquake deformation modeling and geospatial analysis show that [land sinking] from a great earthquake at Cascadia today could double the flood exposure of residents, structures, and roads,” the authors wrote.

A map of the Pacific Ocean and coastal areas and a red zone around it.
This map shows the location of the Cascadia subduction zone.
(FEMA)
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The study, published Monday in the journal Proceedings of the National Academy of Sciences, concluded that the worst-case quake scenario would expand the area at risk of flooding by 116 square miles. That’s 2½ times the size of San Francisco, The Times’ expert earthquake reporter Rong-Gong Lin II noted in his coverage this week.

“Traditionally, scientists and government officials have focused on climate-change-driven sea-level rise to calculate the projected increased risk of coastal flooding,” Ron explained, “But the study argues that neglecting the role of major earthquakes would be shortsighted.”

Some parts of the Pacific coastline are already sinking, “amplifying local relative sea-level rise (RSLR),” the authors noted. That includes California’s Humboldt Bay area, which is sinking at the highest rate along the whole Pacific coastline, according to the study.

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The Humboldt Bay region, which includes the area around Eureka and Arcata, was identified in the study as especially prone to major land sinking in the event of a megaquake. Several other communities along the Oregon and Washington’s coastline were also highlighted.

This from the study caught my eye: Some areas along the Pacific coastline are actually rising slowly due to how the tectonic plates are moving. For now, that’s a bit of a buffer against sea-level rise, but it won’t last much longer, the authors wrote.

“By [about] 2030, rates of climate-driven sea-level rise are expected to outpace gradual uplift,” the study states, adding that over the 70 years after that, sea levels are projected to rise roughly 1 to 3 feet.

You can read more about the study and the history of major quakes in Ron’s full story.

Today’s top stories

A building surrounded by trees.
The settlement includes thousands of claims from victims who said they were sexually abused, including at the now-shuttered MacLaren Children’s Center, above.
(Robert Gauthier/Los Angeles Times)

L.A. County approves a $4-billion sex abuse settlement, the largest in U.S. history

LAFD union head made $540,000 in a year, with huge overtime payouts

  • LAFD union leaders have padded their own paychecks with overtime, even as they complained that the LAFD did not have enough money to keep the city safe.
  • In response to The Times’ inquiries, the LAFD said it has launched a “comprehensive review and overhaul” of its procedures for tracking the hours and reimbursement of those on leave for the union.

What else is going on

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Commentary and opinions

This morning’s must reads

A woman holds a palm frond while standing in rubble.
Sunny Mills stands in the rubble of her home that burned in the Eaton Fire. This self-portrait inspired her to take more tintype photographs throughout Altadena.
(Sunny Mills)

Hauntingly beautiful tintype photos memorialize what was lost in Altadena. While everyone’s seen images of the devastation, no photographers have captured the sadness quite as well as Sunny Mills, a set decorator who lost her home in the fire. Skilled in tintype photography, Mills has leaned into her hobby since Jan. 7, using a pair of cameras she was given and whatever nervous energy she has to head out into the community, shooting pictures of Altadenans with the structures they’ve lost.

Other must reads


How can we make this newsletter more useful? Send comments to essentialcalifornia@latimes.com.

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For your downtime

Rugs are displayed inside a rug shop
(Juliana Yamada/Los Angeles Times)

Going out

Staying in

And finally ... from our archives

A train along bluffs next to an ocean.
A Surfliner train by Amtrak travels along the collapsing bluffs in Del Mar, Calif.
(John Gibbins / San Diego Union-Tribune)

On May 1, 1971, Amtrak began service, operating nearly all intercity passenger trains in the United States.

In California, traveling by car is the most popular way to travel. But the train is the best mode of vacation transportation. Last spring, The Times published seven epic day trips to take by train from Union Station.

Have a great day, from the Essential California team

Ryan Fonseca, reporter
Andrew Campa, Sunday reporter
Kevinisha Walker, multiplatform editor
Christian Orozco, assistant editor
Karim Doumar, head of newsletters

Check our top stories, topics and the latest articles on latimes.com.

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