Ancient quakes may point to sinking risk for part of California coast

The city of Long Beach is seen at dusk, California, U.S., September 8, 201

By Tom James

SEATTLE (Reuters) – The Big One may be overdue to hit California but scientists near Los Angeles have found a new risk for the area during a major earthquake: abrupt sinking of land, potentially below sea level.

The last known major quake on the San Andreas fault occurred in 1857, but three quakes over the last 2,000 years on nearby faults made ground just outside Los Angeles city limits sink as much as three feet, according to a study published Monday in the journal Scientific Reports.

Seismologists estimate the 800 mile-long San Andreas, which runs most of the length of the state, should see a large quake roughly every 150 years.

Scientists from California State University Fullerton and the United States Geological Survey found evidence the older quakes caused part of the coastline south of Long Beach to drop by one-and-a-half to three feet.

Today that could result in the area ending up at or below sea level, said Cal State Fullerton professor Matt Kirby, who worked with the paper’s lead author, graduate student Robert Leeper.

“It’s something that would happen relatively instantaneously,” Kirby said. “Probably today if it happened, you would see seawater rushing in.”

The study was limited to a roughly two-square-mile area inside the Seal Beach National Wildlife Refuge, near the Newport-Inglewood and Rose Canyon faults. Kirby acknowledged that the exact frequency of events on the faults is unclear, as is the risk that another quake will occur in the near future.

The smallest of the historic earthquakes was likely more intense than the strongest on record in the area, the magnitude 6.3 Long Beach earthquake of 1933, which killed 120 people and caused the inflation-adjusted equivalent of nearly a billion dollars in damage.

Today, the survey site is sandwiched by the cities of Huntington Beach and Long Beach, home to over 600,000 people, while nearby Los Angeles County has a population of 10 million.

Seismologist John Vidale, head of the University of Washington-based Pacific Northwest Seismic Network, said after reviewing the study he was skeptical such powerful quakes could occur very frequently in the area.

Kirby noted that the team could only collect soil core samples within the relatively undisturbed refuge, and that taking deeper samples would shed light on the seismic record even further back, potentially giving scientists more examples of similar quakes to work from.

(The story was refiled to correct the second paragraph to clarify timing of last known major quake on the San Andreas fault)

(Reporting by Tom James; Editing by Patrick Enright and James Dalgleish)

New research suggests 20th century sea levels rose at quickest pace since 800 B.C.

Climate scientists studying the Earth’s sea levels have determined that it was “extremely likely” those waters rose more rapidly in the 20th century than any other century in nearly 3,000 years.

Human-induced climate change contributed to the increase, the scientists wrote in Monday’s edition of the Proceedings of the National Academy of Sciences of the United States of America.

The research team found sea levels rose 14 centimeters (5.5 inches) in the 20th century, and its models suggest those numbers may have been different without the effects of climate change.

Without it, the team wrote it was “very likely” that seas would have seen a change that ranged from a 3 centimeter (a little more than an inch) drop to a 7 centimeter (2.75 inch) increase.

The study’s lead author was Bob Kopp, a climate scientist from Rutgers University.

In a message on his website, Kopp wrote that he and his colleagues concluded “with 95 percent probability” that the levels rose more rapidly last century than any other century since 800 B.C.

The study’s cutoff, which stretches back 28 centuries, “is not because the rate of global sea-level rise was probably faster before then,” Kopp wrote on his website, “but simply that the reconstruction quality isn’t good enough before then to have the same level of confidence.”

NASA says the global average sea level has risen another 6 centimeters since January 2000 and is currently rising at a rate of .4 millimeters every year. The agency says the increases are “a direct result of a changing climate,” as melting ice sheets and glaciers fuel the expansion.

Kopp wrote last century wasn’t the only time when global temperatures and sea levels moved together, pointing to a 400-year stretch from the 11th to 15th centuries. Temperatures fell about .2 degrees Celsius during that stretch, while sea levels dipped approximately 8 centimeters.

But the study found it was “very likely” that global sea levels have risen “over every 40-year interval since 1860,” as societies became more industrialized.

In December, 195 countries agreed to a landmark climate change pact that aims to reduce greenhouse gas emissions and prevent temperatures from reaching 2 degrees Celsius above their pre-industrial averages, a long-feared threshold.

But Kopp’s team warned that even with “extremely strong emissions abatement,” their models suggest seas could rise another 24 to 61 centimeters (9 to 24 inches) during the 21st century.

If emissions were to continue at “business-as-usual” levels this century, the research team said that sea levels could potentially rise between 52 and 131 centimeters (20 to 51 inches).

Study Shows Rising Sea-Levels Will Bring Drastic Flooding to the U.S.

In the latest study, a team of scientists discovered that millions of Americans may already live on land that is destined to be reclaimed by the sea.

While some locations are only at risk of flooding, others are doomed to flood in the distant future. However, the process could speed up due to the rise of carbon dioxide emissions and the destabilization of West Antarctica’s ice sheet.

“Future emissions will determine which areas we can continue to occupy or may have to abandon,” note the report’s researchers, led by Benjamin Strauss of Climate Central in Princeton, N.J. The research appeared Monday in the Proceedings of the National Academy of Sciences and was co-authored by Scott Kulp of Climate Central and Anders Levermann of the Potsdam Institute for Climate Impact Research in Germany.

The research states: “Carbon choices determine US cities committed to futures below sea level.” For every one degree Celsius of warming, the scientists estimate that the sea-level will rise about 2.3 meters over the next 2,000 years. However, there is a possibility that it could happen sooner.

Using the link between climate warming and eventual ice melt, the researchers estimate that with current carbon emissions, the world is already destined to see the sea-level rise 1.6 meters – more than five feet. That isn’t taking into consideration the increase of carbon emissions that will exist in the future, which could make the sea-level rise by more than seven feet.

If no action is taken on climate change, the locations of over 26 million Americans could be flooded with more than 1,500 U.S. cities and municipalities overrun with water.

“If we don’t cut emissions,” Strauss said, “we’re talking about losing American land [that’s] home to more people than live in any state, except for California and Texas. Home to more people than the state of Florida and New York.”

The authors of the study also directly acknowledge gaps in the research. This includes cities that have taken steps to deal with extreme flooding scenarios like New Orleans’ 26-foot-high sea wall. Louisiana is also contemplating diversions of the Mississippi River that would not only create new wetlands, but keep pace with the rising seas. This means that as the sea-levels slowly rise, cities might be able to adapt.