Experts Team Up on Tsunami Resilience in California plus 1 more

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Title: USGS Newsroom

Experts Team Up on Tsunami Resilience in California plus 1 more

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Experts Team Up on Tsunami Resilience in California

Posted: 04 Sep 2013 09:00 AM PDT

While scientists can't predict when a great earthquake producing a pan-Pacific tsunami will occur, thanks to new tools being developed by federal and state officials, scientists can now offer more accurate insight into the likely impacts when tsunamis occur. This knowledge can lead officials and the public to reduce the risk of the future tsunamis that will impact California.

What are the potential economic impacts? Which marinas could be destroyed? Who needs to be prepared for evacuations? A newly published report looks at these factors and more.

A hypothetical yet plausible scenario was developed where a tsunami is created by an earthquake offshore from the Alaskan peninsula and extends to the California coast. This is detailed in a new report titled, the U.S. Geological Survey's Science Application for Risk Reduction (SAFRR) Tsunami Scenario.

Some of the issues highlighted in the scenario include public safety and economic loss. In this scenario approximately 750,000 people would need to be evacuated, with 90,000 of those being tourists and visitors. Additionally, one-third of the boats in California's marinas could be damaged or completely sunk, resulting in $700 million in losses. It was concluded that neither of California's nuclear power plants would likely be damaged by this particular event.

Looking back to 2011, not only was Japan devastated by the magnitude 9.1 Tohoku earthquake, but the resulting tsunami also swept through California and caused $50-100 million of damage. This shows that tsunamis near and far can lead to billions of dollars in losses in California.

The SAFRR Tsunami Scenario is a collaborative effort between the USGS, the California Geological Survey, the California Governor's Office of Emergency Services, the National Oceanic and Atmospheric Administration, other agencies, and academic and other institutions.

"The good news is that three-quarters of California's coastline is cliffs, and thus immune to the harsher and more devastating impacts tsunamis could pose," said Lucy Jones, who is the USGS Science Advisor for Risk Reduction and leads the SAFRR Project. "The bad news is that the one-quarter at risk is some of the most economically valuable property in California."

"In order to effectively protect communities from tsunamis, we must first know what to plan for," continued Jones. "By starting with science, there is a clearer understanding on how tsunamis function and their potential impacts. The scenario will serve as a long-lasting resource to raise awareness and provide scientifically-sound and unbiased information to decision makers in California and abroad."

In this scenario, scientists specifically outline the likely inundation areas, current velocities in key ports and harbors, physical damage and repair costs; economic consequences; environmental impacts; social vulnerability; emergency management; and policy implications for California.

This scenario will also be the focus of discussion at a workshop series starting September 4 that is convened in partnership with the California Tsunami Hazard Mitigation Program. USGS scientists and partners will explain the scenario and results to stakeholders in the coastal communities of California. The workshops aims to establish a community of experts while fostering the use of science in decision-making.

The workshops will be hosted by the Cabrillo Marine Aquarium (September 4); Santa Barbara County Office of Emergency Management (September 5); San Diego County Office of Emergency Management (September 6); Santa Cruz County Office of Emergency Management (September 9); and the Port of San Francisco (September 10).

The SAFRR Project is the same USGS research group that produced the ShakeOut Scenario in 2008, examining the consequences of a probable major earthquake on the southern San Andreas Fault, and the ARkStorm Scenario in 2011, examining the risks associated with extreme rain events associated with atmospheric rivers.

The March 11, 2011 Tohoku-oki tsunami caused significant damage to ships and docks within Crescent City Harbor in California. A number of ships were sunk within the harbor. Because of extensive sedimentation and potential contaminated debris within the harbor, recovery efforts took over a year. Photo Credit: Rick Wilson, California Geological Survey. (Larger image)	Maximum current speeds for the Port of Los Angeles (POLA) and the Port of Long Beach (POLB), according to the SAFRR Tsunami Scenario. In the POLA, currents are strongest at Angels Gate, the Cabrillo Marina, the Boat Yard, and the old Navy Yard. Once the tsunami event is underway, navigation through the Gate would be very dangerous. In the Cabrillo Marina and Boat Yard, currents are likely strong enough to break apart floating docks, damage piles, and pull small vessels from their mooring lines. The strongest currents are found in the old Navy Yard; however there are no exposed floating assets in this immediate area. At the POLB, again strong currents are found at the Gate. Also in the POLB, strong and jet-like currents are predicted at the entrance to the main cargo container area (Pier J). Currents here may be strong enough to damage, and possible break, mooring lines. Photo Credit: SAFRR Tsunami Scenario. (Larger image)	Areas that would be inundated (in red) from the SAFRR Tsunami Scenario at Oakland Airport and Alameda in California. Large portions of Bay of Farm Island and Oakland Airport would be flooded. Photo Credit: SAFRR Tsunami Scenario. (Larger image)
Areas that would be inundated (in red) from the SAFRR Tsunami Scenario in Newport Beach in Orange County, California. This includes complete and partial flooding of islands and near overtopping of Balboa Peninsula. Photo Credit: SAFRR Tsunami Scenario. (Larger image)	A map of the California coast in the City of Long Beach showing areas predicted to be inundated (in red) by the SAFRR Tsunami scenario. These include the Long Beach Convention Center and many retail businesses. Photo Credit: SAFRR Tsunami Scenario. (Larger image)

Tsunami on the Delaware River? Study of Historical Quake and Early East Coast Seismicity

Posted: 03 Sep 2013 12:00 PM PDT

PASADENA, Calif. — Imagine the Delaware River abruptly rising toward Philadelphia in a tsunami-like wave of water. Scientists now propose that this might not be a hypothetical scenario. A newly published paper concludes that a modest (one-foot) tsunami-like event on the East Coast was generated in the past by a large offshore earthquake. This result may have potential ramifications for emergency management professionals, government officials, businesses and the general public.

Early in the morning of Jan. 8, 1817, earthquake shaking was felt along the Atlantic seaboard as far north as Baltimore, Md., and at least as far south as Charleston, S.C. Later that morning, a keen observer documented an abrupt rise in the tide on the Delaware River near Philadelphia, commenting on the earthquake felt earlier to the south, and remarking that the tidal swell was most likely "the reverberation or concussion of the earth operating on the watery element."

Scientists have previously interpreted this earthquake to have a magnitude around 6 and a location somewhere in the Carolinas or slightly offshore. In a new study, USGS research geophysicist Susan Hough and colleagues reconsider the accounts of shaking and, for the first time, consider in detail the Delaware River account. They show that the combined observations point to a larger magnitude and a location farther offshore than previously believed. In particular, they show that a magnitude-7.4 earthquake located 400-500 miles off South Carolina or Georgia could have generated a tsunami wave large enough to account for the tidal swell on the Delaware. Using new computer-assisted research techniques, they uncover first-hand accounts from newspapers and ships' logs that give a wider perspective on the 1817 event. Notably, the predicted timing of such a tsunami wave from this location matches the documented timing in the eyewitness account.

The USGS monitors earthquakes offshore, and in recent years has undertaken research to better understand shaking and tsunami hazard from offshore earthquakes and landslides. Scientific understanding of faults and geological processes in this part of the Atlantic is limited. Still, it has long been understood that large, infrequent offshore earthquakes may pose a tsunami hazard to the Atlantic coast. In 1978, a magnitude-6 earthquake occurred roughly 240 miles southwest of Bermuda, even farther offshore than the inferred location of the 1817 earthquake. In 1929, the magnitude-7.2 Grand Banks, Newfoundland, earthquake triggered a submarine landslide that generated a large tsunami. Waves 10-13 feet high struck the Newfoundland coast, killing 29 people and leaving 10,000 temporarily homeless. 

The inferred 1817 tsunami was significantly smaller than the Newfoundland disaster. However, the new interpretation by Hough and colleagues highlights the potential earthquake and tsunami hazard along the Atlantic seaboard from the still poorly understood offshore earthquake faults. The new study highlights that there is still work to be done to characterize this hazard in the southeastern United States. 

The study, "Reverberations on the Watery Element: A Significant, Tsunamigenic Historical Earthquake Offshore the Carolina Coast," by Susan E. Hough, Jeffrey Munsey, and Steven N. Ward, is published in the September/October issue of Seismological Research Letters.