PRESS-NEWS.org - Press Release Distribution
PRESS RELEASES DISTRIBUTION

Quake-triggered landslides pose significant hazard for Seattle, new study details potential damage

2013-10-22
(Press-News.org) Contact information: Nan Broadbent
press@seismosoc.org
408-431-9885
Seismological Society of America
Quake-triggered landslides pose significant hazard for Seattle, new study details potential damage

SAN FRANCISCO -- SAN FRANCISCO -- A new study suggests the next big quake on the Seattle fault may cause devastating damage from landslides, greater than previously thought and beyond the areas currently defined as prone to landslides. Published online Oct. 22 by the Bulletin of the Seismological Society of America (BSSA), the research offers a framework for simulating hundreds of earthquake scenarios for the Seattle area.

"A major quake along the Seattle fault is among the worst case scenarios for the area since the fault runs just south of downtown. Our study shows the need for dedicated studies on seismically induced landsliding" said co-author Kate Allstadt, doctoral student at University of Washington.

Seattle is prone to strong shaking as it sits atop the Seattle Basin – a deep sedimentary basin that amplifies ground motion and generates strong seismic waves that tend to increase the duration of the shaking. The broader region is vulnerable to earthquakes from multiple sources, including deep earthquakes within the subducted Juan de Fuca plate, offshore megathrust earthquakes on Cascadia subduction zone and the shallow crustal earthquakes within the North American Plate.

For Seattle, a shallow crustal earthquake close to the city would be most damaging. The last major quake along the Seattle fault was in 900 AD, long before the city was established, though native people lived in the area. The earthquake triggered giant landslides along Lake Washington, causing entire blocks of forest to slide into the lake.

"There's a kind of haunting precedence that tells us that we should pay attention to a large earthquake on this fault because it happened in the past," said Allstadt, who also serves as duty seismologist for the Pacific Northwest Seismic Network. John Vidale of University of Washington and Art Frankel of the U.S. Geological Survey (USGS) are co-authors of the study, which was funded by the USGS.

While landslides triggered by earthquakes have caused damage and casualties worldwide, they have not often been the subject of extensive quantitative study or fully incorporated into seismic hazard assessments, say authors of this study that looks at just one scenario among potentially hundreds for a major earthquake in the Seattle area.

Dividing the area into a grid of 210-meter cells, they simulated ground motion for a magnitude 7 Seattle fault earthquake and then further subdivided into 5-meter cells, applying anticipated amplification of shaking due to the shallow soil layers. This refined framework yielded some surprises.

"One-third of the landslides triggered by our simulation were outside of the areas designated by the city as prone to landsliding," said Allstadt. "A lot of people assume that all landslides occur in the same areas, but those triggered by rainfall or human behavior have a different triggering mechanism than landslides caused by earthquakes so we need dedicated studies."

While soil saturation -- whether the soil is dry or saturated with water – is the most important factor when analyzing the potential impact of landslides, the details of ground motion rank second. The amplification of ground shaking, directivity of seismic energy and geological features that may affect ground motion are very important to the outcome of ground failure, say authors.

The authors stress that this is just one randomized scenario study of many potential earthquake scenarios that could strike the city. While the results do not delineate the exact areas that will be affected in a future earthquake, they do illustrate the extent of landsliding to expect for a similar event.

The study suggests the southern half of the city and the coastal bluffs, many of which are developed, would be hardest hit. Depending upon the water saturation level of the soil at the time of the earthquake, several hundred to thousands of buildings could be affected citywide. For dry soil conditions, there are more than 1000 buildings that are within all hazard zones, 400 of those in the two highest hazard designation zones. The analysis suggests landslides could also affect some inland slopes, threatening key transit routes and impeding recovery efforts. For saturated soil conditions, it is an order of magnitude worse, with 8000 buildings within all hazard zones, 5000 of those within the two highest hazard zones. These numbers only reflect the number of buildings in high-risk areas, not the number of buildings that would necessarily suffer damage.

"The extra time we took to include the refined ground motion detail was worth it. It made a significant difference to our understanding of the potential damage to Seattle from seismically triggered landslides," said Allstadt, who would like to use the new framework to run many more scenarios to prepare for future earthquakes in Seattle.



INFORMATION:

The paper, "A Scenario Study of Seismically Induced Landsliding in Seattle Using Broadband Synthetic Seismograms," will be published in the December print edition of BSSA, which is the prestigious peer-reviewed journal of the Seismological Society of America.



ELSE PRESS RELEASES FROM THIS DATE:

Major Alzheimer's risk factor linked to red wine target

2013-10-22
Major Alzheimer's risk factor linked to red wine target Buck Institute study provides insight for new therapeutics that target the interaction between ApoE4 and a Sirtuin protein The major genetic risk factor for Alzheimer's disease (AD), present ...

Breast milk protein may be key to protecting babies from HIV infection

2013-10-22
Breast milk protein may be key to protecting babies from HIV infection DURHAM, N.C. – A substance in breast milk that neutralizes HIV and may protect babies from acquiring HIV from their infected mothers has been identified for the first time by researchers ...

Moderate to vigorous exercise boosts teens' academic performance

2013-10-22
Moderate to vigorous exercise boosts teens' academic performance Improvements over long term; particularly noticeable for girls' science results Regular moderate to vigorous exercise improves teens' academic performance, and particularly seems to help girls ...

Use of booze and drugs common among truck drivers on the road

2013-10-22
Use of booze and drugs common among truck drivers on the road Prevalence varies widely, but mainly linked to poor working conditions The use of booze and drugs among truck drivers on the road is common, but seems to be mainly linked to poor working conditions, ...

Study: No known hominin is ancestor of Neanderthals and modern humans

2013-10-22
Study: No known hominin is ancestor of Neanderthals and modern humans The search for a common ancestor linking modern humans with the Neanderthals who lived in Europe thousands of years ago has been a compelling subject for research. But a new study suggests the quest ...

Bottle feeding associated with increased risk of stomach obstruction in infants

2013-10-22
Bottle feeding associated with increased risk of stomach obstruction in infants Bottle feeding appears to increase the risk infants will develop hypertrophic pyloric stenosis (HPS), a form of stomach obstruction, and that risk seems to be magnified when mothers are older ...

Patients report doctors not telling them of overdiagnosis risk in screenings

2013-10-22
Patients report doctors not telling them of overdiagnosis risk in screenings A survey finds that most patients are not being told about the possibility of overdiagnosis and overtreatment as a result of cancer screenings, according to report in a research letter ...

Harvard researchers, pharma experts offer recommendations to expand access to clinical trial data

2013-10-22
Harvard researchers, pharma experts offer recommendations to expand access to clinical trial data Boston, MA – A new report by researchers from Harvard University and others in a working group convened by the Multi-Regional Clinical Trials Center (MRCT) ...

Less sleep associated with brain imaging findings of Alzheimer disease in elderly

2013-10-22
Less sleep associated with brain imaging findings of Alzheimer disease in elderly Getting less sleep and poor sleep quality are associated with abnormal brain imaging findings suggesting Alzheimer disease (AD) in older adults, according to a report published ...

Risk of Amazon rainforest dieback is higher than IPCC projects

2013-10-22
Risk of Amazon rainforest dieback is higher than IPCC projects A new study suggests the southern portion of the Amazon rainforest is at a much higher risk of dieback due to stronger seasonal drying than projections made by the climate models used in the ...

LAST 30 PRESS RELEASES:

Intra-arterial tenecteplase for acute stroke after successful endovascular therapy

Study reveals beneficial microbes that can sustain yields in unfertilized fields

Robotic probe quickly measures key properties of new materials

Climate change cuts milk production, even when farmers cool their cows

Frozen, but not sealed: Arctic Ocean remained open to life during ice ages

Some like it cold: Cryorhodopsins

Demystifying gut bacteria with AI

Human wellbeing on a finite planet towards 2100: new study shows humanity at a crossroads

Unlocking the hidden biodiversity of Europe’s villages

Planned hydrogen refuelling stations may lead to millions of euros in yearly losses

Planned C-sections increase the risk of certain childhood cancers

Adults who have survived childhood cancer are at increased risk of severe COVID-19

Drones reveal extreme coral mortality after bleaching

New genetic finding uncovers hidden cause of arsenic resistance in acute promyelocytic leukemia

Native habitats hold the key to the much-loved smashed avocado’s future

Using lightning to make ammonia out of thin air

Machine learning potential-driven insights into pH-dependent CO₂ reduction

Physician associates provide safe care for diagnosed patients when directly supervised by a doctor

How game-play with robots can bring out their human side

Asthma: patient expectations influence the course of the disease

UNM physician tests drug that causes nerve tissue to emit light, enabling faster, safer surgery

New study identifies EMP1 as a key driver of pancreatic cancer progression and poor prognosis

XPR1 identified as a key regulator of ovarian cancer growth through autophagy and immune evasion

Flexible, eco-friendly electronic plastic for wearable tech, sensors

Can the Large Hadron Collider snap string theory?

Stuckeman professor’s new book explores ‘socially sustainable’ architecture

Synthetic DNA nanoparticles for gene therapy

New model to find treatments for an aggressive blood cancer

Special issue of Journal of Intensive Medicine analyzes non-invasive respiratory support

T cells take aim at Chikungunya virus

[Press-News.org] Quake-triggered landslides pose significant hazard for Seattle, new study details potential damage