Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Researcher assesses the seismic hazard of the central-Eastern United States

10.01.2011

As the U.S. policy makers renew emphasis on the use of nuclear energy in their efforts to reduce the country’s oil dependence, other factors come into play. One concern of paramount importance is the seismic hazard at the site where nuclear reactors are located.

Russell A. Green<http://www.cee.vt.edu/geot/index.php?do=view&content=0&apps=2&level=&id=&pid=e85c461d1d76520542b381b267c20fd1> (http://www.cee.vt.edu/geot/index.php?do=view&content=0&apps=2&level=&id=&pid=e85c461d1d76520542b381b267c20fd1), associate professor of civil and environmental engineering at Virginia Tech, spent five years as an earthquake engineer for the U.S. Defense Nuclear Facilities Safety Board in Washington, D.C., prior to becoming a university professor. Part of his responsibility at the safety board was to perform seismic safety analyses on the nation’s defense nuclear facilities.

“I found the greatest uncertainty in seismic analyses was related to the ground motions used in the analyses. ... Many of the facilities being analyzed were already built and operating, and the facilities were already heavily contaminated with radioactive material,” Green said.

An immediate concern then became how and which buildings to retrofit. The balance in the decision-making process was between using overly conservative ground motions and potentially wasting “hundreds of millions of dollars in unnecessary retrofits” versus using less demanding motions and potentially “placing facility workers, neighboring towns, and cities at risk,” Green added.

Green’s concerns and expertise in earthquake engineering earned him a National Science Foundation (NSF) Faculty Early Career Development (CAREER) award in 2006 valued at more than $400,000. He has used this support for the development of procedures for collecting and analyzing data required for assessing the seismic hazard in regions where moderate to large earthquakes would have significant consequences, yet they remain low-probability events.

Green said a “huge shift” in the engineering profession’s approach to reducing seismic risk has occurred during the past decade. Building codes have been modified to include performance-based earthquake engineering (PBEE) concepts. This differs from the previous traditional design approach that used “life safety as the primary design goal,” Green explained. “PBEE is based on the premise that performance can be predicted and evaluated with quantifiable confidence, allowing the engineer, together with the client, to make intelligent and informed trade-offs based on life-cycle considerations rather than construction costs alone.”

To implement PBEE and to calculate the annual probability of specific losses due to seismic events, engineers need to know the fragility of structural systems and the probabilistically quantified seismic hazard.

To conduct his research, Green is focusing on paleoseismology, the study of the timing, location, and size of prehistoric/pre-instrumental earthquakes, ranging from those that occurred hundreds to tens of thousands of years ago.

“I believe that earthquake engineering encompasses geology, seismology, geotechnical engineering, structural engineering, urban planning, and emergency response,” Green said.

“The appropriate selection of ground motions is particularly difficult because many critical facilities are located in the Central and Eastern U.S. and in the Pacific Northwest,” Green said. “We know moderate to large earthquakes have occurred in these regions. We just do not know how large the events were, how often they occurred, or the characteristics of the associated ground shaking, such as duration, amplitude, and frequency content.”

Unlike many places in the western U.S. where excavations can be used to determine the past movement on earthquake faults, in the central-eastern U.S. the locations of most faults are unknown and/or the faults are too deep to excavate. As a result, Green is concentrating his work on the development and validation of paleoliquefaction procedures. Soil liquefaction is the transition of soil from a solid to a liquefied state. Earthquakes are one cause of liquefaction, with the evidence of liquefaction often remaining in the soil profile for many thousands of years after the earthquake.

“Paleoliquefaction investigations are the most plausible way to determine the recurrence time of moderate to large earthquakes in the central-eastern U.S.,” Green said. “By extending the earthquake record into prehistoric times, paleoseismic investigations remove one of the major obstacles to implementing PBEE across the U.S.”

To determine the age of a paleoliquefaction feature, researchers might use any one of a number of techniques including radiocarbon dating, optically stimulated luminescence, or archeological evidence.

Green said his work will address the “gaps in knowledge that typically stem from uncertainties related to analytical techniques used in back-calculations, the amount and quantity of paleoliquefaction data, and the significance of changes in the geotechnical properties of post-liquefied sediments such as aging and density changes.”

In addition to his work studying paleoearthquakes, Green has also been involved in performing field studies of several recent earthquakes. He has performed post-earthquake field studies of the 2008 Mt. Carmel, Ill., magnitude 5.2 earthquake; the 2008 Iwate Miyagi-Nairiku, Japan, magnitude 6.9 earthquake; the 2010 Haiti, magnitude 7.0 earthquake; and the 2010 Darfield, New Zealand, magnitude 7.1 earthquake. The latter two field studies were National Science Foundation sponsored Geo-Engineering Extremes Events Reconnaissance investigations, with Green serving as the U.S. team leader for the Darfield earthquake study.

The College of Engineering<http://www.eng.vt.edu/> (http://www.eng.vt.edu/) at Virginia Tech is internationally recognized for its excellence in 14 engineering disciplines and computer science. The college's 6,000 undergraduates benefit from an innovative curriculum that provides a "hands-on, minds-on" approach to engineering education, complementing classroom instruction with two unique design-and-build facilities and a strong Cooperative Education Program. With more than 50 research centers and numerous laboratories, the college offers its 2,000 graduate students opportunities in advanced fields of study such as biomedical engineering, state-of-the-art microelectronics, and nanotechnology. Virginia Tech, the most comprehensive university in Virginia, is dedicated to quality, innovation, and results to the commonwealth, the nation, and the world.

Related Links

* Disaster management: A complex world brings new vulnerabilities<http://www.vtnews.vt.edu/articles/2009/12/2009-943.html> (http://www.vtnews.vt.edu/articles/2009/12/2009-943.html)
This story can be found on the Virginia Tech News website:
http://www.vtnews.vt.edu/articles/2011/01/010611-engineering-greenearth.html

Lynn A. Nystrom | VT News
Further information:
http://www.eng.vt.edu/

More articles from Earth Sciences:

nachricht Novel method for investigating pore geometry in rocks
18.06.2018 | Kyushu University, I2CNER

nachricht Decades of satellite monitoring reveal Antarctic ice loss
14.06.2018 | University of Maryland

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Overdosing on Calcium

Nano crystals impact stem cell fate during bone formation

Scientists from the University of Freiburg and the University of Basel identified a master regulator for bone regeneration. Prasad Shastri, Professor of...

Im Focus: AchemAsia 2019 will take place in Shanghai

Moving into its fourth decade, AchemAsia is setting out for new horizons: The International Expo and Innovation Forum for Sustainable Chemical Production will take place from 21-23 May 2019 in Shanghai, China. With an updated event profile, the eleventh edition focusses on topics that are especially relevant for the Chinese process industry, putting a strong emphasis on sustainability and innovation.

Founded in 1989 as a spin-off of ACHEMA to cater to the needs of China’s then developing industry, AchemAsia has since grown into a platform where the latest...

Im Focus: First real-time test of Li-Fi utilization for the industrial Internet of Things

The BMBF-funded OWICELLS project was successfully completed with a final presentation at the BMW plant in Munich. The presentation demonstrated a Li-Fi communication with a mobile robot, while the robot carried out usual production processes (welding, moving and testing parts) in a 5x5m² production cell. The robust, optical wireless transmission is based on spatial diversity; in other words, data is sent and received simultaneously by several LEDs and several photodiodes. The system can transmit data at more than 100 Mbit/s and five milliseconds latency.

Modern production technologies in the automobile industry must become more flexible in order to fulfil individual customer requirements.

Im Focus: Sharp images with flexible fibers

An international team of scientists has discovered a new way to transfer image information through multimodal fibers with almost no distortion - even if the fiber is bent. The results of the study, to which scientist from the Leibniz-Institute of Photonic Technology Jena (Leibniz IPHT) contributed, were published on 6thJune in the highly-cited journal Physical Review Letters.

Endoscopes allow doctors to see into a patient’s body like through a keyhole. Typically, the images are transmitted via a bundle of several hundreds of optical...

Im Focus: Photoexcited graphene puzzle solved

A boost for graphene-based light detectors

Light detection and control lies at the heart of many modern device applications, such as smartphone cameras. Using graphene as a light-sensitive material for...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Munich conference on asteroid detection, tracking and defense

13.06.2018 | Event News

2nd International Baltic Earth Conference in Denmark: “The Baltic Sea region in Transition”

08.06.2018 | Event News

ISEKI_Food 2018: Conference with Holistic View of Food Production

05.06.2018 | Event News

 
Latest News

Carbon nanotube optics provide optical-based quantum cryptography and quantum computing

19.06.2018 | Physics and Astronomy

How to track and trace a protein: Nanosensors monitor intracellular deliveries

19.06.2018 | Life Sciences

New material for splitting water

19.06.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>