Featured Research

from universities, journals, and other organizations

New evidence for regular magnitude 8 earthquakes, study of New Zealand fault shows

Date:
July 25, 2012
Source:
University of Nevada, Reno
Summary:
A new study finds that very large earthquakes have been occurring relatively regularly on the Alpine Fault along the southwest coastline of New Zealand for at least 8,000 years.

University of Nevada, Reno seismologist Glenn Biasi and colleagues at GNS Science in New Zealand dig into layers of silt along the Hokuri River in New Zealand’s Southern Alps on the South Island to find ancient samples of leaves, small twigs and marsh plants for radiocarbon dating. The team established that the Alpine Fault causes, on average, earthquakes of around a magnitude 8 every 330 years. They estimate the 50-year probability of a large Alpine fault earthquake to be about 27 percent.
Credit: Photo courtesy University of Nevada, Reno.

A new study published in the journal Science, co-authored by University of Nevada, Reno's Glenn Biasi and colleagues at GNS Science in New Zealand, finds that very large earthquakes have been occurring relatively regularly on the Alpine Fault along the southwest coastline of New Zealand for at least 8,000 years.

The Alpine Fault is the most hazardous fault on the South Island of New Zealand, and about 80 miles northwest of the South Island's main city of Christchurch.

The team developed evidence for 22 earthquakes at the Hokuri Creek site, which, with two additional from nearby, led to the longest continuous earthquake record in the world for a major plate boundary fault. The team established that the Alpine Fault causes, on average, earthquakes of around a magnitude 8 every 330 years. Previous data put the intervals at about 485 years.

Relative motion of Australian and Pacific plates across the Alpine Fault averages almost an inch per year. This motion builds up, and then is released suddenly in large earthquakes. The 530-mile-long fault is among the longest, straightest and fastest moving plate boundary faults in the world. More than 23 feet of potential slip has accumulated in the 295 years since the most recent event in A.D. 1717.

Biasi, working with the GNS Science team led by Kelvin Berryman, used paleoseismology to extend the known seismic record from 1000 years ago to 8,000 years ago. They estimated earthquake dates by combining radiocarbon dating leaves, small twigs and marsh plants with geologic and other field techniques.

"Our study sheds new light on the frequency and size of earthquakes on the Alpine Fault. Earthquakes have been relatively periodic, suggesting that this may be a more general property of simple plate boundary faults worldwide," Biasi, of the Nevada Seismological Laboratory said. "By comparison, large earthquakes on California's San Andreas Fault have been less regular in size and timing."

"Knowing the average rate of earthquakes is useful, but is only part of the seismic hazard equation," he said. "If they are random in time, then the hazard does not depend on how long it has been since the most recent event. Alpine Fault earthquakes are more regular in their timing, allowing us to use the time since the last earthquake to adjust the hazard estimate. We estimate the 50-year probability of a large Alpine fault earthquake to be about 27 percent."

A magnitude 7.1 earthquake centered near Christchurch, the largest city in the South Island of New Zealand, caused extensive damage to buildings on Sept. 2, 2010, and no deaths. On Feb. 22, 2011, a triggered aftershock measuring magnitude 6.3, with one of the strongest ground motions ever recorded worldwide in an urban area, struck the city killing 185 people.


Story Source:

The above story is based on materials provided by University of Nevada, Reno. Note: Materials may be edited for content and length.


Journal Reference:

  1. K. R. Berryman, U. A. Cochran, K. J. Clark, G. P. Biasi, R. M. Langridge, P. Villamor. Major Earthquakes Occur Regularly on an Isolated Plate Boundary Fault. Science, 2012; 336 (6089): 1690 DOI: 10.1126/science.1218959

Cite This Page:

University of Nevada, Reno. "New evidence for regular magnitude 8 earthquakes, study of New Zealand fault shows." ScienceDaily. ScienceDaily, 25 July 2012. <www.sciencedaily.com/releases/2012/07/120725162446.htm>.
University of Nevada, Reno. (2012, July 25). New evidence for regular magnitude 8 earthquakes, study of New Zealand fault shows. ScienceDaily. Retrieved September 22, 2014 from www.sciencedaily.com/releases/2012/07/120725162446.htm
University of Nevada, Reno. "New evidence for regular magnitude 8 earthquakes, study of New Zealand fault shows." ScienceDaily. www.sciencedaily.com/releases/2012/07/120725162446.htm (accessed September 22, 2014).

Share This



More Earth & Climate News

Monday, September 22, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Hundreds of Thousands Hit NYC Streets to Protest Climate Change

Hundreds of Thousands Hit NYC Streets to Protest Climate Change

AFP (Sep. 22, 2014) Celebrities, political leaders and the masses rallied in New York and across the globe demanding urgent action on climate change, with organizers saying 600,000 people hit the streets. Duration: 01:19 Video provided by AFP
Powered by NewsLook.com
French FM Urges 'powerful' Response to Global Warming

French FM Urges 'powerful' Response to Global Warming

AFP (Sep. 22, 2014) French Foreign Minister Laurent Fabius on Monday warned about the potential "catastrophe" if global warming was not dealt with in a "powerful" way. Duration: 01:08 Video provided by AFP
Powered by NewsLook.com
Ongoing Drought, Fighting Put Somalia at Risk of Famine

Ongoing Drought, Fighting Put Somalia at Risk of Famine

AFP (Sep. 22, 2014) After a year of poor rains and heavy fighting Somalia is again at risk of famine, just three years after food shortages killed 260,000 people. Duration: 01:10 Video provided by AFP
Powered by NewsLook.com
Rockefeller Oil Heirs Switching To Clean Energy

Rockefeller Oil Heirs Switching To Clean Energy

Newsy (Sep. 22, 2014) The Rockefellers — heirs to an oil fortune that made the family name a symbol of American wealth — are switching from fossil fuels to clean energy. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins