Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Punctuated earthquakes for New Madrid area: New research uncovers cluster of past events

07.11.2018

Annual Meeting of The Geological Society of America, Indianapolis, Ind.

In 1811 and 1812, the region around New Madrid, Missouri, experienced a number of major earthquakes. The final and largest earthquake in this sequence occurred on the Reelfoot fault, and temporarily changed the course of the Mississippi River. These earthquakes are estimated to be just shy of magnitude 8.0 and devastated towns along the Mississippi River--soil liquefied, houses collapsed, and chimneys toppled.


Richard Briggs, USGS, takes a close up look at the wall of the sackungen in the trench. The cracks from the earthquake occurred since deposition of the Peoria loess >11,000 years ago -- the light tan sediment seen here.

Courtesy of Ryan Gold.

Because of the 1811-1812 earthquakes, the New Madrid area is recognized as a high-hazard zone for potential future seismic events. Previous investigations found have also found evidence for multiple, older earthquake events preserved in the geologic record.

"We know there were also large earthquakes at ~1450 AD and at ~900 AD," says Ryan Gold of the U.S. Geological Survey (USGS), but frequent earthqakes along the fault may not be the norm.

"If earthquakes happen on the Reelfoot fault every 500 years, and have been doing so for hundreds of thousands of years, we would expect to see a mountain range there -- but we don't," says Gold. Instead, he suggests the modest fault scarp associated with the Reelfoot fault indicate that the earthquakes haven't been sustained over a long period of time.

To test this, USGS researchers wanted to look beyond the last few thousand years. Preserving long-records of past earthquakes can be a challenge for the Reelfoot fault because natural processes like rain and occasional floods on the Mississippi River can conspire to erase the record of past earthquakes. "That's coupled with anthropogenic effects -- lots of farming, forestry, [and] construction," says Gold.

Instead of studying the fault directly, the USGS team moved to the rolling hills around the Mississippi River, east of the Reelfoot fault. They noted a high concentration of depressions called sackungen (German word meaning "to sag") near the fault, and hypothesized that these sags are cracks in the ground caused by strong shaking from large earthquakes.

The USGS excavated a trench across one of the sackung that had formed in Peoria loess -- silt that was blown in during the last glacial period until as recently as around 11,000 years ago. Gold explained how the team hypothesized that a sackung crack forms during an earthquake, the middle of the crack falls downward, and sediment washes in from the shoulders -- thus recording the timing of the earthquake.

Their trench revealed four distinct packages of sediment, says Gold, adding he was pleased to see such a long record. "I figured we would only see the 1811 and 1812 earthquake sequence."

In the sackung, they dated all four packages of sediment and found they corresponded to previously identified earthquakes that occurred on the Reelfoot fault: 1812 AD, ~1450 AD, ~900 AD, and ~2300 BC. Importantly, they didn't find evidence for any additional earthquakes in the interval from ~4,300 to ~11,000 years ago. If the earthquake record preserved in the sackung is complete, "our record confirms that the tempo of earthquakes hasn't been sustained," says Gold.

Gold will present their findings on Tuesday at the Geological Society of America's Annual meeting in Indianapolis, Indiana. "Our results will hopefully encourage the seismic hazard community to consider the possibility that the tempo of faulting may be variable," says Gold. "Sometimes there may be very long intervals between earthquakes and sometimes the earthquakes may be more closely spaced."

The USGS team hopes their new results on New Madrid ruptures can provide insights to those who model risk and seismic hazard in the region. Gold says that refining and updating seismic hazards with more information on how a fault might rupture can help with building codes -- designing buildings just right to keep us safe, but not over-designed, which can waste resources.

Talk title: Four Major Holocene Earthquakes on The Reelfoot Fault, New Madrid Seismic Zone
https://gsa.confex.com/gsa/2018AM/webprogram/Paper320906.html

Presentation Time: 3:40 PM, Tuesday, 6 Nov.

Session: Earthquakes and Deformation in Eastern North America and Other Continental Interiors: What We Know, What We Don't, What We Think, and Which Is Which?
https://gsa.confex.com/gsa/2018AM/webprogram/Session45415.html

###

The Geological Society of America, founded in 1888, is a scientific society with members from academia, government, and industry in more than 100 countries. Through its meetings, publications, and programs, GSA enhances the professional growth of its members and promotes the geosciences in the service of humankind. Headquartered in Boulder, Colorado, GSA encourages cooperative research among earth, life, planetary, and social scientists, fosters public dialogue on geoscience issues, and supports all levels of earth-science education.

Christa Stratton | EurekAlert!
Further information:
http://www.geosociety.org/GSA/News/pr/2018/18-43.aspx

More articles from Earth Sciences:

nachricht Shrinking of Greenland's glaciers began accelerating in 2000, research finds
12.12.2019 | Ohio State University

nachricht One-third of recent global methane increase comes from tropical Africa
11.12.2019 | European Geosciences Union

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Virus multiplication in 3D

Vaccinia viruses serve as a vaccine against human smallpox and as the basis of new cancer therapies. Two studies now provide fascinating insights into their unusual propagation strategy at the atomic level.

For viruses to multiply, they usually need the support of the cells they infect. In many cases, only in their host’s nucleus can they find the machines,...

Im Focus: Cheers! Maxwell's electromagnetism extended to smaller scales

More than one hundred and fifty years have passed since the publication of James Clerk Maxwell's "A Dynamical Theory of the Electromagnetic Field" (1865). What would our lives be without this publication?

It is difficult to imagine, as this treatise revolutionized our fundamental understanding of electric fields, magnetic fields, and light. The twenty original...

Im Focus: Highly charged ion paves the way towards new physics

In a joint experimental and theoretical work performed at the Heidelberg Max Planck Institute for Nuclear Physics, an international team of physicists detected for the first time an orbital crossing in the highly charged ion Pr⁹⁺. Optical spectra were recorded employing an electron beam ion trap and analysed with the aid of atomic structure calculations. A proposed nHz-wide transition has been identified and its energy was determined with high precision. Theory predicts a very high sensitivity to new physics and extremely low susceptibility to external perturbations for this “clock line” making it a unique candidate for proposed precision studies.

Laser spectroscopy of neutral atoms and singly charged ions has reached astonishing precision by merit of a chain of technological advances during the past...

Im Focus: Ultrafast stimulated emission microscopy of single nanocrystals in Science

The ability to investigate the dynamics of single particle at the nano-scale and femtosecond level remained an unfathomed dream for years. It was not until the dawn of the 21st century that nanotechnology and femtoscience gradually merged together and the first ultrafast microscopy of individual quantum dots (QDs) and molecules was accomplished.

Ultrafast microscopy studies entirely rely on detecting nanoparticles or single molecules with luminescence techniques, which require efficient emitters to...

Im Focus: How to induce magnetism in graphene

Graphene, a two-dimensional structure made of carbon, is a material with excellent mechanical, electronic and optical properties. However, it did not seem suitable for magnetic applications. Together with international partners, Empa researchers have now succeeded in synthesizing a unique nanographene predicted in the 1970s, which conclusively demonstrates that carbon in very specific forms has magnetic properties that could permit future spintronic applications. The results have just been published in the renowned journal Nature Nanotechnology.

Depending on the shape and orientation of their edges, graphene nanostructures (also known as nanographenes) can have very different properties – for example,...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

The Future of Work

03.12.2019 | Event News

First International Conference on Agrophotovoltaics in August 2020

15.11.2019 | Event News

Laser Symposium on Electromobility in Aachen: trends for the mobility revolution

15.11.2019 | Event News

 
Latest News

Supporting structures of wind turbines contribute to wind farm blockage effect

13.12.2019 | Physics and Astronomy

Chinese team makes nanoscopy breakthrough

13.12.2019 | Physics and Astronomy

Tiny quantum sensors watch materials transform under pressure

13.12.2019 | Materials Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>