Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Alpine fault in New Zealand not your average fault

19.08.2004


Ents, orcs and hobbits may have trod upon New Zealand soils, but beneath the Southern Island lies a giant earthquake fault that may help seismologists understand how the Earth moves and bends, according to a Penn State seismologist.



"One of the issues that makes the Alpine fault interesting is that while it is a strike slip fault for most of its length, it begins in a transition from a subduction zone to a strike slip fault," says Dr. Kevin Furlong, professor of geosciences. "Most of the major faults in the world that are strike slip faults – San Andreas, Anatolian in Turkey -- initiate quite differently, but this is different because the subduction is ripping off part of the Australian plate before it joins the Alpine fault."

Subduction occurs when one of the Earth’s tectonic plates slides beneath another plate. The subduction area or zone is usually the location for earthquakes and volcanic activity. Mt. St. Helens formed in a subduction zone. The Alpine fault does not have volcanic activity. Strike slip faults occur when two tectonic plates slide past each other.


The origin of the Alpine fault is located in the transition area between Fiordland and the Southern Alps on the South Island of New Zealand near Milford Sound. Here, the Australian plate meets the Pacific plate. While most other strike slip faults begin as an area of many small faults and eventually coalesce into one fault that dominates, the Alpine fault begins as a single fault.

"The fault is moving at about an inch and a quarter (30 mm) a year, tectonic plate speed, right from the beginning, which is very fast for a new fault," Furlong told attendees at the 2004 Western Pacific Geophysics Meeting today (Aug. 18) in Honolulu. "We would like to get at the physics of what is happening on that fault."

At the origin of the Alpine fault, the Pacific plate and the Australian plate have a small jog or notch forming a tiny subduction zone of about 60 miles (100 km) by 120 miles (200 km). On Aug. 20, 2003, an earthquake of magnitude 7.2 occurred in this area.

"We are interpreting this earthquake as a reflection of the tearing of the plate when it transitions from subducting to a strike slip zone," says Furlong. "To match the observations, we need a tear in the plate."

There have been no major earthquakes on the main portion of the Alpine fault in the last 100 years. Paleoseismologists believe that there was an earthquake in the 1700s, but their calculations are still uncertain.

"We know that there is at present significant seismicity at the southern end of the fault and at the northern end where the fault changes directions, but the central portion is relatively aseismic," says Furlong. "We do not know if this is normal or not."

While earthquake monitoring on the Alpine fault is not as dense as on the San Andreas, records show that earthquakes of magnitude 3 occur quite frequently, but not in the central portion of the fault.

"When we take into account the detection level of the monitoring, there in fact appear to be more earthquakes in New Zealand than on the San Andreas in California,""says Furlong.

One indication that things have not always been quite so calm on the Alpine fault is the presence of a rock type called psuedotachylite, which is thought to form either during an earthquake or with a meteor impact. In New Zealand they are formed along the Alpine fault by earthquakes. The rock contains bands of melted rock that seeps into fractures. The melted rock forms by the frictional heating during an earthquake. To form psuedotachylite, the right conditions of temperature and pressure must occur, and along faults, this implies that there must be very high stresses during the earthquake.

"The Alpine fault generates large amounts of psuedotachylite," says Furlong. "Why should the fault have such a high stress level? Something about the mechanical behavior is still puzzling. Perhaps the fresh edge of the plate that joins the fault is rough and that is the reason for the melting during earthquakes."

Because the Alpine fault begins so cleanly, Furlong believes it can tell us something about strike slip faults in general. While the Alpine fault does not impact large populated areas, the other major strike slip faults do, including the San Andreas in California, the Anatolian in Turkey and faults in China and Central Asia.

Andrea Elyse Messer | EurekAlert!
Further information:
http://www.psu.edu

More articles from Earth Sciences:

nachricht Six-decade-old space mystery solved with shoebox-sized satellite called a CubeSat
15.12.2017 | National Science Foundation

nachricht NSF-funded researchers find that ice sheet is dynamic and has repeatedly grown and shrunk
15.12.2017 | National Science Foundation

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: First-of-its-kind chemical oscillator offers new level of molecular control

DNA molecules that follow specific instructions could offer more precise molecular control of synthetic chemical systems, a discovery that opens the door for engineers to create molecular machines with new and complex behaviors.

Researchers have created chemical amplifiers and a chemical oscillator using a systematic method that has the potential to embed sophisticated circuit...

Im Focus: Long-lived storage of a photonic qubit for worldwide teleportation

MPQ scientists achieve long storage times for photonic quantum bits which break the lower bound for direct teleportation in a global quantum network.

Concerning the development of quantum memories for the realization of global quantum networks, scientists of the Quantum Dynamics Division led by Professor...

Im Focus: Electromagnetic water cloak eliminates drag and wake

Detailed calculations show water cloaks are feasible with today's technology

Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...

Im Focus: Scientists channel graphene to understand filtration and ion transport into cells

Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.

To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...

Im Focus: Towards data storage at the single molecule level

The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.

Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

AKL’18: The opportunities and challenges of digitalization in the laser industry

07.12.2017 | Event News

 
Latest News

Engineers program tiny robots to move, think like insects

15.12.2017 | Power and Electrical Engineering

One in 5 materials chemistry papers may be wrong, study suggests

15.12.2017 | Materials Sciences

New antbird species discovered in Peru by LSU ornithologists

15.12.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>