Decoded Science

  • Home
  • Headlines
  • General Science
  • Applied Science
    • Calculations
    • Economics
    • Engineering
      • Aviation
      • Civil Engineering
    • Medical Science
      • Health
      • Neuroscience
      • Oncology
      • Veterinary Science
    • Political Science
      • Polling
    • Mathematics
    • Technology
      • Artificial Intelligence
      • Computing
      • Electronics
      • Gadgets
    • Social Science
      • Cognitive Science
      • Psychology
      • Sociology
      • Anthropology
        • Linguistics
  • Physical Science
    • Archaeology
    • Astronomy
    • Chemistry
      • Materials Science
    • Geoscience
      • Climate Change
      • The Environment
      • Geology
      • Meteorology
      • Oceanography
    • Life Science
      • Biology
        • Botany
        • Zoology
          • Marine Biology
          • Entomology
          • Microbiology
        • Paleontology
        • Ecology
    • Nuclear Science
  • Theoretical Science
    • Physics
    • Math Theory
  • About Us
    • Contact Decoded Science
    • Ask the Expert
    • Meet Our Experts
    • Meet Our Sponsors:
    • Browse All Articles
    • Subscribe
    • Privacy Policy
    • Terms of Use Agreement
  • Support Decoded Science

Tonga, Greece and Alaska: Earthquakes 23-29 October 2014

October 29, 2014 by Jennifer Young Leave a Comment

Share10
+12
Tweet
Share
Pin
12 Shares
Earthquakes 23-29 October 2014. Image credit: USGS

Earthquakes 23-29 October 2014. Image by: USGS.

Just one earthquake of at least magnitude 6 (≥M6.0) appeared on the United States Geological Survey’s real time earthquake map in the week of 23-29 October 2014.

The map, which records all tremors in the US and its territories and those of ≥M4.0 elsewhere, also includes 25 larger than M5.0, 118 of at least M4.0 and 259 of at least M2.5 in its total of 1,552 earthquakes worldwide.

Just one of these larger tremors (≥M5.0 in Alaska) was at a significant distance from one of the earth’s plate tectonic margins, demonstrating the relationship between these margins and larger earthquakes — although local map of smaller tremors show that low-level seismic activity can occur pretty much anywhere on the planet.




The Week’s Biggest Earthquake: M6.1, Tonga

M6.2 at the northern end of the Tonga Trench. Image credit: USGS

M6.2 at the northern end of the Tonga Trench. Image by: USGS.

The congested western Pacific Ocean, with its many microplates and its complex changes in the nature of the margin of the Pacific Ocean, is a regular source of larger earthquakes. This week the largest occurred at the northern end of the Tonga Trench.

Here, the subduction boundary between the Pacific and Australian plates curves sharply around before the margin becomes diffuse and its nature unclear between Tonga and Fiji.

The location of this week’s earthquake, with its epicentre on the over-riding plate, along with its depth (35 km) implies that it is a subduction-related event.

The existence of the spreading centres of the Lau Basin immediately to the south, however, introduce the possibility that it might be associated with rifting and crustal deformation.

Without further detailed information, it isn’t possibly to say for certain.

M5.2 Greece: More Than Meets the Eye

Greece's M5.2 earthquake is close to a subduction zone. Image credit: USGS

Greece’s M5.2 earthquake is close to a subduction zone. Image by USGS.

As noted above, the USGS map records only earthquakes of a certain magnitude.

This week’s M5.2 in western Greece looks isolated but a closer look at the seismicity maps produced by Greece’s Aristotle University of Thessaloniki shows that it’s just the largest in a series in the immediate area.

Tectonically, Greece is trapped in between the African and Eurasian plates, converging along the West Hellenic Trench as the Mediterranean Basin gradually closes. But as in the case of Tonga, this week’s tremor occurred just off the end of the trench at a relatively shallow depth.

In this case the implication is that the cause is crustal deformation rather than subduction — and maps of recent earthquakes, and of larger historic events, confirm that in this area earthquake activity is frequent and diffuse as the continents collide.

US Earthquakes: Alaska

Earthquakes of all magnitudes in Alaska, 23-29 October. Image credit: USGS

Earthquakes of all magnitudes in Alaska, 23-29 October. Image by USGS.

With no large earthquakes in the US this week, it’s instructive to stand back and look at the overall pattern of earthquakes in Alaska. The map shows that there is a clear association between earthquakes and a narrow subduction zone along the Aleutian arc.

Further to the east, on the Alaskan continent, the zone of earthquakes departs from the subduction zone and becomes much more diffuse.

Most of these earthquakes are smaller (although large earthquakes do occur there they are more characteristic of the subduction zone itself) and shallow — the result of crustal deformation.

Earthquakes: Not Always Clear Cut

This week’s featured earthquakes in Tonga and Greece both occur just off the end of a subduction zone and both appear isolated on the USGS map. This illustrates the shortcomings of the map in a world-wide context. Comparing them with Alaska, all of whose earthquakes appear on the USGS map, indicates that medium-sized earthquakes, probably associated with crustal deformation, are a regular occurrence in such tectonic settings.

Share10
+12
Tweet
Share
Pin
12 Shares

Filed Under: Geology, Headlines

Resources for this article

Aristotle University of Thessaloniki. Current seismicity in Greece and its surroundings. (2014). Accessed on October 29, 2014


United States Geological Survey. Real time earthquake map. (2014). Accessed on October 29, 2014


Yeats, Robert. Active Faults of the World. (2012). Cambridge University Press.




Decoded Everything is a non-profit corporation, dependent on donations from readers like you. Donate now! Your support keeps the great information coming!

Donation Information

I would like to make a donation in the amount of:

$500$200$100$50$20$10$5Other
Other:

I would like this donation to automatically repeat each month

Tribute Gift

Check here to donate in honor or memory of someone
Check here if this is a memorial gift
Name of person to be honored:
Send acknowledgement via email
Send acknowledgement via postal mail
Email Name:
Email:
Name:
Address:
City:
State :
Province:
Country:
Postal Code:

Donor Information

First Name:
Last Name:
Email:
Please do not display my name publicly. I would like to remain anonymous
Add me to your mailing list

Leave a Reply Cancel reply

Connect with:
Facebook

Your email address will not be published. Required fields are marked *

About the Author

Jennifer Young

Jennifer Young gained an Honours degree in Geography from Edinburgh University, where her studies included a range of topics in both physical and environmental geography. She subsequently undertook and completed a BSc in ... Read Full Profile

Follow Decoded Science

  • Facebook
  • Google+
  • Twitter
  • Pinterest
signupheredailydosedecsciv2


Science Everyone's Talking About

  • Effects of Poor Sleep: Increased Bickering with Your Partner Effects of Poor Sleep: Increased Bickering with Your Partner New research shows that not only can poor sleep habits... under Headlines, Social Science
  • Chemistry Questions: Organic Compounds, Life, and Vitalism Chemistry Questions: Organic Compounds, Life, and Vitalism Current scientific theories as to the origin of life ar... under Chemistry
  • Comparing the Genetic Code of DNA to Binary Code Comparing the Genetic Code of DNA to Binary Code Does DNA store information in the same way that a compu... under Information Science, Mathematics
  • Himalayan Ice Loss, Extra-Terrestrial Water and the European Settlement of the Americas: Geoscience 1-7 February 2019 Himalayan Ice Loss, Extra-Terrestrial Water and the European Settlement of the Americas: Geoscience 1-7 February 2019 This week we go back in time, travel into outer space a... under Geoscience, Headlines, Weekly Features
  • Air Conditioning and Pressurization Systems in Modern Aircraft Air Conditioning and Pressurization Systems in Modern Aircraft For any modern aircraft to fly at high altitudes, i... under Aviation

Today's Most Popular Science Articles

  • Introducing Math Symbols for Union and Intersection Introducing Math Symbols for Union and Intersection
  • Genetically Modified Organisms: Pros and Cons of GMO Food Genetically Modified Organisms: Pros and Cons of GMO Food
  • Which Chemical Bond is Stronger: Ionic vs. Covalent Bonds Which Chemical Bond is Stronger: Ionic vs. Covalent Bonds
  • Norovirus Facts: 5 Things You Didn't Know About Stomach Flu Norovirus Facts: 5 Things You Didn’t Know About Stomach Flu
  • Cross Multiply to Solve Equations with Fractions Cross Multiply to Solve Equations with Fractions
  • Introducing the Factorial: the Exclamation Mark of Math Introducing the Factorial: the Exclamation Mark of Math
  • Stomach Flu Cramps: Is There Anything You Can Do For Norovirus Symptoms? Stomach Flu Cramps: Is There Anything You Can Do For Norovirus Symptoms?

Copyright © 2019 · Magazine Pro Theme on Genesis Framework · WordPress · Log in

MENU
  • Home
  • Headlines
  • General Science
  • Applied Science
    • Calculations
    • Economics
    • Engineering
      • Aviation
      • Civil Engineering
    • Medical Science
      • Health
      • Neuroscience
      • Oncology
      • Veterinary Science
    • Political Science
      • Polling
    • Mathematics
    • Technology
      • Artificial Intelligence
      • Computing
      • Electronics
      • Gadgets
    • Social Science
      • Cognitive Science
      • Psychology
      • Sociology
      • Anthropology
        • Linguistics
  • Physical Science
    • Archaeology
    • Astronomy
    • Chemistry
      • Materials Science
    • Geoscience
      • Climate Change
      • The Environment
      • Geology
      • Meteorology
      • Oceanography
    • Life Science
      • Biology
        • Botany
        • Zoology
          • Marine Biology
          • Entomology
          • Microbiology
        • Paleontology
        • Ecology
    • Nuclear Science
  • Theoretical Science
    • Physics
    • Math Theory
  • About Us
    • Contact Decoded Science
    • Ask the Expert
    • Meet Our Experts
    • Meet Our Sponsors:
    • Browse All Articles
    • Subscribe
    • Privacy Policy
    • Terms of Use Agreement
  • Support Decoded Science