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Date:
 RE: Earthquake Permalink Read the whole article. It also says that the largest earthquakes occur during the last weeks of December and the first weeks of January. This is due to the gravity wobble as the Earth passes near the Sun. Any thoughts? __________________

L

Posts: 131433
Date:

Measuring the magnitude of earthquakes

Earthquake Magnitude Scale

 Magnitude Earthquake Effects Estimated NumberEach Year 2.5 or less Usually not felt, but can be recorded by seismograph. 900,000 2.5 to 5.4 Often felt, but only causes minor damage. 30,000 5.5 to 6.0 Slight damage to buildings and other structures. 500 6.1 to 6.9 May cause a lot of damage in very populated areas. 100 7.0 to 7.9 Major earthquake. Serious damage. 20 8.0 or greater Great earthquake. Can totally destroy communities near the epicenter. One every 5 to 10 years

Earthquake Magnitude Classes

Earthquakes are also classified in categories ranging from minor to great, depending on their magnitude.

 Class Magnitude Great 8 or more Major 7 - 7.9 Strong 6 - 6.9 Moderate 5 - 5.9 Light 4 - 4.9 Minor 3 -3.9

The Richter magnitude scale, also known as the local magnitude (ML) scale, assigns a single number to quantify the amount of seismic energy released by an earthquake. It is a base-10 logarithmic scale obtained by calculating the logarithm of the combined horizontal amplitude of the largest displacement from zero on a WoodAnderson torsion seismometer output. So, for example, an earthquake that measures 5.0 on the Richter scale has a shaking amplitude 10 times larger than one that measures 4.0. The effective limit of measurement for local magnitude ML is about 6.8.
Source

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L

Posts: 131433
Date:
 Geologic faults Permalink Scientists find that some geologic faults are weaker than they appearSome geologic faults that appear strong and stable, slip and slide like weak faults. Now an international team of researchers has laboratory evidence showing why some faults that "should not" slip are weaker than previously thought.Read more __________________

L

Posts: 131433
Date:
 RE: Earthquake Permalink Tweets are being used by the US Geological Survey (USGS) to get instant public reaction to earthquakes.The agency is trawling the messages to find out what people felt during a tremor - whether there was a lot of shaking in their area or not.There are big spikes in Twitter traffic immediately following a quake and the USGS believes emergency responders might find the information useful. Read more __________________

L

Posts: 131433
Date:
 Permalink The CISN ShakeAlert system An earthquake early warning system for California is feasible in coming years, according to research being presented Dec. 14-15 at the American Geophysical Union meeting in San Francisco.  The ongoing study demonstrates that an earthquake early warning system for California is possible and lays out how such a system could be built.Earthquake early warning systems, already successfully deployed in Mexico, Japan and Taiwan, can detect an earthquake in progress and provide notice of seconds to tens of seconds prior to actual ground shaking. Building on developments in other countries with significant earthquake risk, scientists are exploring early warning in the United States.Read more __________________

L

Posts: 131433
Date:
 Permalink U.S. seismologists have found evidence that the massive 2004 earthquake that triggered killer tsunamis throughout the Indian Ocean weakened at least a portion of California's famed San Andreas Fault. The results, which appear this week in the journal Nature, suggest that the Earth's largest earthquakes can weaken fault zones worldwide and may trigger periods of increased global seismic activity."An unusually high number of magnitude 8 earthquakes occurred worldwide in 2005 and 2006. There has been speculation that these were somehow triggered by the Sumatran-Andaman earthquake that occurred on Dec. 26, 2004, but this is the first direct evidence that the quake could change fault strength of a fault remotely" - study co-author Fenglin Niu, associate professor of Earth science at Rice University. Read more The only link between deadly earthquakes in Indonesia and the South Pacific was the stretch of seismic activity where they struck - the site of most of the world's quakes, according to experts.They said that Tuesday's 8.0-magnitude quake that hit the remote Pacific islands of Samoa and Western Samoa and a 7.6 tremor the next day in Indonesia were along the "Ring of Fire" on the Australian tectonic plate, but too far apart for any connection. Read more __________________

L

Posts: 131433
Date:
 Permalink Distant earthquakes may increase the risk of subsequent earthquakes around the globe, a team of US seismologists reports.Examining 22 years of seismic data from a section of the San Andreas fault near the small central Californian town of Parkfield - an earthquake hotspot - the researchers found a substantial upsurge in the frequency of small earthquakes in 2005. These occurred following the SumatraAndaman earthquake in late 2004, which caused the deadly Indian Ocean tsunami. Read more __________________

L

Posts: 131433
Date:
 Permalink U.S. researchers try to use Twitter in reporting quakesU.S. researchers are studying the possibility of using Twitter to report earthquakes, a U.S. Geological Survey scientist said Saturday. Scientists have begun using a Twitter pipeline to monitor use of words quake, earthquake and terremoto -- the Spanish word for earthquake --  on the Web.Read more __________________

L

Posts: 131433
Date:
 Permalink Author William K. Vogeler Says Gravity Wobble Caused Big EarthquakesAuthor of An Amateur Astronomer's Guide to Gravity to Speak at Pacific Astronomy and Telescope Show Many of the largest earthquakes in history may have been caused by a wobble in the Earth's obit, according to an author of a new book about gravity. William K. Vogeler, speaking to astronomers at the Pasadena Convention Centre this month, will explain how recent gravity measurements support his theory. Vogeler contends that the Earth shudders as it approaches the Sun.Source Ed ~ This is an unusual claim, that somehow seems to goes against preceding research that shows there is no correlation, or pattern, to large earthquakes. __________________

L

Posts: 131433
Date:
 Permalink Typhoons trigger slow earthquakesScientists have made the surprising finding that typhoons trigger slow earthquakes, at least in eastern Taiwan. Slow earthquakes are non-violent fault slippage events that take hours or days instead of a few brutal seconds to minutes to release their potent energy. The researchers discuss their data in a study published in the June 11, issue of Nature. Read more __________________
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