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| t_folk |
 Posted: Mon May 12, 2008 8:02 pm Post subject: Latest Tectonic Activity |
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Forum Freshman
Joined: 07 May 2008
Posts: 4
Location: Georgia
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With the latest string of quakes in the Midwest, on the West Coast, and in China, I was just wondering if anyone sees this as a precursor to something big?
(Please, pardon my ignorance)
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| Ryon |
| Posted: Mon May 12, 2008 8:29 pm Post subject: |
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On Probation
Joined: 06 May 2008
Posts: 85
Location: Virginia
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Possibly. Hurricanes->global warming. Small erosion->mud slides. It could be just a normal event though. There are a lot of theories surrounding it. We over here in the east coast are getting some seismologic activity as well. So that adds to the curiosity about this activity.
Of course, I don't know much about seismology. My area of study is field geology (erosion, surveying, et cetera) and geodesy, so maybe someone can probably go into more depth than me.
(( Oh, and since global warming is coming, plate tectonics is fucked! )!;
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| marnixR |
| Posted: Mon May 12, 2008 11:29 pm Post subject: |
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Forum Isotope
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what are the chances that, if you lived 2 centuries ago, you would even have heard of these events ?
don't underestimate the power of worldwide news coverage to skew our perception of how common disasters really are - how many have you encountered within 100 miles radius from where you live ?
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| Pong |
| Posted: Mon May 12, 2008 11:46 pm Post subject: |
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Forum Professor
Joined: 08 Apr 2008
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| marnixR wrote: |
| don't underestimate the power of worldwide news coverage to skew our perception... |
What I take from it, is, the human front's been relatively uneventful... frustrating to the news providers... which is good news.  |
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| Ophiolite |
| Posted: Tue May 13, 2008 4:01 am Post subject: Re: Latest Tectonic Activity |
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Forum Radioactive Isotope
Joined: 25 Jul 2005
Posts: 4804
Location: Scotland
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| t_folk wrote: |
| With the latest string of quakes in the Midwest, on the West Coast, and in China, I was just wondering if anyone sees this as a precursor to something big? |
The Midwest and West Coast quakes were small. (5.2 for Illinois on April 18, 4.7 for Nevada on April 26, 5.4 for California on April 30th) These are pretty low energy events and are, as far as I can tell from a quick look, in line with normal activity in these regions. I haven't looked at precise locations, but the Nevada and California quakes may be related. Movement on one fault may trigger movement on another realted fault a few days, weeks or months later.
The China quake is large, but we would expect one of this magnitude somewhere in the world at least once a year, on average. As our understanding of earthquake mechanisms improves I suspect we shall find there is a much more systematic inter-relationship between many major (and minor) quakes than we currently recognise. This may have valuable implications for earthquake prediction.
Remember that the majority of quakes are small and most go largely undetected. The US Geological Survey currently detect about 20,000 earthquakes each year, but they estimate the total number approaches one and a half million.
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| t_folk |
| Posted: Tue May 13, 2008 7:36 am Post subject: Re: Latest Tectonic Activity |
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Forum Freshman
Joined: 07 May 2008
Posts: 4
Location: Georgia
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| Ophiolite wrote: |
| t_folk wrote: |
| With the latest string of quakes in the Midwest, on the West Coast, and in China, I was just wondering if anyone sees this as a precursor to something big? |
The Midwest and West Coast quakes were small. (5.2 for Illinois on April 18, 4.7 for Nevada on April 26, 5.4 for California on April 30th) These are pretty low energy events and are, as far as I can tell from a quick look, in line with normal activity in these regions. I haven't looked at precise locations, but the Nevada and California quakes may be related. Movement on one fault may trigger movement on another realted fault a few days, weeks or months later.
The China quake is large, but we would expect one of this magnitude somewhere in the world at least once a year, on average. As our understanding of earthquake mechanisms improves I suspect we shall find there is a much more systematic inter-relationship between many major (and minor) quakes than we currently recognise. This may have valuable implications for earthquake prediction.
Remember that the majority of quakes are small and most go largely undetected. The US Geological Survey currently detect about 20,000 earthquakes each year, but they estimate the total number approaches one and a half million. |
Thanks. I'm always suspect about such things for the very reasons that another poster outlined above - the absolute saturation by the news media. I had taken a geology course as an undergrad and thought I had read something about smaller quakes possibly being precursors to larger ones, though the way my mind works these days I could have just as easily dreamt that.
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| Ophiolite |
| Posted: Tue May 13, 2008 8:47 am Post subject: |
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Forum Radioactive Isotope
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Location: Scotland
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I should have included a link to the USGS site on Earthquakes.
http://earthquake.usgs.gov
From this page you can go to several interesting pages. This one lists global earthquakes over the last seven days. (Greater than magnitude 4+ for the world; greater than magnitude 1+ for the US.)
http://earthquake.usgs.gov/eqcenter/
Picking out individual earthquakes from the maps will return something like this.
Magnitude 3.1
Date-Time Tuesday, May 13, 2008 at 00:44:25 UTC
Monday, May 12, 2008 at 03:44:25 PM at epicenter
Location 51.614°N, 178.805°W
Depth 5.5 km (3.4 miles)
Region ANDREANOF ISLANDS, ALEUTIAN IS., ALASKA
Distances 152 km (94 miles) W (259°) from Adak, AK
322 km (200 miles) W (260°) from Atka, AK
2055 km (1277 miles) WSW (252°) from Anchorage, AK
Location Uncertainty horizontal +/- 4.8 km (3.0 miles); depth +/- 0.5 km (0.3 miles)
Parameters NST=014, Nph=013, Dmin=19.2 km, Rmss=0.57 sec, Gp=292°,
M-type=local magnitude (ML), Version=1
Source Alaska Earthquake Information Center
Geophysical Institute, University of Alaska Fairbanks
Event ID ak00043330
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The Universe is not only weirder than we imagine it is weirder than we can imagine. J.B.S.Haldane. |
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| Pong |
| Posted: Tue May 13, 2008 12:36 pm Post subject: Re: Latest Tectonic Activity |
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Forum Professor
Joined: 08 Apr 2008
Posts: 1392
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| t_folk wrote: |
| something about smaller quakes possibly being precursors to larger ones |
There is a larger one we've been anticipating lately. This is the locked zone located north of California, which rather dramatically unlocks at 500 year intervals, +/- 100 years. It's essentially doing what California does, but, being snagged up, instead of regular quakes (slippage) we just get bent ground and stored energy. The last time this ratchet slipped, in 1700, the ground dropped one meter, and Japan was devastated by tsunami. It's big... imagine all the California quakes of 500 years rolled into one movement. We won't be happy campers. So we really want to know what kinds of precursors this event might send up. We think there will be characteristic wave patterns up to a week before the event, and British Columbia now has warning system in case they appear. |
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