michel123456 Posted September 16, 2015 Share Posted September 16, 2015 The wiki article presents a frequency of roughly 500 years. https://en.wikipedia.org/wiki/1700_Cascadia_earthquake#Future_threats Link to comment Share on other sites More sharing options...
Acme Posted September 16, 2015 Share Posted September 16, 2015 The wiki article presents a frequency of roughly 500 years. https://en.wikipedia.org/wiki/1700_Cascadia_earthquake#Future_threats True. However that's not to say we've nothing to worry about if that's your implication. They go on to say: There is evidence of at least 13 events at intervals from about 300 to 900 years with an average of 570590 years.[15] Previous earthquakes are estimated to have occurred in 1310 AD, 810 AD, 400 AD, 170 BC and 600 BC. ... Recent findings conclude that the Cascadia subduction zone is more complex and volatile than previously believed. In 2010 geologists predicted a 37 percent chance of an M8.2+ event within 50 years, and a 10 to 15 percent chance that the entire Cascadia subduction zone will rupture with an M9+ event within the same time frame.[17] Geologists have also determined the Pacific Northwest is not prepared for such a colossal quake. The tsunami produced could reach heights of 80 to 100 feet (24 to 30 m).[18] The article you cite mentions 13 previous quakes but they list only 6. Quoting from the Wiki article I cited in post #25 on the Cascadia subduction zone: Geological evidence indicates that great earthquakes (> magnitude 8.0) may have occurred sporadically at least seven times in the last 3,500 years, suggesting a return time of about 500 years.[3][4][5] Seafloor core evidence indicates that there have been forty-one subduction zone earthquakes on the Cascadia subduction zone in the past 10,000 years, suggesting a general average earthquake recurrence interval of only 243 years.[6] Of these 41, nineteen have produced a "full margin rupture," wherein the entire fault opens up.[3] By comparison, similar subduction zones in the world usually have such earthquakes every 100 to 200 years; the longer interval here may indicate unusually large stress buildup and subsequent unusually large earthquake slip.[17] ... So, averages are as averages do and they are no substitute for monitoring and study when there are so many lives and so much property at risk. Link to comment Share on other sites More sharing options...
michel123456 Posted September 16, 2015 Share Posted September 16, 2015 (edited) I learned 2 things today! I had no idea about the Cascadia and I learned at last who was Giannis Phokas. --------------- And for those interested, he is a witness of the coast before the 1600 earthquake. page 21 of the electronic book, page 161 of the original document. http://issuu.com/kefalonitikanea/docs/hutchings_40/21?e=1540338/3136700 Edited September 16, 2015 by michel123456 Link to comment Share on other sites More sharing options...
Acme Posted September 16, 2015 Share Posted September 16, 2015 I learned 2 things today! I had no idea about the Cascadia and I learned at last who was Giannis Phokas. --------------- And for those interested, he is a witness of the coast before the 1600 earthquake. page 21 of the electronic book, page 161 of the original document. http://issuu.com/kefalonitikanea/docs/hutchings_40/21?e=1540338/3136700 Perhaps you mean the 1700 quake, as I see no references to one in 1600. I find your citation unreadable as I can't zoom in nor read whatever language it is in. Can you quote a germane translation? Link to comment Share on other sites More sharing options...
Moontanman Posted September 17, 2015 Share Posted September 17, 2015 (edited) I'm more worried about the collapse of the Canary Islands (I think that right) if they do and it would raise a several hundred foot tidal wave on the east coast, that would be my ass for sure... I spend a lot of time on the beach, beach bum, everytime i see a huge wave in a set I think of what I would do if i saw the ocean suddenly start to recede far beyond the normal wave pattern... We have a shallow sea here to several miles offshore, it would be an impressive sight... Evidently not as well supported a threat as I thought. http://blogs.agu.org/landslideblog/2013/12/13/canary-islands-tsunami/ Edited September 17, 2015 by Moontanman Link to comment Share on other sites More sharing options...
Acme Posted September 17, 2015 Share Posted September 17, 2015 I'm more worried about the collapse of the Canary Islands (I think that right) if they do and it would raise a several hundred foot tidal wave on the east coast, that would be my ass for sure... I spend a lot of time on the beach, beach bum, everytime i see a huge wave in a set I think of what I would do if i saw the ocean suddenly start to recede far beyond the normal wave pattern... We have a shallow sea here to several miles offshore, it would be an impressive sight... Evidently not as well supported a threat as I thought. http://blogs.agu.org/landslideblog/2013/12/13/canary-islands-tsunami/ While tsunami danger is unlikely, you're not free & clear of severe quake hazards. North Carolina Earthquake History ... The great earthquakes of 1811 -1812 centered in the Mississippi Valley near New Madrid, Missouri, were felt throughout North Carolina. Intensity VI effects were observed in the western part of the State. The relatively small amount of damage caused by the New Madrid earthquakes is attributable to the low population density. ... The most property damage in North Carolina ever attributed to an earthquake was caused by the August 31, 1886, Charleston, South Carolina, shock. Severe damage occurred in Charleston and in an area within a radius of 160 kilometers. About 60 people were killed in the epicentral area. A number of places in North Carolina had chimneys thrown down, fallen plaster and cracked walls. These included Abbottsburg, Charlotte, Elizabethtown, Henderson, Hillsborough, Raleigh, Waynesville, and Whiteville. ... Not 'really big ones', but not safey wafey either. Link to comment Share on other sites More sharing options...
michel123456 Posted September 17, 2015 Share Posted September 17, 2015 (edited) Perhaps you mean the 1700 quake, as I see no references to one in 1600. I find your citation unreadable as I can't zoom in nor read whatever language it is in. Can you quote a germane translation? Sure 1700 earthquake, my mistake after reading the Juan de Fuca history. You can zoom in, there is a slider on the bottom left. It is in english. Edited September 17, 2015 by michel123456 Link to comment Share on other sites More sharing options...
Acme Posted September 17, 2015 Share Posted September 17, 2015 Sure 1700 earthquake, my mistake after reading the Juan de Fuca history. You can zoom in, there is a slider on the bottom left. It is in english. Screen Shot 09-17-15 at 09.42 AM.JPG Acknowledge mistake. I don't have a slider or any tools visible at the link you give. I backed up a slash and got a download option but when I clicked it I got "you have to be logged in to do that" message. No worries as it doesn't seem to be particularly important to the main topic here. Thanks for trying. Link to comment Share on other sites More sharing options...
Moontanman Posted September 17, 2015 Share Posted September 17, 2015 While tsunami danger is unlikely, you're not free & clear of severe quake hazards. North Carolina Earthquake History Not 'really big ones', but not safey wafey either. We have a phenomena called the Seneca Guns that is often attributed to small offshore quakes, not sure if it is. http://www.starnewsonline.com/section/topic9909 Link to comment Share on other sites More sharing options...
Acme Posted September 17, 2015 Share Posted September 17, 2015 (edited) We have a phenomena called the Seneca Guns that is often attributed to small offshore quakes, not sure if it is. http://www.starnewsonline.com/section/topic9909 While the NC geologist cited in the article suggested quakes, the USGS pointed out there is no such correlation with seismological records. Given that we don't have the phenomena here on the West coast, I hazard the guess that this is an acoustic effect generated by wave action which is tuned and amplified by coastal landforms. Have you heard the guns yourself Moontan? Edited September 17, 2015 by Acme Link to comment Share on other sites More sharing options...
Moontanman Posted September 17, 2015 Share Posted September 17, 2015 While the NC geologist cited in the article suggested quakes, the USGS pointed out there is no such correlation with seismological records. Given that we don't have the phenomena here on the West coast, I hazard the guess that this is an acoustic effect generated by wave action which is tuned and amplified by coastal landforms. Have you heard the guns yourself Moontan? Yes i have heard them many times, sounds a lot like a large wave collapsing on shore, sometimes the ground shakes. I have seen the water in my aquariums suddenly start jumping around in peaks when a "gun" went off. I guess I've heard or thought I did at least a dozen times in the past 45 years. Link to comment Share on other sites More sharing options...
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