DEVASTATING EARTHQUAKES, say, 7.0 or above on the Richter: do more occur in South or North America?

Question

The 8.8 that occurred last night in Chile, was a whopper; but the 9.+ in Alaska's in 1965 I think it was, and an even larger one occurring previously in Chile, was also.

An aside, I've been researching the 1883 Krakatoa eruption, to determine if there is a scientific based estimate of what it most probably would have registered on the Richter scale: anyone happen to know?

Back to my original question - does anyone know which of the North or South American continents and their adjacent island regions, have suffered the most earthquakes, above a 7.0 on the Richter scale?

Just curious,

Alberich

Answer 1

Hello, Alberich.



Coincidentally, Yahoo put a list of the strongest quakes in history (at least the ones they have data for)

http://news.yahoo.com/s/ap/20100227/ap_on_re_la_am_ca/chile_strongest_quakes_glance



Anyone living alongside the 'Ring of Fire' http://www.ceoe.udel.edu/extreme2001/geology/ringoffire.html

is apt to experience at least one 7.0 magnitude quake or higher at some point in history.

As for the Krakatoa eruption, and based on what the USGS (this place is wonderful to learn about geology) states, the explosion was measured in VEI scale. VEI stands for Volcanic Explosivity Index.

VEI is analogous to the Richter magnitude scale for earthquakes. In the 0 to 8 scale of VEI, each interval represents an increase of a factor of ten. An eruption of VEI 4 is 10 times larger than a 3 and one hundred times larger than a 2.

Krakatau's was VEI 6 (Very Large) .



Typically a VEI 6 will produce:



* Eruption column height above vent: greater than 80,000 feet

* Approximate ash thickness at 10 miles: 10 feet

* Approximate ash thickness at 100 miles: 1 foot

* Approximate ash thickness at 300 miles: 1 inch



Now go explore the USGS and don't miss the World Earthquake Chart that is updated hourly.

http://earthquake.usgs.gov/eqcenter/recenteqsww/

Answer 2

You must bear in mind that earthquakes will have been happening along the Pacific rim since before recorded time. According to the USGS the whole of the western pacific basin from the Artic to the tip of South America is an Orogen - or area of mountain building - hence the Rockies and Andes. Therefore, any answer will be purely a guess, based on what has been recorded over the past century or so.

Answer 3

Just confirming those who have said it 'equals' out.



The entire west coast from the top of North America to the tip of South America is a subduction zone - the Pacific plate is slowing grinding under the western American plates.



The Chain of mountains from north to south is all one chain, the Rockies in the north and the Andes in the south are all one ongoing event.



Then there is the North Amercan Yellowstone caldera, which is a real corker.... and the New Madrid fault zone in Missouri - there was a wopper in 1812, with the ground rolling in waves, and felt as far away as Boston, where church belfries swayed enough to ring the bells! http://en.wikipedia.org/wiki/1812_New_Madrid_earthquake



There have been earthquakes on the east coast; in Manhatten in 1737, 1884, 2009....

The earth is not stable, though we think of it as 'solid.'



Here is a link to the Berkely University Seismological site, specifically to the weekly map of earthquakes in California and Nevada. Yup, several per week, easy!

http://seismo.berkeley.edu/weekly/





best regards.

Answer 4

Living in California, you might think I should know. But I don't. Without any statistics I think most large earthquakes actually occur in Northern Asia (Japan, Korea, China) and India ... followed closely by the pacific island nations like the Philippines like Indonesia.

Answer 5

Over a period of time they equal out, the whole region from south of the continent all the way up to Alaska is a 'subductive zone' where the Pacific oceanic plate is sliding below the pacific coast continental plate.



This may be of interest ....



http://vulcan.wr.usgs.gov/Glossary/PlateTectonics/description_plate_tectonics.html

Answer 6

You should find this resource interesting.