Nov 2018 - 7.0 Earthquake 7 miles outside of Anchorage Alaska


#1

Tsunami alert posted for that area.

"NEW YORK, Nov. 30 (Xinhua) – An earthquake with a magnitude of 7.0 jolted 13 km north of Anchorage in U.S. state of Alaska at 17:29:28 GMT on Friday, the U.S. Geological Survey said.

The epicenter, with a depth of 40.9 km, was initially determined to be at 61.34 degrees north latitude and 149.9366 degrees west longitude."
http://www.xinhuanet.com/english/2018-12/01/c_137642798.htm


#2

#3

Just caught that on CNN… glad to see others are in here first though… will keep observing… watch the aftershocks… they will cause a bit more damage…


#4

Live


#5

Update:


#6

Just for clarification, the tsunami warning after the 7.0 was cancelled. There has not been a 6.7 aftershock, or another tsunami warning. :nerd_face: it looks like the link box did not correct 6.7 to 7.0 on the above article.


#7

Note that the quake occurred underneath a basin. The basin is filled with sediments eroded from the surrounding mountains and river drainage. Sedimentary basins, which have a layer of unconsolidated sediments overlying bedrock, result in earthquake energy being “trapped” in the sediments and creating more shaking/ground motion than in the bedrock below. The energy is “trapped” because when it reflects off the ground surface, it travels back toward the bedrock, and when it hits the bedrock, more energy gets reflected back up into the sediments instead of traveling into the bedrock. So all this energy keeps bouncing around in the sediments instead of dissapating as it does in the hard bedrock. So you have more ground shaking in a quake in a basin than an equivalent quake in bedrock, not beneath a basin. In the second map below, see the intensity of shaking increases with warmer colors. The warmest colors are in the basin, not on the mountains. Note the sharpest color gradient between the earthquake location and the mountains to the southeast.



#8

Great explanation…thanks @kateg!


#9

#10

#11

My mom remembers the 1964 quake. She was in her junior year of college and taking a geophysics course which covered earthquakes (she is also a geologist). She remembers how the geology professors were in shock at such a strong quake. The 1960s saw three of the strongest earthquakes in history

  1. Valdivia, Chile, 22 May 1960 (9.5) …
  2. Prince William Sound, Alaska, 28 March 1964 (9.2) …
  3. Sumatra, Indonesia, 26 December 2004 (9.1) …
  4. Sendai, Japan, 11 March 2011 (9.0) …
  5. Kamchatka, Russia, 4 November 1952 (9.0) …
  6. Bio-bio, Chile, 27 February 2010 (8.8)
  7. Ecuador coast, 31 January 1906 (8.8)
  8. Rat Islands, Alaska, 2 April 1965 (8.7)
  9. Sumatra, Indonesia, 28 March 2005 (8.6)
  10. Assam, Tibet, 15 August 1950 (8.6)

It is interesting, though not scientifically significant, to see the years - in order - of the top 10 earthquakes:

1906, 1950, 1952, 1960, 1964, 1965, 2004, 2005, 2010, 2011

It is also interesting that our current understanding of plate tectonics occurred in the late 60s.


#12

Thanks again Kateg you always give us such great explanations!


#13

Geology is in my genes. My parents met in grad school as geology students. My only sibling, my sister, is also a geologist. It’s my defense when people laugh that I talk a lot about rocks :grin::nerd_face:


2018 Geology Rocks Talk
#14

When I was a kid and people asked me what I got for Christmas, I used to tell them, “all I got were rocks.” (A throwback to the Charlie Brown cartoon when he went trick-or-treating. :laughing:).

And as I was reading your post, as soon as I reached

I immediately thought to myself, “like mother, like daughter” - then chuckled. :grinning:


#15

#16

#17