Monday, November 18, 2013

Re: [Geology2] THE SCOTIA SEA keeps rocking with bigger and BIGGER quakes, whats up?



Ok maybe there were after shocks proper.  I only found the large quake and after clicking on 2 dozen more I couldn't find any more recent and no others near the Orkney Island 7+ event.  BUT  Google Earth is a great resource.  Aftershock confirmation usually takes some direct connection with a common fault system but I am not a seismologist with super computer to make those determinations--that's  my story and I am sticking to it.
Eman


On Monday, November 18, 2013 8:33 AM, Lin Kerns <linkerns@gmail.com> wrote:
 
From the USGS:

M7.8 - Scotia Sea 2013-11-17 09:04:55 UTC

Summary

Location and Magnitude contributed by: USGS National Earthquake Information Center

General

30 km
10 mi
Powered by Leaflet
60.296°S, 46.362°W
Depth: 10.0km (6.2mi)

Event Time

  1. 2013-11-17 09:04:55 UTC
  2. 2013-11-17 06:04:55 UTC-03:00 at epicenter
  3. 2013-11-17 03:04:55 UTC-06:00 system time

Location

60.296°S 46.362°W depth=10.0km (6.2mi)

Nearby Cities

  1. 893km (555mi) SW of Grytviken, South Georgia and the South Sandwich Islands
  2. 1440km (895mi) SE of Ushuaia, Argentina
  3. 1686km (1048mi) SE of Punta Arenas, Chile
  4. 1709km (1062mi) SE of Rio Gallegos, Argentina
  5. 1192km (741mi) SSE of Stanley, Falkland Islands

Related Links


Tectonic Summary

The November 17, 2013 earthquake in the Scotia Sea, to the northwest of the South Orkney Islands, occurred as the result of either left-lateral strike slip faulting on an east-west oriented plane, or right-lateral faulting on a north-south plane. The location of the event adjacent to the east-west oriented plate boundary between the Antarctica and Scotia Sea plates implies the left-lateral faulting scenario is most likely. At the latitude of this earthquake, the Antarctica plate moves eastwards with respect to the Scotia Sea plate at a velocity of 6 mm/yr.
The November 17 earthquake is the latest in a series of moderate-to-large earthquakes to strike the same region over the past several days. The sequence began with a M 6.1 event on November 13 approximately 50 km to the west of the November 17 quake. On November 15, a M 6.8 earthquake struck very close to the preceding M 6.1. Since then, 9 aftershocks have been recorded in the area, ranging from M 4.7 to M 5.4, both near the previous earthquakes and in the same approximate location as the November 17 event.
Though the region surrounding the Scotia Sea is familiar with earthquakes, the majority occur around the subduction zone adjacent to the South Sandwich Islands, to the east of the November 17 earthquake. Just two events of M6 or greater have occurred within 250 km of this earthquake over the past 40 years – a M 6.0 230 km to the west in September 1979, and a M 7.6 160 km to the east in August 2003. These two events involved normal and oblique-normal faulting, respectively, associated with the same plate boundary. Neither is known to have caused damage or fatalities.


On Mon, Nov 18, 2013 at 7:25 AM, MEM <mstreman53@yahoo.com> wrote:
 
They are probably not aftershocks and probably not related.  Go to Google Earth and enable Earthquakes and it will show decades of quake epicenters.  I just looked at the Nov 17 7+ quake near the Orkney Islands and while there have been several dozen quakes in the trenches to the north and south within the Scotia Sea, this one is by its lonesome so this one doesn't appear related to the other clusters. Enjoy exploring!

I have noticed that The Scotia Sea was listed several times in reports during the last few weeks but one has to look at how close these epicenters are as the sea is rather large and full of faults/trenches etc. Under this area is an extension of the Andes Range on the subducted Pacific plate which takes a  deep salient to the north, east then, south side of the Scotia plate then back to Antarctica along the Palmerland Peninchula .  But running more directly across the Scotia plate are several converging seafloor segments/trenches where these many quakes are plotted.  On casual observation it looks like the Siota plate may be "accordian folding" back on itself.

Eman


On Monday, November 18, 2013 7:38 AM, Victor G Healey <vic.healey@gmail.com> wrote:
 
AN EARTHQUAKE HAS OCCURRED WITH THESE PRELIMINARY PARAMETERS

ORIGIN TIME -  0905Z 17 NOV 2013
COORDINATES -  60.1 SOUTH   46.0 WEST 
LOCATION    -  SCOTIA SEA
MAGNITUDE   -  7.8








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