View Full Version : Pacific Anomaly

11th Feb 2013, 22:28

Odd picture. Usually there are quakes all round the Pacific rim, even at this 5+ filter setting, but here they are mostly concentrated around the Santa Cruz islands and have been for several days now.

I have an uneasy feeling that something is going to give.

11th Feb 2013, 22:40
Maybe they have not paid up their earthquake insurance? :p

11th Feb 2013, 22:51
There was a M8.0 earthquake in the Santa Cruz Islands last week. The earthquakes you're seeing now are likely aftershocks.

Big Tudor
11th Feb 2013, 23:37
Unusual not to see any around the Japan area though?

11th Feb 2013, 23:46
17 of note since Feb 1, business pretty much as usual: see here. (http://www.hinet.bosai.go.jp/AQUA/max_amp.php?LANG=en)

Recent "big" earthquakes with more seismic data (http://www.hinet.bosai.go.jp/backnumber/?LANG=en). Click on "一元化震源マップ表示 (http://www.hinet.bosai.go.jp/hypo/hinet/largeEQ/20130211000222:03.jma.png) " (Hypocenter Map) for more details.

12th Feb 2013, 02:47
The quake detected at N Korea today may be due to a nuke test, Cookies must be enabled. | The Australian (http://www.theaustralian.com.au/news/world/artificial-earthquake-detected-in-north-korea-may-be-nuclear-test/story-e6frg6so-1226576256804)

Takan Inchovit
12th Feb 2013, 04:38
Id be getting 'off' the beach.

14th Feb 2013, 08:56

USGS, 14 Feb, Filter = 4.0+

This shot includes quakes greater than 4.0 (op was 5.0+) and still shows remarkably little activity around the Pacific rim.

Lower left is active. North Korea had a firecracker. Nevada is way inland, nowhere near the San Andreas fault.

So why so quiet? Is everything sliding like a well-greased bearing at however many cm a year? Or is there a hang-up somewhere accumulating energy?

14th Feb 2013, 09:13
Lower left is active because there are some aftershocks there. The rest looks normal given the snapshot you posted.

14th Feb 2013, 09:23
The beach is still safe. I think if you look closer at the detail, some of those quakes are deep underground where the magnitude figure applies.

14th Feb 2013, 11:56
The beaches in this clip weren't too safe.

Cannikin, largest underground thermonuclear test - YouTube

15th Feb 2013, 07:05

USGS, 14 Feb, Filter = M4.0+

Still remarkably quiet around the north of the Pacific plate. One small quake in Japan, nothing in the Aleutians, Alaska, Van Is, SF-LA. Really unusual.

15th Feb 2013, 07:26
Your self-selecting cutoff shows "one small quake in Japan", my data feed shows 22 significant quakes in the subduction zones of Philippine and Pacific plates under the Amurian and Okhotsk plates so far this month. Do you attach some significance to M4.0+ quakes?

A A Gruntpuddock
15th Feb 2013, 07:46
I found this site quite interesting - never knew there were so many quakes!

Live Earthquakes Map (http://quakes.globalincidentmap.com/)

Maybe this one is coming earlier than predicted?

'Supervolcano' Forming Near New Zealand Says Scientist... | Stuff.co.nz (http://www.stuff.co.nz/science/8299441/Supervolcano-forming-near-New-Zealand)

15th Feb 2013, 07:52
On RJM's Cannikin nuclear test clip the narrator sounds like William Shatner.

15th Feb 2013, 07:58
Bushfiva - I usually keep my filter at M5.0+ but reduce it to M 4.0+ for these screenshots so as not to be accused of missing any.

What you regard as significant depends where you live I guess. In Iceland they monitor right down to M0.1 to check on volcanic activity. In California anything above M4.5 arouses comment. I use M5.0 as convenient everyday figure to see what stands out above the background noise.

Gruntpuddock - Yes, modern monitoring methods permit you to see incredibly small events. Perhaps the best site is usgs, and there are many other original sources. I use an app which permits me to select the source, though I usually default to usgs (United States Geological Survey) with a separate bookmark to vedur (Iceland Met Office).

15th Feb 2013, 08:28

For comparison, this is what USGS are listing as "significant".

15th Feb 2013, 08:34
So your filter will pick up aftershocks from a M8.0 earthquake but not normal seismic activity is what you seem to be saying.

15th Feb 2013, 08:40
Er, showing quite a lot in png, as usual.

15th Feb 2013, 09:12
Oh, I give up. I see nothing unusual going on. Let me know when I have to evacuate the next time a tsunami is on the way.

15th Feb 2013, 12:08
Hokulea - It is always difficult to discuss technical issues on public forums. Some readers may be specialists with PhDs in the subject, others may have no specific knowledge. So apologies if the following is at the wrong level.

You are sat at the centre of the Pacific plate, which is grinding steadily round in an anti-clockwise direction, moving a few cm each year against other plates. Some of the movement is smooth and steady. But in places the rocks catch against each other and there is no relative motion. The plate is still moving so stress builds up locally until eventually something breaks, all the movement happens at once, and all the accumulated stress energy is released.

So a lack of quakes in one locality may indicate smooth motion, whereas in another locality it may indicate a lack of motion and a consequent build-up of stress. Nowadays this is monitored by satellite measurement.

I watch the Pacific plate daily and am accustomed to seeing an even distribution of quakes around the rim as it grinds slowly but surely on its way. Including, of course, the frequent larger shocks at that rather nasty jagged corner at Santa Cruz Islands.

It is the lack of quakes around the northern rim which aroused my attention.

Hope that is helpful.

15th Feb 2013, 12:15
I find it extremely difficult to believe you are in the industry, as it were.

16th Feb 2013, 07:09
Well we have just today had a 6 in Philippines and 6.2 in NZ, so seems normal?

16th Feb 2013, 10:20

USGS, 16 Feb, Filter = M4.0+

Hurrah! Back to normal. Not a lot showing to the East but Van Is, Oregon and SF/LA can often be very quiet.