Quake Watch 2012

just passing through PNSN page while collecting links for QW2013 and seen this one, close to Victoria, BC

Magnitude: 4.0
Time(UTC): 2012/12/27 06:36:46
Time(Local): 2012/12/26 22:36:46 PST
Depth: 55.2Km (34.2miles)
Event Id: 60485982
Network: UW

www.pnsn.org...

felt?

edit:
yep
earthquake.usgs.gov...

reply to post by muzzy


Yes felt

2012-12-27 06:36:46, 48.650, -123.220, 3.3, 59.2, 13 Km E Of Sidney Bc. [F] +-+27+Dec+12++06%3A36%3A46+UTC)&ll=48.65000,-123.22000&spn=2, 2&f=d&t=h&hl=e][Map]

From NR Canada

Public Service Announcement:

Quake Watch 2013 has now been restored to the Fragile Earth forum, with Muzzy's lists of links and other notations edited in to the OP.

Muzzy will likely make another post to add some extra links, as it turns out that his originally planned OP was too large in characters to fit it all in.

Thank you to everyone who has contributed to Quake Watch in the past year/s. Speaking personally, while I don't post in this thread very often I gain a great deal from reading it and I'm looking forward to your ongoing contributions in the coming year.

Hopefully there will not be too much of the "bad news" events. It would be great if our planet has a fairly peaceful year.

Best regards to you all and here's hoping you have a safe and peaceful 2013!

Mike

reply to post by PuterMan

and especially:

Now we see the benefit of the history these threads/posts provide.

Oh, absolutely. That's one of the main reasons I keep follow the quake watch threads. It's remarkable how often magnitudes get revised -- even after the events have (generally speaking) dropped of the public radar. So having a well-compiled resource that now goes back years and is readily accessible is well worthwhile.

I suspect threads like this one are useful well outside of the general ATS community. After all, it's quite typical that there are many more readers (or lurkers) for ATS threads than just the members who are logged in at any given time.

Mike

reply to post by muzzy


hell, some of us do more freaking research then your students who are majoring in this field of work ... and sometimes more research then the scientists them selfs ...

we re doing a public service here ...

reply to post by PuterMan

I was thinking about this and wondered if you meant the SNZO page with the older graphs rather than the LDEO page.
SNZO page is still there for comparing LISS graphs.

I see GFZ has that quake now, at 5.5Mw and EMSC at 5.0M, but the EMSC is from GFZ anyway (with no phase data)
I'm finding that GFZ is the better site to follow, its the go-to page for me after I see LISS SNZO, to find what the wiggles were, if its not there then I go to USGS.
GFZ do miss a few in the Fiji area, so its still best to have a few different sources at your fingertips.

##ATTENTION PLEASE##

IF members continue to publicly whinge and whine about staff actions, they will have their posts deleted and this thread will be closed for a cooling off period.

The member that continues to go down that path will be looking at a several-day post-ban. PM complaints or leave it out completely.


Now please focus on the thread topic or log off and cool off.

reply to post by alysha.angel

indeed, I think here there is more of a tendency to look at the bigger picture, compared to those that work for a Network and have to tow-the-company-line.
Great job on starting Quake Watch 2013 BTW, you had a smoother start up than I did

Thread closed for review and cooling off period.

I should have been clearer in my post above

#Thread Open#

Let's stay on-topic and put the past behind us.

reply to post by muzzy

I'm finding that GFZ is the better site to follow

I am with you on that one. Whilst it is a feed to EMSC it is not of course the only one. I will fix that problem in the program in the next few days so it just goes and gets GFZ anyway even if there are no current quakes.

The only quibble I have with it is that very often that scale used for the quakes is not defined. Sites that say just 'M' drive me nuts.

Great job on starting Quake Watch 2013 BTW

to Alysha

I think you meant Volcano Watch 2013

yes I did mean Volcano Watch, too late now I can't edit it and there is no use whining

yes "M" is a bit wishy-washy isn't it, I'd prefer just a mb over that.
its a bit like the USGS "GS" which means "we couldn't agree here at the office, so lets call it GS"
they have an MTS now, 5.5Mw (if thats the one we are talking about)
I

reply to post by muzzy

The link goes to Alysha's Volcano Watch thread so it doesn't really matter, I guess.

Back to the main subject under discussion: this "M" thing has puzzled me for a while now. It's pretty unprofessional to use something so vague. Question for you or Puter: does it tend to be the case that they eventually resolve the "M" designation into something more precise? And if so, does the final number -- eg a 5.9 (plus a defined type such as Mw) seem to match up with what they gave originally as simply an "M"? Or is there some sort of a trend that would help us to identify what the "M" number might eventually mean -- before they finally tell us? (Assuming that they do.)

I hope those questions make sense... Late here.

EDIT: Oh btw, that Pacific Antarctic Ridge quake was pretty shallow at only 13.2 km (versus originally reported default depth of 33 km; Potsdam has 17 km in its MTS). Does anyone know if such shallow events are typical for the region? Yes, I know I could do a database search and try graphing some averages, but just wondering if anyone has the info to hand.

Mike

Mike good question, that "M" magnitude type shows on USGS as well some times, I've never actually gone back and looked to see if they changed, just this one time on GFZ, I usually keep searching until I find something more definitive than "M" on another network and use that. That is why I use RAS and GCMT as an extra reference for my significant quakes location maps, RAS always has mb, and Ms if its a bigger event, and GCMT always have Mw and usually Ms.

EDIT: Oh btw, that Pacific Antarctic Ridge quake was pretty shallow at only 13.2 km (versus originally reported default depth of 33 km; Potsdam has 17 km in its MTS). Does anyone know if such shallow events are typical for the region? Yes, I know I could do a database search and try graphing some averages, but just wondering if anyone has the info to hand.

Mike

Yes they are, 10km seems to be the default depth for the PacAntRidge and the SEastPacRise since November 1978 on ANSS data, before then it was 33km. I think its more a technology change than the crust suddenly rose 23km
link to text file of the search results for
North -50
South -60
East -118.5
West -150
Its quite confusing as to what the actual depth is measured from, and I have never got my head around this, when they are under the ocean is it the sea floor or the level of the sea the depth measurement is taken from?. The confusion is because when they are on a land mass its measured from the surface at the epi-centre. So if you get a >1km deep quake under a volcano, the odds are if it is high on the flanks it will actually be a surface eruption (as happened at Tongariro volcano a few months back)

This pdf on the PacAntRidge from 1964 says the crust there is on average only 7km thick
and the depth of the sea at the places they measured was approx 4km
so if the depth is measured from the level of the sea then these 10km quakes are very shallow indeed, like 6km below the sea floor.
If I read it correctly

this Pacific Antarctic Ridge quake has rekindled my interest in the PacAntRidge and SEastPacRise, I did some maps earlier in the year but the data must have been on a USB stick that went blank on me so I lost it all.
And maybe I should put LDEO back on too, quakes down there seem to be warnings of something about to hit Chile and the West coast of both Americas, as can be seen from this short LDEO list

event#, when,lat,long,depth,mag,where
1. 2012 12 26 23 2 0.0 -55.75 -144.75 33.0 5.6 PACIFIC-ANTARCTIC RIDGE
2. 2012 12 26 23 49 28.0 -35.75 -105.25 33.0 5.2 SOUTHERN EAST PACIFIC RISE
3. 2012 12 27 0 37 12.0 -35.75 -73.75 33.0 5.7 OFF COAST OF CENTRAL CHILE
4. 2012 12 27 6 57 12.0 -30.25 -111.75 33.0 5.1 EASTER ISLAND REGION
5. 2012 12 27 10 41 4.0 13.75 -92.75 33.0 4.8 OFF COAST OF CHIAPAS, MEXICO
6. 2012 12 27 13 5 4.0 24.25 -109.25 33.0 4.9 GULF OF CALIFORNIA

basically a line right up the western Pacific, all within 14 hours

this is a test I did today to set up Geofon data based maps. goo.gl...
shows the history 2005 to 2012 of the area of the Pacific Antarctic Ridge quake yesterday.

I was wanting the whole PacAntRidge, but obviously this only got part of it, it runs all the way west to Macquarie Triple Junction.
The problem with this area is that it also crosses the -180/180, E/W longitude meridian lines so have to do 2 downloads of the data, as most search engines go all wobbly with the +/- longitude parameters if you are searching both sides

Originally posted by muzzy
this Pacific Antarctic Ridge quake has rekindled my interest in the PacAntRidge and SEastPacRise, I did some maps earlier in the year but the data must have been on a USB stick that went blank on me so I lost it all.
And maybe I should put LDEO back on too, quakes down there seem to be warnings of something about to hit Chile and the West coast of both Americas, as can be seen from this short list
1. 2012 12 26 23 2 0.0 -55.75 -144.75 33.0 5.6 PACIFIC-ANTARCTIC RIDGE
2. 2012 12 26 23 49 28.0 -35.75 -105.25 33.0 5.2 SOUTHERN EAST PACIFIC RISE
3. 2012 12 27 0 37 12.0 -35.75 -73.75 33.0 5.7 OFF COAST OF CENTRAL CHILE
4. 2012 12 27 6 57 12.0 -30.25 -111.75 33.0 5.1 EASTER ISLAND REGION
5. 2012 12 27 10 41 4.0 13.75 -92.75 33.0 4.8 OFF COAST OF CHIAPAS, MEXICO
6. 2012 12 27 13 5 4.0 24.25 -109.25 33.0 4.9 GULF OF CALIFORNIA

That's the way ..



Here you can read what I think about all of that and next "West Coast" EQ ..

www.abovetopsecret.com...

reply to post by JustMike

does it tend to be the case that they eventually resolve the "M" designation into something more precise? And if so, does the final number -- eg a 5.9 (plus a defined type such as Mw) seem to match up with what they gave originally as simply an "M"?

Taking Potsdam first, "M" I believe is often mb as that is the normal scale value calculated from the first seconds of the P wave. When they do a tensor calculation this is then converted to an Mw scale. The page of information tells one absolutely nothing.

If we take the Mag 4.8 in the Molucca Sea....

Prov,Date/Time UTC,Latitude,Longitude,Magnitude,Depth(Km),Location
usgs,2012-12-28 05:21:07, 0.526, 126.178, 4.8, 21.0, Molucca Sea
gfzp,2012-12-28 05:21:08, 0.600, 126.260, 4.5, 10.0, Northern Molucca Sea
emsc,2012-12-28 05:21:11, 0.552, 126.290, 4.8, 47.0, Molucca Sea

...the USGS magnitude is stated to be mb, but the EMSC and Potsdam magnitudes are "M". If you look at the EMSC scientific data (linked above) they state 4.9 mb - so what is 4.8???

Potsdam have 4.5 but if you look in the EMSC data you will find various GTZ (Potsdam) entries some with magnitudes and some without. From their connections they pull 4.1 mb form Indonesia but 5.1 mb from Australia.

Their 4.5 is not even the average of the tw0 (which is the way the USGS lists work). It may be that their are others which are not shown here which give an average of 4.5

If you look at the section for seismologists on the EMSC site however you get the picture

2012-12-28 05:21:11.5 0.56 N 126.30 E 47 M 4.8 A MOLUCCA SEA MIX
2012-12-28 05:21:08.9 0.64 N 126.26 E 10 mb 5.1 A MOLUCCA SEA SC3
2012-12-28 05:21:08.0 0.73 N 126.28 E 10 M 4.5 A MOLUCCA SEA GFZ
2012-12-28 05:21:07.9 0.53 N 126.18 E 21 M 4.8 M MOLUCCA SEA NEIC
2012-12-28 05:21:05.4 0.48 N 126.15 E 20 mb 4.9 M MOLUCCA SEA GSRC

Note that the first entry says MIX. Now we have the source of the EMSC "M" 4.8 and it is the average of the other 4 (4.825) rounded down. (But this is not always the case!!!!)

The list above is of course a perfect demonstration of just how inexact a science the determination of earthquake magnitudes is. None of the latitudes and longitudes are the same, there are three different depths - at least two of which look suspiciously like defaults and I suspect all may be - and a mish mash of automatic and manual solutions.

Somehow, and I have no idea how, EMSC comes up with a depth of 47km from the selection above. Again there are probably some feeds we don't see.

If you like to be accurate about things, as I do, earthquake magnitudes are a source of immense stress (or should that be stress release?)

ETA: I did not answer your question. Mostly the M quakes stay as M as they tend to be the lower magnitude quakes. M on Potsdam will be converted to Mw when a tensor is calculated and there is no specific relationship above or below - but I suspect that most are in fact a version of mb when they are M. mb does not always result in an equivalent Mw value as they are calculated on different elements of the data.

USGS recently confuses the issue even more by using Mi for final solutions and Mwp (Mw calculated on the P wave which is the equivalent of converting mb to Mw) and Mwt and various others along with it's famous GS which I am convinced stands for GuesS

I guess I should also add that many providers of information around the world still use the Richter scale (ML) and that is specific to the area. The ML scale as originally devised for California by Richter is not the same as the Richter scale for Iran or Greece. Each area is calculated according to it's geology. A 4.8ML in Chile may not be exactly the same as a 4.8ML in Iran or a 4.8ML in California.

I have to stop......................this is driving me potty!