Quake Watch 2010

reply to post by zenius


Magnitude Mw 6.2
Region VANUATU
Date time 2010-12-26 02:13:44.5 UTC
Location 19.67 S ; 168.26 E
Depth 60 km
Distances 1083 km W Suva (pop 199,455 ; local time 14:13:44.5 2010-12-26)
174 km NE Wé (pop 10,375 ; local time 13:13:44.5 2010-12-26)
108 km W Isangel (pop 1,437 ; local time 13:13:44.5 2010-12-26)

Not picked up by USGS yet

reply to post by PuterMan

And? You can't stop the story there just as it was getting interesting!

One way to guarantee a lack of action is to tell me there's been a quake.. the only thing that got action was the laptop!!

Question: Lots of locals are asking if our aftershocks today could have been related, in some way, to the Vanuatu 7.6... I say not, but could it be? I do often wonder if one quake triggers others but GeoNet are saying definitely not.. move on.. nothing to see...

reply to post by PuterMan


What's with the depth inconsistencies? USGS says 9.2km and EMSC says only 1km, which of course is questionable because it's a trench area unless it is an almost surfacing volcano? Yours says something else. Or was there more than one 6.2 but not more than one reported?

Originally posted by MoorfNZ
reply to post by PuterMan

 

Question: Lots of locals are asking if our aftershocks today could have been related, in some way, to the Vanuatu 7.6... I say not, but could it be? I do often wonder if one quake triggers others but GeoNet are saying definitely not.. move on.. nothing to see...

I'd tend to agree with Geonet, that there is no direct relationship, save for the fact the Pacific Plate just expanded a bit over the last few days.

Originally posted by muzzy
reply to post by MoorfNZ

 

Yeah seen that when the 4.2 came on earlier, been 22 quakes this morning, all but 5 right under the city area from the look of it. I'll have a closer look later.

Reference, Latitude, Longitude, UTC Date/Time, Depth, Magnitude,
3436844, -43.58792, 172.38579, 2010/12/25 7:41:22, 1, 3.718,
3436850, -43.35941, 172.5677, 2010/12/25 8:2:8, 9, 3.134,
3437085, -43.53735, 172.6377, 2010/12/25 13:7:4, 5, 4.207,
3436949, -43.53391, 172.63316, 2010/12/25 13:8:34, 8, 3.756,
3436956, -43.53146, 172.64995, 2010/12/25 13:32:10, 6, 3.741,
3437014, -43.57077, 172.47076, 2010/12/25 16:24:16, 12, 2.758,
3437016, -43.51685, 172.69968, 2010/12/25 16:34:5, 3, 2.691,
3437026, -43.58006, 172.43468, 2010/12/25 17:3:0, 14, 3.023,
3437061, -43.5377, 172.63081, 2010/12/25 19:3:42, 4, 3.834,
3437070, -43.57824, 172.43958, 2010/12/25 19:41:28, 12, 2.851,
3437091, -43.501, 172.68564, 2010/12/25 20:51:45, 6, 2.747,
3437105, -43.55441, 172.66148, 2010/12/25 21:30:16, 12, 4.893,
3437106, -43.53178, 172.61937, 2010/12/25 21:32:20, 0, 3.695,
3437107, -43.50067, 172.65366, 2010/12/25 21:35:54, 5, 3.55,
3437112, -43.54394, 172.68207, 2010/12/25 21:49:34, 14, 2.879,
3437115, -43.69859, 172.7552, 2010/12/25 21:57:35, 0, 2.855,
3437117, -43.52748, 172.66386, 2010/12/25 22:3:12, 3, 2.926,
3437122, -43.5093, 172.65671, 2010/12/25 22:22:23, 5, 3.17,
3437123, -43.52282, 172.64764, 2010/12/25 22:26:47, 6, 3.067,
3437133, -43.54797, 172.67891, 2010/12/25 22:53:7, 6, 3.503,
3437141, -43.51545, 172.68184, 2010/12/25 23:14:52, 5, 2.925,
3437148, -43.52974, 172.61183, 2010/12/25 23:34:32, 2, 3.73,
3437153, -43.52993, 172.65536, 2010/12/25 23:52:40, 5, 2.95,

edit on 25-12-2010 by muzzy because: (no reason given)

I cant edit the list with the locations (passed 4hrs) so here is the full NZ list page off my blog
dl.dropbox.com...

and the Interactive Map

reply to post by zenius


I posted immediately it hit the popup in my program and that info came form the EMSCs first report. This subsequently got changed. In my system I have the following revised data and I have included the revisions against the 7.9 (original) so you can see how they change things.

Date/Time UTC,Latitude,Longitude,Magnitude,Depth(Km),Location
2010-12-26T02:13:44.500Z,-19.67000,168.26000,6.2000,60.0000,VANUATU
2010-12-26T02:13:37.000Z,-19.66340,168.29800,6.2000,8.5000,Vanuatu

2010-12-25T13:16:42.000Z,-19.77000,168.05000,7.9000,60.0000,VANUATU
2010-12-25T13:16:38.000Z,-19.75890,167.97360,7.6000,24.4000,Vanuatu region
2010-12-25T13:16:37.000Z,-19.77510,167.89460,7.3000,12.3000,Vanuatu region

The depth got changed from 60 to 8.5

Revision 8 changed the depth to the current 9.2 km but by this time they were using 259 stations against 182 on revision 7.

Ver, Date and Time, Latitude, Longitude, Magnitude, Type, Rep Stns, Depth, Location
8 2010-12-26T02:13:37.000Z -19.63260 168.32070 6.2000 Mi 259 9.2000 Vanuatu
7 2010-12-26T02:13:37.000Z -19.66340 168.29800 6.2000 Mi 182 8.5000 Vanuatu

You can also see in the deleted table the 7.9 (original) which as duplicated for a while as a 7.6 on a different network by IRIS. This was on the pt network as opposed to the us network for the others.

Date/Time UTC,Latitude,Longitude,Magnitude,Depth(Km),Location
2010-12-25T13:16:40.000Z,-19.72000,167.96000,7.6000,33.0000,Vanuatu region.

I store all this data so it is reasonably easy to track down what happened.

reply to post by PuterMan


I had no idea there were so many revisions done! So do you know exactly how they come to the final depth? Surely all the stations would be different and the further away the station the less accurate it would be? Or do they use the mean, median or mode from the stations combined?

reply to post by zenius


I think they use some sort of averaging. Muzzy may have a better idea as he studies the phase data more than I do. I think it is all of the above and a wet finger!

One thing I have noticed is that if lat or lon change the depth does not always change but the magnitude or time usually does. I am contemplating adding a facility in my program to read the seismo data myself but you need all the response files for the station to pick up sensitivity etc etc so it may just remain as contemplation!

By the way, I keep mentioning my program and some will be wondering where the hell the next version has got to. Simple answer is that it became very complex and I have been removing dependence on the Windows registry as much as possible for configurations. I have also been making sure that the new windows service for collecting the data is working properly and after about 6 months of testing I am reasonably happy that it is. There are still the occasional glitches, but they are invariably caused by bad data from the providers. I have been running USGS, EMSC and GeoNet and all are working. Between muzzy and myself we came up with a solution to the place names for New Zealand and I think that is now reasonable. I am going to apply a similar solution to the Iceland data since although it has place names the older data does not.

Canada and Australia are the next targets, but I AM going to release the current version for testing on the 1st Jan.

Before that happens I need to sort out assigning a master network since currently it is USGS and that may not make people in other areas happy.

The master network controls assignment of alternative quakes - i.e. identical or near identical data from other networks and this is a complex area since as you are aware every provider gets different results. Automatically choosing identical quakes has taken some time but seems to work now. I still have to manually assign some however.

reply to post by PuterMan


So we really have no idea as to the accuracy of the data? Perhaps they need to find new technologies to measure them. In the meantime, thanks Puterman, for developing your program and giving us all some confidence that someone knows what's going on!

reply to post by MoorfNZ


Was the Akaroa region once a volcano? That's an interesting piece of geography looking at google maps.

Another 5+ in the Bay of Plenty, closer to Tauranga than the 5.9 yesteday, but not reported as felt (yet) probably due to the depth.

Reference Number 3437415/G
Universal Time December 26 2010 at 14:00
NZ Daylight Time Monday, December 27 2010 at 3:00 am
Latitude, Longitude 37.53°S, 176.49°E
Focal Depth 210 km
Richter magnitude 5.4ML (USGS 4.6mb)
Region Bay of Plenty
Location
* offshore north-east of Motoiti Island (my edit)
* 30 km north-east of Te Puke
* 30 km north-east of Tauranga
* 170 km south-east of Auckland
www.geonet.org.nz...

edit: one report in from Ahuriri near Napier, Hawkes Bay Intensity of MM4

reply to post by PuterMan


I think the issue is the various types of magnitude and the conversion thereof.
The number of stations seems to be critical as well because the more stations there are the lower the average is going to end up. The Russians always put the number of stations used beside the magnitude of a quake, so it must be important.

As an example lets look at that last Bay of Plenty quake and compare the USGS magnitude with the Geonet one.
Unfortunately USGS don't show an ML for this one so its not the best example.

USGS used 9 stations to get the result, which isn't many, so taking the average the end magnitude average comes out at 5.2mb.
It already goes off on a muddled tangent right away as they have the number of stations as 5 on the page (in brackets after the mb=4.6)
mb = 4.6 ( 5) ML = 0.0 ( 0) mblg = 0.0 ( 0) md = 4.2 ( 1) MS = 0.0 ( 0)
yet if you count the number of stations with magnitudes there are 9 of them
Even if you just take the first 5 on the list the average is still 4.9, not 4.6.
It would help if they said which 5 stations they used.
Who knows how they work it out.
Geonet doesn't seem to have phase data available to the public so its hard to figure out how they come to the result they do.

USGS are very selective about posting New Zealand quakes, and when they do they usually get a totally different location from Geonet

further to post by muzzy


Then again if you have Google Earth, take a look at the bathometry (undersea terrain) that runs north west from the top of the North Island through Norfolk Island ( and a submarine volcano (1966) ) to New Caledonia and Vanuatu, there is quite a prominent ridge. I read something once about the old subduction trench between Pacific and Australia Plates used to be way over here (prior to the newer one at Colville ridge and now the Kermadec Ridge/Trench). Talking millions of years ago though.
That big gash to the NE of the ridge running from Cape Reianga to Norfolk interest me, can't find much about it, there doesn't seem to be records of many earthquakes along there.

My personal theory is that these quakes ARE related to each other geologically.

If you look at the shape of the Australian Plate betweenVanuatu, NZ Fiji and Samoa its almost exactly the same shape as the East Cape area of New Zealand. If you expand the shape of the North Island out to the scale of the AU plate, the location of the New Hebrides 7.3 quake is exactly in the same place (to scale) as the Ohena Ridge, BOP 5.9 quake.
With the Pac and AU Plates being locked together between Cook Strait and Haast this becomes the pivot point for the expansion of the AU plate, and there has to be some stress reaction at this point as well (your ChCh quakes).

The Google Earth overlay from USGS showing the rates of subduction (click on any USGS GE link off any of their quake reports maps page) has the Australian Plate going under the PP at 123mm/yr at the New Hebrides (Vanuatu)and the PP going under NZ at 88mm/yr at East North Island, NZ, so the whole NZ/Vanuatu/Fiji/NZ section of the AU plate is tilting up from the east side OR the AU plate is just expanding.
They key question is "at the Kermadec/Hikurangi subduction zone, is the PP going UNDER the AU plate OR is the AU Plate going OVER the PP."

or are they both expanding?

now I've got a headache

What may be relevant in connecting all these quakes of the 25th UTC is the Moon was in Perigee ( the point of closest approach) at 12:25UTC www.fourmilab.ch... ;
26 minutes after the BOP 5.9
37 minutes before the Chch 4.2
51 minutes before the Vanuatu 7.3
9hrs 5 minutes before the Chch 4.8

If I was on the jury at the trial wouldn't be able to convict the Moon as guilty beyond reasonable doubt though

Only 2 out of 8 mag 5+ quakes in NZ since Nov 1 have been on a Lunar Phase (Full, New, Perigee or Apogee Moon)

Originally posted by zenius
reply to post by MoorfNZ

 

Was the Akaroa region once a volcano? That's an interesting piece of geography looking at google maps.

Yes, both Akaroa and Lyttelton were once volcanoes but extinct for eons... extraordinary beautiful from the air and one of our favorite local places to visit - scenery is stunning...

I was rudely woken by a 3.6 at 5km depth just along the road from our house this morning grrrrr

www.geonet.org.nz...

reply to post by muzzy


[atsimg]http://files.abovetopsecret.com/images/member/737a021fbcda.png[/atsimg]

It already goes off on a muddled tangent right away as they have the number of stations as 5 on the page (in brackets after the mb=4.6)

I have no idea if this is the answer but if you remove all incomplete lines including S wave lines and the one line that is full but without an X you get 5 lines.

OK I have been through several more now and this is what I find:

The number of stations used in the calculation is:

• The number of complete lines with full data
  
• Unless there is only one in which case it is the number of lines with part data as long as the part data is not less than the average length of the part data
  
• Where all data is part data and some is more part than others then the part data is used but the lines with no station against them (i.e. they are extra lines for the station) are dropped.
  
• But, if there are less lines with an X than without an X then the total used in the lines without an X
  
• If none of the above applies then the first series that leads to an average under a magnitude boundary is used.
  
• If all are within one boundary then as many as are needed to get the lowest reasonable average are used.
  
• Most of that is too much like hard work so we just pluck a figure for the number of stations out of thin air and make the magnitude look something like right visually.
  

You could say that there appears to be absolutely no rhyme of reason in it!

reply to post by PuterMan


Thats pretty confusing alright ( insert smiley with eyes going in circles here)

Geofon is clearer, seems easier to follow IMO

Apropos absolutely nothing at all:

[atsimg]http://files.abovetopsecret.com/images/member/eda7b06478d2.png[/atsimg]

Just thought you might like this list I calculated (by Excel not by hand!)

reply to post by PuterMan


Well that certainly made it a lot clearer...NOT

Magnitude 6.3

Date-Time

* Tuesday, December 28, 2010 at 08:34:17 UTC
* Tuesday, December 28, 2010 at 08:34:17 PM at epicenter
* Time of Earthquake in other Time Zones

Location 23.375°S, 179.794°W
Depth 551.6 km (342.8 miles)

Region SOUTH OF THE FIJI ISLANDS

Distances 320 km (200 miles) SSW of Ndoi Island, Fiji
535 km (330 miles) WSW of NUKU`ALOFA, Tonga
610 km (380 miles) SSE of SUVA, Viti Levu, Fiji
1590 km (980 miles) NNE of Auckland, New Zealand

Just missed that one!

Old Mother Earth sure is trying to ring in a New Year!