Quake Watch 2011

Arkansas just got hit with a 4.7.

4.7 near Conway, AK around 11pm tonight.

earthquake.usgs.gov...

Listening to the Radio while driving today had Thomas Heaton, professor of engineering seismology at the California Institute of Technology (CALTECH) on, he was explaining about how Magnitude is not what causes the damage in earthquakes it is velocity, The Lyttelton quake was 50-100cm/ second in the immediate area, which was very high, but not the highest recorded, there have been higher in Taiwan and California.
When I got home I had to check it out

True enough heres the USGS Velocity Map for the 6.3Mw quake was actaully 70cm/s



edit: heres the data


Compare with todays 5.8Mw Bio Bio Chile, only half a magnitude difference, but look at the velocity, max of 3.6cm/s



Maybe this is what we should be looking at instead of "Mag" and " Felt MM" to get the true scale of an event.

heres the audio of the interview
www.radionz.co.nz...

edit: in comparison the Darfield Sept 3 UTC 7.3Mw quake was only 60cm/s
Darfield Velocity Data

Originally posted by SusanFrey
Arkansas just got hit with a 4.7.

I felt a tremor!!!!

It's the 1st time for me, so pardon my excitement...

I was sitting in my living room and my chair rocked ever so slightly...I though, "WTH was that!"

Then I read on here about Conway AR 4.7 earthquake

I'm in Memphis TN

I think there will come a big one in Arkansas.... thats not good. Damn !!

reply to post by edgecrusher2199


PGV (Peak Ground Velocity) for that one was 2.4cm/second

Originally posted by edgecrusher2199
4.7 near Conway, AK around 11pm tonight.

earthquake.usgs.gov...

And another:

Earthquake Details

This event has been reviewed by a seismologist.
Magnitude
3.8
Date-Time
Monday, February 28, 2011 at 05:17:59 UTC
Sunday, February 27, 2011 at 11:17:59 PM at epicenter
Location
35.243°N, 92.428°W
Depth
5 km (3.1 miles) set by location program
Region
ARKANSAS
Distances
17 km (11 miles) N of Conway, Arkansas
57 km (35 miles) NNW of LITTLE ROCK, Arkansas
63 km (39 miles) W of Searcy, Arkansas
64 km (40 miles) E of Russellville, Arkansas
Location Uncertainty
horizontal +/- 8.1 km (5.0 miles); depth fixed by location program
Parameters
NST= 38, Nph= 56, Dmin=13.4 km, Rmss=1.13 sec, Gp= 54°,
M-type="Nuttli" surface wave magnitude (mbLg), Version=6
Source
USGS NEIC (WDCS-D)
Event ID
usb0001lq8

This was the largest yet and another one after. I went to bed and couldn't sleep, felt uneasy - came downstairs to find Arkansas had a 4.7 quake, significant especially in this region. I hope we don't have any reports of damage.

* This event has been reviewed by a seismologist.

Magnitude 5.2
Date-Time

* Monday, February 28, 2011 at 07:49:07 UTC
* Monday, February 28, 2011 at 09:49:07 AM at epicenter
* Time of Earthquake in other Time Zones

Location 34.963°N, 25.423°E
Depth 53.5 km (33.2 miles)
Region CRETE, GREECE
Distances 48 km (30 miles) SSE of Iraklion, Crete, Greece
142 km (88 miles) ESE of Chania, Crete, Greece
238 km (148 miles) S of Naxos, Cyclades Islands, Greece
368 km (228 miles) SSE of ATHENS, Greece
Location Uncertainty horizontal +/- 13.2 km (8.2 miles); depth +/- 0.5 km (0.3 miles)
Parameters NST=187, Nph=195, Dmin=22.3 km, Rmss=1 sec, Gp= 40°,
M-type=body wave magnitude (Mb), Version=8
Source

* USGS NEIC (WDCS-D)

Event ID usb0001lsj

reply to post by muzzy


That's really interesting Muzzy.
It also seems to slow down in a short distance. So does that mean that the quake will show on seismos at a distance at a time dependant on what the velocity is and how long it takes to get within range of the seismo?
Am I even making sense?

Another one in the Norwegian Sea.

NORWEGIAN SEA
February 26, 2011
Time: 04:30:16.3
Lat./Lon.: 61.932 2.031
National Grid: 611.5 km E, 1345.6 km N
Depth: 37.4
Magnitude: 3.6


BGS

This ones kinda out to Sea (ocean)

Magnitude 4.3
Date-Time Monday, February 28, 2011 at 16:17:16 UTC
Monday, February 28, 2011 at 06:17:16 AM at epicenter

Location 53.043°N, 149.982°W
Depth 10 km (6.2 miles) set by location program
Region SOUTH OF ALASKA
Distances 480 km (298 miles) SE of Chirikof Island, Alaska
551 km (342 miles) SSE of Kodiak, Alaska
912 km (566 miles) S of Anchorage, Alaska
1138 km (707 miles) WSW of JUNEAU, Alaska

Location Uncertainty horizontal +/- 31.7 km (19.7 miles); depth fixed by location program
Parameters NST= 23, Nph= 23, Dmin=511.8 km, Rmss=0.83 sec, Gp=259°,
M-type=body wave magnitude (Mb), Version=3
Source USGS NEIC (WDCS-D)


Event ID us2011hxbb

Chew on this webicorder from Arkansas during the period before the big quakes. I want to know what you guys think.

folkworm.ceri.memphis.edu...

reply to post by zenius

Glad someone else thinks so, I think we have been missing something all along. The Lyttelton quake brought it to my attention.
The Geonet site has always had the readings, I just didn't understand what it meant.
If you go to any quake on the Geonet Recent Quakes Page and click on Felt Reports, when the map comes up you can select 3 choices from the dropdown list. If you pick PGV it shows the peak ground velocity from stations around the area. Obviously the highest reading will be the closest in normal cases, although I seen one yesterday off Cape Runaway, East Cape that it was the 4th or 5th furthest away recorder had the highest velocity.

I found this pdf about velocity and as it happens that guy Thomas Heaton on the radio was a co author, so it must be his speciality ecf.caltech.edu...

Its heavy reading, and I don't understand most of it but this caught my eye,


So it is tied in with the Modified Mercelli Intensity Scale (MM) anyway, but from my understanding it allows the siesmologists to detrmine the intensity quickly, without depending on people sending in their Felt Reports.

It seems every location will react differently because of the geology, so what that means is you just can't compare a 6.3 in Christchurch with a 6.3 in lets say Arkansas. But you can compare velocity as cm/sec is the same anywhere on Earth.

In laymans terms I think cm/sec means how far the ground moved in one second. Being in the building industry I'm used to using millimeters, so when I seen 70cm I didn't think too much of it, but thats 700mm or close to 3/4 metre, no wonder all those buildings fell down in Christchurch!

edit: looking at the Geonet Shaking Map with PGV on for the Lyttelton quake
www.geonet.org.nz...
doesn't show much, only one station close by, at Oxford, and the reading there is quite low at 1.4235cm/s, but using th USGS readings at 70cm/sec the MM should have been IX not VIII

MM 8: Heavily damaging
Alarm may approach panic. A few buildings are damaged and some weak buildings are destroyed.
MM 9: Destructive
Some buildings are damaged and many weak buildings are destroyed.

MMIX (9) better describes what happened I think.

Originally posted by muzzy


In laymans terms I think cm/sec means how far the ground moved in one second. Being in the building industry I'm used to using millimeters, so when I seen 70cm I didn't think too much of it, but thats 700mm or close to 3/4 metre, no wonder all those buildings fell down in Christchurch!

Interesting muzzy.

I was in a corridor on the second floor of the Geology building at University and remember that I stepped about 6 feet/ 2m/ 2000mm at once. As soon as it happened I knew it was bad, but it took over an hour before I realised that the city centre was in ruins. Walking east from Uni to home,passed the city centre there was an increase in liquefaction (first really noticable in Hagley Park Golf Course where they have a load more sand trapsnow!) and the first major (structural) damage was evident at Christ's College. I couldn't see the Square from the Museum at the opposite end of Worcester Boulevard due to dust clouds and the boatshed footbridge had been compressed with the joints at each end splaying up. I saw people with blood and dirt and wet through and already the Civil |Defence operation had begun and roads were blocked off. It tookmequicker towalk home from Uni (c.2 hours) than drive (normally 25 minutes) and was overtaking traffic on foot!

There was mention on the Radio soon after about the PGV saying it was greater than the September 4 'quake, and combined with its proximity to the city and the relative shallowness, as well as the resonance off the peninsula it was particularly damaging to the tired infrastructure.

I can't express how impressed I am with Civil Defence and the entire response. Power, phone, were back on within a day, water is back on, though due to cracked mains on our street we are still using bore water/ boiling/ and a good mate from Timaru brought upsome drinking water. Luckily I have an old commode so the Wife is comfortable. Our rubbish was collected yesterday.
Sorry to give an account here, it's my 'day off'. Everyopne is jaded, dusty and exhausted and the student 'army' along with many other excellent volunteers have been wonderful, getting stuck in helping people. I've been shovelling sandy muddy silty material and need to recharge before I go back out there.

Oh, and bugger, one of my old school friends and fellow cricketer was in the CTV building.


These videos are worth revisiting:

Originally posted by aorAki


Oh, and bugger, one of my old school friends and fellow cricketer was in the CTV building.

Damn, did your friend survive?

Nope, he's a goner.

New from Mark Quigley: drquigs.com...

reply to post by aorAki

I'm really sorry to hear that

good article, he pretty well debunks the Ken Ring prediction racket

reply to post by aorAki


Aoraki, so sorry to hear that. Stay safe x

Puterman - I thought this might interest you - new graph of the energy release from our 7.1 and 6.3.

www.christchurchquakemap.co.nz...