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New online Seismograph

davenn

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Hi gang

something I have been wanting to do for some years is to get real time seismograms from my recorder online.
Finally achieved that last weekend. I use a program called Snagit which runs in the background and every 5 minutes does a screen capture and ftp's it to my www site for anyone to log in and view

Quake recorder

there's an event that happened about an hour ago
a M5.7 far south of Tasmania, Australia visible on the drum at the moment

its ~ 2346 km SSW of my home/recorder here in Sydney, Australia

cheers
Dave
 

Harald Kapp

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Nice work, Dave.

But: how do I read the chart? The vertical axis is time, as it has time stamps. but what is the horizontal axis showing? Or do I have to continue from the right to the left of the next line below as in reading a text?

Also you might want to space the lines a bit wider so the peaks do not so easily overlap.


Harald
 

davenn

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Nice work, Dave.

But: how do I read the chart? The vertical axis is time, as it has time stamps. but what is the horizontal axis showing? Or do I have to continue from the right to the left of the next line below as in reading a text?

OK ... you can see time (in UTC) down the left side incrementing at 30 minute intervals
ie. each line across the screen is 30 minutes. It just labels every 4th line to save text congestion down the side. If you sit on the page for a while and do periodic refreshes you will see the trace moving left to right across the screen.
So X and Y axis are both showing time ;) just to fool you. We are not worried about physically measuring amplitude on this screen.
From within the probram I can pull out an even from any time since the data recorder started --- ie. in this case over the last year and a bit. I can pull out that event and look at it in the analysis software and do distance and magnitude calcs and also add in the quake information for the USGS (United States Geological Survey) or other institution.
eg ... event origin date/time - Lat/Long depth etc

Also you might want to space the lines a bit wider so the peaks do not so easily overlap.
Harald

they are going to overlap anyway on the bigger quakes or big bursts of manmade noise many lines get overlapped. Thats not a real issue, its pretty much similar to any of the institution ones and other fellow amateur seismologists


Dave
 

Harald Kapp

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Thanks, Dave.
they are going to overlap anyway on the bigger quakes or big bursts of manmade noise many lines get overlapped. Thats not a real issue, its pretty much similar to any of the institution ones and other fellow amateur seismologists
I understand that. On old mechanical seismographs this was certainly due to mechanical limitations (if you had more than one trace).
How about coloring every second line in a different color? Even it has been traditionally as you describe, I see no need to stick to the tradition if a fix can make life easier.


But then again ai'm not into seismology. Maybe it is not necessary.

Harald
 

davenn

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OK here's an image of the event after its been put into the analysis program
and have done some FFT lowpass 6 pole filtering with a cutoff at 5Hz to cut out a lot of the manmade and other higher freq noise

attachment.php



now for some other info....

There are 4 wave arrivals nother on the seismogram

P = The P wave is the fastest travelling, ~ 7 - 8km/sec. It is a compressional wave like a sound wave. Their frequency avg's around 1 - 5 Hz, give or take a little

S = S wave it travels a bit slower ~ 5 - 6 km/sec. It is a shear wave ... ground motion is perpendicular to the direction of propagation. Their frequency avg's around .1 - 1Hz, give or take a little

The LQ and LR are the surface waves, they dont penetrate into the earth to any great distance, a few 10's or so of km. They are the slowest travelling at ~ 3 - 4 km/sec
and are complex styles of shear waves.
LQ = Love waves, LR = Rayleigh waves
It is the surface waves that do the damage to buildings and other structures. Their very low frequency from ~ 10 to ~ 200 seconds/cycle. are, along with various ground types allow structures vibrate at their resonant freqs and demolish themselves.

( I will add to that ... there is also the initial hi acceleration pulse that can do initial damage to weaker structures.)

OK there's seismology 101

cheers
Dave
 

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davenn

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Thanks, Dave.

I understand that. On old mechanical seismographs this was certainly due to mechanical limitations (if you had more than one trace).
How about coloring every second line in a different color? Even it has been traditionally as you describe, I see no need to stick to the tradition if a fix can make life easier.


But then again ai'm not into seismology. Maybe it is not necessary.

Harald

we leave the different colours for showing additional channels.
one my system is fully operational there will be 5 channels. At the moment there is 1 within hopefully the next 2 months I will finally find time to get the next 3 sensors online then some time in the future there will be another long period sensor like I have running at present. It will be orientated perpendicular to the current one.
The current one has its pendulum boom orientated east-west so its sensitive to quakes from the north and south. the next one will have the boom orientated north-south so it will pick up the events to the east and west better.
The current sensor doesnt do well recording events perpendicular to its orientation.

Dave
 

Harald Kapp

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Thanks for the explanation. Very interesting.
Could you identify this event? Is it a true seismic event or possibly man-made?
 

davenn

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Oh I meant to add, even when there are 4 or 5 channels being recorded, I will only at most display 2 of them, probably one short period and one long period sensor. and then I will have to cut back on the trace hours visible on the screen.

Currently, it displays ~ 36 hours from the top to the bottom of the screen.... when the trace finally gets to the lower right corner the screen clears, it is set to display the last 15 trace lines and then continue on from there

Have a look at my seismo page to see the sensor I built and the commercial tri axis sensor set etc.

D
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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That's very cool Dave
 

davenn

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Thanks for the explanation. Very interesting.
Could you identify this event? Is it a true seismic event or possibly man-made?

manmade events wont cause traces this big... well not these days anyway
back in the 50's - 70's era of underground nuclear testing, events of M4.5 - 5.5 were easily produced. The New Zealand Institution for recording quakes kept a close eye on Muroroa Atoll in the south Pacific with the French nuclear testing

There was very little difference in the seismograms. The big giveaway was that because the blast is a point source there is a pretty much equal P ( compressional) wave radiating out in all directions.
Natural quakes are not point sources, rather they are on a faultline that has some length to it. and from that we can identify the orientation of the faultline that ruptured

we look at the first motions of the arrival of the P wave at various recorders spread around the world, look at this page of mine for a bit of an explanation NOTE graphic image B that has a fault orientated NE SW note the arrows on each side of the fault and the C compressional quadrants and the D dilational quadrants

Dave
 

davenn

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Thanks Steve

This is really one of my major passions in life ( yeah astronomy is another ;) )

it can be difficult to get me off my soap box once I get started
but if some one is willing to listen, I will waffle and hopefully teach a little for hours

D
 

wingnut

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Davenn

Must be so satisfying to achieve this long term goal.

You left the tectonic plates of New Zealand for the quieter Australia.
I have heard of storm chasers but are there quake chasers? :)

Maybe you can tell be if earthquakes are on the increase or not.

Years ago I remember a site which had a map of the world and recorded every earthquake with a symbol. Have you seen this site?
 

davenn

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Davenn

Must be so satisfying to achieve this long term goal.

You left the tectonic plates of New Zealand for the quieter Australia.
I have heard of storm chasers but are there quake chasers? :)

yeah go figure haha I used to record so many New Zealand events
Yup my wife I also stormchase .. in Aussie and the USA

Maybe you can tell be if earthquakes are on the increase or not.

there is no obvious trend to say that quake numbers are increasing.
over the last ~ 120 years of world data collecting by various institutions ... particularly the USGS .... shows that the number of events is pretty stable

yearly averages are 1 x M8 + ; 18 x M7.0 - 7.9 ; 100 x M6.0 - 6.9 ; 1000 x M5.0 - 5.9
1000's of M4.0 - 4.9 etc etc

some years like this one (2012) we get a couple of M8+ events, other years none, it all averages out to ~ 1 / year


Years ago I remember a site which had a map of the world and recorded every earthquake with a symbol. Have you seen this site?
The USGS produce maps with quake locations over various periods of time

Ohhh BTW you can just call me Dave not davenn ;) the nn are the first and last letters of my surname

cheers
Dave
 
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