GEE (Global Earthquake Explorer) Tips

In an effort to help those that are just getting started with GEE, here are some quick tips that will help save you some time in learning the program. They may also help you to avoid thinking you have the greatest earthquake ever known to man on your screen quickly and easily. This thread is only for the REAL TIME VIEWER portion of GEE. In other words, for those that want to actively monitor incoming information from seismic stations over the internet in close to real time.

GETTING STARTED

1) Immediate Don't

Once you click the REAL TIME VIEWER (RTV), do not try to reset anything or play around in GEE UNTIL THE BLUE AND GREY STATION ICONS HAVE LOADED ON THE MAP. Reason: you may likely crash the program. Yeah, it is a bit buggy, but not too bad. Often times, and especially lately, it can take a long time for these icons to load. In some cases up to 30 minutes or more. Likely Reason: overloaded servers- a lot of people have gotten into this program, and so the load on the servers is often very high. If you don't want to wait, about the only thing you can do is shut the program down, and then restart it, hoping that the station icons reload on the map quick. I have found it's better just to load the program, click on the RTV, and then minimize it and do something else for a bit. When the stations finally load, GEE will pop up usually from being minimized on its own when the station data is received. Patience is your friend, especially with GEE.

2) So wow, the station icons finally loaded, you see the world map, and a bunch of blue and gray triangles finally appear. Now what? Well, the blue triangles mean that you can select those stations under your current channel selection, and the gray ones mean that either the station is not available- or that you don't have the right channel selection for that station. More on that later, but just know for now that when the program loads, you are by default selected to load only broadband channels, and the blue triangles represent those stations which are broadband, and that you can select to monitor right now.

3) Point to any station, and it's network and location are displayed in the status bar, bottom right. This way you can tell what station you are about to select, and where it is located. Very handy, especially in congested areas where there are lots of stations.

4) So choose any blue triangle station and click on it. It will get a white triangle around it, meaning it is selected for loading. Yes, you can select more than one. To deselect all, hit the deselect button on the toolbar (the one with triangles on it). Once you have a station or two selected, hit the "Load Realtime Data" button on the toolbar, and you are in business! The realtime viewer tab opens up with three channels per station being displayed. Give it a minute or two to load the actual seismic waveform data from the station(s). Once you see this data come in, you are now live monitoring the stations you have chosen. Yippee!


THE DEVIL IN THE DETAILS

1) RealTime Viewer Description and Use

A) Let's work our way from left to right. On the far left of each channel is a scale that keeps changing as the displayed waveforms are received. The scale for each channel is dynamic in the sense that it adjusts itself constantly to accommodate the maximum peak of any given waveform in its channel at any time. In each channel's box you will notice it says "Amplitude" and then it has a zero in the middle of the scale and positive numbers above, and negative numbers below. Some critical things about this scale you must know:

1) You will usually, and almost always, see either nm/s (nanometers per second) or microns/sec in the box. In rare cases you may get to see mm/sec (millimeters per second) if you happen to catch an event (quake) that pegs the waveform beyond the microns per second scale. And in extremely rare cases, you may actually get to see centimeters per second, in which case no matter what station you have chosen, that will be a whopper of a quake. As in 8+ or more in Richter scale magnitude. Very rare, and a scale which so far personally I have never seen.

2) Understanding what this scale is measuring: ground velocity, not magnitude! Oh no! Bummer. But but I just wanted something that would give me immediate Richter scale magnitude! Sorry, no can do. Why? The most likely reason is the program has no way of knowing how close it is to the epicenter of a quake. It just measures how fast the ground moves at the station you have chosen. The more intense an event (possibly a quake), the faster it causes the ground to actually move, and the more it will stretch the dynamic scale. But through monitoring various stations in the area, you can get a rough idea, with a little experience, of if it is a quake and if so how roughly big it is. More on this later. Patience.

3) So when you see a bump on your screen on a channel, the VERY FIRST THING YOU DO IS LOOK AT THE AMPLITUDE SCALE, to determine roughly how big this is. If you see the scale stretch to 900 nm/sec, it's tiny tiny tiny, and not even worth thinking about. If it is reaches 50 microns/sec or more however, that is worth taking notice of, and then trying to see if other stations close by have registered it too.

4) Understanding what you are up against here, by example. Let's say you check your GEE, and see a pretty good size spike, or bump, or thick triangle looking thing in the waveform of a channel. You immediately check the amplitude and you see, whoa, 900 microns/sec. That's probably a quake, but not necessarily. An animal may have inadvertently hit the thing. So you need to corroborate this by getting another station close by. And this is one reason I always, where possible, monitor in a triangular, three station pattern for any given area. But let's move on. So you check another station close by, within 200 miles or so, and you see nothing. All other stations you check as close by as possible show nothing out of the ordinary. Well, you have your answer. It was probably an animal, and not a quake.

5) In the interest of saving you time, I am going to list amplitudes of events and some suggested actions:

0 to 1000 nm/sec- Nothing, don't even think about it. Note, 1000 nm=1 micron

1 to 20 microns/sec- most likely nothing, but worth a glance around other stations. Many man made events occur here.

20-50 microns/sec- could be a quake, but check other stations. Many man made events fall into this category.

50 to 100 microns/sec- could be a quake, may be a mine blast, check other stations.

100 to 300 microns/sec- always worth looking into, probably small quake somewhere, but it could be an indicator of a larger quake much further away. Rarely do man made events fall into this category, although some mine blasting can reach here if it is close enough to the station.

300 to 800 microns/sec- 90% chance this is a quake, and immediately seek corroboration from other stations.

800 + microns/sec and ANYTHING into the MM/sec is almost sure it's a quake, and likely a bigger one, 5+ magnitude. Note: 1000 microns=1 millimeter

CRITICAL NOTES TO THESE GUIDELINES:
Remember that the distance from the epicenter to the station plays a critical role in determining what the ground velocity at the station will read. The problem is of course that GEE is roughly 30 seconds to 2 minutes behind realtime, and while you have the data on a quake, you don't know exactly, just from watching GEE, where it is located. But you can get an idea if you are monitoring multiple stations in the same area, because doing this will also give you a direction by simply looking at which stations received the strongest signal. And don't worry, you won't have to wait long before you find out. The USGS will be publishing the quake within minutes, depending on size.

Example: 5.0 mag quake strikes 50 miles from your monitored station. You might see GEE read 900 microns/sec or more on this at that station, that close. But get this: If this same quake strikes, same place, but your closest monitored station is 500 miles away, you may only see this register at 150 microns/sec. This is why monitoring multiple stations per area really helps.

[edit on Sun Oct 4th 2009 by TrueAmerican]

Sorry man.

Trying to get the mods to pull this out.

[edit on 4-10-2009 by KSPigpen]

[edit on 4-10-2009 by KSPigpen]

Realtime Viewer Description and Use (Continued)

B) Middle Top Scrolling Timeline.

At the very top of the RTV tab window is a scrolling timeline, always moving from right to left on its own (unless you stop it or FF or Rewind from the toolbar). This displays what is known as UTC (Coordinated Universal Time). It is much like regular time, but is a world accepted (universal) time in use by all scientists everywhere so that a single time means exactly the same thing to everyone. More on this here:

en.wikipedia.org...

You will notice that the USGS (US Geological Survey, you know, those guys that report on earthquakes and much more) also will display the time of earthquakes in UTC. The fact that GEE uses UTC is very helpful in cross-referencing events to quakes and so forth. Otherwise, we'd have to calculate this every time- yuk!

At the far right of this timeline is the actual point of realtime (the now moment). This is indicated by the all the red flags that say "CURRENT TIME" on each channel. You will notice that incoming data on each channel never quite reaches this line, because the data received is slightly behind realtime. This is due to internet latency, seismograph methods of uploading this information, and the overall system overhead of getting this data to your computer. Expect delays of 30 seconds to 2 minutes behind realtime, and sometimes longer. Also, the more stations you monitor, the higher the load you put not only on your computer, but the GEE servers as well.


C) The Middle Screen Waveform Data and Channel Description

So what in the heck is a channel, and why are there three of them per station?

For most users, understanding that you are monitoring "broadband" seismic stations will probably be enough for simple quake watching. But all this goes way deep for the more serious quake watcher, let alone for a real seismologist.

In a nutshell, there are many different types of seismographic stations. And these stations use different types of seismometers (which all have their own intended specific uses.) Before you try to understand any of the more technical ones, it is probably best you simply get a grip on what Broadband seismometers are first, and how they are used in GEE. And not that broadband ones are simple, either. But since that is what GEE comes up with first, and what you are likely to use most, if not all the time, we should start there.



www.pnsn.org...

When an earthquake happens, there are generally speaking three main components to the way the earth moves. You have east/west, north/south, and up/down motion- and any combination thereof.

Seismometers in general are designed to measure these movements on those three axis. And there is usually a separate meter, one for each of those directions of movement, contained in a single seismometer. Each of those meters outputs its data on a separate channel, and these channels are usually labeled with the last letter of the channel name meaning which one it is.

An E, as in the "BHE" channel means it is measuring movement on the East/Weat axis. An N, as in the "BHN" channel means it is measuring movement on the North/South axis. A Z, as in the "BHZ" channel means it is measuring movement on the up/down (vertical) axis.

More basic information here:
en.wikipedia.org...

So, knowing this now you can look at those three channels per station in GEE and have an idea of what you are looking at! As you might have guessed, any waveform on the BHE channel that goes above the zero line (positive) represents movement in an eastern direction, and any below the zero line (negative) in a western direction. The same applies respectively for the BHN and BHZ channels: Positive movement is north and up, negative movement is south and down on each channel respectively.

The other two letters in the names of these channels mean B for a"Broadband" type of seismometer, and H for "High Gain".

But who really wants to know all this technical stuff? Oh, you? Then hit Google my friend and read all about it, cause I've barely scratched the surface here. It is enough however, to get a general clue of what is going on, and how, more importantly, you can apply it to quake watching in GEE.

[edit on Mon Oct 5th 2009 by TrueAmerican]

Thank you so much for this. I have made most of the mistakes that you are trying to help noobie's from making. Very frustrating when you finaly get one screen up and find you have no idea how to read it.

Installing GEE in Ubuntu Linux 9.04+ (gnome desktop)

Be sure you have sun-java6-jre package installed using the synaptics package manager (approx 30M)

Click on “Places”
Click on “Home”
Create a new folder called “gee”

Download tar.gz from www.seis.sc.edu...
Extract and put folders “bin” and “lib” in your newly created “gee” directory

Make a new text file called GEEstart in your home directory (the same directory you have your new gee folder in) and edit it as follows:

#!/bin/bash
cd gee/bin
export GEE_HOME=/home/lernmore/gee
./gee

(be sure and replace lernmore for your own name/account)

open a terminal, (Applications, Accessories, Terminal) type the following

chmod +X GEEstart

(that makes it executable)

Click on the new GEEstart file in your home directory and select Run


note: There may be an easier way to get it to run, but I couldn't get it to work "out of the box".

Realtime Viewer Description and Use (Continued)

C) The Middle Screen Waveform Data and Channel Description (Continued)

Understanding Seismographic Networks and Channel Naming

There are many networks of seismographic stations run by different entities. Some are private, and some are public. One of the biggest of course is maintained by the USGS, and many sub networks feed data from their own stations to it.

Since you will often encounter stations from this network, you may want to read more about these networks here:

earthquake.usgs.gov...

Another popular network you may encounter is the Transportable Array network, which is part of the EarthScope Project. Read more here:

www.passcal.nmt.edu...
www.earthscope.org...

When you see a channel in GEE in the RTV, there is always a name to each channel in the upper left of each channel's space. The two initials you see identify first the network, and then after the period, the individual station on that network.

So when you see CI.CWC. .BHE for example, this means you are looking at the BHE channel from the CWC station, which is on the CI network. Just remember it goes network.station.channel.

TOOLBAR USAGE IN THE RTV WINDOW

In the upper left you have the toolbar, which gives you a cursor tool, a zoom plus and zoom minus tool, a hand tool, and timeline movement controls.

Cursor Tool- Looks like a big PLUS SIGN +. Click on this when you want to close just one channel in the RTV window by clicking on the X directly to the left of each channel's name.

You will also be able to point to peaks in the waveform data with the cursor tool, and when you do, you will see a new display of text in the channel come up over on the bottom right of the channel your cursor is in. This displays additional information about the waveform you are pointing at.

Zoom Tools- Looks like a magnifying glass. Click on these to either zoom in (+) or out (-) in the RTV window. As you do this, note that YOUR AMPLITUDE SCALE ON THE LEFT ADJUSTS ITSELF TO ONLY WHAT IS CURRENTLY DISPLAYED IN THE CHANNEL. So if you zoom too far in, and leave your computer for a minute, you might possibly miss an event on that channel, because due to the high zoom selection the event went by too fast and you never saw it. The default zoom is usually fine for monitoring until something happens. At that point then it is useful sometimes to use the zoom tools to inspect things closer. But it is also important to note that you may need to adjust the zoom on the RTV window depending on what size window you choose to display the entire GEE program. Play around with this and soon you will get it. I often will actually zoom out further than the default when I am monitoring many stations and channels, because when something happens you can still see it- but it lets me look at many more channels at once.

The Hand Tool - Click on this when you want to move the entire RTV window either right or left in your display. You do this by positioning the hand anywhere in the channels area, holding down the left mouse button, and then dragging either right or left, and then releasing the left mouse button. This is useful when you want to go back in time and see what happened if you were not looking at the screen for a while. Also, I forgot to mention that you won't see the red "CURRENT TIME" flags on each channel on the far right until you click the hand tool and drag the entire RTV display to the left. Unless I am zooming on something, I usually drag it to where I can just barely see the red flags of the current time over on the far right of the RTV display. Anything to the right of the CURRENT TIME flags is not usable, because there is no data received yet AFTER the current time.

The Timeline Transport Controls - Generally you will not need to use these until an event happens. But these provide a way to stop the timeline or fast forward or rewind the timeline. GEE only holds each channel's data for a little while, and then it actually disappears off the screen on the far left, never to be seen again. So if an event happens and you want to inspect it, you might want to stop the timeline so that GEE won't erase it before you can look at it further. Or for instance, you might want to capture a screenshot of an event, and stopping the timeline temporarily is useful for this.

The next posts to come will deal with more in depth usage of GEE.

[edit on Mon Oct 5th 2009 by TrueAmerican]

I've just downloaded the GEE program and I've been playing with it. Trying to educate my eye as to events and your explanations have been really helpful. One thing though. Can you explain how to set the seismographic display so that more than the last 20 minutes is available? I thought I caught one of the 5.1 episodes at the Santa Cruz location this afternoon, using IU.HNR.00.BHZ, but when the notification from eQuake came through and I went to check, the seismograph display only scrolled back 20 minutes.

There has got to be some easy way of setting the display to scroll back for the entire period that I have been watching. Isn't there?

Thanks

Oops - please disregard - I just read the last paragraph in your first post carefully. Serious brainfart in progress.

[edit on 8-10-2009 by tangotemper]