Blogging hiatus is over

Apologies to my regular readers for the prolonged blogging hiatus. I have been somewhat absent from the whole blogging world for the past couple of months. It proved to be too difficult to blog from my last field-trip, and I have been working hard on a paper since getting back last month (the paper was submitted a few days ago, details soon).

In the meantime, a lot has been going on regarding CASE-IPY and other seismology at Concordia:

• The stations we installed during the last Antarctic field trip (CASE01, CASE02, CASE03) have now all gone to sleep for the duration of the Antarctic winter. The updated state of health plot for the stations shows that the longest running station CASE03 went into hibernation on April 18th. Bets are open as to when the first station will awaken in the spring.
• The permanent station CCD is running nicely, with both the heated and the unheated seismometers performing well. You can look up the state of health for the station, as well as journal plots for the data and snapshots of events (including the recent M7.9 Sichuan earthquake) on the Concordia Seismology website.
• We are planning both the 2008-2009 and the 2009-2010 summer campaigns at Concordia. The first campaign will be dedicated to recovering the full data from the CASE prototype stations, re-installing these prototypes for a second year of measurement, and upgrading the permanent station (CCD). We hope to stay longer than two weeks at Concordia this time, which should give us enough time to complete the essentials of the campaign and run a number of extra tests. The 2009-2010 campaign will be dedicated to installing 7 new autonomous seismic stations between Concordia and Vostok. Given the logistical constraints on the transport of all the material required for this deployment, we are building the stations this year. They will be shipped to Antarctica in the fall, will over-winter at Dumont d'Urville station, and will travel up to Concordia on the first land transport of the 2009-2010 season.
  

All in all, plenty to keep me busy and out of mischief! Now that my work load has simmered down to manageable proportions again (!), you can expect to see more of me in the blogging arena, and specifically many more Sismordia posts.


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Keep up to date with the latest developments at http://sismordia.blogspot.com

Launching the Concordia Seismology website

One of the things that has kept me from blogging much lately has been writing and setting up a static website about Concordia seismology, giving access to public domain information about the permanent station CCD and the CASE-IPY experiment, including data snapshots.

The website is unimaginatively called Concordia Seismology, and can be found here: http://case.u-strasbg.fr.

It has dedicated CCD pages, dedicated CASE-IPY pages, and a list of conference (and at some point journal) publications concerning seismology at Concordia.

The Concordia Seismology website is not intended to be a static copy of this blog, rather a place to distribute technical information about the permanent and temporary stations at Concordia. It will act as the official online source of such information.

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Keep up to date with the latest developments at http://sismordia.blogspot.com

Seismology in the freezer

The Concordia seismic station (CCD) has been having a few difficulties lately, which is not surprising given the temperature in the seismic vault is a stable and hideously low -59C. No electro-mechanical system likes working at that kind of temperature, and neither do I.

We have two identical seismometers in the vault. One is heated to a balmy -35C, the other is left cold. A few days ago the heating system stopped working. This sent the "warm" seismometer into a severe drift that drove one of its internal masses to the end of its range. What had been a highly sensitive seismometer was now only a heap of junk metal.

Today, JY and I went down into the seismic vault to localize and fix the problem. The vault is accessed from a shelter (a cabin) a short 1km stroll from Concordia base. At least it is a short stroll in good conditions... in the kind of conditions we had today (28 knot winds blowing snowdrifts everywhere, and a temperature of -30 before wind chill) it was a grueling slog.

Once at the shelter, one opens a trapdoor that leads down to a 45m horizontal snow tunnel. At the end of the tunnel is a short metal ladder, that leads to a longer metal ladder that takes one down to the vault itself. It is bitterly cold beyond the trapdoor, and it only gets worse the deeper into the vault one goes. The air is soon filled with mist from our breath, so visibility quickly becomes poor.

The work we had to do down there included wiring a new power cable for the seismometer heating system, and leveling the seismometer. JY took the cable, I took the seismometer. We were down there around 40 minutes, working often only with thin gloves or bare fingers. At -59C. Excruciating doesn't quite cover it...

But it's over now. The seismometer is working correctly again, and our trip to the vault the stuff of memories. I shall be glad not to have to repeat the operation any time soon!

The photo above shows JY and me just after we opened the cabinet containing the seismometers. It was taken by a CNRS photographer who accompanied us into the vault on an earlier trip this morning to find the cause of the problems. The two instruments are covered by insulation. The "warm" seismometer is on the right.

Photo credits: © CNRS Photothèque - Claude Delhaye.

Concordia data acquisition systems

After last week's post on the RefTek digitizer that we shall use extensively for the CASE-IPY experiment, here is a short post on the digital acquisition systems used by the permanent station at Concordia (CCD).

The permanent station uses two digitizers made by Quanterra - Kinemetrics: the Q4120 (big orange box on the bottom shelf) and the Q330 HR (thin orange box on the left of the top shelf) with its external hard disk called a Baler (squat orange box on the right of the top shelf).

They are two very different generations of machines, the Q330HR is newer than the Q4120, but their purpose is the same:

• to receive analog signals directly from the seismometers (voltage being proportional to the velocity of the ground),
• to digitize them (turn voltages into bit-counts that can be recorded onto hard-disks or data tapes),
• and to date them accurately using the time given by a GPS receiver.

The quality of a digitizer contributes greatly to the overall quality of a seismic station. These two are some of the best in their class.

We shall have work to do on both of these digitizers, to configure them to talk to the SeisComP system that is supposed to make it easier to retrieve and archive the data they record. We have prepared for this by setting up identical systems here in our lab in Strasbourg and going through the entire configuration procedure from A to Z. We suspect, though, that going through the procedure at Concordia will be a bit more difficult given both the cold and the lower oxygen level up there!


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Keep up to date with the latest developments at http://sismordia.blogspot.com

ConCorDia is official

The permanent station at Concordia now officially exists. We registered it this week at the International Registry of Seismograph Stations under the station code CCD (ConCorDia).

Here are the details of the station:

• Latitude: 75.1065 S
• Longitude: 123.305 E
• Elevation: 3240.0 m

This station is part of the French-Italian Concordia project. It is jointly funded by IPEV (F) and ENEA (I), and is jointly operated by EOST Strasbourg (F) and INGV Rome (I).

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Keep up to date with the latest developments at http://sismordia.blogspot.com

Concordia 2006 seismograms

Here is an example of data from the Concordia seismometer in early 2006 (March 31), as promised in this earlier post.

The whole day is split into 6 portions of 4 hours each, shown on separate lines from top to bottom. Each seismogram is plotted with time (in hours) increasing to the right. So the first line contains data for 00:00-04:00 UTC, the second line for 04:00-08:00 UTC and so on.

Seismic waves from an earthquake arriving at about 13:30 UTC are nicely recorded on the fourth line. This magnitude Mw 6.5 earthquake occurred at 31:21 UTC in the Kermadec Islands region, at a depth of 12 km.

Current seismology at Concordia

Seismology is already happening at Concordia. We have a seismic observatory some 12 meters deep, about 1 kilometer away from the base itself. The temperature within the seismic vault is a constant -59 degrees Celsius, much lower than what is reasonable for any mechanical instrument to be working at.

One of the members of the Concordia Winter Team for 2007, Pietro Di Felice, is making sure the seismometer keeps working correctly. Here is the web page he is keeping about his seismological work.

As communication with the base is both difficult and expensive, we cannot as yet obtain the data recorded by the Concordia seismometer in real time. We can ask Pietro to email us short bursts of data for specific earthquakes, but for the rest of the data, we have to wait until somebody actually goes to Concordia and brings them back.

We have recently received in this manner all the 2006 data. As soon as we've taken a good look at them, I'll try to put up some pictures.