Dear Seiji, Winfried, Jim, Pawel, and others in WG1
Here are some of my thoughts on the discussions to date. I will follow
with some suggestions for increasing the FDSN Backbone.
Rhett
On Jul 8, 2008, at 9:43 PM, Winfried Hanka wrote:
Dear Seiji, Rhett and all,
before submitting a concrete proposal for new backbone stations from
our side I would propose to better define the criteria for the
selection. We are installing about 35 new stations around the Indian
Ocean (half of them existing, the rest to be installed until 2010)
and I could surely contribute some of those for the backbone
network. But how many more stations we need e.g. in Indonesia, Sri
Lanka, Madagascar and Kenya? We (will) have two stations each in Sri
Lanka, the Maldives, Yemen (a 3rd one on Socotra), Tanzania, Kenya
and Madagascar. But how many to select for the backbone? On Rhett's
list most cases are obvious ones. But e.g. for another station in
Germany there no justification from poor coverage.
Agreed. On the basis of coverage, it is redundant. Nonetheless, BFO is
an exceptionally quiet site.
As a sidebar, BFO is an Affiliate GSN station. Although data are
distributed by GSN, the station is independent.
So to me the criteria are not totally clear yet and before
submitting a proposal I would like to have this clarified. Also if
we select now only among existing stations or also future ones, and
if yes, how far in future?
Originally when the "FDSN network" was initiated, most of the planned
stations were relatively far in the future. The criteria seemed to be
when there was actual funding. By this old criteria, potentially all
of the new trans-Indian-Ocean Geofon stations should be considered.
Regards,
Winfried
On Jul 9, 2008, at 3:02 AM, Lyons, Jim wrote:
Dear All,
I agree with Winfried that the best place to start is to clearly
enunciate the overall purpose of the FDSN backbone network. Is it
to be
a one-stop-shop for global seismology? All of these FDSN stations are
freebies, in the sense that none are installed or maintained at FDSN
expense for pure FDSN purposes. They are typically used for
national/regional earthquake monitoring +/- CTBT verification.
For the GSN, the primary funding purpose was/is science (at least by
US National Science Foundation's measure). Yes, there are now many
other useful purposes for the data. And, our USGS partners are funded
for earthquake hazard response.
It is a great success of FDSN that its members are willing to sharing
their data freely.
A similar question arises with the insistence on real-time access.
I do not see an insistence upon real-time. There are still existing
Backbone stations without real-time access. Nonetheless, real-time is
a stated FDSN goal, i.e, "Improving Access to data in real time." If
an FDSN network wishes to make its data available to all in real-time,
why not embrace it?
In
the body of Rhett's e-mail of July 7, I believe Paul Wiejacz observed
that most FDSN stations are already real time within some network.
Why
should FDSN get into the business that someone else is already doing?
I agree that the "real-time" component is up to the FDSN member
network. FDSN simply encourages the sharing of data, whether real-time
or not.
I am not trying to be unduly negative here. I understand the credo of
network operators everywhere that more and faster is better. But I
would like to work towards an explicit understanding of what it is we
are trying to achieve with the FDSN backbone.
Best regards,
Jim
On Jul 9, 2008, at 11:34 PM, Pawel Wiejacz wrote:
Dear All,
I also agree with Winfried and Jim.
The issue seems to me more conceptual than purely scientific. FDSN
as it is consists of a growing number of stations and with so
many stations it is no longer as manageable as it was some time ago.
E.g. if data stops flowing in from some particular station, it is no
longer feasible to look after this and inquire why - especially in
places like Europe where FDSN stations are numerous and one
can find another station from an alternate location fairly nearby.
In this sense, redundancy is a good thing.
So - it appears to me - there is this desire to have some stations
designated FDSN-backbone, so that these stations make a
more-or-less uniform global seismic network with some assured
level of data availibility (open to discussion if this availibility
level
is to be 95, 98 or 99%).
There has never been a data-availability standard for FDSN. Perhaps
the best FDSN can do is to have sufficient redundancy to have good
"effective" coverage.
This matter is not easy. On one hand I do not see a reason why FDSN
should not accept another station that is broadband, low
noise and offering free data.
In principle, many networks offer up all of their stations, and some
share only a few (or perhaps none at the moment). Every network is
encouraged to nominate/offer at least one station to the FDSN backbone.
On the other hand I can imagine someone putting up a dense broadband
network on a small area
and offering all its data (e.g. 100 stations) to the FDSN.
This already occurs. The USArray transportable array of 400+ stations
is entirely open to FDSN in real-time. However, there is no intent to
make this a part of the Backbone.
It is not the point so that FDSN becomes a free data repository to
just anyone (who e.g. might wish to save money on disk array - keep
the data just on his PC and have a backup copy at the FDSN
for the just-in-case). The line must be drawn somewhere.
Agreed. The FDSN Backbone data are actually archived and open to the
FDSN. Currently the FDSN archive for the Backbone resides at the IRIS
Data Management System. However, there are a number of other FDSN data
centers, which offer additional/parallel/complementary FDSN data.
A number of FDSN members make their own bilateral arrangements to
archive data at various FDSN archives.
Given our current discussion toward increasing the size of the
Backbone (by a some small factor), the impact of additional stations
is still small.
It should be the FDSN leaders to decide on this, but to my opinion
the FDSN-backbone network should be much denser
than the CTBTOs. Or the interest in the FDSN-gathered data
will be limited.
Currently, CTBTO is not open, and is available only to States Parties.
The CTBTO IMS is composed of about 170 primary (50) + auxiliary
stations (120) + a few "T-phase" stations on islands. The FDSN
backbone is already more dense at 200+ stations. Since the CTBTO IMS
is fixed by the Treaty, our discussion to increase the size of the
FDSN Backbone will make it relative more dense than CTBTO.
In principle, it would be nice someday to incorporate the CTBTO into
the FDSN.
Of course one must keep in mind that the CTBTO network is
cunning - it has been constructed with maximum possible station
density that is still more-or-less uniform throughout the world.
CTBTO uses a lot of arrays for its primary network, and relies heavily
upon FDSN stations for its auxiliary network.
So should FDSN go to a greater station density, then naturally
there would be regions where getting a greater station density
than CTBTO shall not be possible. Moreover, FDSN is unlikely
to surpass CTBTOs resolution in areas like Russia or China where
much of the data is restricted; according to the CTBTO treaty the
data is ported to the ISC, but digital data gets then restricted
there at Vienna.
Although there are some increasing data restrictions, data in Russia
and China are still available through respective joint efforts in
collaboration with GSN.
It is a separate question if FDSN should archive all the data or
perhaps use some distributed-archive scheme. But with distributed
archive, the number of data contributors, and lack of funding for
specifically running the distributed-archive at the contributors'
sites - managing a distributed archive may be a problem.
The FDSN does have utilize distributed data centers with growing
success. However, each of these data centers are funded more-or-less
for their own purposes, for which we are fortunate that these purposes
include international data sharing.
Regards,
Pawel