Date: Wed, 01 Sep 1999 13:46:33 -0700
From: John McRaney Subject: Reilinger Report on
Turkey GPS Response Sender: owner-scecall-l@usc.edu
To: scecall-l@usc.edu, michael@andreas.wr.usgs.gov, jmccarthy@usgs.gov,
kgross@usgs.gov, hstenner@usgs.gov, afrankel@usgs.gov, celebi@usgs.gov
Reply-to: mcraney@terra.usc.edu
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To SCEC Community, I am forwarding this report from Rob Reilinger. John
*******
Colleagues- Following is a brief, preliminary report on our GPS work
around the Izmit earthquake zone.
Continuous GPS Stations:
I believe most of this information is already on the TUBITAK MAM (Marmara
Research Center) Web site.
Four stations were operating in the coseismic earthquake area prior to the
event. These were installed as part of the Marmara Earthquake Hazards
Project under the direction of TUBITAK MAM. Other participants in this
project include Istanbul Technical University, Kandilli Observatory,
General Command of Mapping, and MIT. Data from these stations (before and
after the earthquake) were processed both at TUBITAK MAM and MIT and
indicate offsets of about 20 mm (most distant station) to 600 mm (at
Gebze). All stations continue to operate. Details are on the Web.
TUBITAK MAM installed four additional continuous stations bracketing the
fault within two days of the event. These stations should serve well to
monitor short-term postseismic deformation. They should operate for the
next 5-6 months at a minimum. They are being tied to nearby stable sites
during the current survey campaign to allow extension of the observation
history if this is deemed useful.
All of this work was accomplished prior to my arrival in Turkey (20
August).
Survey Mode GPS:
We received tremendous support form all agencies (universities, military,
government, industry) in Turkey in organizing and deploying teams to
reobserve GPS stations in the effected area. With this help, we were able
to deploy three teams to begin observations on Wednesday, 25 August, about
7.5 days after the main shock. These teams observed a total of 12 site
over a 4-day period (one 12-hour session per site). These sites were
selected on the basis of preearthquake history, and to provide sites at a
range of distances from the fault out to about 50-60 km. Our goal is to
observe these sites on an approximately weekly basis through September (5
reoccupations). Five additional teams were deployed to begin observing on
Sunday, 29 August. Together with the 3 earlier teams, they should observe
about 45 sites in the coseismic deformation region over a six-day period.
A significant number of these sites were observed as recently as May/June
1999, and many have a history of observations dating back to 1992 and
earlier (sorry I can't be more quantitative about this). We planned a
follow-on reoccupation of all sites in early October. We expect that
additional teams will be used in the October survey to allow extending our
reoccupation to sites at greater distances from the fault, but within the
cosesmic deformation zone (perhaps a total of 60 stations).
Data Processing:
Data are being processed continuously at TUBITAK (with contributions from
other Project participants) and MIT. We are receiving data on a daily
basis via ftp from TUBITAK MAM. This will be critical for planning future
occupations to assure best utilization of our resources (i.e., planning
optimal repeat times and spatial sampling).
AGU Special Session:
AGU has agreed to include a "late breaking" session for the December
meeting dedicated to the Izmit earthquake. Perhaps you are already aware
of this. In any case, we are very excited about the results anticipated
and hope to include presentations on secular strain preceding the
earthquake, estimates of coseismic faulting from GPS and mapped surface
offsets, and initial observations of postseismic motions. I believe that
AGU will allow late abstracts up to 27 September. Of course, we encourage
all participants in the NSF/SCEC response team to contribute to this
session.
Final thoughts:
This was an emotionally and physically exhausting experience. But, in
addition to the sadness and pain I felt in the wake of this terrible
tragedy, I was uplifted by the tremendous sense of comradery and the
dedicated effort by the Turkish community. We at MIT have been committed
throughout our program to full transfer of technology and expertise to our
Turkish colleagues (as well as the other countries in which we work) -
they have proven their competence and commitment. Their ability to respond
immediately, and effectively to this event will pay back our investment
immeasurably. We hope and believe that the results of studies of the Izmit
event will provide fundamental information on earthquake processes that
will provide a basis for mitigating future earthquake hazards not only for
Turkey but for California and other continental strike-slip fault systems.
John K. McRaney
Southern California Earthquake Center
University of Southern California
3651 Trousdale Parkway
Los Angeles, CA 90089-0742
213-740-5842; 213-740-0011 (fax)
mcraney@terra.usc.edu
www.scec.org