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Transantarctic Mountains Deformation
Network (TAMDEF)
GPS measurements of bedrock crustal motions
Larry Hothem, USGS, Reston, VA
Terry Wilson, Department of Geological Sciences, OSU, Columbus, OH
Mike Willis, Byrd Polar Research Center, OSU, Columbus, OH
SCAR Antarctic Geodesy Symposium (AGS02)
LINZ Building, Wellington, NZ
26-27 November 2002
h t t p :/ / ww w - b p rc . m ps. oh i o - s ta t e . e d u
Ice Sheet History and
Mass Balance
 Glacial isostatic adjustment
(GIA) vertical motions, James &
Ivins, 1998
 Sense and pattern of motions
differ considerably depending
on model parameters
 Generally assumed vertical
viscoelastic adjustments will
exceed significantly any tectonic
motions
 TAMDEF-VLNDEF network (as
shown in figures) ~1100 km in
length, crosses substantial
predicted vertical motion.
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Tectonic
Framework
 West Antarctic rift system and
the Transantarctic Mountains
– one of the highest and
longest uplifted rift flanks in
the world.
 Crust of West Antarctic
divided into blocks that
moved as microplates with
respect to East Antarctica
 Substantial low-magnitude
seismic activity recorded in
past couple years in South
Victoria Land and central
West Antarctica
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Terror Rift and Major
Strike-slip Faults
 Terror Rift is the only area in the
Antarctica interior with extensive
evidence for neotectonic activity.
 Salvini and Storti (1999) proposed that
the Terror Rift and major dextral strikeslip faults crossing northern Victoria Land
were kinematically linked and remain
active.
 Fault scarps and Holocene volcanic vents
cutting the sea floor have been detected
by bathymetric and seismic profiling.
 GPS measurements from TAMDEF
network between 1996-2002 indicate the
Terror Rift is actively extending at a rate
of 4.2±3.2 mm/yr [2-sigma] relative to the
East Antarctic margin of the TAM.
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Transantarctic Mountains Deformation (TAMDEF) Network
Deployment Strategies
 TAMDEF-I consists of an array of 25
primary sites:
 Stations established in 1996 & 1997.
 GPS measurements conducted 19962000, with a few additional
measurements in 2001 & 2002.
 Initial deployment strategy – attempt
to discriminate between the three
potential mechanisms of crustal
motions thought to be important in
the region:
• isostatic rebound
• rifting
• volcanic loading
 Primary sites augmented with dense
local arrays at three sites:
 JPL/NASA Stations (C. Raymond):
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TAMDEF and VLNDEF GPS Networks
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Typical Statistics for Uncertainties
 Examine errors and biases in relation to baseline length, number of
occupations, and duration of occupations.
 Three stations selected:
• FRK (Franklin Island): critical site to the east of the Terror Rift
• ALN (Allan Hills):
on inland flank of the TAM
• FTP (Fishtail Point): most southerly site with the TAMDEF network
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Cape Roberts: Results relative to MCM4
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TAMDEF First Results – “Horizontal” Motions
 Horizontal velocities between 1996 and 2002
 Fig 6a: Motions referenced to ITRF 1997 frame and relative to MCM4
 Fig 6b: Shows residual horizontal motions when the average motion of local
“East Antarctic craton” reference system is removed.
Fig. 6a
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TAMDEF First Results – “Vertical” Motion
 Vertical motions upward over
entire region.
 Uncertainties in vertical are
larger than those for horizontal.
 Upward motion ranges
• From +0.1 ±3.1 mm/yr
• To +5.6 ±0.6 mm/yr
 13 sites have upward motion
significant at 2-sigma level
 Average vertical motion for
entire network: ~3.6 mm/yr
 Vertical motions approximately
same magnitude as those
suggested by the D91
continental post-glacial
rebound model (James and
Ivins
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2002 1998)
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TAMDEF Station at Arrival Heights (ARR0)
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Results for Cape Roberts “Footprint” Surveys
1996-1999
“i” indicates the result
of a single baseline
session from a stopand-go style survey,
using “2” GPS survey
systems where data
were collected for about
10 minutes for each
static occupation.
All other other surveys
performed with “4” GPS
survey systems; data
collected
simultaneously for
about 60 minutes at 5sec rate.
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Residuals for Baseline Solution – ARR0 to MCM4 – 12 January 2002
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Residuals for Baseline Solution – FLM2 to MCM4 – 12 January 2002
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Residuals for Baseline Solution – FTP1 to MCM4 – 12 January 2002
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Residuals for Baseline Solution – ROB1 to MCM4 – 12 January 2002
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Data Quality – ARGO Stations – JNS EURO-80 Receiver
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ARR0 to MCM4
FLM2 to MCM4
FTP1 to MCM4
ROB1 to MCM4
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TAMDEF-II Network
 13 new sites proposed
 Three new remote GNSS
observatories
•One at Franklin Is. (FRK)
•Two at new stations of
TAMDEF, along inland flank
of the where tectonic
motions are expected to
be negligible.
TAMDEF-II
TAMDEF-I – extends
northward to VLNDEF
network
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November 1996
First season for TAMDEF
project
Establishing station at
Cape Crozier (CRZ0)
Ian Whillans, PI, OSU
and
LINZ personnel
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Thank you
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