The Trans-Antarctic Mountains Seismic Experiment (TAMSEIS):  A prototype for 
large-scale broadband deployments in Antarctica

Douglas A. Wiens, Jesse Fisher, Patrick Shore (Dept. of Earth and Planetary Sciences, 
Washington University, St. Louis, MO)
Sridhar Anandakrishnan, Andy Nyblade, Don Voigt
(Dept. of Geosciences, Penn State University, University Park, PA)

       In November, 2001, we installed 42 broadband PASSCAL seismic stations 
extending from the Ross Sea to the East Antarctic Plateau in order to investigate the 
lithospheric structure beneath the Trans-Antarctic Mountains and East Antarctica.   The 
experiment consists of three components:  1) A 1400 km linear array of 17 broadband 
seismic stations extending from the central regions of the East Antarctic craton to the 
Transantarctic mountains   2) an intersecting 400 km dense linear array of 16 broadband 
seismic stations extending from the coast across the Transantarctic mountains in the Dry 
Valleys region.  3)  11 broadband stations in coastal regions around Ross Island and Terra 
Nova Bay.   The seismographs will remain deployed until the 2003-2004 season.  	Data 
from this experiment will be used to address two outstanding questions:  1)  What 
mechanism is responsible for the uplift of the Trans-Antarctic Mountains?   Many 
mechanisms have been proposed, including delayed phase changes, simple shear, 
lithospheric flexure, and  transform-flank uplift, all of which make assumptions about 
upper mantle structure beneath and adjacent to the mountain front.    2)  What 
lithospheric structure is responsible for the topography and high modal elevations of the 
East Antarctic Craton?   Previous proposals have included unusually thick continental 
crust and buoyant upper mantle.  
	The stations were serviced in January and November, 2002, and operated well 
from October-March.  Station enclosures and many of the sensor enclosures are heated, 
increasing instrument reliability.  The stations have not operated over the winter due to 
failure of the lower-cost windmill in the cold.    Preliminary data analysis includes 
receiver function analysis from stations near McMurdo, showing relatively thin crust 
beneath the Ross Sea and much thicker crust beneath the Trans-Antarctic Mountains.   A 
high level of local seismicity (mb 2-4) was recorded, with numbers as high as 5-10 events 
per day.  The high seismicity rate, very shallow depths (< 5 km), and locations beneath 
glaciers near the crest of the Trans-Antarctic Mountains suggest that these events may be 
associated with ice flow, rather than local tectonics.   An Mw 5.2 event on the Arctic 
Ridge was well recorded across the array at near-antipodal distances (170-177 degrees).   
The PKPdf phase from this event sampled the inner core along near-axial paths, and 
show travel time anomalies of -3.5 to -5.5 seconds resulting from inner core anisotropy.  
The variation in travel time anomalies across the array may provide further constraints on 
models of the inner core.