HR: 0830h
AN: G31B-0718    [PDF]
TI: A large scale velocity inversion for slip rates on South Island, New Zealand Faults
AU: * Pearson, C F
EM: chris.pearson@noaa.gov
AF: National Geodetic Survey, 2300 S Dirksen Parkway, Springfield, IL 62764 United States
AU: Henderson, M
EM: mhenderson@xtra.co.nz
AF: Victoria University of Wellington, Private Bag, Wellington, 0000 New Zealand
AB: This paper presents a velocities for 411 points distributed over the South Island, New Zealand which show the interseismic velocity field for this part of the Pacific Australian plate boundary in significantly higher resolution than previous studies. The velocities were determined by analysis of data observed 15 GPS surveys from 1992 till 2001 and three major triangulation surveys conducted between 1939 and 1982. The velocity field reveals a fairly uniform pattern of velocities across the New Zealand plate boundary in which the velocity is negligible (within errors) in the eastern part of the South Island and increases to up to 85% of the Pacific-Australia relative plate velocity on the west coast. An exception of this pattern is found in the far south of the South Island where the velocities are negligible except for a narrow zone along the west coast where the velocities reach a maximum value of about 45% of the relative plate velocity rate. The velocity field was inverted using a three dimensional model composed of 42 dislocations which model the effects of the Puysegur Trench, The Alpine Fault and the Marlborough Faults. In order to prevent edge effects in the model, the Marlborough Faults and Puysegur plate boundary thrusts were extended a minimum of 500 km north and south of the limit of New Zealand. Inverting the velocity vectors using a dislocation model containing the major faults on the plate boundary zone produces a reasonable match to known slip rates. An exception to this is the Alpine Fault where the calculated dip slip are clearly greater than paleoseismic estimates. This discrepancy may indicate deformation on unmodeled structures within and east of the Southern Alps.
DE: 1204 Control surveys
DE: 1208 Crustal movements--intraplate (8110)
SC: Geodesy [G]
MN: 2003 Fall Meeting