Traditionally tectonic Indian plate motion has been estimated using
closed plate circuit models and summing motions across mid-ocean
ridges. More recently Paul et al., (2001), using limited
GPS velocity vectors, calculated a pole of rotation that suggested
motion slower than that of the rates suggested by sea-floor
spreading. Socquet et al., (2006) estimate an India-Eurasia
geodetic pole with rates 5 mm/yr slower than Paul et
al., (2001). We present new data spanning a larger and more
significant portion of the "stable" Indian plate than previous
studies. Our preliminary India-Eurasian pole estimates are
consistent with Socquet et al., (2006).
In addition to the above mentioned sites, we also include published
data from numerous sources. However, many of the sites in this
region are on or near plate boundaries (eg. along the Himalayan
front or above the Sumatra subduction zone) making it difficult to
use them for plate pole parameter determination. We use a block
modeling approach to incorporate both rigid block rotation and
near-boundary elastic strain accumulation effects in a formal
inversion of the GPS velocities. Considered models include scenarios
with and without independent microplates and a number of different
plate boundary locations and locking depths.
The GPS velocities used in our inversion come from a solution of 164
global stations, including some unpublished campaign style sites
from central and northwestern India. These data were processed using
GAMIT/GLOBK and processed by Paramesh Banerjee from the Wadia
Institute of Himalayan Geology. Processing details can be found in
(Banerjee and Bürgmann, 2002).
In addition to our own analysis, we integrate GPS-station velocities
from published work along the Himalayans, throughout China, and
southeast Asia (Bettinelli et al., 2006; Bock et
al., 2003;Calais et al., 2003; Shen et al., 2005;
Socquet et al., 2006; Zhang et al., 2004). We
integrated these velocities into the reference frame of our own
solutions by estimating translation and/or rotation parameters that
minimized the differences in horizontal velocities for common sites.
Our combined solution contains 1800 global velocities.
We define our plates as rigid blocks on a spherical earth bounded by
dislocations in an elastic halfspace and invert for poles and rates
of rotation that minimize the misfit to the GPS velocities using an
extension of the block modeling code by Meade and Hager
(2005). The segments that bound the blocks represent uniformly
slipping elastic dislocations locked to some specified depth.
Because our inversion combines rigid block rotation with elastic
strain accumulation effects, the parameterization of the block
boundary geometry is critical. Geometry of the block boundaries is
based heavily on seismicity and adopted from prior analyses (eg. Socquet
et al., 2006, Reilinger et al., 2006,
Meade, IN PRESS) or adjusted as indicated by the geodetic
We invert the horizontal GPS velocities for poles of rotation
constrained by the prescribed block geometry defined above.
Systematic patterns in the residual velocities (observed minus
predicted) are used as an indicator of where and how the model
matches the observed surface velocities. Misfit statistics are used
to formally evaluate the statistical significance of the plate
kinematic scenarios we test.
Our preliminary results constrain a pole of rotation for India with
respect to Eurasia to lie at 29.040.7 N
16.741.6 E with a counterclockwise angular
velocity of 0.420.01 Myr. This pole
confirms that the NUVEL-1A rate is 20% too fast and the
India-Eurasia convergence rates computed along the Himalaya front
range from 34 mm/yr to 45 mm/yr between 72 N and
96 N longitude. Residual velocities from our inversion are
shown in figure 18.1 and show near zero motion within
uncertainties. The geographic distribution of stations within the
Indian plate allows us to generate the most robust realization of
Indian plate motion to date.
on the Indian plate from our robust inversion. Dashed lines show
small circle pole traces from the NUVEL-1A IND-EUR pole of rotation,
dotted lines are pole traces from this study. Circles show locations
of GPS sites along the Himalayan range front however, velocity
vectors at these locations have not been shown for the sake of
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Himalaya from GPS measurements, Geophysical Research
Letters, 10.1029/2002GL015184, 2002.
Bettinelli, P. J.Avouac, M. Flouzat, F. Jouanne, L. Bollinger, P.
Willis, G. Chitrakar, Plate motion of India and interseismic strain
in the Nepal Himalaya from GPS and DORIS measurements
Journal of Geodynamics, 10.1007/s00190-006-0030-3, 2006.
Bock, Y., L. Prawirodirdjo, J. F. Genrich, C. W. Stevens, R.
McCaffrey, C. Subarya, S. S. O. Puntodewo, and E. Calais, Crustal
motion in Indonesia from Global Positioning System measurements,
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Miroshnitchenko, S. Amarjargal, and J. Deverchere, GPS measurements
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Implications for current kinematics of Asia, Journal of
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Meade, B. J., and B. H. Hager, Block models of crustal motion in
southern California constrained by GPS measurements, Journal of Geophysical Research, 110, B03403,
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Kumar, D., The motion and active deformation of India, Geophysical Research Letters 28(4), 2001.
Shen, Z.-K., J. Lü, M. Wang, and R. Bürgmann, Contemporary
crustal deformation around the southeast borderland of the Tibetan
Plateau, Journal of Geophysical Research,
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Ambrosius, B., India and Sunda plates motion and deformation along
their boundary in Myanmar determined by GPS, Journal of
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