2 research outputs found
Plate Motion of India and Interseismic Strain in the Nepal Himalaya from GPS and DORIS Measurements
We analyse geodetically estimated deformation
across the Nepal Himalaya in order to determine the geodetic
rate of shortening between Southern Tibet and India,
previously proposed to range from 12 to 21 mm yr^(−1). The
dataset includes spirit-levelling data along a road going from
the Indian to the Tibetan border across Central Nepal, data
from the DORIS station on Everest, which has been analysed
since 1993, GPS campaign measurements from surveys
carried on between 1995 and 2001, as well as data from continuous
GPS stations along a transect at the logitude of Kathmandu
operated continuously since 1997. The GPS data were processed in International Terrestrial Reference Frame 2000
(ITRF2000), together with the data from 20 International
GNSS Service (IGS) stations and then combined using quasi observation
combination analysis (QOCA). Finally, spatially
complementary velocities at stations in Southern Tibet, initially
determined in ITRF97, were expressed in ITRF2000.
After analysing previous studies by different authors, we
determined the pole of rotation of the Indian tectonic plate to
be located in ITRF2000 at 51.409±1.560°N and−10.915±
5.556°E, with an angular velocity of 0.483±0.015°. Myr^(−1).
Internal deformation of India is found to be small, corresponding
to less than about 2 mm yr^(−1) of baseline change
between Southern India and the Himalayan piedmont. Based
on an elastic dislocation model of interseismic strain and
taking into account the uncertainty on India plate motion,
the mean convergence rate across Central and Eastern Nepal
is estimated to 19 ± 2.5 mm yr^(−1), (at the 67% confidence
level). The main himalayan thrust (MHT) fault was found to
be locked from the surface to a depth of about 20km over a
width of about 115 km. In these regions, the model parameters
are well constrained, thanks to the long and continuous
time-series from the permanent GPS as well as DORIS data.
Further west, a convergence rate of 13.4 ± 5 mm yr^(−1), as
well as a fault zone, locked over 150 km, are proposed. The
slight discrepancy between the geologically estimated deformation
rate of 21 ± 1.5 mm yr^(−1) and the 19 ± 2.5 mm yr^(−1)
geodetic rate in Central and Eastern Nepal, as well as the
lower geodetic rate in Western Nepal compared to Eastern
Nepal, places bounds on possible temporal variations of the
pattern and rate of strain in the period between large earthquakes
in this region