FN Archimer Export Format
PT J
TI Instantaneous deformation and kinematics of the India-Australia Plate
BT 
AF DELESCLUSE, Matthias
   CHAMOT-ROOKE, Nicolas
AS 1:1,3;2:1,2;
FF 1:;2:;
C1 Laboratoire de géologie, Ecole Normale Supérieure, Paris, France
   CNRS, UMR 8538, France
   Université Paris XI, France.
C2 ENS, FRANCE
   CNRS, FRANCE
   UNIV PARIS 11, FRANCE
IF 2.112
TC 87
UR https://archimer.ifremer.fr/doc/00238/34944/33246.pdf
LA English
DT Article
DE ;earthquakes;India-Eurasia collision;intraplate deformation;global positioning system (GPS);plate tectonics;strain modelling
AB Active intraplate deformation of the India-Australia Plate is now being captured by far-field global positioning system (GPS) measurements as well as measurements on a few islands located within the deforming zone itself. In this paper, we combine global and regional geodetic solutions with focal mechanisms of earthquakes to derive the present-day strain field of the India-Australia Plate. We first compile an updated catalogue of 131 Indian intraplate earthquakes (M > 5) spanning the period between the two Asian mega earthquakes of Assam 1897 and Sumatra 2004. Using Haines and Holt's numerical approach applied to a fully deformable India-Australia Plate, we show that the use of GPS data only or earthquakes data only has severe drawbacks, related, respectively, to the small number of stations and the incompleteness of the earthquakes catalogue. The combined solution avoids underestimation of the strain inherent to the Kostrov summation of seismic moments and provides details that cannot be reached by pure GPS modelling. We further explore the role of heterogeneity of the India-Australia Plate and find that the best model, in terms of geodetic vectors fit, relative distribution of strain, style and direction of principal strain from earthquakes, is obtained using the surface heat-flow as a proxy for rheological weakness of the oceanic lithosphere. The present-day deformation is distributed around the Afanasy Nikitin Chain in the Central Indian Basin (CIB)-where it is almost pure shortening-and within the Wharton Basin (WB) off Sumatra-where it is almost pure lateral strike-slip. The northern portion of NinetyEast ridge (NyR) appears as a major discontinuity for both strain and velocity. The new velocity field gives an India/Australia rotation pole located at 11.3 degrees S, 72.8 degrees E (-0.301 degrees Myr(-1))overlapping with previous solutions, with continental India moving eastward at rates ranging from 13 mm yr(-1) (southern India) to 26 mm yr(-1) (northern India) with respect to Australia. Taking into account the intraplate velocity field in the vicinity of the Sumatra trench, we obtain a convergence rate of 46 mm yr(-1) towards N18 degrees E at the epicentre of the 2004 Aceh megaearthquake. The predicted instantaneous shortening in the CIB and WB and extension near Chagos-Laccadive are in good agreement with the finite deformation measured from plate reconstructions and seismic profiles, suggesting a continuum of deformation since the onset of intraplate deformation around 7.5-8 Ma. Since no significant change in India convergence is detected at that time, we suggest that the intraplate deformation started with the trenchward acceleration of Australia detaching from India along a wide left-lateral oceanic shear band activating the NyR line of weakness as well as north-south fracture zones east of it. The predicted total amount of left lateral finite strain along these faults is in the range 110-140 km.
PY 2007
PD FEB
SO Geophysical Journal International
SN 0956-540X
PU Wiley-blackwell
VL 168
IS 2
UT 000243754500027
BP 818
EP 842
DI 10.1111/j.1365-246X.2006.03181.x
ID 34944
ER

EF