Geodetic contributions to the study of seismotectonics in India

Earthquakes in India are caused by the release of elastic strain energy created and replenished by the stresses resulting from India’s collision with Asia. Accumulating strain distorts the surface of the Indian plate, which despite its slow development can now be detected using precision geodesy. The largest and most severe earthquakes occur on the boundaries of the Indian plate to the east, north and west of the subcontinent. Historically, these areas have been somewhat neglected by precise geodesy and it is only recently that suitably dense networks capable of spanning entire plate boundaries have been developed. Earthquakes within the subcontinent, though devastating, have also remained unserved by historical geodesy in India because the rupture areas of these events are small and have tended to occur between networks of adequate precision. Since 1990, the widespread availability of GPS geodesy has resulted in a number of significant findings related to the translation, deformation and rotation of the Indian plate, and to deformation of its margins. The next decade is likely to see the uncertainties of these estimates fall by a factor of 4, permitting estimates of changes of rate in space and time. We discuss these new findings and their historical antecedents, and identify current trends in seismogeodetic research that are likely to contribute to a new understanding of future Indian earthquakes.