Flexure of the Indian plate and intraplate earthquakes

Roger Bilham, Rebecca Bendick, Kali Wallace

    Research output: Contribution to journalArticlepeer-review

    Abstract

    The flexural bulge in central India resulting from India's collision with Tibet has a wavelength of approximately 670 km. It is manifest topographically and in the free-air gravity anomaly and the geoid. Calculations of the stress distribution within a flexed Indian plate reveal spatial variations throughout the depth of the plate and also a function of distance from the Himalaya. The wavelength (and therefore local gradient) of stress variation is a function of the effective elastic thickness of the plate, estimates of which have been proposed to lie in the range 40-120 km. The imposition of this stress field on the northward moving Indian plate appears fundamental to explaining the current distribution of intraplate earthquakes and their mechanisms. The current study highlights an outer trough south of the flexural bulge in central India where surface stresses are double the contiguous compressional stresses to the north and south. The Bhuj, Latur and Koyna earthquakes and numerous other recent reverse faulting events occurred in this compressional setting. The N/S spatial gradient of stress exceeds 2 bars/km near the flexural bulge. The overall flexural stress distribution provides a physical basis for earthquake hazard mapping and suggests that areas of central India where no historic earthquakes are recorded may yet be the locus of future damaging events.

    Original languageEnglish
    Pages (from-to)315-329
    Number of pages15
    JournalProceedings of the Indian Academy of Sciences, Earth and Planetary Sciences
    Volume112
    Issue number3
    DOIs
    StatePublished - Sep 2003

    Keywords

    • Continental earthquakes
    • Continental erosion
    • Flexural bulge
    • Flexure
    • India
    • Mid-plate seismicity

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