What is it about?

We illustrate that a simple mechanical model can explain the arcuate shape, as observed in map view, and the post mid-Miocene growth of the Himalayan range. Our study incorporates comprehensive field measurements of shallow deformation along the surface ruptures of the two most recent and significant earthquakes (Muzzafarabad, 2005, and Assam, 1950) near the western and eastern syntaxes of the range. These measurements support the observation that, in these regions, the directions of shortening diverge by up to 130° and shortening rates are lower by a factor of 3 compared to central Nepal (~ 6 mm/yr vs ~18 mm/yr). The return time of large earthquakes is also ≈ 3 times longer (>2,000 y) than in central Nepal (≈ 700 y). Using Discrete Element Modelling, we demonstrate that this is an outcome of the elliptical growth of the range, riding atop the subducting Indian plate since the mid-Miocene. Both syntaxes mark the endpoints of approximately orthogonal strike-slip boundaries on the eastern and western sides (Chaman and Sagaing Faults).

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Why is it important?

This study uncovers how the Himalayan Mountain Arc formed, explaining why it is shaped like a half-ellipse and the relationship to large earthquakes along it. This finding has broad implications and should be of interest to a broad range of Earth scientists from various disciplines including Geodesy, Seismology, Paleo-seismology, and Quaternary Geology.


This paper is of profound significance as it unveils the mystery behind the formation of the curved shape of the Himalayan range and its connection to earthquakes in front of the range. It employs mathematics, geometry, mechanics, and numerical modeling to address crucial questions in Earth science. Sadly, the second author, Paul Tapponnier, passed away on Dec. 24, 2023. Paul was a guiding force, providing invaluable mentorship throughout the research. With nearly 50 years dedicated to studying deformation in Tibet and East Asia, his contributions elevate the depth and innovation of this work. Beyond its scientific value, this paper serves as a special tribute to remember him forever.

Liqing JIAO

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This page is a summary of: The shape of the Himalayan “Arc”: An Ellipse pinned by syntaxial strike-slip fault tips, Proceedings of the National Academy of Sciences, January 2024, Proceedings of the National Academy of Sciences,
DOI: 10.1073/pnas.2313278121.
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