Abstract
AbstractThe India‐Asia collision zone accommodates the relative motion between India and Eurasia through both shortening and pervasive strike‐slip faulting. To gain a mechanical understanding of how fault slip rates are driven across the Tibetan plateau, we develop a two‐dimensional, linear elastic, two‐stage, deformable microplate model for the upper crust based on the behavior of an idealized earthquake cycle. We use this approach to develop a suite of simple India‐Asia collision zone models, differing only in boundary conditions, to determine which combination of edge forces and displacements are consistent with both the slip rate measurements along major Tibetan faults as well as the geodetically observed extrusion of crustal material toward Southeast Asia. Model predictions for the Altyn Tagh (1–14 mm/yr), Kunlun (3–10 mm/yr), Karakorum (5–12 mm/yr), and Haiyuan (3–5 mm/yr) faults are in agreement with geologically and geodetically inferred slip rates. Further, models that accurately reproduce observed slip rate gradients along the Altyn Tagh and Kunlun faults feature two critical boundary conditions: (1) oblique compressive displacement along the Himalayan range front west of the Shillong plateau, and (2) forcing in Southeast Asia. Additionally, the ratio of internal‐block potency rate to the total potency rate for each microplate ranges from 28% to 79%, suggesting a hybrid view of deformation in Tibet as simultaneously localized on major faults and distributed at length scales <500 km.
Highlights
[1] The India-Asia collision zone accommodates the relative motion between India and Eurasia through both shortening and pervasive strike-slip faulting
[2] The India-Asia collision zone spans as least 7 million km2 and encompasses the Tibetan plateau, which stands at a mean elevation of 4 km and is dissected by large-scale strike-slip faults exceeding 1500 km in length
The strength of the kinematic microplate approach is the inclusion of localized deformation and earthquake cycle processes associated with major tectonic structures such as the Altyn Tagh, Kunlun, and Karakorum faults
Summary
[2] The India-Asia collision zone spans as least 7 million km and encompasses the Tibetan plateau, which stands at a mean elevation of 4 km and is dissected by large-scale strike-slip faults exceeding 1500 km in length. Predicting fault slip rates as a function of applied boundary conditions is distinct from the approach taken by Peltzer and Saucier [1996], who assumed fault slip rates and solved for a regional velocity field This class of model incorporates both localized slip along major faults and distributed deformation within microplates with a two-dimensional two-step finite element model. Using this approach, we analyze six Tibetan plateau models to interrogate the force and displacement boundary conditions required to produce geologically and geodetically constrained slip rates along the Altyn Tagh, Kunlun, Karakoram, and Haiyuan and faults. All faults slip left laterally, with the exception of structure (i), which is right lateral
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