PARTITIONING OF LOCALIZED AND DIFFUSE DEFORMATION AT THE INDIA-ASIA COLLISION ZONE FROM JOINT INVERSIONS OF GEOLOGIC AND GEODETIC OBSERVATIONS

The spatial complexity of continental deformation in the greater Tibetan Plateau region can be defined as the extent to which relative motion of the Indian and Asian plates is partitioned between localized slip on major faults and distributed deformation processes below the resolution of a particular fault system realization. Geometric moment rates provide a quantitative metric for determining the magnitudes of on-fault and diffuse crustal deformation. We jointly invert 608 interseismic GPS velocities and 9 Late Quaternary geologic fault slip rates to estimate the 24 tectonic micro-plate rotation rates, kinematically consistent faults slip rates, and internal block strain rates, using quasi-static block models that integrate earthquake cycle processes across the Tibetan Plateau. We find that most geologic slip rates are kinematically consistent with, and may result from, differential micro-plate motions. Monte Carlo simulations are used to quantify the likelihood that internal deformation is statistically distinguishable from the uncertainties in geodetic velocities. Of the total geometric moment rate budget within the Tibetan Plateau, 87% is taken up by slip on major faults, with the remaining 13% accommodated by internal processes at sub-block scale distinguishable from observational noise. The localization of the majority of plate boundary activity is also supported by the spatial distribution historical crustal earthquakes where 89% of historical moment release since 1900 has been released within 25 km of the major faults included in the block model, representing only 10% of the characteristic half-block length scale of ∼250 km. The localization of deformation inferred from geologic, geodetic, and seismic observations suggests that forces applied to tectonic micro-plates drive fault system activity at the India-Asia collision zone over decadal to Quaternary time scales.