Strain Partitioning Within the Indo-Burman Fold-Thrust Belt SW of the Intersection between the Churachandpur-Mao and Dauki Faults.

Strain partitioning among forearc fault systems partly determines the structural evolution and patterns of seismicity at oblique convergent margins. The Indo-Burman Ranges (IBR) are a subaerial fold-thrust belt resulting from the India-Eurasia plate collision, which is locally oblique (70°). Relative motion across the IBR is partitioned into three fault systems: 1) north-striking thrusts in the outer belt of the accretionary prism; 2) the Churachandpur-Mao Fault (CMF), a north-striking dextral strike-slip fault in the internal part of the forearc; and 3) the Dauki Fault (DF), a buried, west-striking crustal-scale reverse fault that uplifts the Indian craton to the north of the accretionary prism. This study utilizes field datasets to constrain the structural transition from west-directed shortening in the outer IBR to transpressional strain near the intersection of these three fault systems. First, we evaluate the kinematic evolution of the fold-thrust belt through cross section construction, structural analyses of faults and folds, and kinematic modeling. Secondly, we use 2D flexural models to address the role of complex flexural loading history on the structural architecture. Preliminary results suggest that the outer belt comprises detachment folds and fault-propagation folds that formed above a more broadly folded décollement. The décollement depth in the study area varies from 4-8 km, deepening in the transport direction to the west in the footwall of the DF. Flexural deformation along the transport direction may influence the décollement geometry. The ~E-W flexure of the décollement is further deformed as it is uplifted in the hanging wall of the DF. Near the CMF, several transpressional fault splays strike NW and modify structures from the fold-thrust belt, forming a positive flower structure. We deduce that the CMF and DF form a kinematically linked fault intersection that partly absorbs the northward component of India-Eurasia convergence. The occurrence of flexural deformation and tilting of the fold-thrust belt raises questions about the seismic potential of the folded décollement near the northern part of the IBR. Ongoing research investigates the structural evolution of these fault intersections that, together with geodetic and remote sensing studies, can inform seismic hazard analyses.