COMBINING SHADED RELIEF MAPS AND FIELD STUDIES TO DOCUMENT ACTIVE FAULTING WITHIN THE CHURACHANDPUR-MAO FAULT SYSTEM; INDO-BURMAN RANGES, NORTHEAST INDIA

The Indo-Burman Ranges (IBR) comprise a ~375 km-wide accretionary prism, located at the northern end of the Sunda subduction zone, which accommodates oblique convergence (~70º; ~46 mm/yr) of the Ganges-Brahmaputra delta on the Indian Plate with the Shan Plateau of SE Asia. GPS measurements indicate that the northward component of convergence is mostly partitioned among two north-striking dextral faults, known as the Sagaing and Churachandpur-Mao faults (CMF). The eastward component of convergence (~13-17 mm/yr) is absorbed by a fold-thrust belt propagating westward at the front of the IBR. While the fold-thrust belt, Sagaing fault, and northern segment (26-24ºN lat., 93.4-94ºE long.) of the CMF are well constrained by GPS measurements and field studies, the extent, structure and significance of active faulting along CMF south of ~24ºN is unknown. Using an ~12 m shaded relief DEM, we identified several structural lineaments which cross-cut the IBR fold-thrust belt within an ~30–40 km wide zone along-strike of the CMF south of 24ºN. The mapped features include an array of NW-striking subvertical fault scarps, N-striking scarps that are subparallel to the CMF, and NE-striking subvertical features that appear to be joints. Preliminary fault-slip data suggest both dip-slip and strike-slip motion along the NW-striking faults. The relative orientation of the mapped faults and joints suggests a Riedel shear geometry compatible with dextral slip on the CMF if the NW-striking faults are dominantly sinistral. Alternatively, the NW features are in a favorable orientation relative to the oblique N20E convergence direction to be reverse faults. We will present results from ongoing field mapping and fault-slip studies to help distinguish between these models. Our preliminary analysis reveals several sets of previously unrecognized faults and suggests the CMF expands south of ~24ºN to form a 10s of km wide fault zone defined by kinematically compatible arrays of secondary faults. We postulate that these structures reflect distributed dextral shear and the active southward propagation of the CMF. Our study contributes new mapping of the potentially seismogenic CMF and describes how oblique convergence is accommodated across a subduction-accretion wedge.