Active faulting and tectonics of Burma and surrounding regions

This study of the active tectonics of Burma and surrounding regions is based mostly on an interpretation of Landsat imagery and on fault plane solutions for shallow and intermediate earthquakes. Fold axes in the Indoburman ranges and an east dipping inclined zone of intermediate depth earthquakes suggest that a slab of oceanic lithosphere was recently subducted to the east under the Indoburman ranges. Fault plane solutions of shallow earthquakes, however, do not show underthrusting at the present time. Instead, P axes are oriented roughly north‐south, parallel, not perpendicular, to the fold axes in the ranges. P axes for fault plane solutions of intermediate shocks also trend north‐south, parallel to the strike of the subducted slab, and may indicate that the hanging slab is being dragged north by India through the surrounding asthenosphere. The Sagaing fault probably accommodates most of the right‐lateral slip of India past Indochina, but India's northward movement also causes internal deformation within Burma, Thailand, and Yunnan. Differences between the tectonic fabric seen on the Landsat images and the tectonic regime compatible with the fault plane solutions throughout the region imply major changes in the directions of relative motion, in the orientations of strain, and in the style of deformation in the late Cenozoic. Presumably, these changes reflect the transition from subduction to collision and strike‐slip motion as India penetrated into Eurasia past Burma. Large parts of Burma and Thailand may have rotated several tens of degrees clockwise in this process.