Kinematics and mechanics of the Indian Ocean diffuse plate boundary zone

Abstract

Data and models are reviewed for the recent tectonics of the region in the N Indian Ocean from the Central Indian Ridge to the Sumatra Trench, long considered an anomalous tectonic region. Seismicity is much greater than expected and the crust and sediments are deformed by both folding and faulting. Analysis of relative plate motion data along the Carlsberg and Central Indian Ridges indicates the presence of distinct Indian and Australian plates. The seismicity and deformation thus reflect a diffuse boundary between these two rigid plates. Further insight can be obtained from mechanical models of the stresses in the Central Indian Basin. The predicted stresses are consistent with the diffuse boundary model and distribution of deformation shown by geophysical data. Futhermore, they provide an explanation for the widespread pattern of compressional folding E, W, and on the Ninetyeast Ridge. These data and the kinematic and mechanical models provide insight into three enigmatic tectonic features: the complex blocky structure of the Ninetyeast Ridge N of 10°S, the trend of the S 85°E Ridge, and the rapid recent subsidence of the S Chagos-Laccadive Ridge. -from Authors