Peculiarities of the Deep Structure of the Lithosphere
in the Northeastern Part of the Indian Ocean

E. L. Mazo^a, A. A. Shreider^b, M. P. Kulikova^a, D. A. Gilod^a, and Al. A. Shreider^b

^a Faculty of Geology, Moscow State University, Moscow, Russia

^b Shirshov Institute of Oceanology, Russian Academy of Sciences, Moscow, Russia

E-mail: emazo@list.ru

Received December 12, 2007; in final form, May 15, 2008

Abstract—The seismicity of the northeastern part of the Indian Ocean in connection with the general structural
peculiarities of the main tectonic structures of the bottom is presented. The three main ranges of higher seismic
activity at the depths of 0–17, 20–27, and 32–35 km divided by aseismic layers are revealed. The seismic activ-
ity at depths of more than 35 km is almost not detected both for the ocean and for the Indian peninsula. The
nature of the distribution of the seismicity as such in the lithosphere is discussed. Using the results of anomalous
gravitational field transformations, the prolongation of the East Indian Ridge structure is revealed to 19 degrees
north, while the relationship of the Afanasy Nikitin Rise and the 85th Degree Ridge is not reflected at the tran-
forms. In the Cocos Basin, the mutually perpendicular disturbance zones of northeastern and northwestern
strike, as well as the point of their crossing, where the maximal number of earthquake foci are concentrated, are
distinguished. A conclusion concerning the substantial disturbance of the strength properties of the lithosphere
in this zone as a consequence of the geodynamical processes, which are accompanied by fracture tectonics, is
reached.

DOI: 10.1134/S0001437009060101

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