Delimitation of domains with uniform stress in the subducted Nazca plate

This work concentrates on the determination of detailed variations of stres s in the descending Nazca plate and is based on the distribution of seismic activity and the orientation of P- and T-axes of fault plane solutions. In ternational Seismological Centre (ISC) and Harvard Centroid Moment Tensor S olutions (HCMT) data were used. The method of Gephart and Forsyth [J. Geoph ys. Res. 89 (1984) 9305-9320] was applied to determine the state of stress. It is shown that the state of stress varies along the whole Wadati-Benioff zone, where 16 different domains with uniform stare of stress were delimit ed. The state of stress tends to change more systematically with the depth of the Wadati-Benioff zone than laterally, and is connected with the morpho logy of the Wadati-Benioff zone. A decreased stability of the state of stre ss in the Wadati-Benioff zone was found in the depth range 50-300 km. The s tate of stress in the depth ranges 0-100 km and deeper than 500 km appears to be very stable. The physical interpretation of the observed phenomena is not the subject of this investigation. (C) 2000 Elsevier Science B.V. All rights reserved.