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This paper presents the first comprehensive analysis of the present- day stress from
boreholes near an active continental rifting zone in the Moatize Basin, Mozambique.
The state of present-day stress in this area that is located ca. 100 km away from the
Eastern African Rift System (EARS) is poorly understood, and most of our knowl-
edge is from earthquake focal mechanisms that provide stress information from the
deeper part of the lithosphere, and to a lesser extent from surface geological fea-
tures in the Malawi region. Considering the limited reliability of earthquake-derived
stress orientations near plate boundaries, poor coverage of low to moderate magni-
tude earthquakes in eastern Africa, and ambiguity about the latest activity of geo-
logical structure; other well- established methods are required to shed light on the
active tectonics of EARS. In this study, we analyse stress orientation using log data
from 95 vertical boreholes in a mine site to investigate the neotectonic stress pattern
of the region. Analysis of 17.9 km of televiewer logs resulted in interpretation of
1188 stress-related borehole failures. The results indicate a mean regional trend of
045° ± 31° for the maximum horizontal stress (SHmax). Our investigation reveals that
the regional state of stress in the study area is controlled by superposition of stress
sources that act at very different spatial scales. The consistency between our results
and predictions by plate-scale geodynamic models of stress orientations confirm that
the regional pattern of stress in this area is mainly controlled by first (>500 km)
and second (distances between 500 and 100 km) order stress sources (i.e., large tec-
tonic forces and lateral density variations). However, high- resolution data used in
this study reveal that third (between 100 and 1 km) and fourth (<1 km) order stress
sources from stiffness contrasts, rock fabric and geological structures have a great
impact on the stress perturbations at smaller and local scales.
