High-resolution Seismic Reflection Surveys Research Articles

Incipient spreading center in the Gulf of Elat, northern Red Sea

The Gulf of Elat, located at the northern Red Sea, is a rift that forms the southern section of the Dead Sea rift system. A recent high-resolution seismic reflection survey showed that lenticular grabens and axial anticlines are the predominant structures at the rift floor. Structural relationships suggest that after the lenticular graben was formed at the rift floor, it was filled with sediments. Axial uplift along the rift caused the widening of the graben and the development of axial anticlines, and at a later stage a new graben started to develop between the flank of the anticline and the boundary fault of the rift. The data indicate that the tectonic regime affecting the southern Dead Sea rift is one of uplift and extension, acting simultaneously. It is presumed that upwelling of magma in the upper mantle, extending northwards from the Red Sea, is the cause for these uplift and extensional phenomena, and that the Gulf of Elat is an incipient spreading center.

High-resolution seismic reflection profiles reveal fracture zones within a ‘homogeneous’ granite batholith

Several countries are investigating the use of plutonic rock bodies for the ultimate disposal of radioactive waste material1. Among criteria2,3 that must be met before a rock body is mined for a repository is that it must have a low in situ permeability. As the permeability of most unfractured plutonic rocks is very low3, the problem reduces to finding those bodies which do not contain major connected fractures that would allow radioactive material to be transported by water to the biosphere. We report here that a high-resolution seismic reflection survey across the central region of an Archaean granitic pluton, which on the basis of other data might be defined as relatively homogeneous, identifies major sub-horizontal fracture zones at depth. Such fracture zones, which could be a major hazard for the containment of radioactive wastes, may therefore be detected before selection of a repository site by a combination of high-resolution seismic reflection surveying and suitably located deep drilling.