TENSIONAL FISSURES IN SEDIMENTS AS SIGNATURE OF RIFT TECTONICS IN THE MAIN ETHIOPIAN RIFT

Abstract

The Main Ethiopian Rift, which forms the northern part of the
East African Rift, is a regime of extensional tectonics with geodetically measured mean spreading rate of 3.6 mm(yr)"l. Earlier studies have shown that the effects of this extension are manifested mainly through ~rthquakes, faults and volcanism. Recently, with the observations of the occurrence of fissures of tectonic origin on the sediment cover of the rift floor. an additional effect of the extensional process has been identified. The importance of this effect in characterizing rift tectonics could be commensurate with the areal size of the sedi~tary cover of the rift floor which is substantial. The object of this study is to 8ssess the significance of these tectonic-induced fissures as signature of the riftink process by comparing them to earthquake and volcanic activities. It is
sho'}'n that fissures on sediments are significant indicators of rift tectoni~ with a corresponding role as agents of strain release.