THE DISTRIBUTION OF EARTHQUAKES AND VOLCANOS ALONG THE EAST-AFRICAN RIFT SYSTEM

The pattern of earthquake epicentres for the period 1904 to 1993 is compared with the distribution of 615 Cenozoic volcanoes in the East African Rift system. Holocene volcanism occurs mostly within the rift valleys while the pre-Holocene volcanoes are more scattered and extend beyond the confines of the rift. Pre-Holocene volcanism is also more extensive, reaching south through Mozambique and Zimbabwe. Most of the volcanoes, of all ages, are associated with the eastern branch of the rift system. In contrast, the western branch appears to be far more seismically active than its eastern counterpart, although most of the epicentres postdate 1963. In general, teleseismic earthquake epicentre data for 1904 through 1993 (noting the short time period) and Holocene volcanism show no apparent simple relationship except for the Ethiopian Rift.