Abstract

In this article, the spatial distribution of earthquake epicenters in Ibb Governorate was investigated. According to the seismic record, this area is characterized by microearthquakes activities, although macro-earthquakes may also occur such as those of Al-Udain earthquake (22 Nov.1991, Mb=4.6 and 19 May 1992, Mb=4.5). Based on these facts. This paper would outline the seismicity of the study area with reference to the prevailing rock formations and associated geological structures. The dominant rock unit is the Tertiary Yemen Volcanic that covers nearly 87% of the total area. Most of the earthquakes (844 events) were reported during the period between 1991 to 2014, with an average about 37 earthquake per year. Their magnitude range from 0.3 to 4.6, in which 18.5% have magnitude of more than 3. The focal depth of the reported earthquakes varies between 1 to 28 km. It is believed that the events are related to lithospherical deformations within the earth crust. The seismic activity in the study area may be classified as low to medium (M≤4.6) and predominantly localized along the major fault trends in three regions: Al-Makhader-Al-Qafr, Hubaysh and Al-Udain.