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1990 South Sudan Earthquakes
In 1990, present day South Sudan was rocked by a series of violent earthquakes. It started with the largest event, a 7.2, and continued with multiple very large aftershocks for the next couple of months. It contains some of the largest recorded earthquakes anywhere in Africa. Tectonic setting The East African Rift System (EARS) is a system of rifts and associated rift lakes within the eastern portion of the African continent. It accommodates the internal breakup of Africa. It is a boundary between the Somali and African Plate. The Victoria and Rovuma microplates help accommodate additional more local stresses. The eastern portion of the rift runs from the Afar rift to Tanzania, while the western portion runs from Lake Albert (Africa) in Uganda all the way down to Mozambique. The Aswa Rift Zone (ARZ) is an important geologic structure in the area near the earthquakes. The ARZ may act as a broad zone of faulting that links together the eastern and western portions of the EARS ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fault (geology)
In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic forces, with the largest forming the boundaries between the plates, such as the megathrust faults of subduction zones or transform faults. Energy release associated with rapid movement on active faults is the cause of most earthquakes. Faults may also displace slowly, by aseismic creep. A ''fault plane'' is the plane that represents the fracture surface of a fault. A ''fault trace'' or ''fault line'' is a place where the fault can be seen or mapped on the surface. A fault trace is also the line commonly plotted on geologic maps to represent a fault. A ''fault zone'' is a cluster of parallel faults. However, the term is also used for the zone of crushed rock along a single fault. Prolonged motion along closely spaced faults can blur the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Focal Mechanism
The focal mechanism of an earthquake describes the deformation in the source region that generates the seismic waves. In the case of a fault-related event it refers to the orientation of the fault plane that slipped and the slip vector and is also known as a fault-plane solution. Focal mechanisms are derived from a solution of the moment tensor for the earthquake, which itself is estimated by an analysis of observed seismic waveforms. The focal mechanism can be derived from observing the pattern of "first motions", that is, whether the first arriving P waves break up or down. This method was used before waveforms were recorded and analysed digitally and this method is still used for earthquakes too small for easy moment tensor solution. Focal mechanisms are now mainly derived using semi-automatic analysis of the recorded waveforms. Moment tensor solutions The moment tensor solution is typically displayed graphically using a so-called ''beachball'' diagram. The pattern of en ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
July 1990 Events In Africa
July is the seventh month of the year in the Julian and Gregorian calendars and is the fourth of seven months to have a length of 31 days. It was named by the Roman Senate in honour of Roman general Julius Caesar in 44 B.C., it being the month of his birth. Before then it was called Quintilis, being the fifth month of the calendar that started with March. It is on average the warmest month in most of the Northern Hemisphere, where it is the second month of summer, and the coldest month in much of the Southern Hemisphere, where it is the second month of winter. The second half of the year commences in July. In the Southern Hemisphere, July is the seasonal equivalent of January in the Northern hemisphere. "Dog days" are considered to begin in early July in the Northern Hemisphere, when the hot sultry weather of summer usually starts. Spring lambs born in late winter or early spring are usually sold before 1 July. July symbols *July's birthstone is the ruby, which symbolize ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
