The East African Rift System (EARS) and by extension the Davie Ridge, which is considered as the seaward extension of eastern branch (Kenya Rift Valley) of the East African Rift Valley (), are characterized by divergence whose maximum rate is estimated to be about 7mm/year (). This rate of divergence is somewhat much slower than that found at most active mid-ocean ridges or even the convergence of India–Burma plates or that between the Australian and Sunda plates (). Despite this slow rate of divergence, the East African Rift Valley and the Davie Ridge are characterized by frequent seismicity with large and shallow earthquakes occurring occasionally. Seismic reflection, gravity, and magnetic data from offshore East Africa allow the Davie Fracture Zone to be traced from 11oS to its intersection with the Kenyan coast at 2oS, constraining the relative motion of Madagascar and Africa (). Further, numerous faults and fractures probably associated with the Davie Fracture have been mapped using recent gravity and magnetic data between latitudes 2o21′S and 3o03′S and longitudes 40o08′E and 40o45′E by . Seasat-derived free-air gravity anomalies and slope/rise positive magnetic anomalies observed in shipboard data help to locate the continent–ocean boundaries (COB) off the shore of East Africa and Madagascar. Furthermore, the EARS, and precisely the Kenya Rift Valley, is characterized by ~3-km-thick sediments and normal-faulting mechanism. Deformation has been active along the Kenya Rift Valley as evidenced by high seismic activity. Surface deformation studies from SAR interferometry in the southern sector of the Kenya Rift Valley in Magadi show that it is characterized by 14cm of deformation over 10-km-long stretches (). If the Davie Ridge is an extension of the East African Rift Valley, we cannot rule out the occurrence of tsunami-generating earthquakes, which are bound to have devastating consequences on the eastern coast of Africa. Earthquakes as deep as 40km have been recorded below Davie Ridge (). However, evaluation of recent seismic data shows that magnitude 6.0–7.2 earthquakes at relatively shallow depths of 10–30km are a common occurrence along the Kenya Rift Valley and the Davie Ridge in the Mozambique Channel. The focal mechanism of these earthquakes supports what has previously been proposed that the Davie Ridge is a southward extension of the eastern arm of the EARS. The earthquake focal mechanism indicates that the Davie Ridge is characterized by predominantly normal faulting with occasional oblique faulting. Consequently, Kenya and generally the East African coast are prone to both seismic hazards on land and tsunami-generating earthquakes. This chapter begins with general overview of the seismicity in Kenya from the 1900s to the present. Seismicity in Kenya up to 1963 is mainly based on macroseismic data while that from 1963 to the present is based on data from instrumental recordings. In the past, a number of microseismic and seismicity studies in Kenya have previously been undertaken and the results from these studies are rather disjointed. In this chapter, we have made an attempt to merge all the existing results into one database from which the general seismicity, and subsequently seismic hazard in Kenya has been evaluated. The main goal of this chapter is to bring into focus the area(s) in Kenya more prone to seismic hazards either due to ground shaking occasioned by an earthquake or due to tsunami as a result of earthquakes occurring along the Davie Ridge.
The East African Rift System (EARS) and by extension the Davie Ridge, which is considered as the seaward extension of eastern branch (Kenya Rift Valley) of the East African Rift Valley (), are characterized by divergence whose maximum rate is estimated to be about 7mm/year (). This rate of divergence is somewhat much slower than that found at most active mid-ocean ridges or even the convergence of India–Burma plates or that between the Australian and Sunda plates (). Despite this slow rate of divergence, the East African Rift Valley and the Davie Ridge are characterized by frequent seismicity with large and shallow earthquakes occurring occasionally. Seismic reflection, gravity, and magnetic data from offshore East Africa allow the Davie Fracture Zone to be traced from 11oS to its intersection with the Kenyan coast at 2oS, constraining the relative motion of Madagascar and Africa (). Further, numerous faults and fractures probably associated with the Davie Fracture have been mapped using recent gravity and magnetic data between latitudes 2o21′S and 3o03′S and longitudes 40o08′E and 40o45′E by . Seasat-derived free-air gravity anomalies and slope/rise positive magnetic anomalies observed in shipboard data help to locate the continent–ocean boundaries (COB) off the shore of East Africa and Madagascar. Furthermore, the EARS, and precisely the Kenya Rift Valley, is characterized by ~3-km-thick sediments and normal-faulting mechanism. Deformation has been active along the Kenya Rift Valley as evidenced by high seismic activity. Surface deformation studies from SAR interferometry in the southern sector of the Kenya Rift Valley in Magadi show that it is characterized by 14cm of deformation over 10-km-long stretches (). If the Davie Ridge is an extension of the East African Rift Valley, we cannot rule out the occurrence of tsunami-generating earthquakes, which are bound to have devastating consequences on the eastern coast of Africa. Earthquakes as deep as 40km have been recorded below Davie Ridge (). However, evaluation of recent seismic data shows that magnitude 6.0–7.2 earthquakes at relatively shallow depths of 10–30km are a common occurrence along the Kenya Rift Valley and the Davie Ridge in the Mozambique Channel. The focal mechanism of these earthquakes supports what has previously been proposed that the Davie Ridge is a southward extension of the eastern arm of the EARS. The earthquake focal mechanism indicates that the Davie Ridge is characterized by predominantly normal faulting with occasional oblique faulting. Consequently, Kenya and generally the East African coast are prone to both seismic hazards on land and tsunami-generating earthquakes. This chapter begins with general overview of the seismicity in Kenya from the 1900s to the present. Seismicity in Kenya up to 1963 is mainly based on macroseismic data while that from 1963 to the present is based on data from instrumental recordings. In the past, a number of microseismic and seismicity studies in Kenya have previously been undertaken and the results from these studies are rather disjointed. In this chapter, we have made an attempt to merge all the existing results into one database from which the general seismicity, and subsequently seismic hazard in Kenya has been evaluated. The main goal of this chapter is to bring into focus the area(s) in Kenya more prone to seismic hazards either due to ground shaking occasioned by an earthquake or due to tsunami as a result of earthquakes occurring along the Davie Ridge.
Bioceramics, Volume 9 contains a compilation of the papers presented at the Ninth International Symposium in Ceramics in Medicine which was held in Otsu, Japan in November 1996. Over 150 papers were submitted to this symposium from 19 countries and 120 contributed papers and 8 invited papers for panel discussion were accepted. The readers will get a good overview of the recent progress in this discipline. The variety of ceramics and fields of their clincal applications are steadily growing and this book will undoubtedly contribute to the progression of this research area. In this symposium, a panel discussion on current status and future trend of ceramics in medicine was held by invited speakers doing research on the next generation of ceramics. General sessions consisting of the contributed papers were classified according to the kind of materials so that active discussion could arise concerning the respective material between ceramic scientists and medical scientists.
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