A note on the isostatic compensation and origin of King's Trough

Abstract

Summary. The depth and seismic source parameters of the three largest reservoir-induced earthquakes associated with the impoundment of Lake Kariba, Africa, were determined, using a moment tensor formalism of the generalized inverse technique. The events, characterized by mb > 5.5, consisted of the foreshock and main event (0640 and 0901 GMT, 1963 September 23) and the principal aftershock (0703 GMT, 1963 September 25). From the analysis of analogue rift valley source crustal models, a threelayer over a half-space model were selected for the analysis of the Lake Kariba events. The epicentral proximity and the comparable source parameters of the three large events suggest a common source fault with an approximate strike of S 9"W k 4", dip of 62" k lo", and rake of 266" k 4".The body wave modelling indicates that the Lake Kariba events occurred at depths of less than 10 km. The inferred source parameters, complemented by the structural maps derived from the photo-interpretation of Landsat imagery of the region, indicate a normal fault that uniquely transects the reservoir's deep Sanyati Basin in a north-south heading. The active fault seems to correlate with the location of the Umi River's submerged river channel. The confirmation of shallow depths and the determination of source parameters establishes a basis for addressing the actual triggering mechanisms of these earthquakes.

Correlation of Seafloor Spreading Magnetic Anomalies across King's Trough, Northeast Atlantic Ocean

“…But the main tectonic events responsible for the formation of its troughs and basins probably occurred much later, during the Miocene. This is in agreement with a post-early Oligocene (< 30 Ma) formation of King's Trough, as suggested by Louden (1983), and an initial hot-spot origin for the King's Trough High.…”

“…Grimaud et al (1983) suggested a leaky-transform origin for King's Trough through a tectonic association with the Pyrenean orogenic phase. Louden (1983) concluded, however, through a spectral analysis of gravity and topographic profiles, that formation of the Trough itself postdated the formation of the Pyrenees, unless that orogeny continued well after 38 Ma, the late Eocene.…”

King's Trough: reactivated pseudo-fault of a propagating rift

“…It is very likely that the two are interrelated and thus correspond to the extensional phase (40-24 Myr) when King's Trough became part of the plate boundary between Eurasia and Iberia (Roest & Srivastava 1991). Based on the analysis of a gravity and bathymetric profile, Louden (1983) suggested that King's Trough was formed no earlier than 30Ma. This would suggest that the major part of the present-day topography of King's Trough was created in the later stages of extension across the plate boundary.…”

“…7) 1991). Based on the analysis of a gravity and bathymetric profile, Louden (1983) suggested that King's Trough was formed no earlier than 30Ma. This would suggest that the major part of the present-day topography of King's Trough was created in the later stages of extension across the plate boundary.…”

“…(1982) and Kidd & Ramsay (1986) from drilling and dredging results. Gravity observations made across the Trough have been interpreted to suggest that the topography of King's Trough is regionally compensated on a lithosphere older than 20 Myr and therefore was formed by intraplate activity no earlier than 30 Ma, late Oligocene (Louden 1983).…”