Although magmatism may occur during the earliest stages of continental rifting, its role in strain accommodation remains weakly constrained by largely 2‐D studies. We analyze seismicity data from a 13 month, 39‐station broadband seismic array to determine the role of magma intrusion on state‐of‐stress and strain localization, and their along‐strike variations. Precise earthquake locations using cluster analyses and a new 3‐D velocity model reveal lower crustal earthquakes beneath the central basins and along projections of steep border faults that degas CO2. Seismicity forms several disks interpreted as sills at 6–10 km below a monogenetic cone field. The sills overlie a lower crustal magma chamber that may feed eruptions at Oldoinyo Lengai volcano. After determining a new ML scaling relation, we determine a b‐value of 0.87 ± 0.03. Focal mechanisms for 65 earthquakes, and 13 from a catalogue prior to our array reveal an along‐axis stress rotation of ∼60° in the magmatically active zone. New and prior mechanisms show predominantly normal slip along steep nodal planes, with extension directions ∼N90°E north and south of an active volcanic chain consistent with geodetic data, and ∼N150°E in the volcanic chain. The stress rotation facilitates strain transfer from border fault systems, the locus of early‐stage deformation, to the zone of magma intrusion in the central rift. Our seismic, structural, and geochemistry results indicate that frequent lower crustal earthquakes are promoted by elevated pore pressures from volatile degassing along border faults, and hydraulic fracture around the margins of magma bodies. Results indicate that earthquakes are largely driven by stress state around inflating magma bodies.
The Proceedings were opened by the Chairman, who delivered the following Introductory Address. I~zlroducfion.-Notwithstanding the fact that the satisfactory working of steel-making and other furnaces, as well as metallurgical operations generally, largely depends upon t tie correct kind of refractories employed, this important subject has not altogether received in this country the attcntion it should have done. A search in the Proceedings of one of the leading Metallurgical Societies shows there have been practically but few papers contributed on the subject, which is really conspicuous by its absence. There are, I believe, about 2 0 0 makers of refractories in Great Britain, comprising about 140 in England, 40 in Scotland, and 30 in Wales ; also about 12 makers of crucibles. The sources of raw products in this country are chiefly:-(a) Derbyshire district. jb) Dirham and Northumberland. (c) Lancashire. (d) North Worcestershire. (e) South Staffordshire. (f) Scotland. (g> South Wales. (11) Yorkshire (including Sheffield and Leeds).
I. T h e possibilities of X-ray examination in steel man'ufscture will be readily apparent. The meanis which it provides for enabling the Metallurgist to see the interior of steel castings and forghgs, and thus to diagnose anld lacalise the diseases to which steel is subject, just in the same manner as the X-rays have been sometimes of such incalculable service to the surgeon, must prove of considerable benefit. 2. The chief difliculty hitherto, and one reaSon why progress in regard to steel has mot been made approaching that in medical science, has been the limite'd thickness of metal which could be penetrated, but considerable strides have been made within the last year or #two in this direction. Thicknesses up to 4 inches are no'w said to have been successfully radiographed.
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