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The Hereford Earthquake of 15th August, 1926

Published online by Cambridge University Press:  01 May 2009

Charles Davison
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Extract

This important earthquake is chiefly of interest on account of its connexion with the strong Hereford earthquakes of 6th October, 1863, 30th October, 1868, and 17th December, 1896. At least three of the four earthquakes (those of 1863, 1896, and 1926) seem to have originated in the same twin-foci, the epicentre of one lying near Hereford and that of the other near Ross. The fourth earthquake (that of 1868) originated in the Ross focus, possibly also in the Hereford focus.

Type
Original Articles
Information
Geological Magazine , Volume 64 , Issue 4 , April 1927 , pp. 162 - 167
Copyright
Copyright © Cambridge University Press 1927

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References

page 162 note 1 I am indebted to the editors of a large number of newspapers for their courtesy in printing my letters of inquiry and to more than 1,200 correspondents for their kindness in answering them; also to Professor H. H. Turner, F.R.S., and the Directors of the Meteorological Office and the Kew Observatory for allowing me to read letters written to them.

page 163 note 1 In the Stafford earthquake of 14th January, 1916, I was able to draw two series of isoseismal lines of intensities 5, 4, and 3, depending on observations made respectively on the ground-floor and on upper-floors. The two isoseismals 5 are practically identical. The areas of the isoseismals 4 and 3 are 6,570, and about 16,500 square miles for ground-floor observations, and 12,500 and 50,200 square miles for upper-floor observations (Amer. Seis. Soc. Bull., vol. ii, 1921, pp. 122–4).Google Scholar

page 165 note 1 The twin-shock would naturally be felt farther towards the south-east than in the opposite direction, as the attention of observers there would be roused by the stronger initial movement.

page 165 note 2 In strong British earthquakes (that is, with disturbed areas of more than 5,000 square miles) the average percentage of audibility is 97 within the central isoseismal, and 94, 87, 68, and 55 within the zones bounded by successive isoseismals.

page 166 note 1 That the fault is situated at a great depth is clearly shown by the magnitudes of the disturbed areas of two fore-shocks of the earthquake of 1896. Both were probably of intensity 4, yet their disturbed areas contained as much as 6,300 and 6,400 square miles. The average disturbed area of British earthquakes of the same intensity is 400 square miles.

page 167 note 1 History of British Earthquakes, 1924, pp. 244–59.Google Scholar