File:The Quarterly journal of the Geological Society of London (1891) (14594962350).jpg

Identifier: quarterlyjournal47189geol (find matches)
Title: The Quarterly journal of the Geological Society of London
Year: 1845 (1840s)
Authors: Geological Society of London
Subjects: Geology
Publisher: London (etc.)
Contributing Library: Smithsonian Libraries
Digitizing Sponsor: Biodiversity Heritage Library

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crosses ( + ), drawn throughthe discs when the shock was also felt, or separately if the shockpassed unperceived. The two continuous lines arc isoseismal linesof intensities V. and IV. respectively ; the dotted lines representthe boundaries of the disturbed areas of three of the subsequentshocks. (See next page.) Outside the isoseismal of intensity lY. I have records from only16 places, and these are not sufficient to determine exactly theboundary of the disturbed area. Except towards the north, how-ever, none of these places is more than ten miles from the isoseismal.At Helmsdale there is an increase of intensity, and I am by nomeans certain that this was not caused by a separate, but perhapsnot independent, earthquake. The area disturbed by the earthquake within the isoseismal ofintensity IV. is 86; miles long and 611 miles broad, the longer axisbeing directed N. 52° E. and S. 52° W. The area contained by thiscurve is about 4340 square miles, including the part covered bythe sea.
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J THE IXVERNKSS EARTHQUAKES OF NOV. 15 TO DEC. 14, 1890. 621 2. Nature of iJte Shocl\—The nature of the shock varied consi-derably throughout the disturbed urea, this variation being of coursea necessary consequence of the position and magnitude of the seismicfocus. I will first give a few descriptions in detail out of a largenumber received. Beauly : A heavy rumbling sound was heard before and duringthe shock. Throe distinct vibrations were first felt, more intenseto begin with, and were followed by a tremulous motion; the wholelasting about 8 or 10 seconds. The vertical motion was very per-ceptible, first upward and then downward. Dingwall: A heavy rumbling sound was first heard, followed bya violent quivering of the ground, consisting of about 10 or 12vibrations, first increasing in intensity and then gradually dyingaway. The duration of the shock, excluding that of the sound,was 5 seconds. Drumnadrochit: First a tremulous shake, then four strongvibrations, and again a tremulous

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