The “London” earthquake of 1580, April 6

Abstract

A large number of accounts of the effects of the 1580, April 6, “London” earthquake have been collected and examined. At least four aftershocks have been identified, the largest of which occurred on May 1 or 2. Intensities have been assigned for a number of localities on the evidence of contemporary reports and other data, including the nature of the constructions employed in damaged structures. An assessment of the suitability of six variants of widely used intensity scales is made by assigning intensities independently on each scale, for the complete data set. Marine effects, the regions affected by the aftershocks and the spatial distribution of intensities show that the epicentre probably lay offshore in the Straits of Dover. The maximum intensity was assigned as an inferred 9 using both the MSK scale and the Modified Mercalli Scale (Brazee version), the two scales found to be preferable. This earthquake affected all of northern France, Britain possibly as far north as Edinburgh, and the Low Countries and Germany beyond Cologne and Duisburg. Employing suitable relationships between intensity, magnitude, and attenuation, yields a Richter magnitude in the range 6.2 to 6.9. It is suggested that this earthquake may have been caused by movement along a fault of Variscan trend at a depth of about 33 km; that is, at the base of the crust.