Abstract

In the early morning of October 9, 1984, northwestern Georgia was shaken by a magnitude mb = 3.5 earthquake. This event is typical of the general seismicity experienced in northwestern Georgia and southeastern Tennessee. Intensity IV effects were felt over 6000 km2. The total felt area was 12,000 km2. The depth of focus was 10 ± 5 km, which places the earthquake focus below the Paleozoic sediments. First motion and relative amplitude data indicate a strike-slip focal mechanism with the preferred fault plane having right-lateral slip on a north-trending near-vertical plane. Spectral data give an equivalent fault radius of 0.6 km, a stress drop of 40 bars and a moment of 2.5 × 1022 dyne-cm. During an aftershock survey of nearly two weeks duration, only one significant (mb = 2.0) aftershock was recorded. It occurred on October 15, 1984, six days after the main event.

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