Abstract

In intraplate settings in eastern North America, paleoseismological studies have been used to obtain recurrence of earthquake at three locations. As causative faults are usually inaccessible at these locations the effects of paleoearthquakes have been studied. While calculating recurrence intervals we have tacitly assumed that the earthquakes at each locality repeatedly occurred on the same faults. Indicators of paleoearthquakes that were studied include deformed soft sediments due to seismically induced liquefaction (New Madrid and Charleston, SC, seismic zones), warped lake sediments and anomalous silt layers in otherwise organic rich sediments (Charlevoix, Canada seismic zone). The resulting recurrence intervals for New Madrid (≈ 600 years) and Charleston (1500–2000 years) are in general agreement with those obtained from statistical studies. At Charlevoix it was estimated that a MM intensity VI event (sufficient to disturb varves) occurs every ≈ 400 years.

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