Dating of historical earthquakes by mud profiles of lake-bottom sediments

Abstract

RECENTLY, Ben-Menahem et al.¹ derived tectonic patterns and slip rates in the Jordan Rift Valley by combining a comprehensive study of seismological, historical, geological and morphological data. It was found that the principal seismic activity along the Jordan Valley is due to a left-lateral strike-slip fault, striking 11° east of north and extending for about 50km from 32°N to 31°30′N along the 35° 30′meridian. Its most active part in the past four millenia has been near the monastery of John the Baptist which, according to tradition, is the place where the Israelites crossed the Jordan and where Jesus was baptised. The fault trace and its role in the historical seismicity of the area is shown in Fig. 1. It has an estimated mean rate of activity of 2–3 events per century at magnitudes from 5 to 7 (ref. 1). An aseismic slip rate of at least 3 mm yr⁻¹ is taking place along this fault¹. Here we show how this activity is reflected in an unusual limnological process which takes place at the bottom of the Dead Sea and which can serve as a ‘geophysical clock’ to date historical events.