A 40,000 year unchanging seismic regime in the Dead Sea rift

We studied breccia beds in lacustrine sediments within the active Dead Sea basin. The beds were deformed by M > 5.5 earthquakes during the past 60 k.y. Our new analysis considers both the thickness of breccia beds and the lithology of beds directly overlying them in order to identify 11 M > 7 earthquakes that originated within the Dead Sea pull-apart between 54 and 16 ka. The resulting time series is a unique long record of earthquakes in a well-constrained segment of a fault system in which the time interval between consecutive earthquakes increased from hundreds of years to a background recurrence interval of similar to 11 k.y. since ca. 40 ka. Since this recurrence interval is similar to the M >= 7.2 recurrence interval in the Dead Sea basin, as extrapolated from present seismicity, we suggest that the present seismic regime in the Dead Sea basin, as reflected in its magnitude-frequency relation as well as in its deficiency in seismic moment, has been stationary for the past similar to 40 k.y. Since the increasing interval between consecutive earthquakes in the studied segment of the Dead Sea fault is time-logarithmic, it may be a result of healing of the brittle crust as well as a diminishing strain rate following the first strong earthquake in the sequence.