Three-dimensional excavations of buried stream channels that have been displaced by the Jordan Fault, the primary strand of the Dead Sea fault zone in northern Israel, demonstrate that late Holocene slip has been primarily strike-slip at a minimum rate of 3 mm/yr. The palaeoseismic study was carried out in the Bet-Zayda Valley, the delta of the Jordan River at the north shore of the Sea of Galilee. The site was chosen where a north-striking scarp with up to 1-m vertical expression crosses the flat valley. One group of trench excavations was located where a small stream crosses the scarp. The active stream, which is incised into the scarp, is not offset by the fault. However we found two palaeo channels about 2 m below the surface offset sinistrally 2.7±0.2 m by the fault and two younger nested channels offset 0.5±0.05 m. Based on radiocarbon dates we attribute the last 0.5 m rupture to the earthquake of October 30, 1759. The older offset of 2.2 m most probably occurred in the earthquakes of May 20, 1202. These two events correlate with the findings at Ateret, about 12 km north of Bet-Zayda, where the 1202 earthquake produced 1.6 m of lateral displacement in E-W-striking defence walls of a Crusader castle, and an Ottoman mosque was offset 0.5 m in the earthquake of 1759. In the second group of trenches some 60 m farther south we found another offset channel. Its northern margin is displaced 15 m sinistrally whereas the southern margin shows only 9 m of sinistral offset. The dip slip component is 1.2 m, west side down. The different amounts of margin offset can be explained by erosion of the southern margin during the first 6 m of displacement. Additional slip of 9 m accrued after the stream had been abandoned and buried by a 2-m-thick lacustrine clay layers. Radiocarbon dates on organic residue provide the age control which indicates that the 15 m of slip has accrued over the past 5 kyr, yielding a short-term slip rate of 3 mm/yr for the late Holocene. It is possible that our study covers only part of the fault zone, hence we regard this mean slip rate to be a minimum for the DST. Based on other palaeoseismic studies the best estimate for Quaternary slip rate is 4±1 mm/yr.
Bibliographical noteFunding Information:
We thank our colleagues Rivka Amit, Ezra Zilberman, Daniel Wachs, Yariv Hami'el, Yuval Bartov, Revital Ken-Tor, Dany Gluck, Yonni Shaked, Meir Abelson, and Ari Matmon for constructive advice and assistance in the fieldwork. Technical assistance by Dany Ergas, Shlomo Ashkenazy, Moshe Arnon, Ya'akov Mizrahi is greatly appreciated. We are also grateful to the farmers of Almagor for their hospitality and for allowing us to work in their fields, in particular Avi Bental and Avishai. Elisabeta Boaretto is thanked for performing C14 analyses and discussing their implications. Gordon Seitz is thanked for contributing C14 analyses. We are thankful to Mustapha Meghraoui and an anonymous referee for constructive reviews. The study was funded by the Binational Science Foundation Israel–U.S. and the Earth Sciences Administration of the Ministry of Infrastructure of Israel.
- Dead Sea fault