12,000-Year-Long Record of 10 to 13 Paleoearthquakes on the Yammouneh Fault, Levant Fault System, Lebanon

Abstract

We present results of the first paleoseismic study of the Yammoûneh fault, the main on-land segment of the Levant fault system within the Lebanese restraining bend. A trench was excavated in the Yammoûneh paleolake, where the fault cuts through finely laminated sequences of marls and clays. First-order variations throughout this outstanding stratigraphic record appear to reflect climate change at centennial and millennial scales. The lake beds are offset and deformed in a 2-mwide zone coinciding with the mapped fault trace. Ten to thirteen events are identified, extending back more than ϳ12 kyr. Reliable age bounds on seven of these events constrain the mean seismic return time to 1127 ‫ע‬ 135 yr between ϳ12 ka and ϳ6.4 ka, implying that this fault slips in infrequent but large (M ϳ7.5) earthquakes. Our results also provide conclusive evidence that the latest event at this site was the great A.D. 1202 historical earthquake, and suggest that the Yammoûneh fault might have been the source of a less well-known event circa A.D. 350. These findings, combined with previous paleoseismic data from the Zebadani valley, imply that the parallel faults bounding the Beqaa release strain in events with comparable recurrence intervals but significantly different magnitudes. Our results contribute to document the clustering of large events on the Levant fault into centennial episodes, such as that during the eleventh through twelfth centuries, separated by millennial periods of quiescence, and raise the possibility of a M Ͼ7 event occurring on the Yammoûneh fault in the coming century. Such a scenario should be taken into account in regional seismic-hazard assessments and planned for accordingly.

Determination of Mmax from Background Seismicity and Moment Conservation

“…Our model suggests an M w > 7 should occur roughly once every 115 years; however, our model is for the entire length of the DST, whereas the Araba Valley segment covers only around one-fifth of the fault. The paleoseismic data do not disagree with our model, though the earthquake rate seems quite variable through time (Daëron et al, 2007).…”

Spatial and temporal variation of palaeoseismic activity at an intraplate, historically quiescent structure: The Concud fault (Iberian Chain, Spain)

“…In regions with seismically active faults, studies covering time windows of a few thousands (or even a few hundreds) of years usually provide a representative picture of fault behavior (e.g., Atwater et al, 2003;Daëron et al, 2007;Ren et al, 2013). On the contrary, in regions with low seismic activity where the characteristic earthquake has not likely been historically registered, the palaeoseismological record of major faults is needed in order to encompass a greater time span.…”

Hydrological variability in the Northern Levant: a 250 ka multi-proxy record from the Yammoûneh (Lebanon) sedimentary sequence

“…It was downfaulted through thick sub-tabular sequence of intensively karstified Cenomanian dolomitic limestones (Dubertret, 1975;Hakim, 1985). The strike-slip Yammoûneh Fault is active (slip rate: 3.8-6.4 mm yr −1 ), but vertical movements likely remained negligible during the Late Quaternary (Daëron et al, 2004(Daëron et al, , 2007A. R. Elias, personal communication, 2009).…”