Regional Tectonic Background

The eastern Mediterranean region is dominated by the collision of the Arabian and African plates with Eurasia, and within this tectonic framework, the left-lateral Dead Sea Fault System (DSFS) forms an ~1,000  km long continental transform fault extending from the Red Sea spreading center northward to the  collisional zone in southern Turkey.  Within Lebanon and southwestern Syria, the DSFS enters a ~200 km long restraining bend in which the simple trace of the southern DSFS (between Jordan and Israel) develops into several prominent splays including the Yammouneh, Serghaya, and Roum faults.  Near the northern border of Lebanon, the DSFS emerges from the bend and can be traced as the relatively simple Ghab fault segment.

Present-day plate tectonic models predict that the relative motion between Arabia and Africa is about 5 - 10 mm/yr, and these predictions are consistent with results from field studies along the southern DSFS (e.g., Garfunkel et al., 1981;  Galli, 1999; Klinger et al., 2000a).  Preliminary results from GPS stations straddling the southern DSFS and the northernmost DSFS in Turkey are also consistent with this range, although associated confidence limits are broad and velocities may reflect local effects of elastic strain accumulation (e.g., McClusky et al., 2000).

Although a paucity of instrumentally recorded seismicity (approximately 1900 to present) along the central and northern SFS (Figure 2a) has in part led to suggestions that the northern DSFS is inactive and that the locus of present-day deformation is offshore to the west (e.g., Butler et al., 1997, 1998; Girdler, 1990), field observations and historical seismicity suggest active faulting of the northern DSFS.

Historical records of large, devastating earthquakes also attest to the activity and seismogenic potential of the central and  northern DSFS (Figure 2b), despite the scarcity of moderate and large events in instrumental records (Figure 2).  One of the best documented and most recent events (M = 7.4) occurred in 1759 affecting the Bekaa Valley of Lebanon (Figure 4) along a rupture of at least 100 km in length (Ambraseys & Barazangi, 1989).  Other significant earthquakes occurred in 551, 1157, 1170,  1202, 1408, and 1837 (e.g., Mouty et al., 1998; Ambraseys & Jackson, 1998).  Although surface ruptures relating to most of these events have not been confirmed with field observations, the macroseismic information demonstrates that the effects of these events were most intense along the trace of the DSFS.

In addition to the DSFS, late Cenozoic deformation has occurred within the adjacent region of the Arabian plate in the Palmyride fold belt, the Jebel Abdel Aziz of northeastern Syria, and the Euphrates fault system .  Whether or not these internal deformations of the northern Arabian plate continue today is unresolved, although seismicity in the Palmyride fold belt (e.g., Mw 5.1 in 1996) suggests this as a possibility.

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Last modified September 4, 2001.