A new tectonic plate identified in the Near East

The Levant fault is a major tectonic structure in the Mediterranean region. Also known as the Dead Sea fault, it forms the western boundary of the Arabian plate. This sinistral transform fault extends approximately 745 miles (1200 km) and connects the oceanic spreading zone of the Red Sea with the continental collision zone of the Caucasus and the East Anatolian fault.

Ruptures along the latter fault triggered two significant earthquakes in February 2023, with magnitudes Mw7.8 and Mw7.6, respectively. In this active region, understanding the geometry and dynamics of these structures is crucial to determine if large earthquakes might also occur along the Levant fault.



To understand the history and evolution of these structures, scientists use various complementary types of data, including archaeological ruins and geomorphological traces left by ancient earthquakes, as well as recent GPS data that measure the immediate velocity of the fault.

While the Levant fault is well-documented historically in its southern and central parts, it is less so in northern Lebanon. Up to the transpressive bend in Lebanon, velocities measured either by GPS or geomorphological approaches converge around a value of 0.16±0.04 inches/year (4±1 mm/year). Conversely, in the north where fault studies are mainly based on documented displacements at archaeological sites, these geological-scale displacements of about 0.16±0.04 inches/year (4±1 mm/year) do not align with recent geodetic data, ranging from 0.04 to 0.08 inches/year (1 to 2 mm/year).

To resolve this inconsistency, an international team, including a CNRS researcher from IPGP, systematically used Sentinels-2 radar images to measure the horizontal velocity along the entire Levant fault. In a study published last March 15 in the journal Science Advances, they demonstrated that the decrease in fault velocity from the south to the north of Lebanon is real.

In the same study, based on observations along the southern part of the fault where seismic activity occurs in temporal clusters, Yann Klinger and his colleagues showed that the probability of two earthquakes occurring in a short time interval, leading to an overestimation of the geological velocity, is significant and may have caused the overestimation of the archaeological fault velocity.

Furthermore, the precise relocation of seismicity in the eastern Mediterranean shows persistent seismicity north of the fault that directly connects the Levant fault to the Cypriot subduction system (called the Carmel fault), while the area south of this fault is completely devoid of seismicity.

These observations suggest that the areas south and north of this discontinuity behave differently and correspond to independent tectonic micro-plates, explaining the observed velocity difference between the northern and southern parts of the Levant fault. The scientists have named this new northern microplate Latakia-Tartous.

Reference:
Xing Li et al., Resolving the slip-rate inconsistency of the northern Dead Sea fault. Sci. Adv. 10 (2024).
DOI: 10.1126/sciadv.adj8408