Seismicity Induced at the Northern Dead Sea Transform Fault, Kinneret (Sea of Galilee) Basin, by Shallow Creep Involving a Salt Body

• Published in: Tectonics (Washington, D.C.) D.C.), 2022-10, Vol.41 (10), p.n/a
• Main Authors: Barnea Cohen, O., Cesca, S., Dahm, T., Hofstetter, A., Hamiel, Y., Agnon, A.
• Format: Article
• Language: English
• Subjects: Boreholes; creep; Dead Sea Transform Fault; Depth; earthquake swarm; Earthquakes; Fault lines; Faults; Gravity; Hypotheses; induced seismicity; Kinneret (Sea of Galilee); Lakes; Methods; Plate boundaries; Plate tectonics; Probability theory; salt flow; Salts; Seismic activity; Seismicity; Seismograms; Seismometers; Solifluction; Stress concentration; Transform faults
• ISSN: 0278-7407; 1944-9194
• DOI: 10.1029/2022TC007247

In October 2013 and July–August 2018, two extensive earthquake swarms shook the northern reaches of Lake Kinneret (Sea of Galilee). Former studies explored the swarms, resulting in discrepant depths and mechanisms. Here, we attempt to settle the discrepant interpretations using alternative seismological methods and some unpublished data from borehole seismometers. We propose a hypothesis for the faulting phenomenon focusing on the interaction of the two plate boundary segments that step‐over the northern Kinneret depocenter: a creeping segment in the south and a locked segment in the north. The energy accumulated from the interaction induces earthquake swarms from time to time. A shallow fault patch (from the surface down to 1.5 ± 1.0 km) south of the swarms is thought to creep in association with a salt formation underlying some of the basin fill. We use regional seismograms, including two near‐source borehole stations, to refine the characteristics of the swarms. We test hypocentral and centroid depths using several methods and different velocity models and corroborate shallow ruptures: the majority are shallower than 6 km (all shallower than ≤10 km). The hypocentral locations and focal mechanisms suggest shallow NW‐SE normal faults splaying from the tip of the creeping segment in a horsetail pattern. We test the hypothesis by Coulomb stress calculations that show stress concentration at the step‐over interaction zone, consistent with focal locations and mechanisms of the earthquake swarms. Plain Language Summary In October 2013 and July–August 2018, two unusually extensive earthquake sequences hit Lake Kinneret (Sea of Galilee). Former studies exploring the earthquakes and the active fault geometry resulted in conflicting views. Here, we investigate with alternative methods and test a new hypothesis for the driving mechanism. The study area straddles two tectonic plates joined by a segmented fault: a step‐over in the northern reaches of the lake separates a southern segment continuously creeping (on the upper approximately 2 km) and a northern temporarily locked segment. The creep is thought to be associated with a flowing salt formation that underlies the lake (at a few km depths). The slip toward the locked northern segment leads to energy accumulation released by the earthquakes. We use the earthquake records to constrain source depths, the majority of which turns out to be shallower than 6 km. Moreover, source distribution and fault plane orientatio