Earthquake Swarms Triggered by Groundwater Extraction Near the Dead Sea Fault

Abstract

In 2013 and 2018, earthquake swarms with a maximum moment magnitude of 4.5 occurred ~5 km from the northern section of the Dead Sea Transform Fault. Here we show that aquifer pressure data, interferometric synthetic aperture radar surface deformation time series, and seismic monitoring suggest that groundwater withdrawal triggered these earthquakes. Continuous groundwater extraction from several wells located ~10 km west of the swarms has accelerated since 2010 and resulted in a total decrease of ~50 m of the groundwater level at the time of the 2018 earthquake swarm. The withdrawal also corresponds to surface subsidence of ~10 mm/year based on repeat interferometric synthetic aperture radar measurements. The temporal correlation, extensive subsidence, anomalous swarm characteristics, and normal faulting orientation suggest a connection between the groundwater withdrawal and recent earthquakes. Poroelastic modeling demonstrates that pumping‐induced pore pressure decrease west of the earthquake could have caused significant dilatational stresses that led to normal faulting events outside the aquifer.

Tectonics of the Dead Sea Fault Driving the July 2018 Seismic Swarm in the Sea of Galilee (Lake Kinneret), Israel

“…Finally, the perturbed stress regime first pointed out by Wetzler et al (2019) is compatible with a fluid-rich environment, where swarm sequences may take place. We agree on the fluid-driven nature of the July 2018 seismic swarm and argue that elevated pore pressures may reactivate secondary fault planes masking the kinematics of the largest events.…”

“…This may have unloaded the hydrostatic column acting on the faults beneath the SoG promoting slip at shallow depths. Wetzler et al (2019) calculated that groundwater pumping (which is operated at 1 km depth and 10 to 16 km to the west of the SoG swarm) may have affected pore pressure distribution at depth with a horizontal stress of 0.1 MPa at 2 km depth causing the 2013 and 2018 earthquakes. This value is within the range of the commonly accepted triggering thresholds (e.g., Bonini, 2007;Lupi et al, 2013;Manga & Brodsky, 2006;Saar & Manga, 2003) and can promote the reactivation of geological systems in a near-critical state.…”

“…This was followed by a sequence that last around 30 days. Wetzler et al (2019) discussed a possible anthropogenic cause for the 2018 earthquake sequence. The authors observed that from the beginning of the instrumental record in 1985 until 2013, the seismicity around the SoG was limited to sporadic events, while more recently (2013–2018) the NW part of the SoG was affected by two main seismic swarms of magnitude M w > 3 along NNW‐SSE strands.…”

The Mid‐eighth Century CE Surface Faulting Along the Dead Sea Fault at Tiberias (Sea of Galilee, Israel)

“…The oldest one in the catalogue (Mw 4.2) occurred in 1972, whereas the two most recent (Mw 4.5 and 4.2) occurred in July 2018 as part of a swarm of shallow earthquakes with normal focal mechanism solutions (focal depth < 10 km). Seismicity is located offshore, in the NW part of the Sea of Galilee, aligned along NNW‐SSE direction (Wetzler et al, 2019).…”

“…Strong earthquakes are known to have hit the Sea of Galilee area in historical times (e.g., in mid‐eighth century CE, 1033, 1759, and 1837; Ambraseys, 2005, 2009; Guidoboni et al, 2007), whereas the instrumental catalogue is limited to M < 6 earthquakes (recorded events since the first half of the twentieth century). A seismic swarm (max Mw 4.5) occurred in July and August 2018, with epicenters located in the NW part of the Sea of Galilee (Wetzler et al, 2019), renewing the interest in seismic risk evaluation in the area.…”