Galilee earthquake swarms caused by increased groundwater extraction
With experts estimating that a major earthquake is statistically due to strike Israel every 80-100 years, another major event is therefore now due.
By EYTAN HALONThe Wider Image: The Sea of Galilee: receding waters of biblical lake(photo credit: REUTERS)
Two recent earthquake swarms affecting the Galilee were likely caused by the accelerated extraction of groundwater from aquifers around Lake Kinneret (the Sea of Galilee), a new study has revealed.While seismic activity in the freshwater lake has been limited to sporadic events since instrumental records began in 1985, earthquakes with a maximum magnitude of 4.5 on the Richter scale were recorded five times in September 2013 – and on 15 occasions in July-August 2018.The seismic swarms were collocated roughly five km. from the northern section of the Dead Sea Transform Fault, also known as the Dead Sea Rift, which runs from the Gulf of Aqaba to eastern Turkey and forms the boundary between the Arabian Plate and the Sinai subplate.According to researchers from the Geological Survey of Israel and the universities of California and Miami, the earthquakes corresponded to the two fastest periods of groundwater decline in the region, during the years 2007-2013 and 2016-2018. Their findings were published in the scientific journal Geophysical Research Letters.“The timing of the earthquake swarms is particularly interesting in light of the hydrological history of the region,” said the researchers, including Nadav Wetzler and Eyal Shalev from the Geological Survey of Israel.While the Sea of Galilee used to be the source for one-third of domestic water in Israel, sharp declines in the water level have caused pumping rates from the lake to drop from 500 million cubic meters per year in the 1990s to 60 mcm/year in recent years. An alternative resource has been groundwater in aquifers around the lake, especially to the northwest.At the time of the 2018 earthquake swarm, continuous groundwater extraction resulted in a total water level decrease of approximately 50 meters. The earthquake swarms were located two km. to 10 km. from the pumping wells.“Although there are many examples of subsidence due to excess withdrawal of groundwater, there are few cases where groundwater extraction has triggered earthquakes,” the researchers said. “The aquifer, deformation and seismic data analyzed here imply that groundwater withdrawal is producing earthquake swarms along the northern Dead Sea Transform fault... The geological history of the fault combined with the close proximity to populated areas suggest that future pumping in the region should be closely monitored.”Archaeological and geological records in northern Israel indicate that the Lake Kinneret segment of the Dead Sea Transform has ruptured several times since the Iron Age, including major earthquakes in 1202 and 1759.In 1927, a major earthquake registering 6.2 on the Richter scale struck the northern Dead Sea. Known as the Jericho Earthquake, the seismic rupture killed up to 500 people and injured 700 more. With experts estimating that a major earthquake is statistically due to strike Israel every 80-100 years, another major event is now due.
A 2016 report by the Knesset Foreign Affairs and Defense Committee’s Home-Front Readiness Subcommittee found that if Israel were to be struck by a 7.5 magnitude earthquake, an estimated 7,000 people would be killed, another 8,600 injured and 377,000 left homeless. In addition, the country could face damage of up to NIS 200 billion.According to the National Emergency Authority, Israel has 80,000 buildings, including schools and hospitals, that are more than three stories high and that were constructed before 1980, making them inadequate according to current earthquake durability standards.
