Every time the chandelier starts to sway and the dog loses it, geologists in Israel feel queasy. A “big one” is overdue, and in southern Israel very overdue. Also, most buildings in Israel predate laws requiring quake-resilient construction.
Israel is riddled with faults. That is because it sits on the Sinai microplate, which geologists mostly agree is a subsection of the gigantic Nubian plate. In fact, the whole Middle East is in a tough neighborhood, jostled between the four major tectonic plates: Nubia (Africa), Sinai (with Israel!), Arabia and Anatolia (Turkey).
Though there are efforts to develop quake prediction, it still can’t be done. The Geological Survey of Israel (GSI) is developing a system called Tru’a, based on sensors placed along the Dead Sea Rift and the Carmel fault. Tru’a is designed to transmit alerts the second a big quake starts to happen. It isn’t supposed to predict earthquakes so much as give people a chance to take shelter. Meanwhile, all geologists can do is study history and calculate probabilities.
Having done all of that, Israeli geologists are uneasy about the entirety of the Dead Sea Rift. They are uneasy about Israel’s north, where towns have been shaken to bits throughout history, but are even more worried about the south, including the Red Sea resort of Eilat.
Eilat boasts beaches, a bit of coral reef, the opportunity to swim with dolphins, Israeli naval facilities, exotic desert landscapes and the propensity for a major temblor. Across the border from it is the Jordanian city of Aqaba, which has exactly the same problem: Both cities were built on the Dead Sea Rift.
“In general, we’re worried about the whole Dead Sea Transform (the Syrian-African great rift) from Eilat to Lebanon,” qualifies Dr. Yariv Hamiel, head of the GSI’s Geological Hazards and Geological Engineering Division. “There could be a strong quake anywhere along it at any time,” he adds.
In recorded history, the Jordan Valley experienced major earthquakes in the years 746 and 1033. Historical sources, and the Bible, tell of others even earlier. In the south, the most recent major quake was in 1212.
Ergo, sections of the Dead Sea Rift along the Jordan Valley have also been locked for centuries.
Off with his head
In antiquity, quakes were interpreted as a sign of divine disfavor. For example, King Uzziah of Judah was blamed for an earthquake about 2,760 years ago (the timing is based less on the ancient sources and more on stratigraphic analysis of destruction debris at Gezer and Lachish, and sediment analysis at the Dead Sea).
Uzziah had begun his monarchical career meekly enough. But after successfully warring against the Philistines, Arabs and Ammonites, rebuilding Jerusalem, settling the desert and becoming enormously prosperous – he waxed proud, explains the Roman-Jewish historian Josephus.
Overriding the appalled priests, Uzziah insisted on himself offering incense to Yahweh in the Temple in Jerusalem:
“And when they cried out, that he must go out of the temple, and not transgress against God, he was wroth at them, and threatened to kill them, unless they would hold their peace. In the mean time a great earthquake shook the ground, and a rent was made in the temple” – Josephus, “Antiquities of the Jews,” Chapter 10.
The king evidently survived because, the sources tell us, the deity then afflicted Uzziah with leprosy.
Jerusalem too is riddled with fault lines, but none are active, says Hamiel. If the Temple cracked and the city was damaged, the cause had to be a major tremor originating in the Dead Sea Rift. Latter-day geologists and archaeologists estimate the 750 B.C.E. quake at a magnitude of 7.5 on the Richter scale.
Trembling in Tiberias
Almost 3,000 years later, in mid-2018, northern Israel experienced a flurry of tremors ranging from “Who cares?” to 4.8 on the Richter scale. Inevitably the press went into a swoon as vases in lakeside Tiberias danced on mantelpieces, but the swarms subsided and that was that. In Jerusalem, they were unmoved, literally and figuratively. Geologists concluded that the swarm stemmed from the tiny local faults beneath or near the Sea of Galilee (aka Lake Kinneret), which branch off from the main fault. The media rustled with speculation about whether the swarm portended a Big One.
It didn’t. Swarms can be indicative of a major quake, but usually they’re not. Big quakes can ensue without foreshocks (as they’re called after the event), Hamiel explained to Haaretz. Absent any ability to predict earthquake, all government can do is consult the geologists who calculate probabilities, and pray. “What matters is to prepare, not obsess over exactly when it might happen,” Hamiel points out.
The statistics, he says, show that on average Israel experiences a strong earthquake every 80 to 100 years, from south to north.
Now let’s get specific. Within Israel itself, the Dead Sea Rift can be technically divided into 10 main fault segments. What happens (on average) every 80 to 100 years is that one of the segments “unlocks” and we get a major quake on that segment – which may or may not have a ripple effect along the rift.
The southern Arava segment hasn’t been active since 1212, as said, which is over 800 years ago.
Based on paleoseismic data, the southern Arava segment “should” experience earthquakes greater than magnitude 6 every 500 years, with a wide margin of error. “We are well past the 500-year mark,” Hamiel says. “We are also well past the 500 + 200 mark.”
Moreover, the geologists have estimated the pent-up energy accruing in the locked sections of the southern Arava segment and foresee a quake greater than 7. “I am very worried about that area,” Hamiel admits.
In 1995, a tremor measured at 7.3 hit the Red Sea coast. But it doesn’t count regarding the Arava – its epicenter was at the Sinai beach resort of Nuweiba 100 kilometers (62 miles) south of Eilat and the jolting ended 40 kilometers south of Eilat, Hamiel explains. Though some aftershocks in Israel and Jordan were associated with it, the Nuweiba quake did not relieve the pent-up energy in the Arava, where the two plates remain locked.
The segment in the northern Jordan Valley hasn’t been active for centuries either.
That absolutely does not mean a big quake in Israel (or the southern Arava or Eilat) is imminent, or even likely anytime soon, Hamiel stresses. It bears repeating: The statistics say precisely squat about probable or even possible timing. But they do mean that with every passing year without quake, the probability grows.
Here are more statistics: Once every 1,000 years, Israel is shaken by a quake bad enough to leave 70,000 people homeless and could kill several thousand. And once every 2,500 years, we can expect a quake that leaves 200,000 homeless and could kill at least 7,000 people, estimate the statisticians.
So, is it time to move away from Israel? Not for that reason. At any given moment, you’re more likely to be hit by a car than by a falling building.
But when it happens, will the Temple Mount be in danger (again)? How about the nuclear reactor in Dimona? Where are the dangers most acute?
As a baby ocean is born
Israel sits on the Sinai microplate, as stated. Local stresses in the crust are caused by the tectonic plates around the Sinai microplate pulling in different directions, each at different speeds.
Happily for Israelis, Palestinians and Jordanians, the Dead Sea Rift is a “strike/slip” kind of fault: The tectonic plates are sliding past each other horizontally. The worst quake this rift could generate would likely max out at about 7.8 on the Richter scale, Hamiel estimates. (The worst earthquake recorded since measurement began in the 1900s was a 9.5 in southern Chile in 1960.)
Though both Africa and Arabia are moving vaguely northward by a few millimeters a year, they are essentially parting ways. The farther Africa and Arabia pull apart, the wider the Red Sea grows: geologists call the Red Sea a baby ocean.
When it reaches the tip of Sinai, the Red Sea culminates in “rabbit ears”: the Gulf of Suez on the “left” and Gulf of Aqaba on the “right.” Between them is the triangle of Sinai, and at the bottom of each rabbit ear is a rift – the Suez Rift on the left and the Dead Sea Rift on the right; the latter continues on land.
Since the Dead Sea Rift began to split open sometime between 16 and 18 million years ago, the Nubian plate (with the Sinai microplate on board) is estimated to have moved 107 kilometers vis-à-vis the Arabian plate.
The Dead Sea Rift faults pass between Israel and Jordan, then through Lebanon, around the Mediterranean basin and end at the East Anatolian Fault in Turkey. Within Israel, along the Dead Sea Rift’s length are depressions formed by the plates pulling apart (geologists call these structures “pull-apart basins”), in which sit the Gulf of Aqaba, the Dead Sea itself and the inland lake called the Sea of Galilee.
The Dead Sea is famously the lowest land point on Earth, more than 400 meters below sea level. The Sea of Galilee is less famously also a couple of hundred meters below sea level.
The great rift aside, Israel also has literally dozens of small faults. Asked how local cracks are created if not by continents slowly crashing into one another or pulling apart, Hamiel explains: by heterogenic bedrock reacting to local strains. The continental plates are in motion, the underlying mantle is unrestful; the crustal rock overlying it experiences stresses; and local faults form when different kinds of rock react in different ways to these strains in the Earth’s crust, to rainfall (over eons), and so on.
So whether because modern Israelis probably have a transgression or two or because of all this crustal cracking, quakes will continue. If we don’t know when, can we ask where?
We discussed Eilat. In far off Tel Aviv, vases haven’t been falling off mantelpieces and the cats haven’t freaked out, but some people notice a bit of a tremble here and there, no more. A few neighborhoods built right on the bedrock are likely to shake more in a national quake-related catastrophe because of “site effects.”
Hamiel believes other coastal cities along the Mediterranean shoreline – Ashdod, Ashkelon and Gaza, plus Dimona inland – are likely to weather a major quake on the Dead Sea Fault quite well.
Jerusalem isn’t in particular danger of seismic wave amplification so neither is Temple Mount, per se. But they’re near enough to the epicenter of trouble to suffer if and when.
Moving onto Haifa: The geological situation of the Zevulun Valley and the northern city, through which local faults run, is so complex – with soft sediments sitting atop hard sediments – that no self-respecting geologist would touch forecasting with a barge pole, say self-respecting geologists.
All the northern coast, however, has heightened the risk of seismic wave amplification; roughly from below Atlit going south, that beachfront amplification threat does not dissipate entirely but shifts inland to the Coastal Plain. The Negev desert is also spotted with areas of anticipated seismic amplification.
Geologists cannot know how much energy is building up in any given fault or what the fault’s breaking point might be. And they certainly can’t predict extraneous influences such as dam breaks, fracking or divine temper tantrums. Also, cats are not predicting earthquakes in Japan: All they’re doing is sensing the ground move before humans do.
If quakes can’t be foreseen, as Hamiel says, all that remains is planning. Chilean cities survive quakes surpassing 9 on the Richter scale thanks to construction standards. At the other end of the spectrum is Nepal, where a 2015 earthquake devastated Kathmandu – a city not known for resilient construction. “In a world of increased urban densification … it is poorly designed and constructed buildings, not earthquakes, which are the real catastrophe,” The Guardian wrote at the time.
In 1927, when the last major quake originated in the Dead Sea Rift, Israel’s population numbered 760,000 and somewhere from 300 to 500 people died, from Tiberias in the north to Jerusalem in the south. Today, Israel has over 10 times as many people, Hamiel points out, and while its rescue and telecom services have improved over the last century, it still has about 810,000 homes that were built before quake-proofing standards became law. Possibly 100,000 of them could be seismically retrofitted – protecting the rich, at least – if the neighbors stop fighting and agree on terms. But this is the Middle East. Enough said.