Most Israelis can remember a day when their furniture started to shake, and can also take credit for surviving that day with little difficulty. But very few people are in a position to know firsthand the effects of a truly disastrous earthquake, on a magnitude of seven or higher on the Richter scale, as the last recorded such earthquake in Israel occurred in 1033.

Tel Aviv as seen in Google Earth

And that's the problem: Geology experts agree that Israel is long overdue for the next "Big One," and it can happen at any time. This poses a significant threat to population centers in the country, since many buildings in Israel were erected prior to the formulation of earthquake-resistant construction codes. There is also substantial doubt that the codes are being strictly enforced. With the barrage of immediate threats competing for Israelis' attention - whether terrorism, car accidents, global warming or secondhand smoke - a major earthquake may seem like an improbable, even paranoid fear.

While predicting the time of the next earthquake is nearly impossible, says Dr. Amos Salamon of the Israel Geological Survey, "We know one thing - we are sure there will be an earthquake in Israel."

This is because Israel is situated on two significant fault lines: the Dead Sea Fault and the Carmel Fault. To understand which parts of the country would be most vulnerable to a major earthquake, geologists must base their knowledge on previous events - and in this case, modern technology is of surprisingly little help.

"In modern times we usually monitor earthquakes by using seismographs," explains geologist Dr. Shmuel Marco of Tel Aviv University.

But seismographs have only existed for about a century, whereas geological processes develop over thousands, if not millions of years. Therefore, there is a dearth of information on the major earthquakes in Israel's past - and such information could be crucial to determining which areas in Israel are in greatest danger.

This is especially true of the Carmel Fault, which poses a threat to Haifa, among other places. Because the fault has been dormant in the recent past, its potential threat is unknown.

For that reason, Marco has made it his mission to build a timeline of Israel's earthquakes by delving into history and archeology, in addition to geology. On the historical side, Marco has studied hundreds of ancient documents that contain references to earthquakes, in translations from the original Greek, Latin and Arabic. The originals of some of these documents are assumed to reside in the Vatican vaults. Even the Bible offers clues, as earthquakes are sometimes mentioned as markers of time, Marco explains. For example, prophets are often said to have become active a certain number of years "after the earthquake."

With the aid of these documents, Marco has helped determine that a series of devastating earthquakes hit Israel in the past two thousand years. The major ones were recorded in the Jordan Valley in the years 31 BCE, 363 CE, 749 CE and 1033 CE, "so roughly," says Marco, "we are talking about an interval of every 400 years. If we follow the patterns of nature, a major quake should be expected any time because almost a whole millennium has passed since the last strong earthquake."

Marco also uses archeological excavations to learn more about the country's earthquake trends. For example, he is participating in the excavation of Megiddo, the site of an ancient Canaanite city situated on the Carmel Fault. He and geologist Prof. Amotz Agnon of the Hebrew University are analyzing findings on the site, together with archeologist Prof. Israel Finkelstein.

The geologists' focus on the archeological site stems from the hope that archeological evidence will provide clues to the 5,000-year-old city's geological past. The geological history of Megiddo would have ramifications for the entire region situated atop the Carmel Fault, Finkelstein explains.

"At Megiddo there's a sequence of cities. If one can keep track of the earthquakes that damaged these cities, one can establish a timeline of earthquakes in the north," he says.

Megiddo is an ideal candidate for such research because it is a site with many layers of history, and each layer tells its own story of the damage that took place. The most important - and only conclusive - piece of evidence that researchers have discovered so far in the investigation of the mystery that is the Carmel Fault, is damage to a monumental temple, says Finkelstein, which corresponds to a biblical reference to a major earthquake that occurred in the late fourth millennium.

The nature of earthquakes is that they result from a buildup of tension in the earth's crust along fault lines. The longer the period between earthquakes, the more tension builds, with catastrophic consequences upon its release. Since the last major earthquake was 1,000 years ago, "We are now in a deficit," Marco explains. "There's been no release of tension, just buildup. It's like if you have a strip of rubber between your hands and keep pulling it - you know that it's going to snap eventually."

WHERE IS the next big quake most likely to hit? "We think that the focus of major earthquakes will be in and around the Dead Sea Fault. The seismic waves will spread around the epicenter and they will affect buildings far away from the focus," says Salamon.

Places along the Dead Sea Fault include Eilat, towns in the North, Kiryat Shmona, Tiberias and Beit She'an. "According to the historical records we have, almost every place in Israel was damaged several times in history [by earthquakes]," Salamon says. This is because places that are not directly above the fault but are relatively close to it, like Jerusalem, are still vulnerable to the effects of an earthquake.

Tel Aviv is a good distance away from the fault and therefore may not incur heavy damage, but on the other hand, Marco says that there is evidence of earthquake damage to ancient Jaffa, possibly as a result of activity along the Carmel Fault.