JERUSALEM, March 12 (JTA) — Israeli researchers warned this week that the country could be in for “the big one” — a massive earthquake that could leave thousands dead and cause extensive property damage. In an appearance before the Knesset Science and Technology Committee, seismologists said they were concerned by the relative quiet recently in seismic activity. Avi Shapira, head of the seismology division at the Geophysics Institute, said Israel’s geographic location, on the Syria-Africa rift, places it in danger of a powerful tremor. He said a tremor with an epicenter in the Jordan Valley could cause a high number of casualties and extensive damage in Tel Aviv, Haifa and Jerusalem. He added that Israeli civil defense authorities were not prepared to handle such a natural disaster. An earthquake destroyed the ancient city of Bet Shean in that area in the eighth century. During the past two years, Israel and neighboring countries have been shaken by periodic tremors.