Yossef H Hatzor

The Masada mountain is located on the western margins of the seismically active Dead Sea rift system. Therefore, dynamic key block stability is of primary concern in the densely fractured East and North rock slopes of the mountain. Recent seismogenic key block motions in the East face, detected by our in-situ monitoring system, are explained by the presently low factor of safety against sliding, and by a pronounced topographic site effect at Masada with peak spectral amplification of about 3.5. Two analysis methods are employed: 1) Static and pseudo-static limit equilibrium analysis of removable key blocks in the East face where failure of large individual key blocks is of primary concern; 2) Static and true dynamic DDA modelling of a stochastically generated block mesh in the North face where the collapse of complete slope segments under dynamic loading is of concern. The deterministic analysis of removable key blocks in the East face reveals that when joint water pressures are considered application of a 2D solution proves unconservative. DDA modelling reveals the expected failure modes in the North face and the maximum depth of deformation as a result of dynamic loading.