The Internal Structure of the Dead Sea Transform and Ground Motions in Northern Israel

Date: 4/25/2019

Time: 08:30 AM

Room: Elliott Bay

The Dead Sea Transform (DST) fault system forms the eastern boundary of the state of Israel. The DST is a left-lateral strike slip fault with an average slip rate of 4 mm/yr, with numerous historic earthquakes of M > 7. The 1927 M 6 Jericho earthquake, the last major event on the DST, predated instrumentation of the region. This makes the assessment of ground motions during future earthquakes difficult and highlights the importance of computational methods to bridge the instrumental data gap.

The DST forms a deep and narrow valley (DSTV) comprised of deep sedimentary basins separated by structural highs. North of the Dead Sea depression these are the Bikaa (BV), the Kinnarot (KV), the Sea of Galilee (SG), and the Hula (HV) valleys. Branching westward from the DST is the Carmel Fault Zone (CFZ) along which the Jezreel, Harod and Bet-Shean valleys are found. Within the deep basins, the young sedimentary fill is several km thick, overlying the hard carbonates of the Judea Gr. The SG and HV are separated by the structural high of the Korazim Saddle (KS).

In this work, we studied the impact of the DSTV internal structure on ground motions and seismic energy distribution in northern Israel, using a series of 3D numerical models (SW4). We developed schematic, yet realistic, geological models, of increasing complexity for the northern DSTV , based on well-log data, seismic surveys and structural maps. We simulated three different source scenarios based on past activity and slip deficit.

We show that the DSTV structure creates a significant ground motion amplification by trapping of seismic waves between the valley walls. We also show that the KS acts as a seismic barrier with a strong edge effect. When source location is south of the KS it effectively shields the HV hence reducing ground motions. When the source location is east of the KS the edge effect amplifies waves traveling in the N-S direction. Northward deepening of the BV refracts waves traveling from the south, focusing them to the surface where they constructively interfere with waves reflected by the KS.

Presenting Author: Michael Tsesarsky

Authors