Modeling Ground Motions in Northern Israel: The Role of 3D Crustal Heterogeneities of the Dead Sea Transform Fault System

Session: Numerical Modeling of Rupture Dynamics, Earthquake Ground Motion and Seismic Noise
Type: Oral
Date: 4/29/2020
Time: 11:00 AM
Room: 230 + 235
Description: 

The seismicity of Israel is dominated by the Dead Sea Transform (DST) a left-lateral strike-slip fault system with a geodetic slip rate of 4 mm/year. The slip deficit on the northern part of the Israel DST is equivalent to a M > 7 earthquake. Whereas the pre-instrumental catalog of the DST contains at least fourteen M > 7 events during the past 2000 years, the instrumental catalog (starting 1986) contains mainly M < 6 events. The instrumental coverage of Israel seismic network is sparse, with almost no coverage of major urban centers and industrial hubs. The application of imported GMPEs requires local calibration to account for non-ergodic path effects using recorded ground motions, which in the case of Israel are limited in coverage and magnitude. This knowledge gap requires a critical assessment of ground motions during future strong earthquakes.

Here we report the results of 3-D numerical modeling of M 6 and M 7 earthquakes on the northern section of the Israel DST, where it forms a deep (up to 10 km) and narrow (up to 10 km) trough comprised of deep sedimentary basins bounded by active faults. The soft post-rifting sediments comprise the upper 5 km, resulting in strong longitudinal, lateral and vertical heterogeneity of the upper crust. The seismogenic depth along the modeled section extends from near-surface to depths of 25 km.

To model the ground motions in Northern Israel we developed an idealized velocity model based on well-log data, geophysical surveys and structural maps that accounts for both regional and local geological structures. We show that ground motions (amplitude and duration) of M 6 events strongly depend on the velocity structure of the ruptured fault segment and the 3-D heterogeneity of the DST faults-basins system results. For the M 7 earthquake, we show the effects of rupture directivity and rupture velocity on the amplitudes and durations of ground motions in Northern Israel.

Presenting Author: Michael Tsesarsky

Authors