Ground Motions in the Zevulun Valley(Haifa Bay) Deep Structure
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Ground motions in the Zevulun Valley (Haifa Bay) Deep Structure Effects Thesis submitted in partial fulfillment of the requirements for the Master of Sciences degree By Alina Goldberg 317518090 Under the supervision of: Prof. Michael Tsesarsky, Ben Gurion University Prof. Zohar Gvirtzman, Geological Survey of Israel January 2020 Ground motions in the Zevulun Valley (Haifa Bay) Deep Structure Effects Thesis submitted in partial fulfillment of the requirements for the Master of Sciences degree By Alina Goldberg 317518090 Alina Goldberg _____ _______________ Date: 14.01.2020 Under the supervision of: Prof. Michael Tsesarsky ____________________ Date: 14.01.2020 Prof. Zohar Gvirtzman ____________________ Date: 14.01.2020 Signature of chairperson of the committee for graduate studies ____________________ Date: ___________ January 2020 Table of contents 1 Introduction ...................................................................................................... 1 2 Scientific Background ........................................................................................ 4 2.1 Ground motion amplification ...............................................................................4 2.2 1D, 2D and 3D methods ........................................................................................6 2.3 Geological setting and seismicity of the studied region .........................................8 2.3.1 Seismicity ................................................................................................................. 8 2.3.2 Zevulun Valley geological background ..................................................................... 9 2.3.3 Potential seismic reflectors .................................................................................... 12 3 Methods ......................................................................................................... 12 3.1 SW4 Wave propagation software ....................................................................... 13 3.1.1 Governing equations and time functions .............................................................. 13 3.1.2 Seismic sources ...................................................................................................... 15 3.1.3 Simulation setup .................................................................................................... 15 3.2 Output options .................................................................................................. 18 4 Model Setup ................................................................................................... 19 4.1 Geological data .................................................................................................. 19 4.2 Raster file construction ...................................................................................... 20 4.2.1 Zevulun Valley model structure ............................................................................. 21 4.2.2 Geological model inaccuracies ............................................................................... 22 4.3 Simulation setup ................................................................................................ 23 4.3.1 Reference model .................................................................................................... 23 4.3.2 Simulation parameters ........................................................................................... 25 4.3.3 Summary of Zevulun Valley simulations ................................................................ 28 4.4 Output plan ....................................................................................................... 28 5 Results ............................................................................................................ 30 5.1 PGV results ........................................................................................................ 30 5.2 Seismograms, arrival times and spectral analysis ................................................ 34 5.2.1 Northern Source (JGF) – observations ................................................................... 36 5.2.2 Southern Source (KNR) – observations .................................................................. 38 5.3 Result interpretation .......................................................................................... 48 5.3.1 PGV analysis ........................................................................................................... 48 5.3.2 Energy and duration of motion .............................................................................. 49 5.3.3 Spectral analysis ..................................................................................................... 53 6 Discussion ....................................................................................................... 56 6.1 Amplification maps ............................................................................................ 56 6.2 Amplification in the Qishon Graben .................................................................... 64 6.3 Simulated frequency content ............................................................................. 66 6.4 Source magnitude .............................................................................................. 67 6.5 Model Limitations .............................................................................................. 69 7 Conclusions ..................................................................................................... 70 8 References ...................................................................................................... 72 List of figures Figure 1- A map of areas suspected of ground motion amplification during an earthquake in the northern region of Israel. 1 Figure 2 - Research zone map of the main tectonic boundaries and ZV structures. 3 Figure 3 - The Mw = 4.3 Landers 1992 aftershock recordings (after Boore 2004). 6 Figure 4 - Top Judea elevation map and ZV geological sections. 11 Figure 5 - Visualization of the Tiff formatted curvilinear surfaces comprising the 3D model. 21 Figure 6 - Visualization of regional GITT05 model. 24 Figure 7 - The distributed slip model used to simulate a strike-slip fault in the ZV model. 26 Figure 8 - Research area, source and synthetic stations locations. 30 Figure 9 - PGV and AR results for the JGF simulations. 32 Figure 10 - PGV and AR results for the KNR simulations. 33 Figure 11 - Reflectors at depth for the six representative stations of the ZV. 35 Figure 12 - Results obtained from the PBZN station, DSM-JGF model. 43 Figure 13 - Results obtained from the NVHB station, DSM-JGF model. 43 Figure 14 - Results obtained from the KMKB station, DSM-JGF model. 44 Figure 15 - Results obtained from the AFK station, DSM-JGF model. 44 Figure 16 - Results obtained from the EHM station, DSM-JGF model. 45 Figure 17 - Results obtained from the PBZN station, DSM-KNR model. 45 Figure 18 - Results obtained from the NVHB station, DSM-KNR model. 46 Figure 19 - Results obtained from the KMKB station, DSM-KNR model. 46 Figure 20 - Results obtained from the AFK station, DSM-KNR model. 47 Figure 21 - Results obtained from the EHM station, DSM-KNR model. 47 Figure 22 - Full PGV maps for (a) DSM-JGF and (b) DSM-KNR. 49 Figure 23 - KNR-DSM Arias Intensity results. 51 Figure 24 - Velocity magnitude propagation with time in the KNR-DSM model. 52 Figure 25 - JGF-DSM Arias Intensity results. 53 Figure 26 – Amplified frequencies correlating to a reflector at the ZV stations. 56 Figure 27 - First resonance frequency peak range and amplificatin ratios from Zaslavsky et al. (2008) compared to the present work’s DSM-KNR model results. 58 Figure 28 - Amplification ratios map combined with polygons of the Krayot Cities. 63 Figure 29 - Component ratio analysis for the PBZN station for KNR-DSM model 65 Figure 30 - Spectral amplification at the PBZN, NVHB and KMKB stations, after Shani-Kadmiel et al. (2018). 67 List of Tables Table 1. Material properties of the simulation based on GITT05 general model. 23 Table 2. Material properties of the main units in the ZV. 26 Table 3. Grid size structure detailed by mesh refinement levels. 27 Table 4. PGV values and amplification values for each of the four simulations. 31 Table 5. PGV values derived from synthetic seismograms in m/sec. 34 Table 6. Comparison of spectral analysis of Zevulun Valley conducted by 4 different studies. 61 Abstract Sedimentary basins are a common subsurface geological structure in the northern region of Israel. Characteristically, sedimentary structures are filled with relatively young sediments with low seismic velocities, which are known to amplify seismic waves during an earthquake. The coastal plain of Haifa Bay (Zevulun Valley) is a densely populated urban zone, with nearly 1 million residents and well-developed industrial facilities such as a marine port, oil refineries, and other chemical plants containing hazardous materials. The subsurface of the Valley consists of a complex geological sedimentary structure of two grabens and a horst. Thus, the area is widely researched in the goals of determining the seismic hazard it presents, and particularly the ground motion amplification that can be expected atop it’s complex sedimentary structure in the case of a strong motion earthquake. In Israel, due to limited coverage of the seismic network and low background seismicity, the empirical research is not sufficient since it requires a large amount of data