PORT-WIDE GROUND MOTION STUDY PORT OF LONG BEACH, CALIFORNIA

Transcription

1 PORT-WIDE GROUND MOTION STUDY PORT OF LONG BEACH, CALIFORNIA FINAL ADDENDUM NO. 3 Prepared For: The Port of Long Beach 4 Airport Plaza Drive Long Beach, CA 95 Prepared By: Earth Mechanics, Inc. 7 Newhope Street, Suite B Fountain Valley, CA 927 EMI Project No May 3, 25

2 Earth Mechanics, Inc. Geotechnical & Earthquake e Engineering May 3, 25 Port of Long Beach 4 Airport Plaza Drive Long Beach, CA 95 EMI Project No Attention: Mr. Cheng Lai, S. E. Deputy Chief Harbor Engineer Subject: Final Addendum No. 3 to Port-Wide Ground Motion Study Report Site-Specific Ground Motion Recommendations per CBC 23 Port of Long Beach, California Dear Mr. Lai: Attached please find our Addendum No. 3 to the Port-Wide Ground Motion Study Report. This report contains the methodology and findings of our study to develop port-wide ground motions recommendations per CBC 23, using the NGA ground motion prediction equations, and incorporating the latest revisionss to local fault activity rates according to the 24 USGS fault data. All review comments received from the Port of Longg Beach on the previous version of the addendum have been incorporated into this report. Thee report hass also been reviewed by Dr. Geoff Martin, Emeritus Professor of Civil Engineering,, University of Southern California, who providedd expert advice during the project. The ground motion recommenda ations presented in this addendum supersede California Building Code based Design Earthquake (DE) recommendations provided in all previous addenda. We appreciate the opportunity to work with you on thiss project. Please let us know if you have any questions. Sincerely, EARTH MECHANICS, INC. Amir Zand, Ph.D., GE 329 Senior Project Engineer (Arul) K. Arulmoli, Ph.D.., GE 29 Project Manager 7 Newhope Street, Suite B, Fountain Valley, California 927 Tel: (74) Fax: (74)

3 TABLE OF CONTENTS Section Page. INTRODUCTION.... Project Description....2 Scope of Work SEISMIC HAZARD ANALYSIS CBC 23 Seismic Design Criteria Probabilistic Seismic Hazard Analysis Earthquake Sources Earthquake Rupture Dimensions Magnitude-Recurrence Model Site Classification for Ground Motion Ground Motion Prediction Equations Directivity Effects Probability Computation and PSHA Results Probabilistic MCER ARS for Firm-Ground Deterministic Seismic Hazard Analysis Deterministic MCE R ARS for Firm-Ground Site-Specific MCE R ARS for Firm-Ground Site-Specific MCE G Peak Ground Acceleration for Firm-Ground SITE RESPONSE ANALYSIS Spectrum Compatible Ground Motions Soil Profile for Site Response Analysis Site Response Analysis Methodology Site Response Analysis Results Site-Specific MCE R ARS Site-Specific MCE G Peak Ground Acceleration for Unimproved Ground DESIGN RECOMMENDATIONS Site-Specific Design Earthquake Spectra for Improved Ground (Firm Ground) Site-Specific Design Earthquake Spectra for Unimproved Ground Recommended DE Time Histories Newmark Displacement Charts Design Earthquake ARS at Other Spectral Damping Ratios Site-Specific MCE G Peak Ground Acceleration Summary of Recommendations REFERENCES...46 APPENDIX A. SPECTRUM-COMPATIBLE GROUND MOTIONS APPENDIX B. SITE RESPONSE ANALYSES RESULTS APPENDIX C. DESIGN EARTHQUAKE TIME HISTORIES Earth Mechanics, Inc. Geotechnical & Earthquake Engineering i

4 LIST OF FIGURES Figure Title Page Figure. Location of Selected Sites for Seismic Hazard Evaluation...3 Figure 2. Map of Principal Fault Sources Used in PSHA... Figure 3. 2,475 Year UHS for the Horizontal Component PSA (g), Fault Normal Component, Ref. V s3 = 3 m/s...4 Figure 4. Probabilistic MCE R ARS for Firm Ground (V s3 = 3 m/s)...5 Figure 5. Site Deterministic 4th Percentile ARS for Controlling Faults for Firm Ground (V S3 = 3 m/s)...7 Figure 6. Deterministic MCE R ARS for Firm Ground (V S3 = 3 m/s)... Figure 7. Site-Specific MCE R ARS for Firm Ground (V S3 = 3 m/s)...2 Figure. Soil Zones Used for Site Response Analyses...22 Figure 9. Idealized Soil Profiles Used for Seismic Response Analyses...23 Figure. Zone I - Site Response Spectra and Site-Specific MCE R ARS...26 Figure. Zone II - Site Response Spectra and Site-Specific MCE R ARS...27 Figure 2. Zone III - Site Response Spectra and Site-Specific MCE R ARS...2 Figure 3. Zone IV - Site Response Spectra and Site-Specific MCE R ARS...29 Figure 4. Comparison between Site-Specific MCE R ARS for Zones I to IV...3 Figure 5. Design Earthquake Areas A and B...3 Figure 6. Comparison between Site-Specific MCE R ARS for Area A and Area B...32 Figure 7. Site-Specific Deisgn Earthquake ARS for Improved Ground Condition...34 Figure. Site-Specific Deisgn Earthquake ARS for Unimproved Ground Condition...35 Figure 9. Newmark Displacement Charts for Design Earthquake...37 Figure 2. Recommended Design Earthquake ARS per CBC Figure 2. Improved Ground Design Earthquake ARS per CBC 23 for Various Damping Ratios...39 Figure 22. Unimproved Ground (Area A) Design Earthquake ARS per CBC 23 for Various Damping Ratios...4 Figure 23. Unimproved Ground (Area B) Design Earthquake ARS per CBC 23 for Various Damping Ratios...4 Figure 24. Improved Ground Design Earthquake Relative Displacement Spectra for Various Damping Ratios...42 Figure 25. Unimproved Ground (Area A) Design Earthquake Relative Displacement Spectra for Various Damping Ratios...43 Figure 26. Unimproved Ground (Area B) Design Earthquake Relative Displacement Spectra for Various Damping Ratios...44 Earth Mechanics, Inc. Geotechnical & Earthquake Engineering ii

5 LIST OF TABLES Table Title Page Table. Port of Long Beach, Site Information Summary...2 Table 2. Summary of Seismic Source Parameters for Local Faults...7 Table 3. Probabilistic Seismic Hazard Parameters and Logic-Tree Weightings... Table 4. Seismic Source Parameters for Other Faults Based on Best-Estimate Values from USGS...9 Table 5. Time Histories Selected for Spectral Matching...2 Earth Mechanics, Inc. Geotechnical & Earthquake Engineering iii

6 . INTRODUCTION Earth Mechanics, Inc. (EMI) performed a port-wide ground motion (PWGM) study for Port of Long Beach (POLB), which was finalized in August 26 (EMI, 26). Since publication of that final report, EMI has prepared two addenda (EMI, 2 and 2) to update/augment the results of that report by comparing the original results to the results from Pacific Earthquake Engineering Research Center s (PEER) Next Generation Attenuation (NGA) Ground Motion Prediction Equations (GMPEs) (Campbell et al., 29), and to provide port-wide recommendations for seismic design criteria per California Building Code (CBC) 27 and CBC 2. For the current study, EMI performed a revised port-wide site-specific ground motion study for POLB to develop ground motion recommendations per CBC 23. The current study uses PEER s 2 NGA GMPEs, and a revised fault catalogue based on the USGS catalogue used in the 24 USGS Seismic Hazard Maps, and provides port-wide seismic hazard criteria in accordance with the current building design code, CBC 23. The ground motion recommendations presented in this addendum supersede California Building Code based Design Earthquake (DE) recommendations provided in all previous addenda. This addendum was prepared under Work Authorization No. 3 of the POLB Contract HD-93.. Project Description For the purpose of this study, the seismic hazard was evaluated for the same 2 sites that were used in EMI s 2 addendum. The descriptions and coordinates of these sites are shown in Table. Figure shows the location of the sites on POLB map. These sites cover the entire port area in terms of distance from the known faults and different soil conditions..2 Scope of Work A detailed seismic study was carried out for the project. The main objectives of this study were as follows: Perform probabilistic and deterministic seismic hazard analyses for the sites representative of the entire POLB. Incorporate the 2 NGA GMPEs and revise fault parameters based on the catalogue used for the 24 USGS Seismic Hazard Maps. Develop seven sets of spectrum compatible earthquake motions corresponding to improved ground (also called firm ground) conditions, for use in site response analyses. Perform site response analyses to evaluate site effects. Develop seismic hazard criteria in accordance with CBC 23 and ASCE 7-, Minimum Design Loads for Buildings and Other Structures. Develop spectrum-compatible time histories for improved ground and unimproved ground conditions based on CBC 23 requirements. Develop design charts for estimating Newmark displacements for improved and unimproved ground conditions. Earth Mechanics, Inc. Geotechnical & Earthquake Engineering

7 Site Number TABLE. PORT OF LONG BEACH, SITE INFORMATION SUMMARY Site Name Lat./Long. Lat./Long. (Deg.) Controlling Faults Fault Dist. (km) Palos Verdes 33 44'34.39"N Site Navy Mole (West) Thums-Huntington Beach 4'25.72"W.24 Cabrillo (Offshore) 4.3 Palos Verdes '7.5"N Site 2 Ocean Blvd./Navy Way Compton 5.4 4'49.5"W.247 Cabrillo (Offshore) 4.7 Palos Verdes '.9"N Site 3 Pier T Thums-Huntington Beach.5 4'2."W.237 Compton 5.3 Compton 5.4 Site 4 Navy Mole (East) 33 44'36.26"N Thums-Huntington Beach.76 3'24.3"W.223 Palos Verdes 3.3 Compton '2."N Site 5 Pier A Cabrillo (Offshore) 6.2 4'2."W.239 Palos Verdes 4. Compton '59."N Site 6 Pier S Palos Verdes 4.3 3'55."W.232 Cabrillo (Offshore) 6. Compton '4."N Site 7 Pier F Palos Verdes 4.5 2'5."W.24 Thums-Huntington Beach.9 Compton '36."N Site Pier E Palos Verdes 5.2 2'4."W.23 Thums-Huntington Beach 2. Thums-Huntington Beach '24."N Site 9 Pier J Compton 5.3 '45."W.96 Palos Verdes 5.2 Thums-Huntington Beach '9."N Site Pier J (East) Compton 5.3 '."W.6 Palos Verdes 5.7 Compton 5.2 New Administration 33 45'."N Site Newport-Inglewood 5. Bldg. '53."W.9 Thums-Huntington Beach 2.5 Compton '3."N Site 2 Pier C Newport-Inglewood 4.5 2'37."W.2 Palos Verdes 6.6 Earth Mechanics, Inc. Geotechnical & Earthquake Engineering 2

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9 2. SEISMIC HAZARD ANALYSIS 2. CBC 23 Seismic Design Criteria Seismic design recommendations in CBC (23) are based on the seismic criteria in ASCE 7-. According to ASCE 7-, the Design Earthquake (DE) ground motion is based on the Risk Targeted Maximum Considered Earthquake (MCE R ) ground motion. MCE R and DE acceleration response spectra (ARS) for Site Class A to E conditions can be developed using either the mapped MCE R acceleration parameters or site-specific hazard evaluations (Mapped acceleration parameters are determined from the.2 sec. and. sec. risk-adjusted MCE R spectral accelerations provided in maps for the entire U.S. in Chapter 22 of ASCE 7-). However, according to Section.4.7 of ASCE 7-, ARS for Site Class F must be based on site-specific evaluations. According to Section 2.3. of ASCE 7-, Soils vulnerable to potential failure or collapse under seismic loading, such as liquefiable soils, quick and highly sensitive clays, and collapsible weakly cemented soils should be classified as Site Class F and a site response analysis in accordance with Section 2. of ASCE 7- shall be performed. Since most sites in POLB have high liquefaction potential due to presence of hydraulic fills, a site-specific procedure in accordance with Chapter 2 of the ASCE 7- was adopted. The procedure for developing DE ARS is as follows: The site-specific DE ARS is defined as two-thirds of the MCE R spectral response acceleration, but not less than % of the acceleration response determined for the same site class in accordance with Section.4.5 of ASCE 7-. For site-specific analyses, the MCE R ground motion is determined using the procedure specified in Chapter 2 of ASCE 7-. Section 2.2 states that: The ground motion hazard analysis shall account for the regional tectonic setting, geology, and seismicity, the expected recurrence rates and maximum magnitudes of earthquakes on known faults and source zones, the characteristics of ground motion attenuation, near source effects, if any, on ground motions, and the effects of subsurface site conditions on ground motions. The characteristics of subsurface site conditions shall be considered either using attenuation relations that represent regional and local geology or in accordance with Section 2.. The analysis shall incorporate current seismic interpretations, including uncertainties for models and parameter values for seismic sources and ground motions. The MCE R response acceleration at each period is the lesser of probabilistic and deterministic MCE R response accelerations. The probabilistic MCE R response acceleration shall be taken as the spectral response accelerations in the direction of maximum horizontal response represented by a 5 percent damped acceleration response spectrum that is expected to achieve a percent probability of collapse within a 5-year period. For the purpose of this study, Method, as described in ASCE 7- Section 2.2.., was adopted. In this method, ordinates of the probabilistic ground motion ARS at each period is determined as the product of the risk coefficient, C R, and the spectral response acceleration from a 5 percent damped acceleration response spectrum having a 2 percent probability of exceedance within a 5-year period (2,475- Year average return period). The value of the risk coefficient, C R, is determined using values of C RS and C R from Figures 22-3 and 22-4 of ASCE 7-, respectively. At spectral response Earth Mechanics, Inc. Geotechnical & Earthquake Engineering 4

10 periods less than or equal to.2 sec., C R is taken as equal to C RS. At spectral response periods greater than or equal to. sec., C R is taken as equal to C R. At response spectral periods greater than.2 sec. and less than. sec., C R is based on linear interpolation of C RS and C R. The deterministic MCE R response acceleration at each period is calculated as an 4th-percentile 5 percent damped ARS in the direction of maximum horizontal response computed at that period. The envelope of the ARS calculated for the characteristic earthquakes on all known active faults within the region shall be used. In addition, the ordinates of the deterministic MCE R ARS shall not be lower than the corresponding ordinates of the ARS determined in accordance with Figure 2.2- of ASCE 7-, where F a and F v are determined using Tables.4- and.4-2, respectively, and the value of S S taken as.5 and the value of S taken as.6. According to Section..3 of ASCE 7-, liquefaction and soil strength should be evaluated for site peak ground acceleration (PGA) consistent with the Geometric Mean Maximum Considered Earthquake (MCE G ). Section 2.3. of ASCE 7- exempts structures having a fundamental period of vibration equal to or less than.5 seconds from site response analysis. Since PGA corresponds to a structure period of zero seconds, site response analysis in not needed to estimate PGA for MCE G. 2.2 Probabilistic Seismic Hazard Analysis The PSHA follows the standard approach first developed by Cornell (96). This approach has been expanded to more fully treat both the randomness (aleatory variability) and the scientific uncertainty (epistemic uncertainty). The methodology used in PSHA was similar to that of the original PWGM study (EMI, 26), however, a revised source model and updated 2 NGA GMPEs (Campbell et al., 29) were used in the analyses. The PSHA was performed using the computer program HAZ43, developed by Dr. Norm Abrahamson (24). The input parameters to PSHA, including earthquake sources, site soil conditions, and GMPEs are discussed in this section Earthquake Sources Key seismic sources at the POLB are the Palos Verdes and Newport-Inglewood fault zones. Other nearby but less active seismic sources include the Compton Thrust, Tums-Huntington Beach fault, Cabrillo fault, and Los Alamitos fault. Figure 2 shows the seismic source used in the PSHA, and Table 2 and Table 3 provide a summary of key seismic sources parameters used in the PSHA. Additional information about source model and geology can be found in the original PWGM study report (EMI, 26). Several modifications to the local earthquake sources were made to bring them in close agreement to the source model USGS uses for 24 Seismic Hazard Maps (USGS, 24). The Compton-Los Alamitos fault is assumed fully active (previously it was assumed 2% active/% inactive) with a revised slip rate. Also the slip rate for Palos Verdes fault was adjusted slightly downward. Earth Mechanics, Inc. Geotechnical & Earthquake Engineering 5

11 The other active faults in the region, shown on Figure 2, were included in the source characterization for completeness. Since these faults do not contribute significantly to the hazard, they were simply modeled using the parameters given in the Uniform California Earthquake Rupture Forecast, Version 2 (UCERF 2) model as described by Field et al. (2). These are included in Table 4, which lists all faults in the region recognized by the USGS and included in their national hazard map analysis. Earth Mechanics, Inc. Geotechnical & Earthquake Engineering 6

12 TABLE 2. SUMMARY OF SEISMIC SOURCE PARAMETERS FOR LOCAL FAULTS Fault (Map Abbreviation) Palos Verdes (PV-PVH, PV-SO) Depth to Top of Fault (km) Depth to Bottom of Fault (km) Dip (deg) Slip Rate (mm/yr) Mean Characteristic Earthquake Style of Faulting 2 to to to 7.2 SS Newport-Inglewood (NI) 3 to to.5 7. to 7.2 SS Cabrillo (CAB) 5 to 5 to to 6.7 SS San Pedro Basin (SPB) to. 7. to 7.2 SS Los Alamitos (LAL) to SS Compton Thrust (CT) to 7.2 Rev Notes: Weights of seismic source parameters are given in parentheses. ) SS = strike-slip, Rev = Reverse Earth Mechanics, Inc. Geotechnical & Earthquake Engineering 7

13 TABLE 3. PROBABILISTIC SEISMIC HAZARD PARAMETERS AND LOGIC-TREE WEIGHTINGS Fault Activity (Weighting) Length in km Width in km (Weighting) Slip-Rate in mm/yr (Weighting) Characteristic Magnitude Palos Verdes Fault Palos Verdes Hill Segment Southern Offshore Segment Active (.) (.5) 2.4 (.4) 5 (.5) 2.7 (.5) 2 (.5) 5 (.5) 3.9 (.) 6.9 (.3) 7. (.47) 7. (.33) 7.2 (.67) 3 (.5).5 (.2) 7. (.33) Newport-Inglewood Active (.) 65. (.6) 7. (.5) 6 (.5).5 (.2) 7.2 (.7) Cabrillo Active (.) 5 (.5) (.5). (.) 6.6 (.25) 6.7 (.75) San Pedro Basin Active (.) 7 5 (.).5 (.6) 7. (.5). (.4) 7.2 (.5) Los Alamitos Active (.) 35 5 (.).25 (.5).5 (.5) 6.5 (.) Compton-Los Alamitos Fault Zone/ Thrust Active (.) 7 2 (.).9 (.) Ramp 2 7. (.67) 7.2 (.33) Notes: Logic-Tree Weightings are given in parentheses. ) The Santa Monica Bay segment of the Palos Verdes fault is modeled as a separate segment with zero slip rate, deeming it to be an inactive case. 2 ) THUMS-HB fault is included as part of the Compton-Los Alamitos fault. Earth Mechanics, Inc. Geotechnical & Earthquake Engineering

14 TABLE 4. SEISMIC SOURCE PARAMETERS FOR OTHER FAULTS BASED ON BEST-ESTIMATE VALUES FROM USGS Fault (Map Abbreviation) Depth to Top of Fault (km) Depth to Bottom of Fault (km) Dip (deg) Slip Rate (mm/yr) Mean Characteristic Earthquake Style of Faulting Whittier (WH) 5 75 NE R/O Santa Monica (SN) 3 75 N. 6.6 R/O Hollywood (HY) 3 7 N. 6.4 R/O Malibu Coast (MC) 3 75 N. 6.7 R/O Sierra Madre (San Fernando) (SM-SF) 3 45 N R Sierra Madre (SM) 3 45 N R Cucamonga (CM) 3 45 N R Santa Susana (SS) 3 55 N R Raymond (RY) 3 75 N R/O Chino (CH) Verdugo (VD) 3 45 NE R San Jose (SJS) 3 75 NW R/O San Gabriel (SG) SS San Andreas Carrizo (SA-C) SS San Andrea Mojave (SA-M) SS San Andreas San Bernardino Mountains (SA-SBM) San Jacinto (San Jacinto Valley + San Bernadino) (SJ-SJV+SB) SS SS San Jacinto (Anza) (SJ-A) SS Elsinore (EL) SS Northridge (NR) S.5 7. SS Upper Elysian Park (EP) NE R Puente Hills N.7 7. R San Joaquin Hills (SJH) 2 23 S R Notes: ) R = Reverse; O = Oblique; SS = strike-slip Earth Mechanics, Inc. Geotechnical & Earthquake Engineering 9

15 FIGURE 2. MAP OF PRINCIPAL FAULT SOURCES USED IN PSHA Earth Mechanics, Inc. Geotechnical & Earthquake Engineering

16 2.2.2 Earthquake Rupture Dimensions Earthquake rupture dimensions were established using three magnitude-area relations reported by Wells and Coppersmith (994), USGS (23), and Hanks and Bakun (22), as given below by Equations (3.), (3.2) and (3.3), respectively. M M log A (3.) 42. log A (3.2) 2 M 39. loga for A 46 km, and M 39 4 (3.3). loga for A 46 km 2 3 where M = magnitude, and A = rupture area. The latter two models are used in the USGS (23) and UCERF 2 (Field et al., 29) source models. The Wells and Coppersmith (994) model is included as there is support for this model from numerical modeling (Pitarka et al., 2) Magnitude-Recurrence Model The approach used to derive the magnitude recurrence is to balance the long-term moment-rate on the faults. Given this approach, the Youngs and Coppersmith (95) characteristic earthquake model is used for the magnitude probability density function (pdf). The standard truncated exponential model is not considered because it tends to overestimate the rate of moderate magnitude earthquakes when moment-rate is balanced. The Youngs and Coppersmith model is a combination of a pure characteristic model and an exponential model. The key aspect of the Youngs and Coppersmith model is that about 94% of the moment-rate is accommodated in characteristic earthquakes and only about 6% of the total moment-rate is accommodated by the exponential tail Site Classification for Ground Motion The current study did not include any additional site investigation. The subsurface soils were characterized using the data from the original PWGM Study (EMI, 26). Since soil deposits at the POLB area are very deep, extending the site response analysis model to bedrock is impractical. Therefore in compliance with Section 2..2 of ASCE7-, the site response analysis models were terminated at a depth corresponding to Site Class D. Following the recommendations in the PWGM Study, the site classification for firm-ground was characterized with average shear wave velocities of 3 m/sec (, ft/sec) over a depth of Earth Mechanics, Inc. Geotechnical & Earthquake Engineering

17 3 m ( ft). This shear wave velocity was used in PSHA to evaluate deterministic and probabilistic firm-ground MCE R ARS for the sites Ground Motion Prediction Equations The development of ground motion prediction equations (GMPEs) in the last 5 years represents a significant improvement in the understanding of ground motions from crustal earthquakes located in active tectonic environments. Since the 26 PWGM study, the PEER/Lifelines NGA project (Campbell et al., 29) has resulted in four new GMPEs by Abrahamson and Silva (2), Chiou and Youngs (2), Campbell and Bozorgnia (2), and Boore and Atkinson (2). These new models are based on a greatly expanded and improved empirical database. In particular, there is a great increase in the number of recordings from large magnitude earthquakes resulting from the 999 Kocaeli (M7.5), 999 Chi-Chi (M7.6), 999 Duzce (M7.), 2 Hector Mine (M7.), and 22 Denali (M7.9) events. Nowadays these NGA equations are widely used for shallow crustal earthquakes. Equal weights were applied to the above four GPMEs in the analyses. The fifth NGA GMPE by Idriss was not applicable because the site V s3 was outside the recommended range for this GMPE. It should be noted that the suite of the 2 NGA GPMEs have been recently revised as part of the PEER NGA-West 2 Project (PEER, 24). These GMPEs were considered for this study; However, it was decided to postpone their use until they are formally adopted in the future revisions of the ASCE 7 standard and CBC code Directivity Effects The NGA GMPEs discussed in the previous section do not explicitly incorporate the effects of rupture directivity. At long periods, the ground motion on the fault normal component will be larger than on the fault parallel component due to directivity effects. In order to estimate the maximum horizontal ground motion component, a modified form of the Somerville et al. (997) fault directivity model was used in PSHA. This modification (Abrahamson, 2) was implemented to reduce the predicted directivity effects to be more consistent with the empirical data and numerical modeling and has been accepted for use in other bridge studies in California. The Somerville et al. (997) model was developed based on empirical data to quantify the effects of rupture directivity on horizontal response spectra that can be used to scale the average horizontal component computed from attenuation relations. The Somerville et al. model comprises two period-dependent scaling factors that may be applied to any ground motion attenuation relationship. One of the factors accounts for the increase in shaking intensity in the average horizontal component of motion due to near-fault rupture directivity effects. The second factor reflects the directional nature of the shaking intensity using two ratios: fault normal (FN) and fault parallel (FP) versus the average (FA) component ratios. The fault normal component is Earth Mechanics, Inc. Geotechnical & Earthquake Engineering 2

18 taken as the major principal axis resulting in an FN/FA ratio larger than, and the fault parallel component is taken as the minor principal axis with an FP/FA ratio smaller than. The two scaling factors depend on whether fault rupture is in the forward or backward direction, and also the length of fault rupturing toward the site Probability Computation and PSHA Results The PSHA was performed for a 5-percent damped acceleration response spectrum having a 2 percent probability of exceedance within a 5-year period (2,475-Year average return period). The analysis was performed for fault-normal component to produce ARS for ground motion in the direction of maximum horizontal response. The seismic hazard is computed at spectral periods from. to seconds. The analyses were performed for the 2 sites previously discussed. The computed spectral amplitudes for 5% damping and for return period of 2,475-year for firm-ground site conditions are shown in Figure 3. Based on these results Sites, 3, 5, and were selected to estimate probabilistic and deterministic MCE R ARS Probabilistic MCE R ARS for Firm-Ground The probabilistic MCE R ARS for firm ground at each period is determined as the product of the risk coefficient, C R, and the spectral response acceleration from a 5-percent damped acceleration response spectrum having a 2 percent probability of exceedance within a 5-year period (2,475- year average return period). The value of the risk coefficient, C R, is determined using values of C RS and C R from Figures 22-3 and 22-4 of ASCE 7-, respectively. At spectral response periods less than or equal to.2 sec., C R is taken as equal to C RS. At spectral response periods greater than or equal to. sec., C R is taken as equal to C R. At response spectral periods greater than.2 sec. and less than. sec., C R is based on linear interpolation of C RS and C R. The USGS web-based U.S. Seismic design Maps tool (USGS, 24) was used to determine C RS and C R for each site. The resulting probabilistic MCE R ARS for firm-ground, together with original MCE ARS and corresponding spectral amplitudes are shown on Figure 4. Based on these results, Site generally has the highest spectral acceleration within the estimated period range, however, the MCE R spectral accelerations for all four sites are relatively close. The largest difference is 7.5% (Site at 3. second), and average difference among all sites and spectral periods is about 3%. Since the difference between MCE R spectral accelerations for different sites was insignificant, a single firm ground ARS from Site was used as MCE R ARS for the entire Port area. Earth Mechanics, Inc. Geotechnical & Earthquake Engineering 3

19 Spectral Acceleration (g) % Damping Site Site 2 Site 3 Site 4 Site 5 Site 6 Site 7 Site Site 9 Site Site Site Period (sec.) Period (sec) Site Site 2 Site 3 Site 4 Site 5 Site 6 Site 7 Site Site 9 Site Site Site 2 SA (g) SA (g) SA (g) SA (g) SA (g) SA (g) SA (g) SA (g) SA (g) SA (g) SA (g) SA (g) POLB Ground Motion Study EMI Project No: 4-37 Date: 5//25 2,475 Year UHS for the Horizontal Component PSA (g), Fault Normal Component, Ref. V s3 = 3 m/s Figure 3

20 Spectral Acceleration (g) Site Site 3 Site 5 Site Probabilistic MCEʀ ARS 5% Damping Period (sec.) Period (sec) SA (g) Site Site 3 Site 5 Site % Difference from Maximum SA (g) % Difference from Maximum SA (g) % Difference from Maximum SA (g) % Difference from Maximum Probabilistic MCEʀ ARS SA (g)..6.% % %.76-4.% % % % % %.6-2.% % % % %.35 -.% % %.6 -.6% % % % % % % % % %.64-5.% % %.6-2.2% % % % %.29-6.% % %.5-2.%.6-6.% % %.3-2.% % % % %.5-7.3% %.4-3.%.49 -.% % % % % % % % % % % %.2.%.7-6.5% %.6-2.%.9 -.4%.3-5.9% %.7-2.%.7.%.6-4.%.7 POLB Ground Motion Study EMI Project No: 4-37 Date: 5//25 PROBABILISTIC MCE R ARS FOR FIRM GROUND (V S3 = 3 M/S) Figure 4

21 2.3 Deterministic Seismic Hazard Analysis The deterministic MCE R response acceleration at each period was calculated as an 4thpercentile 5 percent damped ARS in the direction of maximum horizontal response computed at that period. The envelope of the ARS calculated for the characteristic earthquakes on all known active faults within the region shall be used. The controlling active faults at the project site include Compton Thrust, Thums-Huntington Beach Fault, and Palos Verdes Fault. Deterministic 4-th percentile ground motion ARS for these faults were estimated using the spreadsheet downloaded from the PEER website (Al Atik, 29). The average of acceleration responses from the four GMPEs, as discussed in Section 2.2.5, was used to determine deterministic MCE ARS. The ARS determined using this procedure is for the median horizontal component of ground motion. It is known that ground motion intensity is not uniform in all directions and can be polarized with significant higher intensity in one direction. Various factors contribute to directionality of ground motions, including near-fault effects (Abrahamson, 2). New ground motion directionality models have been proposed by Shahi and Baker (23) as part of NGA- West2 project. However, for this study, in order to estimate the deterministic ARS in the direction of maximum horizontal response, the spectral accelerations were multiplied by nearfault adjustment factors, as recommended by Caltrans Seismic Design Criteria (23). The reason for adopting this method is that for POLB sites the deterministic criteria is controlled by large magnitudes events occurring on major near faults. In addition, this approach will result in a deterministic spectrum that is more consistent with probabilistic spectrum. Nevertheless, using larger directionality factors will not affect the final design criteria because it is entirely controlled by the probabilistic criteria, as discussed in Section Deterministic MCE R ARS for Firm-Ground The deterministic ARS was taken as the envelope of the ARS spectra for three controlling faults. Figure 5 shows the deterministic 4 th percentile ARS for the controlling faults for firm ground conditions for Site. The ordinates of the deterministic MCE R ARS shall not be lower than the corresponding ordinates of the minimum deterministic MCE R ARS, determined in accordance with Figure 2.2- of ASCE 7-, where F a and F v are determined using Tables.4- and.4-2, respectively, and the value of S S taken as.5 and the value of S taken as.6. The deterministic lower limit determined using the following parameters: short period, S s =.5, at sec period, S =.6, F a =., and F v =.5, where F a and F v are site coefficients determined from Tables.4- and.4-2 of ASCE 7- for Site Class D, corresponding to firm-ground conditions. The deterministic MCE R ARS for Site, including ASCE 7- Lower Limit, is shown on Figure 5. Figure 6 shows a comparison between deterministic MCE R ARS for Sites, 3, 5, and. Based on this figure, the envelope of the deterministic MCE R ARS for Sites, 3, 5, and was used as the deterministic MCE R criteria for the entire port. Earth Mechanics, Inc. Geotechnical & Earthquake Engineering 6

22 2.5 5% Damping Cabrillo Thrust - No Directivity Cabrillo Thrust - W/ Directivity Spectral Acceleration (g) Thums-Huntington Beach Fault - No Directivity Thums-Huntington Beach Fault - W/ Directivity Palos Verdes Fault - No Directivity Palos Verdes Fault - W/ Directivity Deterministic Lower Limit on MCER Deterministic MCER (with Lower Limit) Period (sec.) Period (sec) Cabrillo Thrust Thums Huntington Beach Fault Palos Verdes Fault SA (g) (Avg.) SA (g) (W/ Directivity) Period (sec) SA (g) (Avg.) SA (g) (W/ Directivity) Period (sec) SA (g) (Avg.) SA (g) (W/ Directivity) POLB Ground Motion Study EMI Project No: 4-37 Date: 5//25 Site Deterministic 4th Percentile ARS for Controlling Faults for Firm Ground (V S3 = 3 M/S) Figure 5

23 Spectral Acceleration (g) Site Site 3 Site 5 Site Deterministic MCEʀ ARS 5% Damping Period (sec.) Period (sec) SA (g) Site Site 3 Site 5 Site % Difference from Maximum SA (g) % Difference from Maximum SA (g) % Difference from Maximum SA (g) % Difference from Maximum Deterministic MCEʀ ARS %.2-4.5% %.923.% % %.93 -.%.93.% % % %.97.% % %.65 -.%.74.% %. -3.9% %.236.% % % % % % % % % % % %.3.% %.33-3.%.7 -.7%.92.% % % %.927.% % %.75 -.%.9.% % %.73 -.%.745.% % % %.49.% % % %.244.% %.36-7.%.3 -.3%. -.5% % % % % %.43 -.% % % % % % % % % % % %.3-7.7%.2-5.5%.2-5.5% % % % %.79 POLB Ground Motion Study Deterministic MCE R ARS for Firm Ground (V s3 = 3 m/s) EMI Project No: 4-37 Date: 5//25 Figure 6

24 2.4 Site-Specific MCE R ARS for Firm-Ground The MCE R response acceleration at each period is the lesser of probabilistic and deterministic MCE R response accelerations. Figure 7 shows the probabilistic, deterministic, and site-specific MCE R ARS for firm ground for the project. It can be seen that the probabilistic MCE R ARS is smaller than the deterministic MCE R ARS at all periods. The site specific MCE R ARS, as shown on Figure 7, was used to develop spectrum compatible ground motions for site response analyses. This process is discussed in the following section of the report. 2.5 Site-Specific MCE G Peak Ground Acceleration for Firm-Ground The MCE G PGA (PGA M ) is the lesser of the probabilistic and deterministic geometric mean peak ground accelerations. The site-specific MCE G PGA shall not be taken as less than percent of PGA M determined from Equation.- of ASCE 7-. The probabilistic MCE G PGA is the geometric mean PGA with a 2 percent probability of exceedance within a 5-year period. Based on PSHA results presented in Section 2.2.7, probabilistic MCE G PGA for firm ground is.9 g. The deterministic MCE G PGA is the largest 4th-percentile geometric mean peak ground acceleration for characteristic earthquakes on all known active faults within the region, but not lower than.5 F PGA, determined from ASCE 7- Table.- assuming a PGA of.5 g. Based on deterministic seismic hazard results in Section 2.3., a deterministic MCE G PGA of.923 g shall be used for firm ground conditions. Based on these results a PGA M of.9 g is recommended for firm ground conditions. Earth Mechanics, Inc. Geotechnical & Earthquake Engineering 9

25 2.5 Probabilistic MCEʀ ARS Spectral Acceleration (g) Deterministic MCEʀ ARS Site-Specific MCEʀ ARS for Firm Ground 5% Damping Period (sec.) Probabilistic MCE ʀ ARS Deterministic MCE ʀ ARS Site Specific MCE ʀ ARS for Firm Ground Period (sec) SA (g) Period (sec) SA (g) Period (sec) SA (g) POLB Ground Motion Study EMI Project No: 4-37 Date: 5//25 SITE-SPECIFIC MCE R ARS FOR FIRM GROUND (V S3 = 3 M/S) Figure 7

26 3. SITE RESPONSE ANALYSIS 3. Spectrum Compatible Ground Motions The seven set of ground motions from Port Wide Ground Motion Study (EMI, 26) were used as startup motions. These ground motions were selected based on similarity to the controlling earthquake scenarios at the Port, and having similar magnitude, distance, and spectral shape to the controlling events. The selected recordings are listed in Table 5. These ground motions were modified to match the MCE R spectra for firm ground using the program RSPMATCH (Abrahamson, 99), which uses the time-domain approach. The goal of this approach is to preserve the general non-stationary character of the ground motion in acceleration, velocity, and displacement. The 2-component horizontal spectrum-compatible ground motion time histories and comparison of the matched spectra with the firm-ground MCE R ARS are shown in Appendix A. TABLE 5. TIME HISTORIES SELECTED FOR SPECTRAL MATCHING Set Earthquake Magnitude Station Distance (km) Directivity Parameter x cos θ 999 Hector Mine 7. Hector Loma Prieta 6.9 Gilroy Imperial Valley 6.5 Brawley Duzce 7. Lamont Erzikan 6.7 Erzikan Imperial Valley 7. El Centro Kobe 6.9 Kobe University Soil Profile for Site Response Analysis During the original PWGM Study (EMI, 26), subsurface soil condition at the Port were divided into four zones; Zones I through IV. The approximate extents of these zones are shown in Figure. The four idealized soil profiles and shear wave velocity profiles corresponding to each zone are shown in Figure 9. These soil profiles were used in the site response analyses to estimate the ground motions for unimproved ground conditions. Earth Mechanics, Inc. Geotechnical & Earthquake Engineering 2

27 FIGURE. SOIL ZONES USED FOR SITE RESPONSE ANALYSES Earth Mechanics, Inc. Geotechnical & Earthquake Engineering 22

28 ZONE I ZONE II Fill + Fill + Design Water Table + Design Water Table - Hydraulic Fill Hydraulic Fill ELEVATION (FT) Alluvial/Gaspur Deposits Input Motion ELEVATION (FT) Alluvial/Gaspur Deposits Input Motion Shear Wave Velocity (ft/s) Shear Wave Velocity (ft/s) ZONE III ZONE IV Fill + Fill + Design Water Table + Design Water Table - - Hydraulic Fill -2 Hydraulic Fill -2 Hydraulic Fill ELEVATION (FT) Harbor Sediments Alluvial/Gaspur Deposits Input Motion ELEVATION (FT) Harbor Sediments Alluvial/Gaspur Deposits - - Input Motion Shear Wave Velocity (ft/s) Shear Wave Velocity (ft/s) FIGURE 9. IDEALIZED SOIL PROFILES USED FOR SEISMIC RESPONSE ANALYSES Earth Mechanics, Inc. Geotechnical & Earthquake Engineering 23

29 3.3 Site Response Analysis Methodology Equivalent linear site response analyses were conducted using the computer program SHAKE9 (Idriss and Sun 992) to estimate ground motions at various depths. The dynamic shear modulus and damping of soil layers were estimated using relationships provided in the Electric Power Research Institute (EPRI) for sands (EPRI, 993) and the Vucetic and Dobry relationships for clay (99). These relationships have been adopted by Caltrans for major toll bridges as well as by the Nuclear Regulatory Agency for nuclear power plants. The spectrum-compatible firm-ground motions were applied as outcrop motion in SHAKE9 models at the bottom of soil columns, as shown in Figure. 3.4 Site Response Analysis Results Site response analyses were conducted for the 7 sets of ground motions and four soils profiles zones. In addition to the upper bound shear wave velocity values shown in Figure 9, analyses were repeated for a lower bound shear wave velocity case, with shear wave velocities reduced by about 2 percent (shear modulus reduced by about 25 percent). Five percent damped response spectra for the free field outcrop motions from the site response solutions were compiled for development of the ground surface ARS. Ratios of 5 percent damped response spectra of surface ground motions to input base ground motions were calculated for each analysis. The surface MCE R ground motion response spectrum for each soil profile was estimated as the MCE R response spectrum of the base motion multiplied by the average surface-to-base response spectral ratios (calculated period by period) obtained from the site response analyses for that soil profile. This procedure resulted in two surface MCE R for each soil profile, one for the upper bound and one for the lower bound shear wave velocities. A summary of site response analyses results are included in Appendix B. 3.5 Site-Specific MCE R ARS The site-specific MCE R ARS spectrum was determined as the envelope of surface ARS from site response analyses for upper bound and lower bound soil profiles, as well as firm-ground MCE R ARS, representing the non-liquefied soil conditions. The site-specific MCE R spectra for Zones I to IV are shown in Figure to Figure 3, respectively. Figure 4 shows a comparison between site-specific MCE R ARS for Zones I to IV. Based on this figure, the difference between site-specific MCE R ARS for Zones II to IV is insignificant, while Zone I is considerably different. Therefore, in order to determine the design earthquake ARS, the POLB was divided into two Areas: Area A, encompassing Zones II to IV, and Area B, representing Zone I, which is limited to the area above the Cerritos Channel. These two areas are shown on Figure 5. Figure 6 shows the resulting site-specific MCE R ARS for Areas A and B. Earth Mechanics, Inc. Geotechnical & Earthquake Engineering 24

30 3.6 Site-Specific MCE G Peak Ground Acceleration for Unimproved Ground Since the short period range of the MCE ARS curve is controlled by the firm ground ARS, the MCE G peak ground acceleration (PGA M ) for unimproved ground conditions for both Area A and Area B is the same as firm ground condition, as discussed in Section 2.5. This is consistent with recommendations in Section 2.3. of ASCE 7-, which implies that for periods below.5 sec, site response analysis is not needed for liquefiable sites. Based on these results a PGA M of.9 g is recommended for unimproved ground conditions in both Area A and Area B. Earth Mechanics, Inc. Geotechnical & Earthquake Engineering 25

31 2. MCEʀ ARS for Firm-Ground (Vs3 = 3 m/s) SA (g) (UB Vs) Spectral Acceleration (g).5..5 SA (g) (LB Vs) Site-Specific MCEʀ Spectrum 5% Damping Period (sec.) MCEʀ ARS for Firm Ground (V s3 = 3 m/s) Site Response MCEʀ Spectra Site Specific MCEʀ Spectrum Period (sec) SA (g) Period (sec) SA (g) (UB V s ) Period (sec) SA (g) (LB V s ) Period (sec) SA (g) POLB Port-Wide Ground Motion Study EMI Project No: 4-37 Date: 5//25 Zone I - Site Response Spectra and Site-Specific MCE R ARS Figure

32 2. MCEʀ ARS for Firm-Ground (Vs3 = 3 m/s) SA (g) (UB Vs) Spectral Acceleration (g).5..5 SA (g) (LB Vs) Site-Specific MCEʀ Spectrum 5% Damping Period (sec.) MCEʀ ARS for Firm Ground (V s3 = 3 m/s) Site Response MCEʀ Spectra Site Specific MCEʀ Spectrum Period (sec) SA (g) Period (sec) SA (g) (UB V s ) Period (sec) SA (g) (LB V s ) Period (sec) SA (g) POLB Port-Wide Ground Motion Study EMI Project No: 4-37 Date: 5//25 Zone II - Site Response Spectra and Site-Specific MCE R ARS Figure

33 2. MCEʀ ARS for Firm-Ground (Vs3 = 3 m/s) SA (g) (UB Vs) Spectral Acceleration (g).5..5 SA (g) (LB Vs) Site-Specific MCEʀ Spectrum 5% Damping Period (sec.) MCEʀ ARS for Firm Ground (V s3 = 3 m/s) Site Response MCEʀ Spectra Site Specific MCEʀ Spectrum Period (sec) SA (g) Period (sec) SA (g) (UB V s ) Period (sec) SA (g) (LB V s ) Period (sec) SA (g) POLB Port-Wide Ground Motion Study EMI Project No: 4-37 Date: 5//25 Zone III - Site Response Spectra and Site-Specific MCE R ARS Figure 2

34 2. MCEʀ ARS for Firm-Ground (Vs3 = 3 m/s) SA (g) (UB Vs) Spectral Acceleration (g).5..5 SA (g) (LB Vs) Site-Specific MCEʀ Spectrum 5% Damping Period (sec.) MCEʀ ARS for Firm Ground (V s3 = 3 m/s) Site Response MCEʀ Spectra Site Specific MCEʀ Spectrum Period (sec) SA (g) Period (sec) SA (g) (UB V s ) Period (sec) SA (g) (LB V s ) Period (sec) SA (g) POLB Port-Wide Ground Motion Study EMI Project No: 4-37 Date: 5//25 Zone IV - Site Response Spectra and Site-Specific MCE R ARS Figure 3

35 2. Zone I Spectral Acceleration (g).5..5 Zone II Zone III Zone IV 5% Damping Period (sec.) Zone I Zone II Zone III Zone IV Period (sec) SA (g) Period (sec) SA (g) Period (sec) SA (g) Period (sec) SA (g) POLB Port-Wide Ground Motion Study EMI Project No: 4-37 Date: 5//25 Comparison Between Site-Specific MCE R ARS for Zones I to IV Figure 4

36

37 2. Area A Spectral Acceleration (g).5..5 Area B 5% Damping Period (sec.) Area A Area B Period (sec) SA (g) Period (sec) SA (g) POLB Port-Wide Ground Motion Study EMI Project No: 4-37 Date: 5//25 Comparison Between Site-Specific MCE R ARS for Area A and Area B Figure 6

38 4. DESIGN RECOMMENDATIONS 4. Site-Specific Design Earthquake Spectra for Improved Ground (Firm Ground) The firm-ground condition with V s3 of 3 m/s can be used for sites which have undergone ground improvement. The site-specific Design Earthquake (DE) ARS for improved ground condition is defined as two-thirds of the MCE R spectral response acceleration for firm-ground condition, but not less than % of the acceleration response determined for the same site class in accordance with Section.4.5 of ASCE 7-. All ARS curves are developed for 5 percent damping. The lower limit for DE acceleration response was calculated for Site Class D for Site 2 (the ASCE 7- design spectra for Site 2 was higher than Site ), according to the Section.4.5 of ASCE 7- using the following parameters: S s =.772 g (from ASEC 7- Figure 22-) S =.6 g (from ASEC 7- Figure 22-2) F a =. (from ASEC 7- Table -4.) F v =.5 (from ASEC 7- Table -4.2) T L = sec. The site-specific DE ARS for improved ground condition (larger of the two-thirds of the sitespecific MCE R from Figure 7 and % of the ASCE 7-5 ARS for Site Class D) is shown on Figure Site-Specific Design Earthquake Spectra for Unimproved Ground The site-specific Design Earthquake (DE) ARS is defined as two-thirds of the MCE R spectral response acceleration, but not less than % of the acceleration response determined for the same site class in accordance with Section.4.5 of ASCE 7-. All ARS curves are developed for 5 percent damping. The lower limit for DE acceleration response was calculated for Site Class E for Site 2 (the ASCE 7- design spectra for Site 2 was higher than Site ), according to the Section.4.5 of ASCE 7- using the following parameters: S s =.772 g (from ASEC 7- Figure 22-) S =.6 g (from ASEC 7- Figure 22-2) F a =.9 (from ASEC 7- Table -4.) F v = 2.4 (from ASEC 7- Table -4.2) T L = sec. The site-specific DE ARS for Areas A and B (larger of the two-thirds of the site-specific MCE R from Figure 6 and % of the ASCE 7-5 ARS for Site Class E) are shown on Figure. Earth Mechanics, Inc. Geotechnical & Earthquake Engineering 33