SEISMIC HAZARD ANALYSIS AND SEISMIC SLOPE STABILITY EVALUATION USING DISCRETE FAULTS IN NORTHWESTERN PAKISTAN BY BYUNGMIN KIM DISSERTATION Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Civil Engineering in the Graduate College of the University of Illinois at Urbana-Champaign, 2012 Urbana, Illinois Doctoral Committee: Professor Youssef M.A. Hashash, Chair, Director of Research Associate Professor Scott M. Olson, Co-director of Research Professor Gholamreza Mesri Professor Amr S. Elnashai Associate Professor Junho Song ABSTRACT The Mw 7.6 earthquake that occurred on 8 October 2005 in Kashmir, Pakistan, resulted in tremendous number of fatalities and injuries, and also triggered numerous landslides. Although there are no reliable means to predict the timing of the earthquake, it is possible to reduce the loss of life and damages associated with strong ground motions and landslides by designing and mitigating structures based on proper seismic hazard and seismic slope stability analyses. This study presents the methodology and results of seismic hazard and slope stability analyses in northwestern Pakistan. The first part of the thesis describes the methodology used to perform deterministic and probabilistic seismic hazard analyses. The methodology of seismic hazard analysis includes identification of seismic sources from 32 faults in NW Pakistan, characterization of recurrence models for the faults based on both historical and instrumented seismicity in addition to geologic evidence, and selection of four plate boundary attenuation relations from the Next Generation Attenuation of Ground Motions Project. Peak ground accelerations for Kaghan and Muzaffarabad which are surrounded by major faults were predicted to be approximately 3 to 4 times greater than estimates by previous studies using diffuse areal source zones. Seismic hazard maps for PGA and spectral accelerations at periods of 0.2 sec and 1.0 sec corresponding to 475-, 975-, and 2475-year return periods were produced for NW Pakistan. Based on deaggregation results, a discussion of the conditional mean spectra for engineering applications is presented. The second part of the thesis proposes factors that affect distribution of shallow landslides triggered by an earthquake. Landslides are the most common consequence of earthquakes, resulting in significant amount of damages of structures and lives. Significant damage was induced from the landslides triggered by the 2005, Kashmir, Pakistan, earthquake. Therefore, predicting locations and severity of landslide is an essential part of earthquake engineering. However, the currently used seismic slope stability analysis cannot capture the actual trend of landslide distribution, especially high landslide concentration near field. This study proposes the effect of vertical ground acceleration, topographic effects, and bond break effects, in addition to the strong horizontal ground acceleration, as factors that contribute to the landslide distribution near earthquake source. Landslide database from four earthquake cases (1989 Loma-Prieta, U.S.; 1999 Chi-Chi, Taiwan; 2005 Kashmir, Pakistan; and 2008 Wenchuan, China) were selected to verify these factors for slope stability analysis. ii To my parents and grandparents iii ACKNOWLEDGEMENT I would like to express my deep appreciation and respect to my advisor, Professor Youssef M.A. Hashash, and my co-advisor, Professor Scott M. Olson, for their careful attention, patient guidance, enthusiastic advice, and constant support throughout the period of study. Having a chance to study under their supervision was one of the most fortunate things in my life. I would like to extend my sincere appreciation to the members of the committee, Professors Gholamreza Mesri, Amr S. Elnashai, and Junho Song for their insightful advice which significantly enhanced this dissertation. I also appreciate Professors Timothy D. Stark and James H. Long for their skillful and passionate lectures that inspired me greatly. I deeply appreciate Professor Duhee Park at the Hanyang University who led me to Illinois inspiring to aspire to higher education. I would like to thank my gentle officemates, David Groholski, Camilo Phillips, Sungwoo Moon, Michael Musgrove, for making a vibrant research environments with pleasant casual chats as well as helpful discussion. Special thanks are extended to GESO members: Randa Asmar, Fangzhou Dai, Joseph Harmon, Maria Ines Romero, Mark Muszynski, Janson Funk, Andrew Tangsombatvisit, Mohamad Jammoul. I believe we will be all connected as we move forward careers in our own professions, Oscar Moreno-Torres. I am grateful to all members of the Korean Student Association in Civil Engineering, especially to Seung Jae Lee, Junhan Kim, Robin Kim, Hongki Joe, Moochul Shin, Hyungchul Yoon, Seungmin Lim, Junho Chun. I would also like to thank Professors Kyungsoo Park, Sunghan Sim, Taekeun Oh. Most importantly, I would like to thank my parents and younger brother for their love, support, and encouragement. I specially thank my grandparents who passed away during the period of my study. No words can express how grateful I am for their endless love and support on me. The supports from USAID and Higher Education Commission of Pakistan under Award No. AID NAS PGA-7251 are gratefully acknowledged. iv TABLE OF CONTENTS LIST OF SYMBOLS ..................................................................................................................... vi LIST OF ABBREVIATIONS ...................................................................................................... viii Chapter 1. INTRODUCTION ..................................................................................................... 1 Chapter 2. PRIOR SEISMIC HAZARD STUDIES IN NW PAKISTAN .................................. 3 Chapter 3. DETERMINISTIC SEISMIC HAZARD ANALYSIS .............................................. 8 Chapter 4. PROBABILISTIC SEISMIC HAZARD ANALYSIS ............................................. 32 Chapter 5. SEISMIC HAZARD RESULTS .............................................................................. 54 Chapter 6. CURRENT SEISMIC SLOPE STABILITY APPROACH ..................................... 92 Chapter 7. FACTORS THAT AFFECT PSEUDO-STATIC SLOPE STABILITY ............... 111 Chapter 8. PROPOSED NEW APPROACH TO PSEUDO-STATIC SLOPE STABILITY ANALYSIS AND VERIFICATION USING EARTHQUAKE CASES .............. 121 Chapter 9. CONCLUSIONS AND RECOMMENDATION FOR FUTURE RESEARCH ... 154 Appendix A. ESTIMATION OF MOHR-COULOMB STRENGTH PARAMETERS ............. 159 REFERENCES ........................................................................................................................... 168 v LIST OF SYMBOLS ah horizontal acceleration ah,max maximum horizontal acceleration amax maximum acceleration av vertical acceleration av,max maximum vertical acceleration ay yield acceleration b slope of exponential recurrence model bl slip rate at greater depths bs slip rate at sesimogenic depths c’ cohesion intercept of the failure mass D depth to the bottom of rupture d average displacement over the slip surface Dt failure mass thickness Fh horizontal pseudo-static force Fv vertical pseudo-static force h slope height i slope angle kbond pseudo-static coefficient for bond break effects kh horizontal pseudo-static coefficient kv vertical pseudo-static coefficient M earthquake magnitude mb body wave magnitude mi material constant for intact rock ML local magnitude Ms surface wave magnitude mu upper bound magnitude for the exponential recurrence model Mw moment magnitude M0 seismic moment 0 m threshold magnitude for the exponential recurrence model Ṅ(mc) Characteristic rate vi R source-to-site distance RA rupture area R-factor seismogenic scaling factor S average seismic slip rate Sa Spectral acceleration T spectral period Ts recurrence interval T* period of interest Vs,30 shear wave velocity in the upper 30 m W weight of the failure mass Ztor depth to the top of rupture Z1.0 depth to shear wave velocity of 1 km/s Z2.5 depth to shear wave velocity of 2.5 km/s unit weight of the failure mass ε ground motion uncertainty λ m annual activity rate of earthquakes of magnitude greater than m μ rigidity of shear modulus which is usually taken to be 3×1011 dyne/cm2 ν activity rate, complementary cumulative earthquake rate for m > m0 ρ correlation coefficient of CMS ci uniaxial compressive strength of the intact rock t tensile strength 1 major effective principal stress 3 minor effective principal stress ’ friction angle of the failure mass vii LIST OF ABBREVIATIONS AFPS French association for earthquake engineering BAAS British association for the advancement of science CMS conditional mean spectra COV coefficient of variation DF disturbance factor DSHA deterministic seismic hazard analysis EC European seismic code provision FS factor of safety GMPE ground-motion prediction equation GSI geological strength index ISC International seismological centre KPSZ Kohat-Potwar-Salt range seismic zone LC landslide concentration LS least square method MBT main boundary thrust MCT main central thrust MKT main karakoram thrust ML maximum likelihood method MMT main mantle thrust NEHRP national earthquake hazards reduction program NGA next generation of ground-motion attenuation models NOAA national oceanic and atmospheric administration PGA peak ground acceleration PGV peak ground velocity PMD Pakistan meteorological department PHSZ Peshawar-Hazara seismic zone PSHA probabilistic seismic