Geotechnical Earthquake Engineering by Dr. Deepankar Choudhury Humboldt Fellow, JSPS Fellow, BOYSCAST Fellow Professor Department of Civil Engineering IIT Bombay, Powai, Mumbai 400 076, India. Email: dc@civil.iitb.ac.in URL: http://www.civil.iitb.ac.in/~dc/ Lecture 29
Module 7 Seismic Hazard Analysis IIT Bombay, DC 2
Code Implications UBC 10% probability of exceedance in 50 years. IIT Bombay, DC 3
Code Implications AASHTO 2% probability of exceedance in 50 years?? IIT Bombay, DC 4
Example Case Study on Gujarat, India Ref: Ph.D. Thesis of Jaykumar Shukla (2013), IIT Bombay, Mumbai, India. IIT Bombay, DC 5
Location of Gujarat, India IIT Bombay, DC 6
25 Cities studied representing the all seismic zones in Gujarat. 4 port sites are also studied for site specific ground motion estimations (Kandla port, Mundra Port, Hazira Port and Dahej Port ) Urban areas selected Kachchh Anjar Bhuj Dholavira Gandhidham Mandavi Saurashtra Amreli Bhavnagar Dholera Dwarka Jamnagar Junagadh Morvi Porbundar Rajkot Surendranagar Veraval Mainland Gujarat Ahmedabad Baroach Gandhinagar Mehsana Palanpur Patan Surat Vadodara Valsad
Location of urban areas selected Seismic Zones of Gujarat, IS: 1893-Part I (2002)
Components of hazard study Earthquake Catalogue Sensitivity Analysis Regional Seismicity Parameters Seismic Hazard Estimation for Gujarat region Site specific ground motions for Ports Probabilistic Seismic Hazard Analysis (PSHA) Deterministic Seismic Hazard Analysis (DSHA)
Seismicity of Gujarat, India Pakistan Gujarat, India Seismotectonic setting of the region Arabian Sea Seismic Zones of Gujarat Region as per IS:1893 Part I (2002) Epicenters of earthquakes recorded from 2007 to 2011 ( modified after ISR report 2010-11)
% of total Earthquake occured in Gujarat Seismicity across Gujarat Year Region Numbers of Earthquake recorded M w 4 M w (3 to 3.9) M w (2 to 2.9) M w <2 Total Kachchh 1 51 292 1155 1499 2010-11 * Saurashtra 2 12 101 571 684 Mainland Gujarat 1 2 11 38 52 100 90 80 70 2010-11* 2009 2008 Kachchh 4 72 422 1594 2092 60 50 2009 2008 Saurashtra --- 6 22 420 448 Mainland Gujarat --- --- 36 65 41 Kachchh 5 52 343 493 893 Saurashtra 2 12 221 424 659 Mainland Gujarat --- 3 17 26 46 40 30 20 10 0 Kachchh Saurashtra Mainland Gujarat Gujarat Region Note: * up to March 2011 The seismicity within the Gujarat is not same across the Gujarat. The single seismicity parameter for entire Gujarat may not represent the true seismicity within the Gujarat
Seismicity in Saurashtra Seismicity migration is observed in the Saurashtra Modified after ISR Report 2009
Earthquake Moment Magnitude (Mw) Cumulative Earthquake occurence Catalogue completeness 120 100 80 60 40 20 0 8.0 7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 1800 1820 1840 1860 1880 1900 1920 1940 1960 1980 2000 2020 1962 Catalogue Completeness is evaluated in the present study using CUVI (Tinti and Mulargia, 1985) method and Stepp s method (Stepp, 1973) Time (Years) Shukla and Choudhury (2012) in NHESS, 12, 2019-2037.
Regional Seismicity parameters Log N 2.25 2.00 1.75 1.50 1.25 1.00 0.75 0.50 Entire Gujarat Saurashtra Mainland Gujarat Kachchh Gutenberg Richter recurrence relations are derived using Least Square Fit method using prepared earthquake catalogue for M w 4. 0.25 0.00 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 Earthquake Moment Magnitude (M w ) Rastogi et al. (2013) recommended b value = 0.67 for Saurashtra region. Region Past seismicity used (Year) a-value b-value G-R relation R 2 Saurashtra 135 4.03 0.64 Log N=4.03 0.64 M w 0.9783 Mainland 175 4.02 0.62 Log N=4.02 0.62 M w 0.9370 Kachchh 189 3.41 0.41 Log N=3.41 0.41 M w 0.9821 Gujarat 189 4.13 0.51 Log N=4.13 0.51 M w 0.9899 Choudhury and Shukla (2011) in Disaster Advances, 4(2), 47-59.
b-value using ML method Another popular method for estimation of b- value is by using Maximum Likelihood (ML) method (Aki, 1965; Utsu, 1965) b 1 ln(10)( u m ) min u is the sampling average of the magnitudes Region b-value using ML estimate Kachchh 0.526 Saurashtra 0.572 Mainland Gujarat 0.642
Probability models for earthquake recurrence In time predictable methodology many researchers has applied various probability models to predict the next earthquake within the some specified time. In another words fitting the recurrence time of earthquake using various probability distributions. Key researcher are Utsu (1984); Nishenko and Buland (1987); Sykes and Nishenko (1984); Rikitake (1991); Shimazaki (2002); Kagan and Knopoff (1987); Papazachos (1989); Ferreas (2003, 2005); Yilmaz et al. (2004); Shankar and Papadimitriou (2004) and many others. Specifically for Indian Peninsula, Pervez and Ram (1997, 1999); Tripathi (2006); Jaiswal (2006) and Yadav et al. (2008)
Cumulative Probability Various Probability Distributions No Year Month Date Date (Years) Latitude (0N) Longitude (0E) Mw Recurrenc e Time (Years Location 1 1819 6 16 1819.5 24 69 7.8 Kachchh 2 1845 4 19 1845.333 23.8 68.9 6.3 25.833 Lakhpat 3 1848 4 26 1848.333 24.4 72.7 6 3 Mount Abu 4 1856 12 25 1857 20 73 5.7 8.667 Surat 5 1864 4 29 1864.333 22.3 72.8 5.7 7.333 Ahmedabad 6 1871 1 31 1871.083 21.2 72.9 5 6.75 Surat 7 1872 4 14 1872.372 21.75 72.15 5 1.289 Bhavnagar 8 1882 6 10 1882.5 23.2 71.38 5 10.128 Bhachau 9 1903 1 14 1903.083 24 70 5.6 20.583 Kachchh 10 1919 4 21 1919.391 22 72 5.7 16.308 Bhavnagar 11 1921 10 26 1921.833 25 68 5.5 2.442 Kachchh 12 1935 7 20 1935.583 21 72.4 5.7 13.75 Surat 13 1938 3 14 1938.25 21.6 75 6 2.667 Satpura 14 1950 6 14 1950.5 24 71.2 5.3 12.25 Kachchh 15 1956 7 21 1956.583 23.3 70 6 6.083 Kachchh 16 1963 7 13 1963.583 24.9 70.3 5.3 7 Pakistan 17 1965 3 26 1965.25 24.4 70 5.1 1.667 Kachchh 18 1966 5 27 1966.417 24.46 68.69 5 1.167 Pakistan 19 1970 2 13 1970.167 24.6 68.61 5.2 3.75 Kachchh 20 1976 6 4 1976.5 24.51 68.45 5.1 6.333 Allah Band 21 1985 4 7 1985.333 24.36 69.74 5 8.833 Kachchh 22 1993 8 24 1993.732 20.6 71.4 5 8.399 Rajula 23 2001 1 26 2001.083 23.44 70.31 7.7 7.351 Kachchh 24 2006 3 7 2006.25 23.79 70.73 5.7 5.167 Gedi, 25 2007 11 6 2007.933 21.16 70.54 5 1.683 Junagadh 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 Pareto Distribution Rayleigh Distribution Weibull Distribution Exponential Distribution Earthquakes 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 Earthquake (M w >= 5) in Gujarat region Choudhury and Shukla (2011) in Disaster Advances, 4(2), 47-59.
Selection of the best distribution Exponential Distribution Rayleigh Distribution Pareto Distribution Weibull Distribution Parameters μ= 7.851 δ=11.436 α=0.573 θ=0.118-76.016-74.255-79.189-71.868 Maximum Log Likelihood A-D value 0.760 2.643 0.841 0.273 Modified K-S test value 0.164 0.277 0.170 0.105 P-value 0.554 0.051 0.502 0.955 Weibull Model η 1 f( T) ( θη) T e Pareto Model f( T, α, x ) αx T α 0 0 θt ( α 1) η Rayleigh Model f ( T) T δ Exp T 2δ 2 2 Exponential Model f( T) e μ T μ
Recurrence Estimation Probability Distribution Model Recurrence interval (years) Predicted Last Event occurred on Next Earthquake Expected on Study Date Considered (Nov 10 th 2009) Year Left from Present Date Next earthquake expected before Exponential 7.853 2007.933 2015.786 2009.85 5.936 Oct 2015* Rayleigh 16.173 2007.933 2024.106 2009.85 14.256 Feb 2024 Pareto 3.135 2007.933 2011.068 2009.85 1.218 Jan 2011 Weibull 7.011 2007.933 2014.944 2009.85 5.094 Dec 2014* *Note: This research output published in Journal Disaster Advances in Aug. 2011 was validated by actual occurrence of earthquake of September 2011. Choudhury and Shukla (2011) in Disaster Advances, 4(2), 47-59.
Comparison of Earthquake return periods Choudhury and Shukla (2011) in Disaster Advances, 4(2), 47-59.
b-value proposed & those by other researchers Study Application area b- value Reference Periods for Number study taken 1 Kachchh 0.417 Based on least square fit, Present Study (1820-2008) 2 Saurashtra 0.64 (1872-2008) 3 Mainland 0.62 (1872-2008) 4 Entire 0.51 (1820-2008) 5 Kachchh 0.526 Based on ML estimate, Present Study (1820-2009) 6 Saurashtra 0.572 (1872-2009) 7 Mainland 0.642 (1872-2009) 8 Saurashtra 0.67 Rastogi et al. (2013) (1970-2010) 9 Gujarat 0.87 WCE NDMA (2010) (*1800-2009) ( 0.06) 10 Gujarat 0.72 Tripathi et al., (2005) - 11 Kachchh 0.43 Ashara et al., (2006) - 12 Kachchh 0.71 Jaiswal (2006) (1842-2002) 0.03 13 Gujarat 0.7 to 0.9 0.07 Raghukanth (2010) (1250-2008) 14 Gujarat 0.4 to 0.6 Kolathayar et al. (2011) (250 B.C. -2010) for Clustered catalogue 15 Gujarat 0.4 to 0.8 Kolathayar et al. (2011) (250 B.C. -2010) for declustered catalogue 16 Peninsular 0.92 Jaiswal and Sinha (2007) (1842-2002) 17 Gujarat region 0.55 Bhatia et al. (1999) - 18 Gujarat 0.89 Thaker et al. (2012) 1818-2008 Shukla and Choudhury (2012) in NHESS, 12, 2019-2037.
DSHA - Some starting points Entire Gujarat is divided into three regions Kachchh Saurashtra Mainland Gujarat Earthquake catalogue is divided as per these three regions Only fault sources are used as seismic sources Poisson distribution for earthquake occurrence All the faults are Normal faults, depth ranging 10 to 15km from ground surface.
Seismicity model: DSHA requirements describes geographical distribution of potential active source zones (seismotectonic sources) and distribution of magnitudes in each source. (Fault Map and Seismicity parameters- maximum earthquake magnitude) Attenuation model: describes effect of an earthquake originating from a specific seismotectonic source, at any given site, as function of magnitude and source-to-site distance (Ground Motion Prediction Equations GMPEs)
DSHA 1 Describes the potential for dangerous, earthquake-related natural phenomena i.e. Maximum Considered Earthquake (MCE) 2 The earthquake hazard for the site is a peak ground acceleration of 0.57g resulting from an earthquake of magnitude 5.7 on the Narmada Son Fault at a distance of 11.42 km from the site. 3 Sometimes called Deterministic Scenario in Magnitude, Distance pair i.e. (5.7, 11.42)
Selection of urban areas
Fault Map of study region 67 68 69 70 71 72 73 74 75 26 26 25 24 23 22 21 20 Legend : n th Fault, Fn F18 F14 F13 F15 F17 F12 F25A F5 F2 F1 F4 F3 F6 F7 19 19 67 68 69 70 71 72 73 74 75 F8 F10 F9 F33 F35 F34 Shukla and Choudhury (2012) in NHESS, 12, 2019-2037. F21 F23 F48 F28 F29 F30 F49 F27 F24 F26 F31 F43 F32 F45 F37 F46 F38 F41 F42 25 24 23 22 21 20 Total 40 major faults are considered. Length derived from referred literature and maps. Maximum earthquake magnitude calculated from relationships recommended by few researchers considering one third length as rupture surface.
GMPEs selected GMPE Applicability Remark Abrahamson and Worldwide shallow crustal Silva (1997) earthquake Boore et al. Shallow crustal earthquake (Rock site definition is in accordance (1997) of Western north America with NEHRP seismic code) Campbell (1997) Worldwide shallow crustal (for Mw > 5 and sites with distance to earthquake seismogenic rupture 60 km in active tectonic region) Sadig (1997) Shallow crustal earthquake (Moment magnitude Mw = 4 to 8 and of California Toro et al. (1997) Crustal earthquake of Intraplate region in Eastern and Central North America Frankel et al. (1996) Raghukanth and Iyengar (2007) Intraplate region of Central and Eastern North America Peninsular India distance up to 100 km). (For spectral period less than 0.2 sec, values limited to 1.5 g and periods less than 1 sec are limited to 3 g.) (For sites with shear wave velocity Vs 3.6 km/sec.)
Spectral accelerations (g) Various GMPEs 0.1 Abra.-Silva (1997) Boore-Joyner-Fumal (1997) Campbell (1997) Frankel (1996) Sadigh (1997) Rock Toro (1997) Raghu Kanth & Iyengar (2007) 0.01 1E-3 0 20 40 60 80 100 120 140 160 180 200 Distance from Hypocenter (km)