Oct.20 2010

1. VARANS- JNES Seismic Safety Information exchange MeetingLecture 5:Method for Determining Design Basis Seismic Ground Motion No. 6 Oct.202010 Shizuo Noda Incorporated Administrative Agency Japan Nuclear Energy Safety Organization (JNES)‏ Seismic Safety Division

2. [Contents] • Case of Damage - Hyogo-ken Nambu Earthquake • Relations between Earthquake Ground Motion and Earthquake/Ground • Regulatory Guide for Reviewing Seismic Design of Nuclear Power Reactor Facilities (The Nuclear Safety Commission of Japan) • Method of Formulating Basic EarthquakeGround Motion Ss • 4.1 Fault Model • 4.2 Response Spectrum • 4.3 The Earthquake Ground Motions with no Specific Earthquake Source Locations(Formulating Sample) • 5. Information Necessary for Formulating Basic Ground Motion Ss Including Seismic Fault Model • 6. Outline of Seismic Observation In Japan • 7. Afterword

3. 1.Case of earthquake damage- Hyogo-Ken Nambu Earthquake - 17 Jan. 1995, 05h46m52s(JST) 34d36.4mN, 135d02.6mE focal depth=14.3km Mj=7.2 By Japan Metrological Agency Ms=6.8 By USGS Mw=6.9 By Kikuchi(1995)&HCMT Mo=2.5e19Nm

4. I-2 Distribution of active faults [Ka] atomic [ka] safety committee atom safety research the Panel

5. Broken wall by the fault displacement

6. Damaged pier during the 1995 Hyogo-ken Nanbu earthquake

7. Collapsed crane in harbor http://geot.civil.metro-u.ac.jp/archives/eq/95kobe/index-j.html

8. Boiled soil in the aftermath of liquefaction http://geot.civil.metro-u.ac.jp/archives/eq/95kobe/index-j.html

9. Damaged building in Kobe

10. Simultaneously occurred fires

11. 2. Relations between Earthquake Ground Motion and Earthquake/GroundWhat Is Earthquake Ground Motion? Earthquake ground motion is defined as a quake of the ground resulting from an earthquake, which is represented by a numerical value (digitized) for every time interval (Δt). Amplitude Duration (whole hours) = N (No. of pcs.) x Δt (time interval) By digitization, it is possible to represent earthquake ground motion in the frequency domain. ＋ Amplitude of each component wave resolved ＋ Gap in the time axis of each component wave resolved ＋ Extracted from "What is dynamic analysis?!"

12. What Is the Response Spectrum? Characteristics where the maximum value of response of single-degree-of freedom system at natural period Ti against earthquake ground motion is computed with the natural period changed and the relations between the natural period and maximum response value are cited 2.Relations between Earthquake Ground Motion and Earthquake/Ground Amplitude A3 A1 A2 A4 Period

13. Relations with Earthquakes and Ground Structure 2.Relations between Earthquake Ground Motion and Earthquake/Ground Site characteristics Engineering bedrock (Vs≧700m/s) Seismic bedrock (Vs≒3.0km/s) Propagation path characteristics Seismic source characteristic Nature of earthquake ground motion = “seismic source characteristics” x “propagation path characteristics” x “site characteristics” Seismic source characteristics: nature of earthquake ground motion near seismic source Propagation path characteristics: decomposition of earthquake ground motion from seismic source to seismic bedrock Site characteristics: decomposition of earthquake ground motion due to the linearity of three- dimensional ground structure and ground materials on seismic bedrock Fault If the points subject to review differ assuming the same earthquake, earthquake ground motion differs because of difference in propagation path characteristics and site characteristics.

14. Earthquake Ground Motion in Various Areas Caused by the Hyogo-ken Nambu Earthquake Kobe PI Kobe 0.8G 0.4G Kakogawa Takarazuka Osaka 2.Relations between Earthquake Ground Motion and Earthquake/Ground Hyogo-ken Nambu Earthquake in 1995 Nishi-akashi Relations between seismic source and location

15. What Is Intensity of Earthquake Ground Motion? Even if the maximum acceleration is the same, the shape, maximum velocity and response spectrum of earthquake ground motion differ greatly. 2.Relations between Earthquake Ground Motion and Earthquake/Ground

16. What Is Bedrock Outcrop (in the Site) If there is a bedrock surface underground, the earthquake ground motion on it will be affected by the ground over it. The earthquake ground motion on the bedrock surface considered to be outcropped will not be affected by the ground over it. 2.Relations between Earthquake Ground Motion and Earthquake/Ground Position of input into a building structure Reflected wave affected by surface bedrock (descending wave) The engineering bedrock stratum is notunderground but outcrops. →Consider it to be a ground surface. Prescribed position of basic ground motion Engineering bedrock stratum Vs≧700m/s

17. Definition of Basic Ground Motion Ss Definition of basic ground motion Ss Definition: earthquake ground motion likely to occur, though rarely, during the use of a facility and to impact heavily on the facility The earthquake ground motions with the site specific earthquake source locations The earthquake ground motions with no specific earthquake source locations Subjected active faults: 125 thousand years ago late in the Pleistocene period and thereafter Location of definition: site free bedrock surface (Vs = not less than 700m/s) Component: earthquake ground motion in the horizontal and vertical directions Feature: S1 and S2, seismic safety evaluation earthquake ground motion, have been integrated. 3. Regulatory Ｇuide（ NSCJ ）

18. Source Location to be Considered for the Basic Ground Motion Ss The earthquake ground motions with the site specific earthquake source locations Formulation of earthquake ground motion according to the type of occurrence of earthquakes: active faults (earthquakes in inland crusts), inter-plate earthquakes, ocean intraplate earthquakes, ocean intraplate earthquakes (intraslab earthquakes) Active faults to be considered: those which, there is no denying, have been active since late Pleistocene The earthquake ground motions with no specific earthquake source locations 3. Regulatory Ｇuide（NSCJ） Nuclear facilities e. Earthquake near a site that is hard to be associated with active faults Japanese Archipelago c. Ocean intraplate earthquake a. Active faults Earthquakes in inland crusts b. Inter-plate earthquake Continental plate Ocean plate d. Ocean intraplate earthquake (intraslab earthquakes)

19. Method of Formulation According to Subjected Seismic Source The earthquake ground motions with the site specific earthquake source locations Approach for formulating earthquake ground motion： Approach based on the response spectrum Approach employing a fault model Matters to be considered in formulation: classify earthquakes according to the type of occurrence of earthquakes, and thenselect plural earthquakes for reviewthat is expected to greatly affect the site, taking uncertainty into consideration with an appropriate approach. The earthquake ground motions with no specific earthquake source locations Approach for formulating earthquake ground motion: ・　Approach based on a response spectrum Method of preparation: collect observation records near the seismic source of earthquakes in inland crusts in the past with which it is hard to associate the seismic source with active faults, and obtain the response spectrum, duration, amplitude envelope and phase. 3. Regulatory Guide（ NSCJ）

20. Flowchart determining basic earthquake ground motion 3. Regulatory Ｇuide（ NSCJ） Earthquake survey , investigation The earthquake ground motions with the site specific earthquake source locations e. The earthquake ground motions with no specific earthquake source locations a. Inland earthquake b. Interplate earthquake c.d. Intraplate earthquake Fault model Response spectra for design purpose Determining basic earthquake ground motionSs

21. Methods by Means of Fault Model and Response Spectrum Mi Xeq 4.Method of Formulating Basic Ground Motion Ss Method by Means of Fault Model Method by Means of Response Spectrum ・Detailed evaluation of earthquake ground motion taking the expansion of faults and fracture propagation characteristics (causative faults near sites, among others) Response spectrum attenuation relation Sa = f (M, Xeq , f ) Seismic spectrum Seismic force property Evaluation site = = ( ( ( F F ( ( S S ( ( f f ) ) P P ( ( f f ) ) G G ( ( f f ) ) f f f ) ) ) S S f f ) ) ･ ･ ･ ･ A A A A A A A A A A Hypocentral distance Xeq Size of earthquake （Magnitude, M） Fault plane Evaluation Consideration of uncertainty Earthquake ground motion Causative fault Waveform composite method Fault sliding Site amplification property Dispersion of attenuation relation G G G ( ( ( f f f ) ) A 100 Propagation characteristics P P ( ( f f ) ) SA(cm/s2) A A 10 Dispersion of size, location and parameter of fault Pseudo-velocity response spectrum (cm/s) １ Xeq(km) Consideration of uncertainty Evaluation of response spectrum in the horizontal and vertical motion 0.1 0.01 5 10 1 0.1 Period (s)

22. Fault Rupture Scenario - Irikura Recipe Recipe for a rational method of setting of a seismic source rupture scenario (also referred to as the characterized seismic source model) Modeling of heterogeneous fault rupture in places where a fault is strong (asperity) and where it is comparatively fragile (background domain) 4.1 Fault Model Asperity Background domain Potential fault earthquake Surface fault earthquake

23. Progress in Modeling of Fault Rupture Scenario by Characterized Seismic Source Model (Irikura Recipe) Step 1: Fault rupture area (S=LW) Step 2: Seismic moment (M0) Step 3: Mean stress drop (DSC) Step 4: Total area of asperity (Sa) Step 5: Stress drop of asperity (DSa) Step 6: Number of pieces (N) and location of asperity Step 7: Average slip rate of asperity (Da) Step 8: Effective stress of asperity (Sa) and of background domain (Sb) Step 9: Setting of slip rate function 4.1 Fault Model

24. Comparison of Methods Based on Fault Model Grasp the features of the earthquake ground motion evaluation approach and select an approach according to the features of the points and structures. A method with the small earthquake waveform as an element Empirical Green Function method: use of small earthquake observation waveform as an element wave (Green Function) Statistical Green Function method: use of simulation wave as an element wave (Green Function) Theoretical computation of seismic waveform by means of fault rupture (difference calculus, etc.) Advantage: theoretical waveform just as the model set is available. Disadvantage: the scope of application is restricted to long wavelength (long period) due to the limitation of minute models and computational capacity. Hybrid method (Statistical Green Function method + theory) With the advantages of the two approaches, the long-period theoretical waveform and the short-period statistical simulation wave are added together in the time domain via the matching filter. 4.1 Fault Model

25. Empirical and Statistical Green Function Methods 4.1 Fault Model Fault displacement of a small earthquake Observation point A large earthquake is the further growth of the fault area of a small earthquake and the sliding displacement. Rupture of a small earthquake Displacement Small fault Time Synthesize large earthquake ground motion by adding together observation records of small earthquakes according to the temporal and spatial growth of rupture. Fault displacement of a large earthquake Rupture of a large earthquake Small earthquake Displacement Point of occurrence of an earthquake Superposition Large earthquake Time Spatial superposition on a fault plane Temporal superposition of rupture process • Computation method of earthquake ground motion: Add together records on small earthquakes according to progress in fault rupture → Records of large earthquakes can be synthesized. • Requirements of records on small earthquakes → The propagation path characteristics and site amplification characteristics of records on large earthquakes are almost the same. (because the observation accuracy of records on small earthquakes (especially long period) affects the results of syntheses.)

26. Features of Empirical and Statistical Green Function Methods 4.1 Fault Model • Empirical Green Function method • Feature: seismic source, propagation path and amplification characteristics are included. Advantage: the observation wave includes many features that cannot be represented by computation. Disadvantage: it is rare that an ideal small earthquake observation waveform can be obtained before the occurrence of an anticipated large earthquake. • Statistical Green Function method • Feature: seismic source characteristics are considered as an element wave, and propagation path and amplitude characteristics are modeled. Advantage: a short-period waveform of statistical nature can be obtained. Disadvantage: too average in the long periodic area which is affected by fault rupture and ground response.

27. Evaluation of Earthquake Ground Motion by Means of Statistical Green Function MethodExample: 1995 Hyogo-ken Nambu Earthquake 4.1 Fault Model NS component NS component Acceleration Acceleration Velocity Velocity Displacement Displacement EW component EW component Acceleration Acceleration Velocity Velocity Displacement Displacement Observation waveform Simulation waveform

28. Approach to Response Spectrum Earthquake ground motion formulated with seismic source specified for each site Evaluate spectra with average seismic source, propagation and site amplification characteristics taken into consideration by means of attenuation relations (relations between distance from seismic source and amplitude according to the size of an earthquake) (computed from observation records) Earthquake ground motion formulated with seismic source unspecified Directly evaluate spectral characteristics from observation records 4.2 Response Spectrum Attenuated earthquake ground motion Complicatedly amplified earthquake ground motion Strong motion in source areas Crust Sedimentary bed Fault rupture Site amplification characteristics Propagation path characteristics Earthquake ground motion formulated with seismic source specified for each site Seismic source characteristics Observed earthquake ground motion seismic source characteristics propagation path characteristics site amplification characteristics Earthquake ground motion formulated with seismic source unspecified

29. 4.2 Response Spectrum ◆Improved Response Spectra Method of Japan Electric Association Evaluating response spectra by Magnitude,Equivalent hypocentral distance with new EQ. knowledge Response spectra (cm/s) very near near Magnitude intermediate far M8.5M8.0 Period(s) Characteristic of this Method ・Stiffness of rock is considered. ・Fault plain is evaluated by the Equivalent hypocentral distance. ・Correction Coefficients of Inland EQ. are determined . ・Correction Coefficients of Near Field Directivity Effect are determinedlarger than Period 0.3s. Magnitude Magnitude Hypocentral distance(km) High Quality EQ. Records on the rock

30. Method of Formulating Earthquake Ground Motion Based on Response Spectrum Preparation method: obtain the time history waveform from the relations between the amplitude and phase of earthquake ground motion and adjust the amplitude in order to minimize the difference between the target and the response spectrum. 4.2 Response Spectrum Acceleration Time domain (relations between time and amplitude) → conversion into frequency domain Response spectrum Ａk，BkFinite Fourier coefficient Amplitude Phase (Relations between frequency and amplitude/phase)

31. Method of Formulating Basic Ground Motion SsExample of Evaluation by Response Spectrum Earthquake ground motion that satisfies a target response spectrum used for design. Also referred to as a simulation wave. Besides the spectrum, phase characteristics are necessary. 4.2 Response Spectrum [Phase characteristics] [Example of target spectrum] Acceleration 1995 Hyogo-ken Nambu earthquake - Kobe Marine Observatory (NS) [Constructed waveform: Simulation wave] Acceleration Specifications for Highway Bridges (with Commentary) Part 5: Seismic Design Level 2, type II class I Ground Simulation waveform conforming to the spectrum of Level 2 (type II, class I Ground), whose phase characteristics are of the simulation wave of the Kobe Marine Observatory NS components.

32. 4.3 The earthquake ground motions with no specific earthquake source locations(Formulating sample) ■Formulating the ground motion directly from earthquake records with no specific source locations which are not seemed to survey before earthquake events ・The objective events are Inland earthquakes ・Collecting earthquake ground motionrecords near source field ・Considering site condition (soil, earthquake ,etc) ・Referring Probabilistic evaluation if necessary Response spectra (cm/s) ・内陸地殻内地震を対象 ・震源近傍の観測記録を収集 ・敷地の地盤物性を加味 ・確率論的な評価等を必要に応じて参照 Period(s) Red lines: Earthquake records with no specific source locations determined before earthquake events

33. Information on Seismic Source, Propagation and Site Characteristics (1) Study of seismic source for each type of earthquake occurrence Earthquake observation records: necessary for grasping a phenomenon (Evaluation of empirical Green Function and site amplitude characteristics, etc.) → Set a seismometer on the subjected site and conduct an observation. Collect and analyze records on observation points near the site. Characteristics of earthquake source faults: modeling of earthquake fault rupture (Macroscopic fault model, heterogeneous fault model) → Set them empirically from the analysis of fault rupture in the past. ・Study of active faults: detailed study of faults (size, location, shape, interval of activity, etc.), ・Survey of historical earthquakes in the past, ・Damaging earthquakes based on historical materials 5.Information Necessary for Formulating Basic Ground Motion Ss Including Seismic Fault Model

34. Information on Seismic Source, Propagation and Site Characteristics (2) Study of earthquake ground motion propagation and site characteristics Study of the geology and underground structure of a site: necessary for constructing a ground structure model to evaluate site amplification (Tertiary ground structure, surface ground structure, nonlinear response characteristics) → Collect and analyze the results of structural survey surrounding the site. (Set a favorable model by continuing a survey steadily since ground structure undergoes no sudden change.) 5. Information Necessary for Formulating Basic Ground Motion Ss Including Seismic Fault Model

35. 5. Information Necessary for Formulating Basic Ground Motion Ss Including Seismic Source ModelModeling of Ground Structure: Method of Study of Underground Structure Seismic reflection method A method by where the seismic waves (mainly P-waves) which are originated from a artificial seismic source on the ground surface and reflected on the underground geological boundaries are observed with seismometers arranged on the line along roads, and the resultant records are analyzed for the cross section of underground structure. This method is similar to CT scanning. Array microtremor survey A method where microtremors are concurrently measured with seismometers arranged on plural points and underground structure including S-wave velocity is roughly estimated from wave propagation characteristics between seismometers. Gravity prospecting Gravitational acceleration varies according to location depending on underground density structure. In this method, underground structure is estimated from the property that gravitational acceleration is large where hard and heavy bedrock is shallow and small where it is deep. Seismic source Group of seismometers Instrument truck Reflected wave Sedimentary bed Basement Human activity Natural phenomenon Traffic Wind Plant Microtremors Pressure change Wave Depth of foundational ground of the Osaka Basin estimated from gravity anomaly

36. 5.Information Necessary for Formulating Basic Ground Motion Ss Including Seismic Source ModelModeling of Ground Structure: Study of Deep Ground Structure Distance (km) A layer A layer (1600 - 1700 m/s) B layer Measured value Calculated value C layer B layer (1800 - 1900 m/s) Uemachi fault zone D layer Abut unconformity Bedrock C layer (2000 - 2800 m/s) D layer (>3000 m/s) Bedrock P-wave reflection section, velocity analysis → layer division, P-wave velocity Depth (m) Distance (km) North South Shot-point Figures mean density (p: g/cm3) Depth (km) N-S cross-section Gravitational analysis → Density structure Seismic refraction method → P-wave velocity of foundational ground

37. 5.Information Necessary for Formulating Basic Ground Motion Ss Including Seismic Source ModelComparison between Results of Detailed Study of Ground and Analytical ModelLogging Information (1,700 m) in Higashinada Ward, Kobe City by Kansai Electric Power Co. and NUPEC (now JNES) The actual ground is complicated and is heterogeneous. As a result of representation of the detailed ground with a simplified four-layer model, the frequency response functions of the two are relatively similar to each other. Frequency response function: Ratio of earthquake ground motion spectra on the ground surface to underground Amplitude Ground surface Period Vs Vp Density 密度 Amplitude Underground Blue: detailed information Red: four-layer model + surface ground Period

38. 5. Information Necessary for Formulating Basic Ground Motion Ss Including Seismic Source ModelFormulation of Earthquake Ground Motion based on the Study of Deep and Shallow Ground Structure Earthquake ground motion on the surface Nonlinear ground response equivalent linear method Shallow ground model (database for boring data) Earthquake ground motion on engineering bedrock Hybrid method Statistical Green Function method + Tertiary difference calculus Fault rupture scenario and deep ground model Topographical and geological information and dynamic seismic source rupture simulation Active Fault research Center Geological Survey of Japan-AIST (2005)

39. 6. Outline of seismic observation in Japan Setup data of seismographs [Ka] atomic [ka] safety committee atom safety research the Panel Excerpt from Earthquake Research Institute of the University of Tokyo HP (www.eri.u-tokyo.ac.jp) (Headquarters of Earthquake Research Promotion summary as of March, 2007)

40. Observation of Earthquake with Strong Ground Motion The mission of the strong motion seismograph is to record the ground motion without exceeding the record range against a strong shake generated by a severe earthquake. For that purpose, it is necessary that the seismograph is robust. And the seismograph should be a system that maintains acquired records without fail. The acquired records is used as data of the input earthquake ground motion in the seismic design and also used in the research of the amplification characteristics of the strong ground motion depending on soil nature. Observation points of strong quake network (K-NET) [Ka] atomic [ka] safety committee atom safety research the Panel Excerpt from HP material at the Disaster Prevention Science and Technology Laboratory Example of observed wave form

41. Observation of Wideband Earthquake The wideband earthquake seismograph is a seismograph that can record a wide spectrum of earthquake ground motions from fast to very slow quakes at the ground surface . Analyses are made on the CMT solution* of large earthquakes that take place all over the world and on the seismic source time functions that show elapsed time of fault movement at the epicenter using seismic waves that were obtained by the seismograph. *CMT stands for the Centroid Moment Tensor. This is an analytical techniques to obtain a location (Centroid) of the earthquake that can best describe the observed earthquake wave form, scale (moment magnitude) and quake mechanism at the same time. Chart wideband earthquake observation point [Ka] atomic [ka] safety committee atom safety research the Panel Figure. Example of observing wideband earthquake Excerpt from and addition to Headquarters of Earthquake Research Promotion HP and National Research Institute for Disaster Prevention HP

42. High Sensitivity Observation of Earthquake The high sensitivity earthquake observation facility is a facility where the quake due to a small earthquake not felt by human beings is obtained. A quiet place is chosen as much as possible, the observation well is dug up, and the physical instrument is set up at the bottom. Because the frequency of occurrence of the small earthquake is very high, it is expected that the understanding of activity levels of earthquakes and modes of earthquake occurrence and underground structures at various places can be promptly made by implementing small earthquake observations. Depth of setup N. of observations 1 1～99m 457 100～199m 184 200～499m 16 500～999m 13 1000～1999m 11 2000～2999m High sensitivity earthquake observation points 2 3000～3999m Example of observation [Ka] atomic [ka] safety committee atom safety research the Panel Excerpt from HP material at the Disaster Prevention Science and Technology Laboratory Excerpt from and addition to Headquarters of Earthquake Research Promotion HP and National Research Institute for Disaster Prevention HP

43. 7. Afterword Basic ground motion Ss employs a strong motion prediction method developed as a method for evaluating natural ground motion. Formulated ground motion is only a prediction model. It is necessary to give full consideration to various types of uncertainty concerning seismic fault, ground structure and characteristics. In the act of design, the relations between an action of earthquake ground motion and performance to be possessed by structures are inseparable in the sense of guaranteeing safety to be possessed by structures. It is necessary to see basic ground motion Ss from the viewpoint of a ground motion employed for design.

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