in the Kanto area, Japan Shigeki Senna, Atsushi Wakai, Kaoru Jin, - PowerPoint PPT Presentation

Taipei Taiwan 5 th IASPEI/IAEE International Symposium: August 15-17, 2016 Effects of Surface Geology on Seismic Motion Modeling of the subsurface structure from the seismic bedrock to the ground surface for a broadband strong motion evaluation in the Kanto area, Japan Shigeki Senna, Atsushi Wakai, Kaoru Jin, Takhiro Maeda, Hiroyuki Fujiwara National Research Institute For Earth Science and Disaster Resilience

Introduction In Japan, In order to estimate damages caused by strong ground motions from a mega-thrust earthquake, it’s important to evaluate broadband strong motion in wide area. To realize it, it’s necessary to sophisticate subsurface structure models, on which shallow and deep subsurface structures are integrated. We think that a period characteristic and an amplification characteristic are the most important for modeling of subsurface structure. We make high- accuracy structure models, and we're available for the earthquake damage estimate of the building. 2

Contents 1) Subsurface structure model construction procedure 2) 3D Shallow subsurface structure models(Initial) 3) 3D Deep subsurface structure models (Initial) 4) Microtremor observation methods 5) Joint inversion and verification methods(Final) 6) Other topics(microtremor observation systems) 3

1) Subsurface structure model construction procedure Collected by Geological Microtremor and Seismic Data ( Single point observation) and Physical Data H/V, R/V Spectrum Final Structure Model Borehole Data Microtremor Data Microtremor(Array) (About 250m grid models) About Initial Structure Model Phase Velocity Structure Model (Geological Models) (About 250m grid model) 4

2) Outlines of 3D Shallow subsurface structure Models ・ Various methods for making Models. Conventional method using geomorphologic classifications :J-SHIS （ 250m grid ） Detailed methods using a lot of boring data :recent NIED projects (250m grid ） → fo foll llowin ing d descrip iptio ion PGV site amplification factor (ARV) converted from Vs30 5

Flow chart of modeling the Shallow subsurface structure models Various Civil engineering projects ⇒ Boring data ⇒ Database(Geo-station) Number of data are over 500,000 data Relatinships of Boring columns (stratigraphic divisions,N-Value) N-Value and Vs 3-D geological structure Laterally continuous layers with each N-Value S-wave velocity layered models 6

Development of Integrated Geophysical and Geological Information Database Geo-Station(NIED) Tokyo Institute of NIED-DB Technology 被害予測イメージ （モデル建物Aの場合） 崩壊 大破 中破 小破 軽微 underground structure ERI of AIST-DB Tokyo University geological information http://www.geo-stn.bosai.go.jp Municipalities DB PWRI-DB GJI-DB soil dynamics MLIT KuniJiban 7

Initial shallow models (Geological models) Collected borehole data in the Kanto district(N=200,000) Number of data(/250m grid) Chiyoda Urayasu City Hall Soil models(250m grid) Altitude(m) Stratigraphic classification Geological models Engineering Bedrock(Vs350) 8

3) Outline of 3D Deep subsurface structure model ・ Based on geological data and geophysical exploration data. ・ Composed of different seismic velocity layers. ・ Vertically divided into cubes with about 1km mesh surface. 1km 1km 9

Flow chart of modeling the Deep subsurface structure models Subsurface structure data Surface geological data ・ Deep borehole, Logging ・ Topographical Map ・ Seismic reflection , refraction survey ・ Geological Map ・ Micro tremor survey ・ Gravity survey Distribution of physical properties Structure of Sedimentary layers ・ Seismic wave velocity ・ Density ・ depth ・ thickness ･ faluts ・ folds Layered structure model of physical property (0th-order geological model ） Model modification compared to observed waveform data Simulation of seismic waveform using the Layered Model Deep subsurface structure model for Strong-motion Evaluation = JIVSM(2012) (1st-order model and so on ） 10

Initial value of physical properties <Deep model> J-SHIS 37 Depth(m) Seismic bedrock of deep and shallow models 3500 Vs=3200(m/s) 36.5 36.5 3000 upper depth Level(GL-m) 2500 2000 <Shallow model> 36 1500 800 400 35.5 35.5 200 100 60 35 40 20 10 0 34.5 34.5 138.5 139 139.5 140 140.5 141 141.5 ρ (g/cm 3 ) Layer Vs(km/s) Vp(km/s) 1 0.35 1.6 1.85 2 0.40 1.6 1.85 3 0.45 1.7 1.90 4 0.50 1.8 1.90 5 0.55 1.8 1.90 6 0.60 2.0 1.90 7 0.65 2.0 1.95 8 0.70 2.1 2.00 9 0.75 2.1 2.00 10 0.80 2.2 2.00 11 0.85 2.3 2.05 12 0.90 2.4 2.05 13 0.95 2.4 2.10 14 1.0 2.5 2.10 15 1.1 2.5 2.15 16 1.2 2.6 2.15 17 1.3 2.7 2.20 18 1.4 3.0 2.25 19 1.5 3.2 2.25 20 1.6 3.4 2.30 21 1.7 3.5 2.30 22 1.8 3.6 2.35 23 1.9 3.7 2.35 24 2.0 3.8 2.40 25 2.1 4.0 2.40 26 2.1 4.0 2.40 27 2.7 5.0 2.50 28 2.9 4.6 2.55 29 2.7 5.0 2.50 30 3.1 5.5 2.60 11 31 3.2 5.5 2.65 11 Yellow hatch are physical-properties value of the Kanto district.

Integration model (Shallow and Deep) Geological strata line landfill , loam Alluvium, Diluvium etc. This model is ‘Initial model’ 12

4) Microtremor observation methods Normal Size Miniture and Irregular Array Method Array Method (R=800,400,200,100,50,25m) (ex.Cho et al.(2013)) ＜ Observation Spec ＞ ＜ Observation Spec ＞ ・ Seismometers = 6units ・ Seismometers = 7 ～ 10units ・ Sampling=200(Hz) ・ Sampling=100Hz ・ Observation Time 15(min.) ・ Observation Time 30 ～ 80(min.) R=200m R=400m Illegular array Miniature array R=800m Dispersion analysis SPAC and (nc-)CCA( < 200m) methods 13

Microremor observation for a subsurface structure model construction （ Two types of observation method ） Nomal Size Array about every 5km Miniature and Irregular Array about every 1km 2014 （ black ） 76points 2014 （ black ） 992 points 2015 （ red ） 244points 2015(red ） 7532 points 2016 （ blue ） 103points 2016 （ blue ） 5500 points Data base （ green ） 460points 2017 （ green ） 3500 points Miniature and Irregular array ( ～ Vs700(m/s)) Normal size array ( Vs300 ～ Vs3000(m/s)) 14

5) Correction of subsurface structure models using joint inversion method JIVSM(2009-2012) 15 15

Final structure models(Deep Model Part) J-SHIS Model(Initial) This Study Model(v7.4) Predominant period( >2s ) Top surface depth of the Vs=900(m/s) layer J-SHIS 37 36.5 NIED 36 Mt. Tskuba 35.5 35 NARITA Airport Top surface depth of the Vs=3,200(m/s) (Seismic bedrock) J-SHIS 37 (sec) HANEDA Airport 36.5 ※ Vs ≦ 3,200(m/s) 36 35.5 35 16

The final structure models (Shallow model Part) Geomorphological Classification Models (reference information) This Study Structure Models Matsuoka and Wakamatsu(2013) NIED Edogawa river Edogawa river Edogawa river Mt. Tskuba Arakawa river Arakawa river Arakawa river Tone river Tone river Tone river Tokyo bay’s Tokyo bay’s Tokyo bay’s Reclaimed land Reclaimed land Reclaimed land Predominant Period AVS30(m/s) AVS30(m/s) (sec) ※ Vs ≦ 350(m/s) 17

Verification analysis of models Long Period Side Short Period Side （ 1.0(s) ～ 10(s) ） （～ 1.0(s) ） Finite Difference One dimensional Method multi-reflection (FDM) Theory Mountain 18

Verification of f peri riod and amplify fying chara racteri ristics b by FDM ① ＦＤＭ Aoi and Fujiwara(1999) Structure model for FDM Grid size(m) number of grids Interval(s) shallow part Shallow part Deep part dx1 dy1 dz1 nx1 ny1 nz1 nx2 ny2 nz2 70 70 35 3789 4146 231 1263 1382 400 0.003125 ※ hypocenter is JMA , Hypocenter mechanism and seismic moment depend on F-net. SCEC(Southern California Earthquake Center) GOF （＝ goodness-of-fit ： 𝐇𝐏𝐆 = 𝐦𝐨⁡ (𝐞𝐛𝐮𝐛/𝐧𝐩𝐞𝐟𝐦) ） mean S.D. 𝐃𝐇𝐏𝐆 = 𝟐 + 𝟐 𝐩𝐞𝐟𝐦) 𝐩𝐞𝐟𝐦) 𝐦𝐨(𝐞𝐛𝐮 𝐛 𝐧 𝐦𝐨(𝐞𝐛𝐮 𝐛 𝐧 𝟑 𝟑 （ Dreger et al., 2015 ） ※ Two horizontal components synthesis of fourier spectrum is used 19

Verification of period an and am amplifyi ying char arac acte teristi tics by y FDM ② KiK-net CHBH13(NARITA) KiK-net IBRH20 (HASAKI-2) Result of joint inversion Result of joint inversion Initial model Initial model This study model This study model Obs. Dispersion,H/V Obs. Dispersion,H/V V7_4 : This Study Model JIVSM ： Japan Integrated Velocity Structure Model Ver.1(2009) CDMC ： Cabinet Office, Government of Japan Model(2012) JSHIS ： J-SHIS(ver2.0)(2009) 20

Verification of period an and am amplifyi ying char arac acte teristi tics by y FDM ③ （ Compar arison with th o oth ther pas ast m t models ） V7_4 This Study Model CDMC ： Cabinet Office, Government of Japan Model(2012) JSHIS J-SHIS(ver2.0)(2009) 21

Verification of f peri riod a and amplify fying chara racteri ristics b by FDM ③ （ Com ompariso son with ot other past st mod odels ） Average of all K-NET and KiK-net points(197points) in Kanto area. The distribution of the mean and the S.D. mean S.D. V7.4 : This Study Model JIVSM ： Japan Integrated Velocity Structure Model Ver.1(2009-2012) CDMC ： Cabinet Office Government(Disaster Management) Model(2012-2016) JSHIS ： J-SHIS(ver2.0) Model (2009) 22