Invited Workshop on Strong-Motion Record Processing Convened by The Consortium of Organizations for Strong-Motion Observation Systems (COSMOS) Pacific Earthquake Engineering Research Center Richmond, California May 26, 27, 2004 Strong Motion Data Processing in Taiwan and its Engineering Application Chin-Hsiung Loh Department of Civil Engineering National Taiwan University

Strong Motion Instrumentation in Taiwan Taiwan Strong Motion Instrumentation Program (TSMIP) –700 free-field stations –60 sets of strong motion arrays in structures – samples/sec –16/24-bits resolution Taiwan Rapid Earthquake Information Release System (TREIRS) –80 rapid stations –50 samples/sec –16-bits resolution –An integrated seismic early warning system

Chi-Chi earthquake No. of Earthquake Time (year)

Using TREIRS to determine the earthquake intensity

CWB Earthquake Information Backup System Cisco7206 Cisco 3640 HUB ( 集線器 ) Computer HPP& Router IDU CWB 陽明山 HUB CWB Meteorology Station ATM/FR T1 專 線 ISDN/PSTN Main Line First Backup Line Second Backup System Second Backup System 2nd Backup Line 1st Backup line Third Backup Line 3rd Backup Line 3rd Backup line Satellite Telephone Fax Tel Line

Site Investigation at Each Strong Motion Station

Flow Chart for the Baseline Correction of Accelerogram (1) Input Least square straight line fit a 0 and a 1 Low-pass filter f H(f) f1f1 f2f2 Integrate for v(t) Least square fit for v & a High pass Integrate for v 2 (t) Least square fit for v 01 and a 2 Correct accelerogram Low-pass filter f to get v 4 (t)Differentiate V 4 (t) to get a 10

Correct Accelerogram a 6 (t) Integrate a 6 (t) for v 4 (t) Least square fit Low-pass filter to get v 6 (t) Correct velocity Integrate for displacement d 1 (t) Low-pass filter to get d 2 (t) Correct displacement Calculate Velocity & Displacement from Corrected Accelerogram

Flow Chart for the Baseline Correction of Accelerogram & Generation of Velocity and Displacement (2) & Generation of Velocity and Displacement (2) Input Accelerationa’(t) Noise Level Estimate Noise Level From Pre-event Record a 1 (t) = a’(t) - (noise level) Trend removal (using least square method) Error correction on measurement system: Low-pass filter: < 25 Hz 100% High-pass filter: >0.2 Hz 100% A 1 (  ) F {a 1 (t)} Fourier transform Inverse Fourier Transform Output: a(t) = F -1 {A 1 (  )} V 1 (  )=A 1 (  ) ∙(1/i  ) Inverse Fourier Transform Output: v(t) = F -1 {V 1 (  )} D 1 (  )=V 1 (  ) ∙(1/i  ) Inverse Fourier Transform Output: d(t) = F -1 {D 1 (  )}

Empirical Mode Decomposition & Hilbert Transform (EMD+HHT) Application damping estimation Hilbert transform: Empirical mode decomposition 1 Extreme Sifting 2 Curvature Sifting 3 Intermittency Hilbert spectrum: (Time_frequency energy) Loss damping factor Q(f) ( Q(f)=2 * damping ratio )

Example: Using Chi-Chi Earthquake data recorded at Station TCU052 (Near-fault Ground Motion Data) Direct Integration Applied trend removal on velocity data

Example: Using Chi-Chi Earthquake data recorded at Station TCU068 (Near-fault Ground Motion Data) Direct Integration Applied trend removal on velocity data

Example: Using Chi-Chi Earthquake data recorded at Station CHY088 (Far-field Ground Motion Data) Direct IntegrationApplied trend removal on velocity data

Engineering Application of Taiwan Strong Ground Motion Data

PGA Attenuation Model

Site amplification: Predicted vs. Observed

Site Amplification Factor Site Amplification Factor ▪ Using RTD & TSMIP data ▪ Depend on Intensity Level

HAZ-Taiwan : Potential Earthquake Ground Motion Analysis Earthquake Parameters (Magnitude, Depth, Epicenter etc.) Attenuation Model Site Effect Site Effect Modification Modification Update estimation using Taiwan Rapid Information Release System Spatial Distribution of Ground Motion Estimation Taiwan Rapid Earthquake Information Release System (TREIRS)

Estimation Estimation Sa(1.0sec & Sa(0.3 sec) Observation Observation Sa(1.0 sec) & Sa(0.3 sec) Generate Shake Map

Taipei Basin Taipei City

地 震 參 數地 震 參 數 Microzonation Study of Taipei basin

Map of Acceleration Response Spectrum S S D (T=0.3 s) : 475 Yrs S 1 D (T=1.0 s): 475 Yrs ■ ︰ 0.8g ■ ︰ 0.7g ■ ︰ 0.6g ■ ︰ 0.5g ■ ︰ 0.45g ■ ︰ 0.40g ■ ︰ 0.35g ■ ︰ 0.30g ■ ︰ 1.0g ■ ︰ 0.9g ■ ︰ 0.8g ■ ︰ 0.7g S S M (T=0.3 s) : 2500 Yrs ■ ︰ 0.55g ■ ︰ 0.50g ■ ︰ 0.45g ■ ︰ 0.40g S 1 M (T=1.0 s) : 2500 Yrs

Modeling of phase spectra Wavelet analysis Concept of group delay time Stochastic characteristics of group delay time Mean value & Standard deviation of Group Delay time tj gr (  )=  J (  )/   j tgr  j tgr t j gr (  ) J()J() t-distribution (  =3) Given earthquake Magnitude & Epicenter Distance

CWB Structural Seismic Monitoring Array

Transverse Direction Longitudinal Direction Output Measurement: Bridge response data (EMD+HHT method) Mode 1: f = Hz

Conclusions 1.The Taiwan Strong Motion Array (TSMIP-CWB) provides valuable ground motion data for both seismology and engineering application. 2.These high resolution seismographs can record ground motion accurately up to frequency of 50Hz. In engineering application there is no correction on the original data except the constant DC trend removal. 3.Engineering applications of these Strong Motion Array Data include: a. Generate ground motion attenuation model b. Generate shake map for use in seismic emergency response, c. Generate site amplification factor, d. Develop Sa-value for short period and long period for Taiwan Seismic Design Code, e. Damage assessment program is now under developing and will be used in building/bridge seismic monitoring array,

The End

Taiwan-Luzon Velocity field 80 mm/yr convergence across the active Taiwan arc-continent collision zone

Basin Effect : Site Amplification Taipei Basin

北二高碧潭橋橋體 -2 Z-Direction

Empirical Mode Decomposition