by dr. sarosh .h. lodi professor, department of civil engineering
DESCRIPTION
PREDICTION OF RESPONSE SPECTRAL PARAMETERS FOR BHUJ EARTHQUAKE (26TH JANUARY 2001) USING COMPONENT ATTENUATION MODELLING TECHNIQUE. By DR. SAROSH .H. LODI Professor, Department of Civil Engineering NED UNIVERSITY OF ENGINEERING AND TECHNOLOGY KARACHI, PAKISTAN & MUKESH KUMAR - PowerPoint PPT PresentationTRANSCRIPT
PREDICTION OF RESPONSE SPECTRAL
PARAMETERS FOR BHUJ EARTHQUAKE
(26TH JANUARY 2001) USING COMPONENT
ATTENUATION MODELLING TECHNIQUE
ByDR. SAROSH .H. LODI
Professor, Department of Civil EngineeringNED UNIVERSITY OF ENGINEERING AND TECHNOLOGY
KARACHI, PAKISTAN&
MUKESH KUMARResearch Assistant, Department of Civil Engineering
NED UNIVERSITY OF ENGINEERING AND TECHNOLOGYKARACHI, PAKISTAN
PRESENTED BY: MUKESH KUMAR
PRESENTATION LAYOUT
Research Background
Available Data
Component Attenuation Modeling
Methodology
Input Parameters & Comparative Analysis
Conclusions and Future Research Direction
Discussion Session
BHUJ EARTHQUAKE
It was one of the most devastating earthquake in the history of Indian sub-continent.
Mw=7.7 earthquake, hypocentral depth of 23.6 km, epicenter located near Bhachau city.
There exists a debate whether the earthquake was interplate or intraplate.
Li et al., developed a viscoelastic finite element model and concluded that the cause of plate-interior earthquake was intracontinental thrusting and shearing along the northwestern Indian plate boundary.
RESEARCH BACKGROUND
RESEARCH OBJECTIVES
The objective of the research endeavor is to pave way towards the development of Design Response Spectra for Southern Coastal Region (SCRS) for future design of engineering structures and seismic evaluation of existing structures, in the most data scarce environment.
It also aims at assessing the applicability of Component Attenuation Modeling Technique, and future improvements in the technique.
RESEARCH BACKGROUND
AVAILABLE DATA
The event remained least recorded in the near vicinity of the source.
Digital Strong-motion Accelerographs located at a distanceof 238 km provide the Ground Acceleration Records, but the recordings have been infected due to the location of accelerograph in a high rise building.
Only usable recordings are Structural Response Recorders (SRR) data.
AVAILABLE DATA
STRUCTURAL RESPONSE RECORDER DATA
Thirteen SRR located within a periphery of 300 km from the epicenter recorded spectral acceleration for varying natural time period of 0.4 sec, 0.75 sec and 1.25 sec with a fixed damping ration of 5%.
SRR stations have been divided into three categories based on site soil conditions. The sites have been categorized into Rock, Quaternary, and Tertiary; using NEHRP site classification scheme.
The sites are categorized into three schemes using Geologic Map of India (1962), at a scale of 1:2,000,000, which may be cause of uncertainty.
AVAILABLE DATA
TABLE SHOWING SRR VALUES
EpicentralDistance
(Km)
Sa-5% Damped
Site Condition0.4 sec 0.75 sec 1.25 sec
44 1.616 0.705 0.423 T
53 0.863 0.571 T
97 0.811 0.65 0.300 Q
147 0.72 0.216 T
150 0.181 0.065 0.023 R
166 0.220 0.152 0.072 R
188 0.211 0.058 Q
207 0.191 0.248 0.054 Q
216 0.187 0.063 0.023 R
225 0.096 0.066 0.028 R
238 0.288 0.230 0.219 Q
266 0.488 0.041 Q
288 0.144 0.061 0.045 Q
AVAILABLE DATA
CAM is the modified version of stochastic simulation method using wave attenuation model, developed by Boore (1983).
It is a technique proposed by Lam et al., to predict response spectral parameters of an earthquake for regions with scarcity of earthquake ground motion data.
The idea is based on the finding of Atkinson and Boore, that the source models for interplate and intraplate regions exhibit similar frequency content properties.
COMPONENT ATTENUATION MODELING (CAM)
COMPONENT ATTENUATION MODELING
Component Attenuation Modeling Technique
*
)(M
)()()()(*78.0 crustRRGM
)(RG
)(R
)(crust
Response spectral parameter of interest (SDmax, SVmax and SAmax)
Constant pertaining to spectral parameter of interest
Source factor
Geometric factor
Anelastic attenuation factor
Upper crust factor, product of Cm and Cu for mid-crust amplification and combined upper crust amplification and attenuation
COMPONENT ATTENUATION MODELING
METHODOLOGY
The SRR values have been divided into two sections.
Data recorded on Rock sites.
Data recorded on Quaternary and Tertiary sites.
Recorded is compared with prediction of CAM and orthodox stochastic simulation.
METHODOLOGY
PARAMETERS USED FOR CAM
Mw=7.7
Mid-crust exhibits Pre-Cambrian Crystalline basement and upper crust consists of Phanerozoic sedimentary sequence Lozios et al.
The thickness of the crust is taken to be 40 km, so the Geometric Attenuation characteristics are similar to ENA.
INPUT PARAMETERS
Predicted V/s Recorded
Distance (km)
Sa/g Values Corner Periods Peak Spectral Parameters
0.4 0.75 1.25 T1 T2 Sd Sv Sa
150 0.192 0.102 0.060 0.17 1.97 37.77 0.12 0.465
166* 0.176 0.094 0.056 0.17 2.03 35.54 0.11 0.411
216 0.144 0.077 0.046 0.190 2.18 30.11 0.09 0.287
225 0.128 0.068 0.041 0.200 2.210 29.31 0.08 0.27
COMPARATIVE ANALYSIS
Graph Illustrates the predicted DRS V/S SRR values at the distance of 150 km
COMPARATIVE ANALYSIS
Graph Illustrates the predicted DRS V/S SRR values at the distance of 166 km
COMPARATIVE ANALYSIS
PREDICTION ON TERTIARY SEDIMENTS
Distance (km)
Sa (g) ValuesObserved
Sa (g) ValuesPredicted
Ratio Observed/Predicted
0.4 0.75 1.25 0.4 0.75 1.25 0.4 0.75 1.25
44 1.616 0.705 0.423 0.416 0.222 0.133 3.88 3.17 3.18
53 0.863 0.571 N.A. 0.336 0.179 0.107 2.56 3.18 N.A.
147 0.72 0.216 N.A. 0.192 0.102 0.061 3.75 2.19 N.A.
COMPARATIVE ANALYSIS
PREDICTION ON QUATERNARY SEDIMENTS
Distance (km)
Sa (g) ValuesObserved
Sa (g) ValuesPredicted
Ratio Observed/Predicted
0.4 0.75 1.25 0.4 0.75 1.25 0.4 0.75 1.25
97 0.811 0.65 0.300 0.272 0.145 0.087 2.98 4.48 3.44
188 0.211 N.A. 0.058 0.16 0.085 0.051 1.46 N.A. 1.26
207 0.191 0.248 0.054 0.144 0.079 0.046 1.32 3.14 1.17
238 0.288 0.230 0.219 0.128 0.068 0.041 2.25 3.38 5.34
266 0.488 0.041 N.A. 0.114 0.061 0.036 4.28 0.67 N.A.
288 0.144 0.061 0.045 0.104 0.055 0.033 1.38 1.11 1.36
COMPARATIVE ANALYSIS
USING STOCHASTIC SIMULATION METHOD
Distance (km)
Recorded values Predicted with CAMPredicted With (AB95) Model
0.4 1.0 1.25 0.4 1.0 1.25 0.4 1.0 1.25
150 0.181 0.065 0.023 0.192 0.102 0.060 0.298 0.147 0.07
166 0.220 0.152 0.072 0.176 0.094 0.056 0.27 0.136 0.066
216 0.187 0.063 0.023 0.144 0.077 0.046 0.210 0.109 0.053
225 0.096 0.066 0.028 0.128 0.068 0.041 0.201 0.104 0.051
COMPARATIVE ANALYSIS
CONCLUSION
The observed data seem to be in overall agreement with that predicted by CAM and stochastic simulation of AB95 model.
The sites classified as sediments are under predicted by the applied technique, due to soil amplification.
The maximum value of amplification due to sedimentary site condition is observed at a distance of 238 km, shows that SRR was stationed in Ahmedabad City; which was the worst affected in the earthquake.
CONCLUSION
CONCLUSION (Contd)
CAM successfully predicts Response Spectral Parameters in the available period range i.e. in velocity controlled regime.
Due to unavailability of ground acceleration data, in near-source region, restricts to assess its applicability in all period ranges.
Yet, It may be concluded that an ad-hoc design response spectra may be developed using CAM, for region with scarcity of data.
CONCLUSION