verification Pulse Decomposition of OpenSeismoMatlab

Contents

Reference

Baker, J. W. (2007). Quantitative classification of near-fault ground motions using wavelet analysis. Bulletin of the seismological society of America, 97(5), 1486-1501.

Description

The velocity pulse of a strong motion velocity time history is extracted according to Figure 4 of the above reference. The velocity time history of the fault-normal component of the 1994 Northridge, Rinaldi, recording is considered. The Daubechies wavelet of order 4, shown in Figure 2c, is used as the mother wavelet. Initially, the largest velocity pulse is identified (Figure 4b). For the ground motion under consideration, the ten largest velocity pulses are extracted, the combination of which is shown in Figure 4c, and the residual ground motion after the pulses have been removed is shown (Figure 4d).

Earthquake motion

Load earthquake data of fault-normal component of the 1994 Northridge, Rinaldi, recording

eqmotion={'RSN1063_NORTHR_RRS228.txt'};
data=load(eqmotion{1});
t=data(:,1);
dt=t(2)-t(1);
xgt=data(:,2);

Perform modification so that the initial velocity time history agrees with the plot of Figure 4a of the above reference.

xgt=-xgt;

Perform pulse decomposition of earthquake motion

Switch

sw='pulsedecomp';

Wavelet family of Daubechies wavelet of order 4

wname = 'db4';

Apply OpenSeismoMatlab for 1st largest pulse decomposition

S1=OpenSeismoMatlab(dt,xgt,sw,wname);

Plot the velocity time histories (initial motion and largest pulse)

Initialize figure

figure('Position',[7.4,508.2,1517.6,253.8],...
    'InnerPosition',[7.4,508.2,1517.6,253.8],...
    'OuterPosition',[0.2,501,1000,343.2])
hold on
% Plot the velocity time history of the initial ground motion
plot(t,xgt, 'Color', [0 0 0], 'LineWidth', 2)
% Plot the time history of the largest velocity pulse
plot(t,S1.pulseTH, 'Color', [0.7 0.7 0.7], 'LineWidth', 2)
% Finalize figure
hold off
grid on
title('Northridge Rinaldi recording, 1994')
ylim([-200,200])
xlim([0,20])
xlabel('Time (sec)')
ylabel('Velocity (cm/s)')
legend({'Original ground motion','Largest wavelet'})
drawnow;
pause(0.1)

Apply OpenSeismoMatlab for extracting the 2nd up to 10th largest pulses from the residual motion after extracting the 1st pulse as above

Sout{1}=S1;
for i=2:10
    S1=OpenSeismoMatlab(dt,S1.resTH,sw,wname);
    Sout{i}=S1;
end

Plot the velocity time histories (residual motion and 2nd largest pulse)

Initialize figure

figure('Position',[7.4,508.2,1517.6,253.8],...
    'InnerPosition',[7.4,508.2,1517.6,253.8],...
    'OuterPosition',[0.2,501,1000,343.2])
hold on
% Plot the velocity time history of the residual ground motion
plot(t,Sout{1}.resTH, 'Color', [0 0 0], 'LineWidth', 2)
% Plot the time history of the largest velocity pulse
plot(t,Sout{2}.pulseTH, 'Color', [0.7 0.7 0.7], 'LineWidth', 2)
% Finalize figure
hold off
grid on
title('Northridge Rinaldi recording, 1994')
ylim([-200,200])
xlim([0,20])
xlabel('Time (sec)')
ylabel('Velocity (cm/s)')
legend({'Residual after 1st wavelet removed','2nd largest wavelet'})
drawnow;
pause(0.1)

Sum the 10 largest pulses extracted from the input motion

sum10=zeros(size(S1.pulseTH));
for i=1:10
    sum10=sum10+Sout{i}.pulseTH;
end

Plot the velocity pulse using 10 largest pulses

Initialize figure

figure('Position',[7.4,508.2,1517.6,253.8],...
    'InnerPosition',[7.4,508.2,1517.6,253.8],...
    'OuterPosition',[0.2,501,1000,343.2])
% Plot the time history of the largest velocity pulse
plot(t,sum10, 'Color', [0.7 0.7 0.7], 'LineWidth', 2)
% Finalize figure
grid on
title('Northridge Rinaldi recording, 1994')
ylim([-200,200])
xlim([0,20])
xlabel('Time (sec)')
ylabel('Velocity (cm/s)')
legend({'Sum of 10 largest pulses'})
drawnow;
pause(0.1)

Plot the final residual ground motion

Initialize figure

figure('Position',[7.4,508.2,1517.6,253.8],...
    'InnerPosition',[7.4,508.2,1517.6,253.8],...
    'OuterPosition',[0.2,501,1000,343.2])
% Plot the time history of the largest velocity pulse
plot(t,S1.resTH, 'Color', [0 0 0], 'LineWidth', 2)
% Finalize figure
grid on
title('Northridge Rinaldi recording, 1994')
ylim([-200,200])
xlim([0,20])
xlabel('Time (sec)')
ylabel('Velocity (cm/s)')
legend({'Final residual ground motion'})
drawnow;
pause(0.1)

Copyright

Copyright (c) 2018-2023 by George Papazafeiropoulos

Published with MATLAB® R2022b