Here is a link to the data: https://www.dropbox.com/s/po4injxygj3tnm1/data.rtf T

Question

Here is a link to the data:

https://www.dropbox.com/s/po4injxygj3tnm1/data.rtf

The Northridge earthquake was an earthquake that occurred on January 17, 1994, at 04:31 a.m. Pacific Standard Time and was centered in the north-central San Fernando Valley region of Los Angeles, California. It had a duration of approximately 10-20 seconds. The earthquake had a ground acceleration was one of the highest ever instrumentally recorded in an urban area in North America measuring 1.8g with strong ground motion felt as far away as Las Vegas, Nevada, about 220 miles (360 km) from the epicenter. The file eq_data.txt contains lateral acceleration data in g's recorded approximately 20 miles from the epicenter. The data was filtered with a high-pass filter limit of 0.12 Hz and a low pass filter limit of 25.0 Hz. There are 2999 data points and it was sample every 0.020 seconds. Load the data into matlab and plot the acceleration data (ordinate) versus time (abscissa). What was the peak acceleration magnitude? At what time in the data docs the peak acceleration occur (assume the data starts at time equal to 0)? Estimate the frequency of the largest acceleration peaks.

Explanation / Answer

Code:

%%

Data = importdata('data.rtf');

k =0;

for i = numel(Data)-2999+1 : numel(Data)

b = Data{i};

b = b(1:end-1);

k = k+1;

Value(k) = str2double(b);

end

x = 0:0.02:2998*0.02;

plot(x,Value);

Peak1 = max(Value);

Peak2 = min(Value);

if abs(Peak1) > abs(Peak2)

Peak = Peak1;

else Peak = Peak2;

end

ind = find(Value == Peak);

frequency = histc(Value, Peak);

sprintf('Peak acceleration Magnitude is %f , occurred at time %f seconds', Peak, x(ind))

sprintf('Frequency of the Peak acceleration is %f', frequency)

%%

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