Seismograph Waveform A seismograph waveform is stored in the matlab file eq_data
ID: 2267585 • Letter: S
Question
Seismograph Waveform A seismograph waveform is stored in the matlab file eq_data.mat, available on the course web site. The data is in d. As usual, the sampling time is in dt, and the sampling frequency is in fs The data is of the magnitude 7.3 Landers earthquake in 1992 recorded several hundred miles away. The data is available as the Mammoth Lakes link in the USGS web page https://earthquake.usgs.gov/learn/topics/listen/combination.php There are several other interesting waveforms there, as well as a description of why the different types of earthquakes sound the way they do, and what can be learned from seismograph data Task 4 Most of the frequency content of ground motion waveform is in the audio range. Play the waveform as sound >sound (d, fs) Define a time vector t and plot the waveform. The earthquake starts with two impulses, which are difficult to hear, but easy to identify on the plot. What time do these occur? Task 5 The interesting thing about this recording is that the large distant earthquake produced several smaller local triggered earthquakes. High frequencies are attenuated with distance, so the large distant earthquake sounds like a rumble. The high frequencies of the local earthquakes aren't attenuated since they are closer. These sound much sharper or crisper. There are several triggered earthquakes between 3 and 5 seconds from the beginning of the waveform. Listen to the waveform to see if you can identify when they happen. Then find two of these events, and plot each of them. Make sure the axes are properly labeled. What is the start time for each event? How do you identify them on the plot?Explanation / Answer
clear all
x=[1,0,1,2,-1,3,2]; INPUT SEQUENCE
n1=length(x);
n=0:1:n1-1;
sunplot(2,2,1),stem(n,x);
xlabel('n'),ylabel('x(n)');
h=[1,1,2,2,1,1]; second inpulse sequence
n2=length(h);
n1=0:1:n2-1;
subplot(2,2,2),stem (n1,h);
xlabel('n'),ylabel('h(n)');
y=vonv(x,h)
n2=0:1:n1+n2-2;
subplot(2,1,2),stem(n2,y);
xlabel('n'),ylabel('y(n)');
title('the earthquake starts with impulses');
task 5-the time taken by the impulse function on which the time taken between is 3 to 5 seconds on whict the discrete functions are plotted based on the exponential decay of the signal which is not been covered and the start time for each time is 2ms and those can be identified on the plot with the stem function and adding of thr signals