2 The second page of this PDF file shows the seismogram reco

2. The second page of this PDF file shows the seismogram recorded for an earthquake at a seismic station, along with a nomogram for determining its Richter magnitude. The steps are l) Identify the P and S arrivals, and measure the time between P and S. This tells us the distance between the seismic station and epicenter. For the example shown, the time between P and S is 24 seconds, so the earthquake epicenter is 210 km away 20 Measure the amplitude of the largest peak or trough. For these data which don\'t include surface waves, this will always be the first or second S-wave peak or trough. For the example shown, the amplitude is 23 mm. 3) Put a point on the left scale bar indicating the time between P and S arrivals. Put a point on the right scale bar indicating maximum amplitude. Draw a line between the two points, and read the earthquake magnitude on the center scale. For the example shown, the quake\'s magnitude is 5 a) For the example shown, suppose the amplitude were only a tenth as big, or 2.2 mm. How big an earthquake would produce such a small-amplitude record? Magnitude b) For the example shown, suppose the earthquake were only magnitude 3. How big an amplitude would be recorded? mm. Note that both #2 and #3 are examples of the fact that the Richter scale is logarithmic, with a factor of 10 variation in seismic wave amplitudes representing only a difference of 1 in Richter magnitude. c) The bottom two plots on p. 2 of this PDF file are imaginary seismograms for the same earthquake, recorded at Sandy and the University of Utah seismic stations. For the Sandy seismogram (shown at lower left), label the P-wave and S-wave arrivals. The time between P and S arrivals is seconds. The amplitude of the largest peak or trough is mm. Plot these values on the P-S scale and amplitude scale, then draw a line connecting them. The earthquake is km from the Sandy station and is magnitude d) For the University of Utah seismogram shown at lower right), label the P and S-wave arrivals. The time between P and S arrivals is seconds. The amplitude of the largest peak or trough is mm. Plot these values on the P-S scale and amplitude scale, then draw a line connecting them. The earthquake is km from the University of Utah station and is magnitude e) Did you calculate roughly the same magnitude from the two seismograms, as expected if they are detecting the same earthquake?

Solution

Answer- The difference between p and s wave arrival in Sandy is = 16 sec

so the distance between epicentre and seismic station willl be = 160km

the amplitude of largest peak in sandy station is = 50mm

on placing straight scale between distance of epicentre and seismic amplitude

the magnitude of the earth quake is = 5

answer- the difference between p and s wave in Utah is = 35sec

so distance between seismic station and epicentre will be = 320km

the amplitude of largest peak in Utah station is = 15mm

the magnitude of the earthquake is = 5.3

answer- if amplitude is 10mm then magnitude will be = 4.5

if amplitude is small like 2.2 mm then magnitude will be = 3.5

answer- if an earthquake have magnitude of 3 then its seismic amplitude will be = 1.5mm