Numerical modeling of waves for a tsunami early warning system

Numerical modeling of waves for a tsunami early warning system
Comparing the model results at the gauges located in the rear side of the
island (figure 4.33) it can be noted that this error is here attenuated.
ηR1
ηR3
ηR5
ηR7
ηR10
0.02
0
−0.02
10 15 20 25 30 35
0.02
0
−0.02
10 15 20 25 30 35
0.02
0
−0.02
10 15 20 25 30 35
0.02
0
−0.02
10 15 20 25 30 35
0.02
0
−0.02
10 15 20 25 30 35
t(s)
ηR2
ηR4
ηR6
ηR8
0.02
0
−0.02
10 15 20 25 30 35
0.02
0
−0.02
10 15 20 25 30 35
0.02
0
−0.02
10 15 20 25 30 35
0.02
0
−0.02
10 15 20 25 30 35
t(s)
Figure 4.35: Comparison of the free surface elevations at the first 10 run up
gauges position, measured (red dashed line) and obtained from the numerical
model (black solid line). The numerical results are achieved by using the
registration of the free surface elevation at the first run up gauge 1R to
estimate the wave source term.
Again use is made of the wave spectra in order to analyze how the wave
energy is distributed in frequency. In figure 4.34 only the results at gauges
12S and 15S are presented. Assuming that the wave energy spectra at gauge
12S as to be equal to that measured in the laboratory, and using this identity
to estimate the wave generation term, bring to an overestimation of the wave
energy in high frequency, as can be seen from the wave spectra at gauge
15S reproduced numerically. Therefore, using a near field measurement to
estimate the correct source term for the wave field calculation, generates an
error specially in the far field forecasting, because the source term will be
wrongly affected by the high frequency component which are typical just of
the near field close to the tsunamogenic source.
Università degli Studi di Roma Tre - DSIC 80