Tsunamis: can engineering research mitigate the risk?€¦ · • 231,594 deaths • 125,000...
Transcript of Tsunamis: can engineering research mitigate the risk?€¦ · • 231,594 deaths • 125,000...
Tsunamis: can engineering research mitigate the risk?
Giorgio Bellotti
2011 Junior Enrico Marchi Lecture
• 231,594 deaths• 125,000 injured• 45,752 missing• 1.69 million displaced
The Sumatra tsunamiDecember 26 2004
The Sumatra tsunamiDecember 26 2004
• Readiness level: zero• No ability of recognising warning signs
• No tsunami warning system• Sri Lanka (35,000 deaths) and the east coast of India (18,000 deaths) were hit 1.5‐2 hours later
• Thailand (8,000 deaths) was hit 2 hours later
The Sumatra tsunamiDecember 26 2004
Tsunamis in Italy80 events (200 b.C – 2000 a.C.)
Tsunami generation and propagationEarthquakes Subaerial and submerged landslides
• Tsunami wave length (offshore): 10‐500 km• Wave period: 100 s – 30 min• Wave celerity (offshore) 600‐900 km/h• Wave height (offshore): 0.1 – 1.0 m• Wave height (inshore): 1 – 20 m
5 km
• December 30th 2002.• A landslide of 10‐20 Mm3: run‐up of about 10 m
along the coast of the village.
Aerial view from West
Sciara del Fuoco
Stromboli villageSea level gauges
Ginostra village
Ginostravillage
The tsunami at Stromboli
• Civil Protection needed scientific cooperation to set‐up a warning system,
• inundation maps for managing future emergencies,
• to prepare the population: guidance on how read warning signs.
• Previous researches carried out for the National Dam Office (coordinators: prof. A. Noli & prof. P. De Girolamo)
The tsunami at Stromboli
The tsunami at Stromboli
• No formulae for simple run‐up prediction in such specific conditions
• No benchmarks for the validation of numerical models
• Research projects funded by Civil Protection and PRIN 2005+2007 (coordinator: prof. P. De Girolamo)
The tsunami at Stromboli
The island physical model
New data for • Study of the generation/propagation hydraulics• Numerical/analytical models validation• Study the feasibility of an early warning system
The conical island and the landslide model are similar to Stromboli, if scaled down 1:1000 using the Froude law
800m
600m 0.8m
Circular undisturbed shoreline
12S
24S
22S
16S
11S
15S
7S
20S
The island physical model
Experiments carried out at the Coastal Engineering Laboratory (LIC) of Politecnico di Bari, Italy, in collaboration with LIAM
The island physical model
The island physical model
40 cm
Surface level gauges
•Landslide thickness=5 cm
•At the prototype scale the volume of the landslide is of about 8 Mm3
•48 surface + run up gauges
80 cm Run‐up gauges
The generation process
depressionsuperelevation
superelevation
Submerged landslide Subaerial landslide
coast coast
sea sea
Cross sectio
nsPlan
views
Run‐up time series
14 16 18 20 22 24 26 28 30-2
-1
0
1
2
Ru 1 (c
m)
14 16 18 20 22 24 26 28 30-2
-1
0
1
2
Ru 4 (c
m)
14 16 18 20 22 24 26 28 30-2
-1
0
1
2
Ru 5 (c
m)
t(s)
The second wave gives an inundation larger than the first wave
(subaerial landslide)
14 16 18 20 22 24 26 28 30-2
-1
0
1
2
Ru 1 (c
m)
14 16 18 20 22 24 26 28 30-2
-1
0
1
2
Ru 6 (c
m)
14 16 18 20 22 24 26 28 30-2
-1
0
1
2
Ru 7 (c
m)
t(s)
Run‐up time series
First wave: small crest and large trough ‐> receding
waters
Second wave: large inundation
(subaerial landslide)
Run‐up time series
14 16 18 20 22 24 26 28 30-2
-1
0
1
2
Ru 1 (c
m)
14 16 18 20 22 24 26 28 30-2
-1
0
1
2
Ru 9 (c
m)
14 16 18 20 22 24 26 28 30-2
-1
0
1
2
Ru 11
(cm
)
t(s)
Receding waters The maximum inundation is given by the 3rd wave
(subaerial landslide)
• Tsunamis are (partially) trapped by the bathymetry
• Edge waves• Despite shallow waters conditions frequency dispersive effects take place
• The first crest becomes smaller as the waves propagate around the island
Output of the research–part 1
• For subaerial landslides, only very close to the landslides the first wave gives the largest inundation
• In the far field the first wave has a small crest and a large trough (receding waters), then the second wave gives the largest inundation
• In the very far field the maximum inundation is given by the 3rd and then by the 4th waves
• Di Risio M., De Girolamo P., Bellotti G., Panizzo A., Aristodemo F., Molfetta M., A.F. Petrillo (2009). Landslide generated tsunamis runup at the coast of a conical island: new physical model experiments. Journal of Geophysical Research‐Oceans, 114, C01009.
• Di Risio M., Bellotti G., Panizzo A., P. De Girolamo (2009). Three‐dimensional experiments on landslide generated waves at a sloping coast. Coastal Engineering, vol. 56, pp. 659‐671.
Output of the research–part 1
Output of the research–part 2• Validation/calibration of numerical models
Output of the research–part 2
3D modelVOF
• High accuracy
• good for run‐up
• high computational costs
• Precomputed scenarios
• preparation of inundationmaps
• Validation/calibration of numerical models
Output of the research–part 2• Full 3d Navier‐Stokes solver: careful modelling of the run‐up
• Montagna F., Bellotti G., Di Risio M. (2011). 3D numerical modeling of landslide‐generated tsunamis around a conical island. Natural Hazards, in press.
0 5 10-2
-1
0
1
2
0 5 10-2
-1
0
1
2
0 5 10-2
-1
0
1
2
0 5 10-2
-1
0
1
2
Run‐up
(cm)
t (s)
Run‐up
(cm)
Run‐up
(cm)
Run‐up
(cm)
t (s)
numeric
experimental
Output of the research–part 2
3D modelVOF
Depth‐integrated modellinear MSE with full frequency
dispersion
• High accuracy
• good for run‐up
• high computational costs
• Reasonable accuracy
• good for the far field
• low computational costs
• Precomputed scenarios
• preparation of inundationmaps
•Computations duringemergencies
•Support to the warning system
• Validation/calibration of numerical models
Output of the research–part 2• Depth integrated model: focus on the far field• Frequency dispersion effects dominate the propagation
• Bellotti G., Cecioni C., P. De Girolamo (2008). Simulation of small‐amplitude frequency‐dispersive transient waves by means of the mild‐slope equation. Coastal Engineering, vol. 55 (6), pp. 447‐458.
Hyperbolic – ok for narrow banded spectra seas
Elliptic in the freq domain– ok for broad banded spectra seas
New method for considering the tsunami generation
• Perfect reproduction of frequency dispersion of small tsunamis in the far field
Output of the research–part 2• Depth integrated model: focus on the far field
• Cecioni C., G. Bellotti (2010). Modeling tsunamis generated by submerged landslides using depth integrated equations. Applied Ocean Research, 32, pp. 343‐350.
• Cecioni C., G. Bellotti (2010). Inclusion of landslide tsunamis generation into a depth integrated wave propagation model. Natural Hazards and Earth System Sciences, vol. 10, pp. 2259‐2268.
experimental
numeric
Output of the research–part 3• Numerical model to support in real‐time a tsunami early warning system
• Precomputed landslide scenarios to produce a database of results
• Using (partial) measurements of water level the model results are used to predict the waves atsome reference gauge
• An inversion technique is applied (the model equations are linear and solved in the frequencydomain)
Output of the research–part 3Inversion gauge
Control gauge
• Blu: the real‐time measurements
• Red: the real‐time prediction
• Black: experimental data
Inversion gauge Control gauge
Unpublishedpreliminary results
• Evaluate the feasibility of a Tsunami early warning system for a small island
• Bellotti G., M. Di Risio, and P. De Girolamo (2009). Feasibility of Tsunami Early Warning Systems for small volcanic islands. Natural Hazards and Earth System Sciences, vol. 9, pp. 1911‐1919.
Distance from the landslide (laboratory scale)
Arriv
al time (labo
ratory sc
ale)
Arriv
al time (100
0 tim
es Fr scale)
Output of the research–part 4
Distance from the landslide (1000 times Fr scale)
Conclusions:Has this research mitigated the risk?• Better understanding of the hydraulic processes: guidance to correctly recognize the warning signs of a tsunami attack
• Benchmark for models validation/calibration: more reliable preparation of inundation maps (parametric studies with validated models), development of new models
• Feasibility of warning systems: the results allow to test and optimize the system
Work in progress
neutrino
Weak interaction
Hadronic shower
e.m.shower
Pressure wave
…byology, particle physics and…tsunamis
Tsunami Early Warning Systems for large scale tsunamis
• Systems based on seismic measurements• Tsunami measurements are essential to increase the reliability of the system
Location of DART stationsDeep‐ocean Assessment and Reporting of Tsunamis
Location of DART stations
…but in small seas (Mediterranean Sea), waiting for measurements of the tsunami waves implies a large
reduction of the time for spreading the alert
Can we use acoustic waves instead of surface waves?
30 km
3 km
70 km
Simplified earthquake
The movement of the bottom generates pressure waves and surface waves (tsunamis)
t = 1 s
t = 10 s
t = 30 s
t = 50 s
70 km
Surface waves (not to scale)
30 km
Acoustic waves
Tsunami front
Acoustic wave front
P (kPa)
pp
p
Unpublishedpreliminaryresults
• Acoustic waves travel much faster than tsunamis• Measurements in deep water• Real‐time transmission to coastal stations
Tsunami early warning systems based on acoustic waves
• Very expensive measurement networks
LNS Test Site Laboratoryat the port of Catania
LNS-INFN Catania
Internet Radio Link
NEMO JBTest Site South
Installation at 2100 m depth
20 km
INGV
Test Site North
The Catania test site infrastructure
Acoustic neutrino detection
neutrino
Weak interaction
Hadronic shower
νee.m.shower
Pressure wave
INGV
Sperm‐whales (capodogli) detection and tracking
N. Nosengo, G. Pavan and G. Riccobene, Nature 462 (2009), 560
Measurement of Inter-Pulse-Interval permits to determine the size of the sperm whale
New FIRB (2008) research project:Design, construction and operation of theSubmarine Multidisciplinary Observatory
• Giorgio Riccobene, INFN (national coordinator)• Giorgio Bellotti, University of Roma Tre• Francesco Simeone, University of Rome Sapienza
Work in progress: comments
• Multidisciplinarity: the road to build/use expensive measurement networks and research infrastructures
• Cooperation with researchers of other areas: not obvious
Conclusions• Part 1 of the presentation: Research on landslide tsunami: new experiments and numerical modelling.
• Part 2 of the presentation: Work in progress‐use acoustic waves for tsunami early warning systems.
• Research carried out thanks to the funding of several national institutions (Registro Italiano Dighe, Protezione Civile, PRIN, FIRB)
• Research carried out in Italian hydraulic laboratories (Universities of L’Aquila and Bari)
Acknowledgement‐part 1• The Organizing Comittee (special thanks to prof. Andrea Rinaldo and prof. Piero Ruol)
• Prof. Mario Calabrese• Prof. Alberto Noli• Prof. Leopoldo Franco• Prof. Paolo De Girolamo
Acknowledgement‐part 2• Prof. Antonio Felice Petrillo, prof. Leonardo Damiani, Matteo Molfetta (Polytechnic of Bari)
• Mario Nardi, Lucio Matergia (technicians of L’Aquila University)
• Claudia Cecioni, Francesca Montagna and Alessandro Romano (PhD students at UR3)
• Marcello Di Risio (researcher at the University of L’Aquila)