Tsunami hazard associated to earthquakes along the French Mediterranean coastslines
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DE LA RECHERCHE À L’INDUSTRIE [EGU2020-5554]
Tsunami hazard associated to earthquakes along
the French Mediterranean coastslines
A probabilistic approach (PTHA)
6 May, 2020
E.G.U. General Assembly 2020 Viviane Souty & Audrey Gailler
viviane.souty@cea.fr, audrey.gailler@cea.fr
Commissariat à l’énergie atomique et aux énergies renouvelables – www.cea.fr
Commissariat à l’énergie atomique et aux énergies renouvelables Souty & Gailler | EGU2020-5554 | page 1
Outline
1. Introduction
1.1 Two recent critical events
1.2 Events within the Western Mediterranean Sea
1.3 Previous studies
1.4 Finding and response
2. Method
2.1 Seismic hazard
2.2 Tsunamis
2.3 From seismic hazard to PTHA
3. Results: Tsunamis impacting Cannes area (z05)
3.1 Extension of the period of observation
3.2 A first overview of the magnitude uncertainties
4. Conclusions and perspectives
4.1 Conclusions
4.2 Perspectives
Commissariat à l’énergie atomique et aux énergies renouvelables Souty & Gailler | EGU2020-5554 | page 2
About N.A.R.S.I.S.
New Approach to Reactor
Safety ImprovementS
2017–2021
www.narsis.eu
Commissariat à l’énergie atomique et aux énergies renouvelables Souty & Gailler | EGU2020-5554 | page 3
The work I will present you is co-founded by Euratom H2020 NARSIS project and CEA. NARSIS
means New Approach to Reactor Safety ImprovementS. It is an European project involving 18
partners in 10 countries. The main objective of the project is to improve safety and reliability of
Generation II and III reactors. The project includes the characterization of potential physical threats
due to different external hazards and scenarios (WP1), especially using probabilistic hazard as-
sessment for tsunamis, extreme weather and flooding and their impacts on facilities and extreme
earthquakes effects.
Outline
1. Introduction
1.1 Two recent critical events
1.2 Events within the Western Mediterranean Sea
1.3 Previous studies
1.4 Finding and response
2. Method
2.1 Seismic hazard
2.2 Tsunamis
2.3 From seismic hazard to PTHA
3. Results: Tsunamis impacting Cannes area (z05)
3.1 Extension of the period of observation
3.2 A first overview of the magnitude uncertainties
4. Conclusions and perspectives
4.1 Conclusions
4.2 Perspectives
Commissariat à l’énergie atomique et aux énergies renouvelables Souty & Gailler | EGU2020-5554 | page 3
Introduction
Two recent critical events
26 Dec., 2004 Sumatra-Andaman 11 March, 2011 Tohoku earthquake and
earthquake and tsunami tsunami
➢ Mw9.1 Burma and Indian plates ➢ Mw9.0 Pacific and Northern Honshu plates
➢ 250 000–300 000 dead people ➢ Low altitude of the Fukushima NPP
➤ The deadliest one ➤ Nuclear accident
Two time scales
✔ Warning time scale: starting with the triggering event in real time
✔ Historical time scale:
❏ Study of past events and extrapolation to future events
❍ DTHA: conservative
❍ PTHA: determination of the most affected zones, determination of the most
threatening zones
➢ Evacuation plannification, building engineering
Commissariat à l’énergie atomique et aux énergies renouvelables Souty & Gailler | EGU2020-5554 | page 4
Since the major tsunamigenic earthquakes at Sumatra in December 2004 and Tohoku in March
2011, the determination of the tsunami hazard is questioned worldwide.
The Sumatra tsunami is known as the deadliest tsunami within living memory (250 000–300 000
dead people). The lack of information and communication is responsible for part of this situation
(Okal, 2011).
The 2011 Tohoku tsunami caused a great deal of attention, strengthened by the Fukushima Nuclear
Power Plant accident. The reactors were stopped after the Mw9.0 earthquake, but the elevation of
the NPP was too low in altitude to be preserved from the tsunami waves that exceeded 10 m-height
at the NPP place.
These two high-profile events illustrate the interest to correctly determine the tsunami hazard
in order to communicate truthful analyses.
They also illustrate that the tsunami hazard must be studied at several time scales:
1) the warning time scale, from the triggering event (often an earthquake), and
2) the historical time scale.
At historical time scale, we study past events to extrapolate to probable future events. Two ap-
proaches exist:
1) The Deterministic Tsunami Hazard Assesment (DTHA) look for the worst probable scenario that
can threaten a place.
2) The Probabilistic Tsunami Hazard Assesment (PTHA) look for all probable scenarios. A weight is
given to each probable scenario in order to get the probability of exceeding a threshold value in
a return period (i.e. the maximum water elevation).
This study at historical scale is necessary to plan evacuation and design buildings.
Introduction
Events within the Western Mediterranean Sea
354˚15' 0˚00' 5˚45' 11˚30'
Tsunamigenic Earthquakes 1564 1818
Mw=6.0 Monaco 1846 N
Mw=7.5
1887 1742
Mw=6.5
Andorra
Mw=8.0 Rome
Mw=7.0
79
Amplitude lower than 1m
40˚15' Amplitude greater than 1m
1562 40˚15'
1905
1726 1783 1783
1908
1804 1365 2003 1856 1823 1818
Algiers Tunis 1169
1693
1954 2003
1680 1802 km
1980
34˚30' Non-exhaustive list 0 200 400
34˚30'
354˚15' 0˚00' 5˚45' 11˚30'
Adapted from fig. 1 in Gailler et al. (2013)
Commissariat à l’énergie atomique et aux énergies renouvelables Souty & Gailler | EGU2020-5554 | page 5
Tsunamis in the Western part of the Mediterranean Sea are not frequent and little destructive at
regional scale (i.e. Western Mediterranean Sea area).
However they exist. This map show most of the earthquakes that triggred tsunamis in this part of
the Mediterranean Sea.
Yellow circles show earthquakes that generated less than 1m water elevation along the Western
Mediterranean coastlines. Red circles show earthquakes that triggered tsunamis with waves locally
upper than 1m.
Especially, the Mw6.7 earthquake, that occured offshore in front of Imperia in 1887, impacted a lot
the coastlines along the Ligurian Sea.
The red dashed lines, on the map show the intensity distribution of the tsunami that was generated
by the Mw6.7 earthquake.
The vertical lines show the wave heights that were observed in some cities along the coastlines.
Notably, waves have reached heigths between 1 m and 2 m at Cannes [3] and Antibes [4] cities.
The question of what is the risk naturally arises.
Here we focus on the characterization of the tsunami hazard that is a part of the risk.
Introduction
Feb. 23, 1887 Mw6.7 earthquake, Imperia (Italy)
23 Feb., 1887, Mw6.7
Tsunami effects
hmax: 0 < a < 0.5 m 0.5 < b < 1 m 1 < c < 2m
Locations: 1, Marseille; 2, Fréjus; 3, Cannes; 4, Antibes;5, Nice; 6, St Jean-Cap-Ferrat; 7, Monaco; 8, Menton; 9, Ospedaletti; 10, San Remo; 11, Arma di Taggia;
12, Riva Ligure; 13, Imperia; 14, Oneglia; 15, Diano Marina; 16, Andora; 17, Alassio; 18, Genoa; 19, Bogliasco; 20, Recco; 21, Sestri Levante; 22, Livorno.
Dotted red lines: distribution of the intensity of the tsunami [intensity scale from Sieberg (1923) modified by Ambraseys (1962), compilation by A. Laurenti].
What’s next? Adapted from fig 5 from Larroque et al. (2012)
Commissariat à l’énergie atomique et aux énergies renouvelables Souty & Gailler | EGU2020-5554 | page 5
Tsunamis in the Western part of the Mediterranean Sea are not frequent and little destructive at
regional scale (i.e. Western Mediterranean Sea area).
However they exist. This map show most of the earthquakes that triggred tsunamis in this part of
the Mediterranean Sea.
Yellow circles show earthquakes that generated less than 1m water elevation along the Western
Mediterranean coastlines. Red circles show earthquakes that triggered tsunamis with waves locally
upper than 1m.
Especially, the Mw6.7 earthquake, that occured offshore in front of Imperia in 1887, impacted a lot
the coastlines along the Ligurian Sea.
The red dashed lines, on the map show the intensity distribution of the tsunami that was generated
by the Mw6.7 earthquake.
The vertical lines show the wave heights that were observed in some cities along the coastlines.
Notably, waves have reached heigths between 1 m and 2 m at Cannes [3] and Antibes [4] cities.
The question of what is the risk naturally arises.
Here we focus on the characterization of the tsunami hazard that is a part of the risk.
Introduction
Previous studies
Sørensen et al. (2012)
✔ Tsunami hazard, due to earthquakes, in the Mediterranean Sea using PTHA
✔ Long-wave offshore to get peak offshore tsunami amplitudes
✔ Extrapolation to PCTAs using Green’s law
✔ Contribution to tsunami hazard per seismogenic zone
TSUMAPS-NEAM
✔ European project
✔ Tsunami hazard along European coastlines
✔ Peak offshore tsunami amplitude extrapolated to PCTAs using Green’s law
TANDEM
✔ French project
✔ Tsunami hazard along French coastlines (North Atlantic Ocean and French Channel)
✔ DTHA using high-resolution simulations
✘ Green’s law approximation are not accurate nearshore
✘ DTHA only look at the worst probable scenario
Commissariat à l’énergie atomique et aux énergies renouvelables Souty & Gailler | EGU2020-5554 | page 6
Several studies had the aim to study the tsunami hazard along the European coastlines. Among
other, we can cite
1. The study of Sørensen et al. (2012)
2. TSUMAP-NEAM project
3. TANDEM project.
Sørensen et al. (2012) quantified the tsunami hazard in the Mediterranean Sea using PTHA. They
simulated tsunamis using long-wave model to get the peak offshore tsunami amplitude and
extrapolated it to Peak Coastal Tsunami Amplitude (PCTA) using Green’s law (Green, 1838) taken
at low depth, generally around 1 m depth (e.g. Glimsdal et al., 2019; Selva et al., 2016).
TSUMAPS-NEAM was a European project with the objective to evaluate the tsunami hazard along
the European coastlines (TSUMAPS-NEAM, 2020). In this project, peaks offshore amplitudes were
also extrapolated to PCTAs, also using Green’s law.
One of the objectives of the French project TANDEM was to estimate the tsunami hazard along
the French coastlines, especially in the North Eastern Atlantic Ocean and in the French Channel
(TANDEM). DTHA was used on high resolution grids.
However PCTAs obtained from Green’s law approximations provide a crude approximation of wave
heights at the coast only, within a factor of 2 at best (e.g. Gailler et al., 2018).
Also if the results from TANDEM project are more accurate, they only consider the worst probable
scenario. However, smaller events can be significant, especially since they are more frequent.
Introduction
Finding and response
✔ Few historical tsunamis along the French Mediterranean coastlines
✔ Few earthquakes can potentially generate a significant tsunami along the
French Mediterranean coastlines on a human scale
✘ Large coastal populations: Cannes, Nice, Marseille...
✘ non-optimal adaptation of equipment
➜ Evaluation of the hazard down to the coastal level for large return times
✘ Deterministic analysis: a large but far earthquake might generate lower water
height along the French coastlines than a small and close earthquake
✓ Probabilistic Tsunami Hazard Assessement (PTHA)
Commissariat à l’énergie atomique et aux énergies renouvelables Souty & Gailler | EGU2020-5554 | page 7
We foccuse on the tsunami hazard along the French Mediterranean coastlines that is due to
earthquakes.
There are few historical tsunamis and few earthquakes can potentially generate a significant
tsunami along the French Mediterranean coastlines on a human scale.
This is a great thing but it can also become a danger because there are large coastal populations,
such as in Cannes, Nice, especially during summer holidays, that are not aware of the danger.
Moreover there are few adaptations of equipments.
It is then necessary to determine the tsunami hazard along the French Mediterranean coastlines
down to the coastal level (beaches, harbours).
A DTHA approach is not the most adapted due to the few occurence of great events.
We then use Probabilistic Tsunami Hazard Assessment to evaluate the hazard along the
French Mediterranean coastlines down to coastal level.Outline
1. Introduction
1.1 Two recent critical events
1.2 Events within the Western Mediterranean Sea
1.3 Previous studies
1.4 Finding and response
2. Method
2.1 Seismic hazard
2.2 Tsunamis
2.3 From seismic hazard to PTHA
3. Results: Tsunamis impacting Cannes area (z05)
3.1 Extension of the period of observation
3.2 A first overview of the magnitude uncertainties
4. Conclusions and perspectives
4.1 Conclusions
4.2 Perspectives
Commissariat à l’énergie atomique et aux énergies renouvelables Souty & Gailler | EGU2020-5554 | page 7Method
Process overview
Earthquake Fault
datasets dataset
historical unity segments
instrumental Seismogenic
Scaling
zones factor
Rupture
Source
Concatenation
combination catalog
Earthquake Synchronisation
Selection per zone
catalog CLIONA
Seismic hazard per seis-
per zone mogenic zone
multi-grid
shalow water
Calculation of Tsunami
the magnitude PCTAs per tsunami
distribution simulations
Keeping PCTA
from simulation
Distribution results
law per zone PCTA
Aggregation
PTHA
Commissariat à l’énergie atomique et aux énergies renouvelables Souty & Gailler | EGU2020-5554 | page 8
Here is an overview of the method we use to determine tsunami hazard, due to earthquakes, along
the French Mediterranean coastlines.
On the left side, we determine the seismic hazard, from the collect of the data to the distribution
law of the magnitude.
This is necessary as the probability of having a tsunami with a given intensity is directly linked to
the probability of the earthquake that can triggered that tsunami.
On the right side, we determine all the probable scenarios of rupture that can trigger a tsunami and
simulate these scenarios to get the PCTAs down to the coastal level.
Whether for seismic hazard or for tsunamis scenarios, we work by seismogenic zone (more details
are given here after).
The distribution law of the magnitude and the PCTAs are
then combined to process the PTHA.Method
Seismic hazard
Catalogue of reference
−5°45' 0°00' 5°45' 11°30'
✔ Synchronization of several datasets∗
Mw1 Offshore andMethod
Tsunamis
−5° 0° 5° 10° 15°
45° 45° cannes [6.9810°E; 43.5438°N; -201m]
Zones
0.4
1 2 3 4 5 6 7 8
Reverse fault 0.3
Normal fault
Strike-slip fault
0.2
Water elevation [m]
0.1
0.0
40° 40°
(1) (2) −0.1
−0.2
−0.3
−0.4
(3)
hmax on crude grid: 0.46m
hmax-apriori (z=1m):1.73m
−0.5
B) Rupture combination 0 20 40 60 80
Propatation time [min]
100 120
C) Simulation on crude grid
Elevation
(Gailler et al., 2013)
35° 35°
−4 −2 0 2
0 125 250
km
−5° 0° 5° 10° 15°
Zone z05
A) CENALT fault database Scenarios having h_apriori=1cm
80
E) High resolution simulations (15cm,72%)
5cm
h_thr=1cm
z05-001577-74-3u 60
h_simu>=hthr[1cm] [%]
6°57' 7°00' 7°03'
43°36' m43°36'
40
F) Peak Coastal Tsunami Amplitudes
0 1 2 3 4 5
Maximum water elevation
6'
43°3
u 20
4-37°
1 2 3 4 5 6
5 77-7 03'
-001'
z05
hmax
7°00
m 0 148 scenarios 10 scenarios
' 6
6°57
4 n
atio 43°33' 43°33'
2 elev 3' 0 2 4 6 8 10 12 14 16
water 43°3
(5)
6'
43°3 0
im um max(h_simu) [cm]
Max
(4) D) Selection of
0'
significative events
43°3
using Green’s law
3'
43°3
43°30' 43°30'
0' 7° 03'
43°3
'
7°00
6°57' 7°00' 7°03'
'
Commissariat à l’énergie atomique et aux énergies renouvelables
6°57
Souty & Gailler | EGU2020-5554 | page 10
(A) We use the fault database of the French Tsunami Warning Center (CENALT) to build a cata-
logue of ruptures. The fault database consists in a unit source function system which follow the
major structural trends of the Western Mediterranean basin seismogenic context (Gailler et al.,
2013).
(B) We combine unit sources to build a rupture (20 km wide, 25 km length, 1 m slip, Gailler et al.
(2013)).
Lengths and widths of combined unit sources follow Wells and Coppersmith (1994) laws (fixing
L = 200 km for Mw = 8.0) and the slip is scaled by a factor Fs in order to fit the moment magnitude
Mw .
The combination is controlled geometrically by the distance between two unit sources and the
azimuth difference between these two sources. The distance between two faults is set between
18.5 km and 37.5 km and the azimuth difference is set lower than 40◦ .
The available combinations of unit source in a seismogenic zone give the maximum moment mag-
nitude in the zone.
(C) A first tsunami simulation of each rupture is done in a crude grid in order to collect Peak Off-
shore Tsunami Amplitde (POTA) where the water depth is ∼100 m (CLIONA code, CEA). We then
use the Green’s law (Green, 1838) to extrapolate each POTA to an a priori PCTA hmaxapriori (PCTA).
(D) We then select all rupture for which hmaxapriori is greater than or equal to 1 cm. This reduces
the number of high-resolution simulation to do, and thus reduces the computational time. This
method of selection was configure using high-resolution simulations, on Cannes area, of all ruptures
in the Ligurian zone (z05), for magnitudes between 5.5 and 7.4.
(E) We run CLIONA code (CEA, e.g. A.Poupardin et al., 2018) using shallow water equations and
nested-grid resolution down to the coastal level (10 m) for each rupture selected in (D). The length
of the simulation is adapted for each seismogenic zone, here again to reduce the computational time.
(F) Last step, here consists in collecting the PCTAs. The resultant files are smaller and easier to
use than grids.Method
From seismic hazard to PTHA
A) Seismic hazard
Best distribution law per seismogenic zone
B) Tsunamis
43°36'
101 4-3u
1 2 3 4 5 6
z01 z05 77-7 7°03'
0015
z02 z06 z05-
hmax
7°00'
m
0
10 z03 z07 6°57'
6
tion
Annual rate (1/yr)
4
z04 z08 2 eleva
43°36' water 43°33'
0 um
Maxim
10−1
10−2
43°33' 43°30'
10−3
7°03'
10−4 43°30'
no magnitude conversion 7°00'
6°57'
4 5 6 7
Moment magnitude (Mw)
C) Probability of occurence
` of´a rupture scenario
– Mw
i
Pi = ` ´
Nscenario Mw
i
D) Probability
` of exceedance
´ P of a`PCTA at a site of referecence´
P (x, y)ref , PCTAref = Pi (x, y )ref , PCTA ≥ PCTAref
i
E) Hazard maps F) Probability maps
riod
20 40 60 80 100
30 60 90 120 150
d 43°36'
rio
rn pe7°03' rn pe 43°36'
r retu7°03'
Probability [%]
r retu
hmax [cm]
-yea -yea
25000'
6°57'
2500
120
cm
150
7°00'
PTHA 50cm
6°57'
in a 7°0
100
%
90 80
43°36' 30
60 43°33' 40
60
y 43°33'
0
hmax 43°36' 0
20
abilit
Prob
43°33' 43°30' 43°30'
43°33'
od of
Peri A: od of
: z05. the PTHarii: Peri A:
ce zone to
do
of scen of : z05. the PTHarii:
do
Sour rvati on ber Num ber es. ce zone to of scen of
obse 0yr. Num s. quak Sour rvati on ber Num ber es.
1000 scen ario 80 earth obse 0yr. Num s. quak
1577 quakes: 14:2
6:37 1000 scen ario 80 earth
earth -04-08 1577 quakes: 14:1
3:00
ation 0 2020
ation
earth -04-08
Elev −500 0 2020
m
Elev −500 m
43°30' 00 7°03' 7°03'
−10 43°30' −10
00
7°00' 7°00'
6°57' 6°57'
Commissariat à l’énergie atomique et aux énergies renouvelables Souty & Gailler | EGU2020-5554 | page 11
(C) The annual probability P of each scenario i, during the period T , is given by the (A) annual
rate of its moment magnitude Mw which is determined from the distribution law and by the (B)
number of probable scenarios that can generate an earthquake of magnitude Mw .
The annual probability of each PCTA is equal to
the annual probability of its rupture scenario.
(D) The annual probability of exceeding a PCTA, at each place, is computed by aggregation of
any rupture scenario that can exceed a given PCTA, such that the annual probability is the sum of
the annual probability of each rupture scenario triggering a tsunami that exceeds the chosen PCTA
at the chosen place.
We can use these annual rates and this probabilities to plot (E) hazard maps, which give the maxi-
mum water elevation in a return period, or to plot (F) probability maps, which show the probability
of experiment a water elevation during a return pediod. Probability curves can also be given.Outline
1. Introduction
1.1 Two recent critical events
1.2 Events within the Western Mediterranean Sea
1.3 Previous studies
1.4 Finding and response
2. Method
2.1 Seismic hazard
2.2 Tsunamis
2.3 From seismic hazard to PTHA
3. Results: Tsunamis impacting Cannes area (z05)
3.1 Extension of the period of observation
3.2 A first overview of the magnitude uncertainties
4. Conclusions and perspectives
4.1 Conclusions
4.2 Perspectives
Commissariat à l’énergie atomique et aux énergies renouvelables Souty & Gailler | EGU2020-5554 | page 11Results: Tsunamis impacting Cannes area (z05)
Extension of the period of observation
1a) Hazard map using recorded events 1b) Probability map using recorded events
20 40 60 80 100
od
20 40 60 80 100
od 43°3
6'
eri 6'
rn p
43°3
peri 03'
Probability [%]
turn r retu 7°03'
hmax [cm]
a
0-ye
7°
-ye ar re
500 00' a 507°00'
7°
m in
' cm 20c ' %
6°57 6°57
100 100
80 80
60 3' 60
6' 40 43°3 9° ty 3'
6' 40 43°3
43°3
max
6° 7° 8°20
abili
20 43°3
0
h
Prob
0
Historical earthquakes (Mw>6.0)
z05
0' 0'
43°3
3' 44° 43°3 3' 44° 43°3
Mw6.1 (1644) 43°3
Mw6.7 (1887)
d of d of
Pe rio HA : Pe rio HA :
z05 . the PT z05 . the PT
ne : rii: 11 Cannes area ne : rii: 11
e zo n to do scena r o f e zo n to do scena r o f
So urcrva tio mber of u m b e ke s. So urcrva tio mber of u m b e ke s.
ob seyr. Nu s . N thq ua ob seyr. Nu s . N thq ua
827 n a r i o es : 4 ear Mw6.3 (1963)
:25 Mw6.3 (1854) 827 n a r i o es : 4 ear
sce qu ak 15:51 sce
:30
qu ak 15:55
n ea rth -04-08
n
atio
ea rth -04-08
Elev −500
0 2020
atio 0 2020
m
' 43° 43° Elev −500 m
'
43°3
0'
−100
0 7°03 0' 0 7°03
43°3 −100
' 6° 7° 8° 9°
7°00 '
7°00
'
Recorded earthquakes
6°57 '
6°57
2a) Hazard map using synthetic events 2b) Probability map using synthetic events
od
20 40 60 80 100
20 40 60 80 100
6'
eri 6'
rn p
d 43°3 43°3
erio
Probability [%]
rn p 7°03' a r retu 7°03'
hmax [cm]
retu 0-ye
ear a 507°00'
5 00-y 7°00' m in
' cm
20c ' %
6°57 6°57
100 100
80 80
60 3' 60 3'
6' 40 43°3 6' 40 ty 43°3
43°3 20
hma
x 43°3 20
abili
Prob
0 0
0' 0'
43°3
3' 43°3 43°3
3' 43°3
d of d of
Pe rio HA : Pe rio HA :
z05 . the PT rii: z05 . the PT rii:
ne : na ne : na
e zo n to do of sce er of e zo n to do of sce er of
So urcrva tio mber Nu mbuakes. So urcrva tio mber Nu mbuakes.
ob se00yr. Nurio s. ob se00yr. Nurio s.
earthq earthq
100 sce na : 36 :57 100 sce na : 36 :38
11 12 quakes 16:35 11 12 quakes 16:46
n earth -04-08 n earth -04-08
atio 0 2020
atio 0 2020
Elev −500 m
'
Elev −500 m
'
43°3
0'
−100
0 7°03 43°3
0'
−100
0 7°03
' '
7°00 7°00
57' '
Commissariat
6°
à l’énergie atomique et aux énergies renouvelables 6°57
Souty & Gailler | EGU2020-5554 | page 12
We now present some results of the PTHA along the coastlines in Cannes city area.
Earthquakes sources are located in the Ligurian Sea (z05). High-resolution simulations from other
seismogenic zones are not finished yet.
The hazard maps for a 500yr return period are shown on the left side, and the probability
to experiment at least 1 tsunamic wave having hmax ≥ 20 cm in a 500yr return period on
the probability maps on the right side.
At the top, results are given using only the 4 earthquakes, with Mw ≥ 6.0, recorded in the
real period of observation of 827yr. The 4 earthquakes are shown in the centered map.
At the bottom, results are given for the 36 earthquakes of Mw ≥ 6.0 that can occur during
an extended period of observation of 10 000yr. This number of earthquakes is obtained
using the distribution law (MBS+Weichert, dM0.2, dy1).
11 scenarios correspond to the 4 recorded earthquakes, 1112 scenarios can generate
earthquakes of Mw ≥ 6.0 in the Ligurian Sea seismogenic zone.
Looking at the hazard maps, we observe that the maximum water elevation is quite similar whether
we choose to use the (1a) real period of observation or the (2a) extended period of observation.
However, the probability of experiment at least one wave height equal to or greater than 20 cm in a
500yr return period is different whether we choose to use the (1b) real period of observation or the
(2b) extended period of observation.
Indeed the extension of the period of observation allows the model to take into account much more
probable scenarios.
This first result illustrates that hazard maps are not
self-suficiant to describe the tsunami hazard.Results: Tsunamis impacting Cannes area (z05)
Extension of the period of observation
3a) Hazard map using recorded events 3b) Probability map using recorded events
20 40 60 80 100
d
20 40 60 80 100
od 43°3
6'
erio 6'
peri03' rn p 43°3
r retu7°03'
Probability [%]
turn
hmax [cm]
r re
7°
ea
-yea 00-y
2 500 7°00
'
a 25 7°00'
m in
6°57
' cm 50c % '
100 6°57
80 100
60 3' 80
60
6' 40
x 43°3 3'
43°3
bility 43°3
20 6° 7° 6' 8° 40 9°
0
hma 43°3 20
a
Prob
0
Historical earthquakes (Mw>6.0)
z05
0'
43°3
3' 44° 43°3 3' 44° 43°3
0'
Mw6.1 (1644) 43°3
Mw6.7 (1887)
d of
Pe rio HA : d of
z05 . the PT Pe rio HA :
ne : rii: 11 Cannes area z05 . the PT
e zo n to do scena r o f ne : rii: 11
So urcrva tio mber of u m b e ke s. e zo n to do scena r o f
ob seyr. Nu s . N thq ua So urcrva tio mber of u m b e ke s.
827 n a r i o es : 4 ear Mw6.3 (1963) ob seyr. Nu s . N thq ua
sce
:25 Mw6.3 (1854) 827 n a r i o es : 4 ear
qu ak 15:51 sce
:30
qu ak 15:55
n ea rth -04-08
atio 0 2020
atio
n ea rth -04-08
Elev −500
0 2020
m
' 43° 43° Elev −500 m
43°3
0'
−100
0 7°03 0' 0 7°03
'
43°3 −100
' 6° 7° 8° 9°
7°00 7°00
'
'
Recorded earthquakes
6°57 6°57
'
4a) Hazard map using synthetic events 4b) Probability map using synthetic events
d
20 40 60 80 100
20 40 60 80 100
6' erio 6'
erio
d 43°3
rn p 43°3
r retu7°03'
Probability [%]
rn p 7°03' ea
r retu
hmax [cm]
-yea 00-y
500 ' a 25 7°00'
2 7°00
m in
' cm 50c % '
6°57 6°57
100 100
80 80
60 3' 60 3'
6' 40 43°3 6' 40 ty 43°3
43°3 20
hma
x 43°3 20
abili
Prob
0 0
0' 0'
43°3
3' 43°3 43°3
3' 43°3
d of d of
Pe rio HA : Pe rio HA :
z05 . the PT rii: z05 . the PT rii:
ne : na ne : na
e zo n to do of sce er of e zo n to do of sce er of
So urcrva tio mber Nu mbuakes. So urcrva tio mber Nu mbuakes.
ob se00yr. Nurio s. ob se00yr. Nurio s.
earthq earthq
100 sce na : 36 :57 100 sce na : 36 :38
11 12 quakes 16:35 11 12 quakes 16:46
n earth -04-08 n earth -04-08
atio 0 2020
atio 0 2020
Elev −500 m
'
Elev −500 m
'
43°3
0'
−100
0 7°03 43°3
0'
−100
0 7°03
' '
7°00 7°00
57' '
Commissariat
6°
à l’énergie atomique et aux énergies renouvelables 6°57
Souty & Gailler | EGU2020-5554 | page 12
We now increase the length of the return time of the analysis from 500yr to 2500yr.
The hazard maps for a 2500yr return period are shown on the left side, and the probability
to experiment at least 1 tsunamic wave having hmax ≥ 50 cm in a 2500yr return period
on the probability maps on the right side.
At the top, results are given using only the 4 earthquakes, with Mw ≥ 6.0, recorded in the
real period of observation of 827yr. The 4 earthquakes are shown in the centered map.
At the bottom, results are given for the 36 earthquakes of Mw ≥ 6.0 that can occur during
an extended period of observation of 10 000yr. This number of earthquakes is obtained
using the distribution law (MBS+Weichert, dM0.2, dy1).
11 scenarios correspond to the 4 recorded earthquakes, 1112 scenarios can generate
earthquakes of Mw ≥ 6.0 in the Ligurian Sea seismogenic zone.
Here the hazard maps are different whether we are looking at (3a) real period of observation or (4a)
the extended period of observation.
Indeed, the return time is now greater than the period of observation. It is then a non-sens to
look at the results from the real period of observation.
The maximum water elevation is here biased because the same 11 scenarios are repeated here
to reach the 2500yr return period instead of creating earthquakes elsewhere in the seismogenic
zone.
This also leads to inconsistent probabilities. Indeed according to the (3b) probability map, there
is almost no-probability to experiment a 50 cm in a 2500yr when considering only the recorded
earhtquakes.
Yet, when we look at the (4b) probability map when using the extended period of observation, the
probabiliy to experiment a 50 cm in a 2500yr is rarely lower than 30 %.
The bias induded by the period of observation can have a great impact on the PTHA and thus
on civil and building engineering.
It is then necessary to enlarge the period of observation using distribution laws.Results: Tsunamis impacting Cannes area (z05)
A first overview of the magnitude uncertainties
Adding uncertainties to
the magnitude
×100
or more
Processing PTHA
Aggregation
Commissariat à l’énergie atomique et aux énergies renouvelables Souty & Gailler | EGU2020-5554 | page 13
We want to look at the sensibility of the model due to the uncertainty on magnitudes.
We then duplicate, let’s say 100 times, the catalogue of reference and add an uncertainty on the
magnitude of each record.
The uncertainty is added following a normal law where the mean is the recorded magnitude and the
standard deviation is the error on the magnitude. Here we have choosen a 0.2 uncertainty.
We then process the PTHA for each duplicated catalogue as described in the method section.
Finally, we aggregate the results.
In this example we choose to show the results as hazard curves.Results: Tsunamis impacting Cannes area (z05)
A first overview of the magnitude uncertainties
Aggregation
Annual Probability of
Case
probability (%) experiment1 (%)
Reference 5.72 94.74
Mean 9.65 99.37
2nd percentile 5.72 94.74
16th percentile 5.94 95.32
Median 6.98 97.32
84th percentile 13.60 99.93
98th percentile 15.40 99.98
1 Probability of experiment at least one wave tsunami
equal to or greater than 1 m in a 50-year return period.
✔ Annual probability of exceedance of a
maximum water elevation at any place
along the coastline
➟ Work in progress...
➟ Annual probability of exceedance of a
maximum water elevation at a chosen
place along the coastline
Commissariat à l’énergie atomique et aux énergies renouvelables Souty & Gailler | EGU2020-5554 | page 13
At the top left, the curves in the show the annual probability of exceedance of a PCTA at any
place along the coastlines of the studied area.
Each grey curve show the results from 1 duplicated catalogue.
The cyan curve show the results from the catalogue of reference.
The blue and red curves show the mean and mediane hazard curves, respectively, from
all the duplicated catalogues and the catatalogue of reference.
The median curve show that the probability to experiment a 1 m PCTA anywhere in the Gulf of La
Napoule (Cannes city area) in a 50-year return period is ∼97.32 %1 (annual probability of∼6.98 %).
In the present case, it increases the probability in regards of the probability we would have using
only the catalogue of reference (∼94.74 %, annual probability of∼5.72 %).
This work is still in progress, but a particular place could have been chosen to study the sensibility
due to uncertainties on the magnitudes.
Sensibility analyses can also be done on other parameters during the PTHA process. Such
as the choice of the method to determine the distribution laws.
1
P = 1 − (1 − pannual )TOutline
1. Introduction
1.1 Two recent critical events
1.2 Events within the Western Mediterranean Sea
1.3 Previous studies
1.4 Finding and response
2. Method
2.1 Seismic hazard
2.2 Tsunamis
2.3 From seismic hazard to PTHA
3. Results: Tsunamis impacting Cannes area (z05)
3.1 Extension of the period of observation
3.2 A first overview of the magnitude uncertainties
4. Conclusions and perspectives
4.1 Conclusions
4.2 Perspectives
Commissariat à l’énergie atomique et aux énergies renouvelables Souty & Gailler | EGU2020-5554 | page 13Conclusions
Current results: Tsunami-earthquakes from Ligurian Sea impacting Cannes area
✓ Needs of synthetic catalog to improve the analysis
✓ Probability of experiment a 1 m PCTA anywhere in the Gulf of La Napoule in a 50-year return period
❏ ∼94.7 % when considering no uncertainty on the magnitude
❏ ∼97.3 % when considering uncertainties on the magnitude (median curve)
➟ Simulations in progress
Challenges
❏ Large amount of data to manage Earthquake entries, Results of the tsunami, Aggregation of the results
❏ Many uncertainties to take into accounts at different steps of the analysis Earthquake parameters, Distribution law,
Rupture scenarios, Tsunami simulations
❏ High number of high-resolution simulations: long computational time
Our answers
❏ Semi-automatic processing with structured data hierarchy (➟ work in progress)
❏ Sensibility analysis (➟ work in progress)
❏ Reduction of the number of the high-resolution simulations using Green’s law on low-resolution
simulations (hmaxapriori )
Commissariat à l’énergie atomique et aux énergies renouvelables Souty & Gailler | EGU2020-5554 | page 14Perspectives
PTHA
❏ Highlighting the areas that can be the most affected at the level of a municipality
❏ Tracking the most threatening areas (deaggregation)
Other high-resolution maps (10 m)
2° 3° 4° 5° 6° 7° 8° 9°
44° 44°
❏ Antibes [5] 5
6
4
2
❏ Bandol [3] 43° 3
B3
43°
1
Leucate [1]
B2
❏ B1
Nice [6]
42° 42°
❏
Sete [2]
A
❏ 41° −2000
Elevation
0 2000 41°
m
2° 3° 4° 5° 6° 7° 8° 9°
Application to the North Atlantic French coastlines
❏ Increase of the quantity of data
❏ Increase of the time of propagation to simulate
❏ Increase of the number of simulations
Commissariat à l’énergie atomique et aux énergies renouvelables Souty & Gailler | EGU2020-5554 | page 15DE LA RECHERCHE À L’INDUSTRIE [EGU2020-5554]
Thank you for your attention.
6 May, 2020
E.G.U. General Assembly 2020 Viviane Souty & Audrey Gailler
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