Tsunamis in the European-Mediterranean Region : from historical record to risk mitigation

280 Pages·2016·28.586 MB·English

by  Papadopoulos, Gerassimos A

TSUNAMIS IN
THE EUROPEAN-
MEDITERRANEAN
REGION
From Historical Record
to Risk Mitigation
GERASSIMOS PAPADOPOULOS
Institute of Geodynamics, National Observatory
of Athens, Greece
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This book is dedicated to Ioanna with all my love.
PREFACE
Tsunamis are one of the most important sea-related natural hazards. Practi-
cally speaking, coastal zones of all the oceans around the globe are exposed
to tsunami hazard. This is also the case in the European and Mediterranean
region where the historical tsunami record is the oldest on Earth. After the
mega tsunami of December 26, 2004 in the Indian Ocean, which was very
likely the most lethal in history, claiming around 220,000 human lives, the
international community was mobilized aiming to develop actions for the
tsunami risk mitigation. Writing this book is a contribution in this direction
for it contains material which is useful not only to specialists but also to civil
protection personnel and decision makers as well as to the general public.
After the introductory Chapter 1, which reviews fundamental global
tsunami issues, including essays on the tragic tsunami events of 2004 in
Indian Ocean and 2011 in Japan, the book covers all the aspects regarding
the tsunami science, engineering, and risk mitigation in the European and
Mediterranean region (EM).
Chapter 2 is an exhaustive overview of the historical evidence which is
available for the tsunami documentation in the EM region. The geological
record, both onshore and offshore, dated either in prehistoric or in historic
times, has not been neglected. On the contrary, it is critically discussed as
potential discriminator between tsunamis and other extreme sea waves, such
as storm surges. The picture of the tsunami history is completed by archaeo-
logical observations. The instrumental documentation of the EM tsunamis
in the last century or so is valuable for understanding important tsunami
events, including the earthquake-generated tsunamis of 1908 in the Messina
Strait (Italy), 1956 in the South Aegean (Greece), 1969 in Portugal, 1999 in
Marmara Sea, and 2003 in North Algeria, as well as the landslide tsunamis of
1963, 2002, and 2014 in the west Corinth Gulf (Central Greece), Stromboli
volcano (Italy), and western Norway, respectively.
Thanks to the long historical record, the tsunami impact in the EM region
is also documented and analyzed in Chapter 3. An inventory of past tsunami
impact has indicated that the main impact attributes are people killed and
injured, damage to buildings, vessels, cultivated land, and to other property.
In addition, of interest are also the various types of tsunami environmental
impact, such as soil erosion, coastal geomorphological changes, boulder re-
placement and tsunami sediment deposition. On the basis of tsunami impact
ix
x Preface
data, it was possible to assign tsunami intensity in the 12-point Papadopoulos
and Imamura (2001) scale for the majority of the events listed in the histori-
cal record (Appendix). It has been found that historically the largest impact
happened in the eastern Mediterranean Sea basin.
Chapter 4 focuses on the tsunami generation mechanisms. In the EM
region, a variety of seismic and nonseismic tsunami source types have been
recognized, such as seismic, volcanic, landslides. However, the generation
mechanisms are precisely known only for a limited number of tsunamis.
Even for instrumentally recorded events, such as the 1908 Messina and 1956
South Aegean tsunamis, the precise generation mechanism remain undeter-
mined due to their high complexity which may involve several mechanism
components, for example, seismic and landslide or volcanic and landslide,
and so on. Criteria used to discriminate between the different source types
include empirical relationships concerning the attenuation and the runup
of tsunamis, as well as the slowness factor which characterizes the slip in the
earthquake fault. The geographic zonation of tsunami sources is illustrated
and some good examples of tsunami-generation mechanisms are analyzed.
Rare types of tsunamis are also examined, such as meteotsunamis, tsunamis
caused by asteroid impacts and from landslides in dams, as well as tsunami-
like disturbances in lakes. Numerical simulations are a particularly valuable
tool in the effort to understand the tsunami-generation mechanisms and
source types. The relevant progress noted in the EM region is remarkable
and internationally recognized. Therefore, this is particularly examined in
Chapter 5.
The assessment of the tsunami hazard, vulnerability, and risk is a major
issue since it is the basis to organize and apply land planning, crisis manage-
ment, and other risk mitigation actions. Chapter 6 starts with a review of
the glossary which is in use to express terms such as hazard, vulnerability,
exposure, damage, intensity, risk, and the like. Then, the various methods
and tools used for the assessment of the tsunami hazard, vulnerability, and
risk in the EM region and beyond are examined. It has been found that
significant progress has been made in the probabilistic and scenario-based
assessment of the hazard and vulnerability although several sources or errors
and uncertainties are involved. The tsunami risk assessment, however, is less
developed. Therefore, more research effort should be put in this direction.
On the other hand, the vulnerability and risk are strongly dependent on the
degree of the community exposure to hazard. Of crucial importance are
factors that control the time dependency of vulnerability and risk. All the
various methods applied for the hazard assessment, qualitative, statistical, and
Preface xi
probabilistic ones, agree that the most hazardous geotectonic structure in
the EM region is the Hellenic Arc, in both the local (near-field) and remote
(far-field) domains.
Chapter 7 provides an updated overview of the local, national, and re-
gional tsunami early warning systems, either operational or prototype ones,
that have been developed in the EM region particularly after 2004. Tsunami
warning operations are supported by a variety of instrumental networks, al-
gorithms, databases, communication technologies, and empirical tools. The
most important regional system is the North East Atlantic and Mediter-
ranean Tsunami Warning System, which is based on a number of national
tsunami warning centers, for example, in France, Greece, Italy, Portugal,
Turkey, and is coordinated by the ICG/NEAMTWS/IOC/UNESCO
with the active collaboration of more than 30 country members. The activi-
ties of NEAMTWS are supported by the educational and training program
of NEAMTIC. Of special value is also the JRC (European Commission)
Tsunami Program which supports building up infrastructures, algorithms,
databases, and training activities in emergency procedures. Good examples
of local systems are the ones developed for early warning in the near-field
domain against landslide-generated tsunamis in Stromboli Island (Italy), and
against earthquake-generated tsunamis in Rhodes Island (Greece). More
and more new emerging technologies appear, thus providing promises for
the drastic improvement of the early warning services in the years to come.
Of particular importance are also tsunami exercises, drills, communication
tests, education, and training activities as well as other actions aiming to
mitigate the tsunami risk in the EM region.
ACKNOWLEDGMENTS
My first involvement in the tsunami science dates back to 1983. Writing
this book would not be possible without the research, educational and
operational experience accumulated since then. Of particular value to me
has been my participation in several relevant projects supported by the
European Union, such as GITEC, GITEC-TWO, TRANSFER, SAFER,
SCHEMA, SEAHELLARC, NEARTOWARN and ASTARTE as well
as in national and bilateral projects supported mainly by the General Secre-
tary for Research and Technology, Greece. Serving from various positions
and with a variety of roles in the program of ICG/NEAMTWS/IOC/
UNESCO, in the JRC Tsunami Program and in the national tsunami cen-
ter of Greece, is highly appreciated.
In the last 30 years or so I have had the opportunity to collaborate with
a large number of colleagues, students, and decision makers. I would like
to extend to all of them my sincere thanks and deep appreciation for their
constant spirit of collaboration, support, and friendship. Our collaboration
in research projects, field expeditions, jointly writing papers, participating
in conferences and various committees as well as exchanging ideas and
experiences constitute valuable inputs for collecting material, organizing,
and writing this book. The list is too long to mention all of them but cer-
tainly includes S. Tinti, A. Armigliato, R. Caputo, P. Gasparini, S. Lorito, A.
Maramai, A. Michelini, D. Pantosti (Italy); A. Yalciner, N. Karanci, U. Kuran,
O. Necmioglu, N. M. Ozel (Turkey); M.-A. Baptista, F. Carrilho, L. Matias,
L.-V. Mendes (†) (Portugal); R. Dov, A. Salamon, A. Shapira (Israel); R.
Guillande, H. Hebert, F. Lavigne, O. Lesne, F. Schindele (France); A. Dawson,
T. Guymer (UK); F. Imamura, H. Matsumoto, K. Minoura, T. Nakamura,
K. S atake, D. Sugawara, T. Takahashi (Japan); V. Gusiakov, B. Levin, L. I.
Lobkovsky, R. Mazova, E. Pelinofsky, A. Rabinovich, E. Sasorova (Russia);
D. D ominey-Howes (UK/Australia), S. Kortekaas (The Netherlands/ Australia);
B. Ranguelov ( Bulgaria); A. Rudloff, J. Zschau (Germany); M. González, E.
Gràcia (Spain); G. Georgiou (Cyprus); C. Ionescu, G. Marmureanu (Romania);
C. B. H arbitz (Norway); A. Kijko, A Smit (S. Africa); E. Bernard, B. McAdoo,
F. McCoy, V. Titov (USA); E. Argyris, Th. Dermentzopoulos, Ch. Koutitas,
V. Lykousis, M. Papathoma, J. Papoulia, S. Pavlides, D. Sakellariou (Greece);
A. Annunziato (JRC, EC) and O. Imperiali (DG-ECHO, EC).
xiii
xiv Acknowledgments
I also thank warmly all my colleagues at the Institute of Geodynam-
ics and the Hellenic National Tsunami Warning Center, National Obser-
vatory of Athens (Greece), particularly M. Charalambakis, E. Daskalaki,
A. Fokaefs, A. Ganas, V. Karastathis, N. Liadopoulou, G. Minadakis, T.
Novikova, K. Orfanogiannaki, A. Plessa, G. Stavrakakis (†), A. Tselentis,
to mention a few. Thanks to their encouragement, support, and collabora-
tion that made it possible not only to promote the tsunami research at our
institute but also to build up and run the national tsunami-warning center.
My close collaboration with the Tsunami Unit of IOC/UNESCO goes
back to the 1990s. I am grateful to all the people that served and still serve
with IOC for their constant support, collaboration, and friendship.
G.A. Papadopoulos
August 2015
INTRODUCTION
A tsunami is a series of sea waves with long period and long wavelength
generated by an abrupt deformation of the seafloor or by other sudden dis-
turbance of the sea water level. The energy of vertical movement of such a
disturbance is transferred to the water mass and causes a sea level change at
the source region. Underwater and/or coastal earthquakes, volcanic erup-
tions, as well as landslides are natural processes that can generate a tsunami.
However, strong earthquakes remain the most frequent cause of tsunamis.
Large meteorites that may impact the ocean should not be ruled out as pos-
sible agents of tsunami generation. One should not neglect anthropogenic
actions that may result in tsunami production, for example, submarine nu-
clear bomb testing. Tsunami waves propagate outward from the generating
area in all directions, the main direction of energy propagation being con-
trolled by the dimensions and orientation of the causative source. During
its propagation in deep water, the tsunami proceeds as a series of ordinary
gravity waves with a speed depending on the water depth. In the near-shore
domain, a large amount of energy is carried by both the amplified water
level and strong currents. Hence, tsunamis cause scouring, erosion, deposi-
tion, slope failures as well as damage or even destruction in coastal com-
munities, marine structures and other facilities, cultivated land, and natural
environment.
In the European-Mediterranean (EM) region, tsunami generation has
been documented with frequency that varies from one area to another. In
the Mediterranean region, the seismic activity is high due to active geo-
dynamic processes such as the convergence of the Eurasian and African
lithospheric plates (Argus et al., 1989; De Mets et al., 2010). Subduction
of oceanic crust and/or collision takes place along active orogenic belts,
namely from west to east, the Gibraltar Arc, the Calabrian Arc, the Hellenic
Arc, and the Cyprus Arc. Ongoing motion along transform boundaries of
adjacent plates, such as the Arabian plate and smaller crustal blocks, such
as the Anatolian “micro-plate,” add more complexity to the active Medi-
terranean geodynamics and the resulting geological processes (see also in
Mascle and Mascle, 2012). Instead, the regions of the North East Atlantic
Ocean, the North Sea and the Baltic Sea are characterized by low seismic-
ity, with the exception of the area offshore South West Iberia. The Black
Sea is also of low seismicity. Therefore, the tsunami activity is much higher
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xvi Introduction
in the Mediterranean, including the area offshore of South West Iberia, as
compared to the other European sea regions. Although the frequency of
tsunamis in the Mediterranean is much less than the frequency of strong
earthquakes, tsunamis threaten seriously the communities along the coastal
zones of the Mediterranean basin (e.g., CIESM, 2011). This is also the case
for the rest of the European coastal zones.
Tsunami generation in the EM region is dependent on several geo-
dynamic processes taking place in submarine or in coastal environments,
which mainly include earthquake activity, several mechanisms associated
with volcanic eruptions, and landslide processes. Tsunami activity from pre-
historical times up to the present has been documented in the EM region
from a variety of information sources. In fact, geological evidence, mainly
onshore and more rarely offshore tsunami sediment deposits, geomorpho-
logical features, historical documentary sources, archeological findings, as
well as instrumental data and observations collected during post-event field
surveys, have provided a long record of tsunami events (Papadopoulos et al.,
2014a). Only a few of those events were basin-wide; others, however, were
either regional or only local tsunamis. In addition, in the EM region it
has been reported the presence of the so-called meteotsunamis (Monser-
rat et al., 2006) that are tsunami-like sea waves attributed to atmospheric
changes rather than to seismic and other geodynamic processes.
With the aim to organize actions toward the tsunami risk mitigation,
there is need to have a good knowledge of the past tsunami activity, to iden-
tify potential tsunami sources and better understand the generation mecha-
nisms particularly in the frame of complex geodynamic setting such as the
one which, for example, characterizes the Mediterranean region. Another
important issue is to characterize tsunami sources, in other words to im-
prove our capabilities to discriminate between seismic and aseismic mecha-
nisms. As a matter of fact, for many historical and recent tsunami events the
causative sources and generation mechanisms still remain unidentified.
After the devastating Indian Ocean tsunami that generated in Sumatra
on the December 26, 2004, a systematic effort was put forward for building
up the North East Atlantic and Mediterranean Tsunami Warning System
(NEAMTWS), beginning in November 2005. The country members of
the Intergovernmental Oceanographic Commission (IOC) of UNESCO,
working together under the umbrella of IOC, have established the NEAM-
TWS which today functions in an interim operational status based on the
synergy of a number of national tsunami warning centers. In parallel to this,
other actions aiming at tsunami risk mitigation, such as tsunami alerting