This is Chapter 2, First Part, the Main Events
New Catalogue of the book Historical Earthquakes and Tsunamis
in the Corinth Rift, Central Greece, G.A. Papadopoulos (Ed.),
Publication No. 12, Institute of Geodynamics, National Observatory
of Athens, 129pp., Athens, 2000.
The book includes a set of another three Chapters
as follows:
Chapter 1: Editorial
Chapter 2: consists
of the present explanatory text and the
New Historical Earthquake Catalogue.
Chapter 3: A New
Tsunami Catalogue of the Corinth Rift:373-B.C.-A.D.2000
Chapter 4: An Unknown
Historical Earthquake in the Fili Region?
For further information about the book please contact
with
Dr G.A. Papadopoulos
Research Director
Institute of Geodynamics
National Observatory of Athens
11810 Athens , Greece
tel.+fax: 30210-3490165
e-mail: g.papad@gein.noa.gr
A New Catalogue of Historical Earthquakes in
the Rift of Corinth, Central Greece
G.A. Papadopoulos * , A. Vassilopoulou and A. Plessa
Institute of Geodynamics , National Observatory of Athens, 11810
Athens, Greece
*e-mail: g.papad@gein.noa.gr
I. Introduction
The region covered by the New Earthquake Catalogue
is that of the Corinth Rift as it defined in Chapter 1 of the
present volume. The catalogue covers the time interval from the
5th century B.C. to the A.D.1910 inclusive because from 1911 onwards
a systematic instrumental monitoring and recording of the Greek
earthquakes started by the Institute of Geodynamics, National
Observatory of Athens (NOAGI,) after the installation on 1910
of a good-quality Mainka type seismograph .
Thanks to the data sources used and the method of data analysis
applied (see section "IV. Method"), we were able to
identify not only main events but also dependent events, that
is foreshocks and aftershocks associated with some of the main
events . The long aftershock sequences associated with particular
large earthquakes occurring in the Corinth Rift during the 19th
century were already noticed by the end of that century. For example,
Mitzopulos (1893) reported on that the aftershock sequence of
the 1 August 1870 large shock lasted for about three years.
The New Earthquake Catalogue consists of four main parts: the
First Part is the Main Events New Catalogue, the Second
Part consists of the Dependent Events New Catalogue, the
Third Part contains documentation and some additional material,
while further reading and a list of references is included in
the Fourth Part .
II. Data Sources for the New Earthquake Catalogue
A variety of data sources has been collected and
examined: texts of ancient writers,
chronicles, travellers reports, anonymous reports, earthquake
files, books, previous catalogues and modern scientific publications.
Of particular interest are four different data sources that were
not utilized, or were only partly taken into account, by previous
researchers. Three of them, refering in general to the Greek seismicity
and, therefore, include the Corinth Rift, cover three sequential
periods of the time interval from1850 to 1910 inclusive, while
the fourth one covers only the particular area of Galaxidi for
the time interval from 996 to 1660.
The first source consists of two books of Schmidt (1875,1879)
where a detailed list of even small earthquake events, that occurred
in Greece from 1850 to 1878 inclusive, can be found. The operation
of Julius Schmidt at the position of the Director of the National
Observatory of Athens (NOA) started on December 1858 and terminated
on February 1884. Soon after his operation started , J. Schmidt
organized a system of local observers in several places of the
already liberated part of Greece that included the geographical
region of the Corinth Rift. The observers were educated persons,
like medical doctors or school teachers, keeping daily reports
on earthquakes felt in the particular places of their residence.
This information was sent to NOA and systematic earthquake files
were organized by J. Schmidt and his collaborators who were also
checking and correcting the time of the earthquake occurrences.
Additional earthquake information was collected from the press.
This procedure resulted in the compilation of a very long, highly
homogeneous earthquake catalogue containing not only strong earthquakes
but also events of even small size. For each event the date and
time of occurrence as well as a short description of the felt
intensity are listed in the books of J. Schmidt. For strong and
large events some further details about their impact are given
.
On the basis of a systematic newspaper reading , Galanopoulos
( 1953) completed the work of J. Schmidt for the time interval
1879 - 1892. This publication constitutes the second important
data source for earthquake events of mainly medium and small size.
The third data source that diserves particular attention consists
of two manuscript volumes of NOAGI listing earthquake events that
occurred in Greece in the time interval
1893 - 1901 (Anonymous , a) and 1902 - 1915 (Anonymous, b) . The
volumes, written in Greek, contain observational material based
also on local observers and press reports, and arranged in the
format the catalogue of Schmidt is prepared . Since 1898 primitive
seismic instruments of Agamennone type started to operate in Greece
and, therefore, information on recording parameters, like first
arrivals, are contained for some events of the period 1898 - 1915.
For each one event an indication of the intensity felt is listed
as well. However, for strong and large earthquakes detailed macroseismic
descriptions are included. It is worth noting that for the time
interval 1893 - 1897 only qualitative intensity indications or
descriptions are given, while for the post-1987 time interval
quantitative intensity estimates are also supplied. The macroseismic
scale used is a version of the Forel Scale which is displaced
in Greek at the end of the manuscript volume of Anonymous ( b
) . In the Third Part of the present Chapter a reproduction of
the Forel Scale description, exactly as it stands in Anonymous
( b), along with an English translation made by us, can be found.
The raw observational material included in Anonymous (a ,b ) ,
after some corrections , elimination of details and editorial
standardization , was published in French in the Bulletins of
NOA (BNOA) under the title " Annales de l' Observatoire National
d' Athenes" supervised by D.Eginitis, NOA Director for the
period from June1890 to March 1934. The fact that we were able
to examine the original source of information , that is the two
manuscript volumes of Anonymous (a,b), on which the earthquake
information contained in BNOA Bulletins is based on, has been
of special value for the evaluation of the earthquake observational
material collected for the time interval 1893 - 1910. From 1904
onwards the macroseismic scale used in BNOA is the Rossi-Forel
scale. The version of this scale used is not included in Anonymous
(b) or BNOA. We suggest that it was the version of 1883 (e.g.
Sieberg, 1923).
The fourth data source that diserves special attention is the
"Unpublished Chronicle of Galaxidi". Én this
book, Sathas (1865) published the monk's Efthimios manuscript
entitled "A History of Galaxidi" written in Galaxidi
in 1703 . Several editions of the book followed in more recent
times, the most recent of them being the edition made in Athens
by Charisis (1996). A comparison of the editions of 1865 and1996
made by us indicated that there is no any discrepancy as for the
reproduction of the manuscript.
The above mentioned manuscript is of improtance from seismological
point of view because it contains information about four earthquake
events occurring in the area of the town of Galaxidi, in the central
part of the Corinth Gulf, from A.D.996 to A.D.1660. However ,
it is not clear whether all the earthquake events described by
the monk Efthimios in his manuscript were or not real earthquake
events .We evaluated this information and our result is reflected
in the reliability scores assigned to each one of the above four
earthquakes (see Main Events New Catalogue, First Part of this
Chapter) as well as in the section "Comments on Some Particular
Earthquakes" that can be found in the Third Part of this
Chapter.
III. Structure of the New Earthquake Catalogue
The New Earthquake Catalogue consists of the Main
Events New Catalogue and
the Dependent Events New Catalogue contained in the First Part
and the Second Part of this Chapter, respectively. Both the New
Catalogues are arranged in a chronological order . The earthquake
parameters introduced and the respective symbols used in the New
Catalogues are explained in section "IV. Method". As
already mentioned above, the New Earthquake Catalogue is supported
by documentation and some additional material in the Third Part
of this Chapter, which includes the Forel intensity scale used
by Anonymous (b), original documentation for some particular earthquake
events, a commentary on events not included in the New Earthquake
Catalogue , a list of earthquake events identified by archaeological
and palaeoseismological methods, some pictorial material, as well
as previous cataloguing of both the main and dependent events.
The New Earthquake Catalogue is also supported in the Fourth Part
of this Chapter by a list of further reading, a key of references
used in both parts of the New Earthquake Catalogue and a list
of all references cited in the present volume.
IV. Method
IV.1. Material Used
For each earthquake event listed in either the
Main Events New Catalogue or the Dependent Events New Catalogue
we collected information from various data sources and created
two different files . File A lists sets of earthquake parameters
determined by previous authors (see Third Part of this Chapter).The
inclusion of this material makes easier the evaluation of the
earthquake parameters determined by previous authors for one and
the same event. It is understandable that more than one sets of
parameters correspond to each particular earthquake event because,
as a general rule, more than one authors dealt with the parametric
description of each event. File B consists of the original descriptions
of the respective event . For most of the strong events (maximum
intensity I ? VI) original descriptions have been published by
other authors, like Ambraseys and Finkel (1992, 1993) and Ambraseys
(1996) for the 1705 earthquake, Ambraseys and Finkel (1999) who
supplied Ottoman archival information on several earthquakes of
the time period from 1500 to 1800, Georgiades (1904) for the time
period from 12000 B.C. to the Birth of Christ, Guidoboni et al.
(1994) for several earthquakes that occurred before the year A.D.1000,
,Papadopoulos (1998) for the 373B.C. event. However, for some
of the strong events original documentation has not been internationally
accessible so far and , therefore, we decided to include the respective
material in the Third Part of this Chapter.
IV.2 Events Listed
All the earthquake events reported in the several data sources
examined for the time interval from the beginning of the catalogue,
that is from 480 B.C., to 1849 inclusive are listed in the New
Earthquake Catalogue. Those events were strong ones given that
the maximum intensity , I , assigned to most of them , in the
modified Mercalli-Sieberg or the Forel Scale, is of degree VI
or larger . However, for some particular cases intensity I has
not been introduced in the New Earthquake Catalogue because of
data inadequacy. From about 1800 onwards, however, the reporting
capabilities increased drastically, in particular from about 1850
onwards, thanks to the observation activities undertaken by the
newly established NOA. Therefore, a long number of seismic events
of I < V were introduced in the earthquake lists, thus often
creating confusion as for the place(s) each event was reported
from. As a consequence, in the Main Events New Catalogue we included
only events of I ? V . However, in the Dependent Events New Catalogue
we were able to include shocks of I < V.
In the Dependent Events New Catalogue the selection of foreshocks,
if any, was a rather easy task because they were only a few and
did not occur for a long time before the respective main shock
occurrence. A more painful procedure has been the aftershock selection.
In several cases their number was very long and the aftershock
sequence lasted for several months or even for a few years (e.g.
the aftershock sequences of the large main shocks of 26th December
1861 and 1st August 1870, code numbers 61 and 68 in the Main Events
New Catalogue , First Part of this Chapter, respectively). In
these cases the selection has been in a way that the sequence
roughly conforms with the Omori law for the exponential decrease
of the number of aftershocks with time. It is understood that
some events may have erroneously introduced as aftershocks of
a particular main shock and that some others possibly did not
considered as aftershocks although they indeed were. Nonetheless,
the very carefull selection we made guarantees that the possible
mistakes introduced do not affect the general value of the Dependent
Events New Catalogue and of each one of the sequences included
in it. Before introducing in the New Earthquake Catalogue an event
strongly felt in place(s) of the Corinth Rift we checked for the
possibility of having its origin outside the Corinth rift. In
view of this some events were excluded from the New Earthquake
Catalogue (see examples in section "Third Part: Documentation
and Additional Material" of this Chapter.
IV.3 Earthquake Parameter Determination
The construction of the New Earthquake Catalogue
in a parametric form has been made under three main rules: ( a
) A particular earthquake parameter , like time of occurrence
, epicentral coordinates, maximum intensity felt, Richter magnitude
and focal depth, is introduced in a particular earthquake event
only when it is justified by the available observation data; otherwise
we prefered to leave blank the respective entry. ( b ) When a
particular parametric value has been introduced then it is the
"best" value that has either selected from one of the
existing previous catalogues or determined by us. Therefore, the
New Earthquake Catalogue constitutes an amalgamation of the best
output of our new determinations and of previous catalogues .
( c ) In our determinations we often prefered rather to indicate
value intervals of the form " equal to or larger (smaller)
than…" than to determine a single value not well justified
by the observation data.
IV.3.1 Time of Occurrence and its Reliability
The earthquake parameters adopted in the New Earthquake
Catalogue were decided on the basis of a two step procedure. In
the first step we relied on Files A and B to control the justification
of the time and place of occurrence for each particular event.
With this procedure we were able to correct the time and the place
of earthquake occurrences, to avoid dublications and false entries
and to control possible time and place inconsistencies between
the different sets of earthquake parameters given in different
catalogues in the past. At the same time for each event we were
able to identify the Accuracy (Acc) or the error involved in the
time of occurrence. An effort has been made to provide dates in
the new style (Gregorian) . Nevertheless, in some particular cases
it is not clear whether or not in the original documents the earthquake
dates are given in the old (Julian) or in the new style.
IV.3.2 Epicenter, Maximum Intensity, Richter
Magnitude, Focal Depth
The second step was devoted to the determination
of the earthquake epicenter , the maximum intensity reported and
the Richter magnitude of the event. We first examined
File B for whether the parameters determined by previous authors
are justified or not by the original documents . In cases of positive
conclusion we accepted for the New Earthquake Catalogue parametric
values already given by someone of the previous authors. For some
particular events, however, different parameter determinations
were adopted from different authors. In cases that according to
our understanding the parameter determinations were not justified
by the original ducumentation we redetermined the parameters and
they were introduced in the New Earthquake Catalogue. As for the
earthquake epicenters of strong events, in general we adopted
those listed in someone of the previous catalogues with only very
few exceptions. However, a large number of moderate and small
earthquake events are reported only from a very limited number
of observation localities. Then , the macroseismic information
available is not adequate to support a reliable epicenter determination
and , therefore, we conventionally indicate in parenthesis the
geographical coordinates of the region where the maximum intensity,
I , was reported.
The maximum intensity and the Richter magnitude assigned to several
earthquake events have also been adopted by previous author(s).
In a considerable number of events, however, we considered that
the past intensity and / or magnitude determinations were not
justified by the original observational material available and
, therefore, those determinations were not adopted. Instead, we
either redetermined the respective parameter(s) or avoided to
do so because of data inadequacy. In our intensity and magnitude
determinations we often prefered rather to indicate value intervals
of the form " equal to or larger (smaller) than…"
than to determine a single value not well justified by the observation
data.
The focal depth of the earthquakes listed in the New Earthquake
Catalogue is assumed to be shallow given that it is the general
rule for the Corinth Rift earthquakes as it results from the modern
seismograph data. Only the large event of 25th August 1889 (code
number 87 in the Main Events New Catalogue ) was suggested by
previous authors to have been of intermediate focal depth. According
to our opinion, however, the large number of aftershocks felt
indicate a shallow focal depth for this event.
IV.3.3 Event Reliability
A reliability score, Rel, for a particular earthquake
of being a " real earthquake" event or not has been
introduced in the New Earthquake Catalogue. Rel is measured in
a scale ranging from 0 to 4 and constructed in a way to represent
probability for a real earthquake occurrence or for a false earthquake
reporting:
0: very improbable event
1: improbable event
2: questionable event
3: probable event
4: definite event
This approach was developed by Iida (1984) for the creation of
a tsunami reliability scale in Japan and adopted with minor modifications
by the GITEC group working on the new European Tsunami Catalogue
(see Chapter 3). The criteria applied to assign Rel to each event
were the number of independent sources reporting the event, the
credibility of each one of the reporting sources as well as the
consistency between the several sources. Events assigned with
a 0 were not included in the New Earthquake Catalogue.
IV.4 Symbol Key to the New Earthquake Catalogue
The Symbol Key contained in this section is the
same for both the Main Events and the Dependent Events New Catalogues.
ID : code number
YY: year
MM: month
DD:day
An effort has been made to provide dates in the new style (Gregorian)(see
section "IV.3.1").
hh: hour (UT)
mm:minute
ss: second
Acc: accuracy of the time of earthquake occurrence.
Acc usually refers to the last entry of time. However, if it is
followed by Y, M, or D then it refers to the respective entry
that is to Year, Month or Day. Acc is measured in units of the
respective time entry . For instance, in the event of ID =3 (First
Part of this Chapter, Main Events New Catalogue) the Acc = 0 means
that the time accuracy is on the order of one month, while in
the event of ID = 12 it is on the order of two years. In the event
of ID = 1, however, Acc is on the order of 30 days.
lat:geographic latitude of epicenter
long: geographic longitude of epicenter
The epicentral coordinates are given without parentheses when
adopted by other authors.
Coordinates in parentheses indicate only the place of the maximum
intensity felt. This option has been prefered when either we did
not adopt determinations of other authors or the data available
were inadequate for an epicenter determination.
I : maximum intensity in MM (modified Mercalli-Sieberg
scale ) unless otherwise indicated (F = Forel scale, RF = Rossi
- Forel scale)
M: Richter magnitude equivalent to surface-wave magnitude
h: focal depth (in km)
n: shallow event
All the events listed are suggested to be of shallow focal depth
given that we have no evidence for a particular event to be of
intermediate focal depth. For reasons of emphasis symbol n is
placed only in the case of the ID = 87 event (First Part of this
Chapter, Main Events New Catalogue) which has been particularly
discussed in section " IV.3.3".
Rel: reliability of the event (see scale of reliability
in section "IV.3.2")
Ref 1: references used for the adoption of earthquake parameters
including time of occurrence
Earthquake parameters are either adopted by other authors or revised
by us ( see section "IV. Method" ).
( + ) after a particular value means "equal to or
larger than"
( - ) after a particular value means "equal to or
less than"
* indicates parameter either determined or revised by us
- before the year of occurrence means "Before Christ"
c after the year of occurrence means "circa".
REFERENCES
Ambraseys, N.N., 1996. Material for the investigation
of the seismicity of Central Greece. In: Archaeoseismology, Stiros,S.
and R.E. Jones (Eds.), 23-36.
Ambraseys, N.N. and Finkel, C.F., 1992. The
seismicity of the Eastern Mediterranean region during the turn
of the 18th century, Ismit, 42,323-343.
Ambraseys, N.N. and Finkel, C., 1993. Material
for the investigation of the seismicity of the Eastern Mediterranean
region during the period 1690-1710. In: Historical investigation
of European earthquakes, Stucchi M. (Ed),1,173-194.
Ambraseys, N.N. and Finkel, C., 1999. Unpublished
Ottoman archival information on the seismicity of the Balkans
during the period 1500-1800. In: Natural disasters in the Ottoman
Empire, Institute for Mediterranean studies, Halcyon Days in Crete
III, A Symposium held in Rethymnon, 10-12 January 1997, Crete
University Press, 89-107.
Anonymous,a. Book of the earthquakes observed
in Greece in the time interval 1893-1901, Insitute of Geodynamics,
National Observatory of Athens, 181pp. (Manuscript in Greek).
Anonymous, b. Book of the earthquakes in Greece
in the time interval 1902-1915, Institute of Geodynamics, National
Observatory of Athens, 399pp. (Manuscript in Greek)
Charissis, A. (Ed.), 1996. Chronicle of Galaxidi,
Athens, pp. 245, in Greek.
Galanopoulos, A. G., 1953. Katalog der Erdbeben
in Griechland für die zeit von 1879 bis 1892. Ann. Geol.
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Guidoboni, E., Comastri, A. and Traina, G.,
1994. Catalogue of ancient earthquakes in the Mediterranean area
up to the 10th century. SGA Storia Geofisica Ambiente,
Mitropoulos, I.D., 1970. Galaxidi, Athens,
461pp, in Greek.
Mitzopoulos, K., 1893. Elements of Geology.
A. Constantinides (Ed.), 1, Athens, 568pp. (in Greek).
Papadopoulos, G.A., 1998a. A reconstruction
of the great earthquake of 373 B.C. in the western gulf of Corinth.
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Schilardi, D. (Eds.) 479-494.
Sathas, K.N., 1865. Unpublished Chronicle
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and the suroundings from ancient times to present, Publ. By I.
Kassandreus, Athens, pp. 221,in Greek.
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324pp.
Schmidt, J., 1879. Studien über Erdbeben.Leipzig,
360pp.
Shebalin, N.V., Karnik, V. and Hadzievski,
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Sieberg, 1923. Geologische, physikalische und Angewandte Erdbebenkunde.
Jena, Verlag von Gustav Fischer, 572pp.
G.I.
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