...and especially with the up to 9 m uplift of a more than 100 km long segment of Crete.
The magnitude of the uplift would indicate one of the largest earthquakes
ever recorded on the earth (magnitude over 8).[...]
Historical data concerning earthquakes and tsunami destruction
circa AD365 are fragmentary, ambiguous and imprecise. However,
a destructive tsunami which affected the coasts of Egypt and
widespread seismic destructions in Crete, Sicily and Libya seem
documented beyond any reasonable doubt (for a summary, see
Guidoboni et al., 1994; Stiros, 2001; Stiros and Papageorgiou, 2001;
Kelly, 2004).[...]
The famous text by Ammianus Marcelinnus (26.10.15–19)
reports that on July 21st, AD365, a tsunami-associated earthquake
affected Alexandria in Egypt, and later authors report that this
event became a legend for more than a millennium commemorated
in this city for more than 200 years as the ‘‘Day of Horror’’ (for
a summary, see Guidoboni et al., 1994; Stiros, 2001). On the
contrary, in the Chronicle of John, Bishop of Nikiu in Egypt, it is
clearly stated that at least a large part of the ancient city was not
affected by the tsunami (LXXXII, 19–21, English 1916 translation
from a 7th c. version).[...]
Further contribution to the study of the AD365 tsunami provide
models of propagation of tsunami generated south of Crete (Tinti
et al., 2005; Yolsal et al., 2007; Shawet al., 2008; Lorito et al., 2008).
These models cannot support the hypothesis of tsunami from this
area seriously affecting Alexandria in Egypt, especially the polarity
of the tsunami (retreat of waters prior to the tsunami flooding,
explicitly described by Ammianus Marcelinus). In particular, Lorito
et al. (2008) indicate that tsunami generated in SW part of the
Hellenic arc can only have a minor impact (waves of sub-meter
amplitude) along the Croatian coasts in the Adriatic Sea.[...]
In one of these graphs new land formed after the AD365 event is
marked, while the diagram of Flemming (1978) for the whole of
Crete shows the contrast between uplift in the western and
subsidence in the eastern part of the island. As shown in Fig. 2a, the
AD365 uplift extends as far as the Antikythira Islet. No evidence of
uplift or of subsidence was found in Kythira or Gavdos Ilset (Fig. 2a;
P. Pirazzoli, personal communication). After this uplift, relative sealevel
remained essentially stable on an island-wide scale, raising
questions as to whether the earthquake cycle in Crete is a ‘‘typical’’
one (Stiros, 1996a).[...]
Evidence of a major earthquake
There are several lines of evidence that the uplift dated by
radiocarbon at circa 1550BP was associated with a major earthquake
in AD365:
Biological evidence: very fragile Bryozoans of the infralittoral
zone are preserved exposed above the water. This is evidence that
Bryozoans rapidly crossed the midlittoral zone, where erosion is
intense, without been eroded (Thommeret et al., 1981; Pirazzoli
et al., 1989). Hence there is biological evidence of a rapid,
conspicuously seismic uplift of Crete, and not of slow, non-seismic
uplift during a relatively long period (e.g. tens or hundreds of
years).[...]
Archaeological evidence: Stiros (2001), Stiros and Papageorgiou
(2001) and Stiros et al. (2004) presented or summarized widespread
evidence of destruction layers that are related to earthquake(
s) in circa AD365 in at least three towns of Crete along
a distance of the order of 150 km (see Fig. 4). Evidence of an
earthquake was clear, for instance people killed and buried by
fallen roofs of houses, in some cases with glasses at hand and with
coins in their pockets (compare with Stiros, 1996b). Numismatic
and other evidence indicates that all these destructions are likely to
have occurred in AD365 (Table 3).[...]
Recent evidence summarized elsewhere provides additional
evidence for a major seismic destruction shortly after AD364 in
various parts of Crete, including at Knossos, near Herakleion in
central Crete, where a ‘thesaurus’’ (treasure, hoard) of about 1000
coins was found hidden in the remains of the walls of an ancient
house. In the absence of banks, such ‘‘thesauroi’’ reflect a tradition
in antiquity to safely hide money. The distribution of the date of
production of the coins of this ‘‘thesaurus’’ clearly indicates that it
was deposited between AD364–AD367 (Fig. 5), and it was then
abandoned (presumably) because its owner disappeared (Sidiropoulos,
2004)...However, several forgotten hoards of
this period were found in Crete, and this provides evidence suggesting
a wider extinction of their owners during an event of
unprecedented scale in the history and archaeology of the region. If
on the basis of the available data, epidemics and war can be
excluded, extensive seismic destruction remains the likely reason.
In addition, since coins of a slightly later age have been found in
Crete, demonstrating a continuity of coin circulation in this island
(Fig. 5), the most recent coins in the hoards provide a reliable and
precise estimate of the date of their deposition (Stiros, unpublished
data).
Except for Crete, systematic archaeological excavations in
Cyprus, Libya and Southern Italy have revealed clear signs of
extensive seismic destruction which in many cases fall within
a period some months to a few years, correlating with literary
evidence for a regionally destructive event (or sequence of events)
circa AD365 (Fig. 1; Table 3). The most spectacular and clear are
earthquake victims, people, occasionally whole families, and horses
at Kourion, near Paphos, Cyprus (see Sorren and Davis, 1985;
Sorren, 1988). In many cases the dating of these events, based on
inscriptions and on numismatic evidence, is accurate to within
months or years. These data are summarized in Table 3 and permit
identification of at least large parts of the regions which were hit by
earthquakes circa AD365.[...]
Evidence summarized above indicates that the up to 9 m uplift
and tilting of Crete was an episodic event which correlates with
large-scale seismic destruction of the island in AD365. Elastic
dislocation analysis of this uplift indicates that it can be associated
with a thrust offshore of southwestern Crete, which produced an
earthquake of a magnitude (M > 8.5), unusual in the geologic
history of the island, at least over a period of 120,000 years (since
the Last Interglacial, Pirazzoli et al., 1982; Pirazzoli, 1986; Kelletat,
1991). This was not an isolated event, but belonged to a seismic
sequence which affected Cyprus, Libya, Sicily and probably other
areas, and it was clustered in a short time period, short enough to
be regarded by the ancients as a single, universal event (‘‘terraemotu
per totum orbem facto’’, Migne, PL 27, 694). Such a seismic
sequence is clearly consistent with current understanding of other
giant earthquakes, for instance the 1960 Chile earthquake (Plafker
and Savage, 1970).
If the AD365 earthquake had produced a tsunami by faulting of
the seabed, the propagation of this tsunami would be very similar
to that modelled by Tinti et al. (2005), Yolsal et al. (2007), Shaw
et al. (2008) and Lorito et al. (2008). It is, however, questionable
whether modelled tsunami can account for the reported destruction
in the Nile Delta (see above).
Another characteristic of the AD365 earthquake is that, in spite
of its magnitude, the scale of the destruction produced and its
association with a series of other major destructive earthquakes
(Pirazzoli, 1986; Pirazzoli et al., 1996), it does not represent a catastrophic
event leading to the collapse of the Roman Empire which
was indeed in a deep crisis. The AD365 earthquake, indeed, seems
to represent only a rather minor cultural discontinuity in Crete,
marking the transition from the Roman to the Christian era in the
island, as stratigraphic data summarized in Stiros (2001) and Stiros
and Papageorgiou (2001) reveal. It is interesting that Gortyn, capital
of Crete in antiquity, was destroyed by the AD365 and other
smaller, subsequent earthquakes, but every time it rapidly recovered,
until it was finally destroyed by a lesser earthquake in the 7th
c. AD, because the political background at this period did not
support its post-seismic recovery (DiVita, 1996).
