Relative Sea Level Changes and Morphotectonic Implications Triggered by the Samos Earthquake of 30Th October 2020

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Journal of Marine Science and Engineering

Article Relative Sea Level Changes and Morphotectonic Implications Triggered by the Samos Earthquake of 30th October 2020

Niki Evelpidou 1,* , Anna Karkani 1 and Isidoros Kampolis 2

1 Faculty of Geology and Geoenvironment National and Kapodistrian University of Athens, Panepistimiopolis, 15774 Athens, Greece; [email protected] 2 Department of Geological Sciences, School of Mining & Metallurgical Engineering, National Technical University of Athens, 15773 Athens, Greece; [email protected] * Correspondence: [email protected]

Abstract: On 30th October 2020, the eastern Aegean Sea was shaken by a Mw = 7.0 earthquake. The epicenter was located near the northern coasts of Samos island. This tectonic event produced an uplift of the whole island as well as several cases of infrastructure damage, while a small tsunami followed the mainshock. Underwater and coastal geological, geomorphological, biological obser- vations and measurements were performed at the entire coast revealing a complex character for the uplift. At the northwestern part of the island, maximum vertical displacements of +35 ± 5 cm were recorded at the northwestern tip, at Agios Isidoros. Conversely, the southeastern part was known for its subsidence through submerged archaeological remains and former sea level standstills. The 2020 underwater survey unveiled uplifted but still drowned sea level indicators. The vertical displacement at the south and southeastern part ranges between +23 ± 5 and +8 ± 5 cm suggesting a gradual fading of the uplift towards the east. The crucial value of tidal notches, as markers of co-seismic events, was validated from the outcome of this study. The co-seismic response of Samos coastal zone to the 30th October earthquake provides a basis for understanding the complex tectonics of this area.

Citation: Evelpidou, N.; Karkani, A.; Keywords: earthquake; uplift; co-seismic; palaeoshorelines; East Aegean Sea Kampolis, I. Relative Sea Level Changes and Morphotectonic Implications Triggered by the Samos Earthquake of 30th October 2020. J. 1. Introduction Mar. Sci. Eng. 2021, 9, 40. http://doi.org/10.3390/jmse9010040 Samos Island is located in the mid-eastern Aegean Sea (Figure1), less than 1.5 km from the west Anatolian coast. The Aegean Sea is considered one of the most active areas in the Received: 26 November 2020 SE Mediterranean from a seismological perspective. It is delimited by the North Anatolian Accepted: 28 December 2020 Fault to the north and the Hellenic subduction zone to the south [1,2]. The broader Samos Published: 3 January 2021 region is situated in an interaction area between the Aegean microplate, the subducting African plate and the Anatolian microplate. The latter bears a westward extrusion into Publisher’s Note: MDPI stays neu- the Aegean Sea due to its collision with the Arabian Plate at a fast rate along the North tral with regard to jurisdictional clai- Anatolian Fault since 5 Ma [3–8]. This regime affecting Samos is characterized by a N-S to ms in published maps and institutio- NNE-SSW trending extension producing normal faults [9,10] and earthquakes. These faults nal afﬁliations. exhibit an E-W trending close to Samos, whereas an oblique-normal motion is revealed at the opposite Turkish shores. The current extension began in Pliocene-Quaternary [11] and resulted in the reactivation of older fault structures striking NE-SW and NW-SE [11]. Samos is located on a shallow plateau that extends from Mt. Samsun Da˘gıpeninsula, Copyright: © 2021 by the authors. Li- censee MDPI, Basel, Switzerland. with which it was connected during the Pliocene- Pleistocene [13]. The island lies at This article is an open access article the western edge of an area with intense earthquakes and seismic faulting, along the distributed under the terms and con- Greater Menderes River [14,15]. The island’s geology comprises of the metamorphic ditions of the Creative Commons At- basement, an ophiolite sequence, Miocene-Pliocene sediments and volcanic rocks [11]. tribution (CC BY) license (https:// The metamorphic basement is composed of four tectono-metamorphic units [10]. Kerketeas creativecommons.org/licenses/by/ marbles are the lowermost unit, which outcrop at the western part of Samos. The Ampelos 4.0/). unit overthrusts the latter and spans in the central part of the island. The overlain Selçuk

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nappe takes place in the center of the island [16] and the Vourliotes nappe lies at the J. Mar. Sci. Eng. 2021, 9, x FOR PEER REVIEW 2 of 18 eastern Samos, representing the upper metamorphic unit (mainly schists and marbles). Additionally, the Miocene-Pliocene basins of Samos cover a large area of the island [17,18].

FigureFigure 1. Samos 1. Samos island island and and the the main main tectonic tectonic structures structures in andand around around the the island island of Samos,of Samos, where where KF: Karlovassi ΚF: Karlovassi fault is fault a is a dextraldextral strike-slip strike-slip fault, fault, and and PF: PF: Pith Pithagoreioagoreio fault fault zone, zone, VF: VF: Vathy Vathy fault, fault, MF: MarathokambosMF: Marathokambos fault, OF: fault, Offshore OF: Offshore Samos fault Samos fault areare normal faults faults (after (after [12 [12]).]). The The location location of the of earthquakethe earthquake of 30th of October 30th October 2020 is shown2020 is withshown a red with star. a red star.

SamosThe geomorphologyis located on a ofshallow Samos plateau island is that inﬂuenced extends by from the WNW-ESE Mt. Samsun tectonic Dağ activityı peninsula, withas which the main it was basin connected of the island, during smaller the Pliocene- valleys and Pleistocene the drainage [13]. network The island are devel- lies at the oped parallel to this direction [12]. The coast of Samos is partly controlled by faulting western edge of an area with intense earthquakes and seismic faulting, along the Greater (Figure1) [12]. Rather linear coastlines are formed in the same direction of the main coastal Menderesand offshore River faults. [14,15]. Offshore, The island’s North Samosgeology fault comprises (Figure1) of deﬁnes the metamorphic two different geomor-basement, an ophiolitephological sequence, regions, Miocene-Pliocene which are the island sediments itself and the and deep volcanic Samos depressionrocks [11]. [12 The]. Inland, metamor- phicthe basement Pithagoreio is composed normal fault, of strikingfour tectono- WNW–ESEmetamorphic and dipping units south [10]. at Kerketeas 45◦, is expressed marbles are thein lowermost various outcrops unit, which where outcrop slickensides at the are west preservedern part (Figure of Samos.1) and The controls Ampelos this area’s unit over- thrustsmorphology the latter [12 ].and spans in the central part of the island. The overlain Selçuk nappe takes placeThe earliestin the center historical of earthquakethe island [16] in Samos and the dates Vourliotes back to 1766, nappe while lies during at thethe eastern Samos,period representing 1700–1799, eightthe upper seismic metamorphic events have un struckit (mainly the island schists (Hellenic and marbles). Macroseismic Addition- database after [19]; http://macroseismology.geol.uoa.gr/query_eq/). Moreover, a total of ally, the Miocene-Pliocene basins of Samos cover a large area of the island [17,18]. 416 earthquakes affected Samos in the 19th century [19]. Nevertheless, ancient earthquakes, suchThe as geomorphology the 200 BC event, of are Samos also known island [ 9is]. influenced by the WNW-ESE tectonic activity as the mainOn 30th basin October of the 2020 island, 11:51 smaller GTM, anva earthquakelleys and the of Mwdrainage = 7.0(according network are to EMSC- developed parallelCSEM) to tookthis direction place north [12]. of SamosThe coast island of Samos (37.88◦ isN, partly 26.71 E).controlled According by tofaulting preliminary (Figure 1) [12].reports, Rather the linear focal mechanismcoastlines ofare the formed mainshock in the was same normal direction faulting of of E-Wthe main strike coastal [20,21]. and offshore faults. Offshore, North Samos fault (Figure 1) defines two different geomorphological regions, which are the island itself and the deep Samos depression [12]. Inland, the Pithagoreio normal fault, striking WNW–ESE and dipping south at 45°, is expressed in various outcrops where slickensides are preserved (Figure 1) and controls this area's morphology [12]. The earliest historical earthquake in Samos dates back to 1766, while during the period 1700–1799, eight seismic events have struck the island (Hellenic Macroseismic database after [19]; http://macroseismology.geol.uoa.gr/query_eq/). Moreover, a total of 416

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earthquakes affected Samos in the 19th century [19]. Nevertheless, ancient earthquakes, such as the 200 BC event, are also known [9]. On 30th October 2020 11:51 GTM, an earthquake of Mw = 7.0 (according to EMSC- J. Mar. Sci. Eng. 2021, 9, 40 3 of 17 CSEM) took place north of Samos island (37.88° N, 26.71 E). According to preliminary reports, the focal mechanism of the mainshock was normal faulting of E-W strike [20,21]. The ruptured fault, fault, 36 36 km km long long and and 18 18 km km wide, wide, slipped slipped for for1.8 1.8m [22]. m [22 On]. Samos, On Samos, two teenagerstwo teenagers were were killed killed while while returning returning from from school school to their to their home, home, nine nine persons persons were were injured,injured, and and 1100 1100 buildings buildings were were recorded recorded as unsuitable as unsuitable for use. for use.The temblor The temblor was far was more far devastatingmore devastating for Turkey, for Turkey, resulting resulting in 116 incasu 116alties, casualties, more than more 1034 than injured 1034 injured persons persons and 20 reportedand 20 reported building building collapses collapses in Izmir.in Soon Izmir. after Soon the mainshock, after the mainshock, a tsunami awas tsunami triggered. was Itstriggered. impact affected Its impact the affected north coast the north of the coast island of with the island 1.7 to 2 with m recorded 1.7 to 2 mcoastal recorded inundation coastal atinundation Karlovasi at(NW Karlovasi Samos) (NW and Samos)Vathy (NE and Samos) Vathy (NEtowns Samos) [23]. The towns latter [23 ].was The hit latter by a wastsu- namihit by with a tsunami two successive with two successive waves with waves 20’ withtime 20’difference time difference [23]. Three [23,24 hours]. Three after hours the mainshockafter the mainshock at 15:14 UTC at 15:14 an UTCaftershock an aftershock of Mw of= 5.2 Mw occurred = 5.2 occurred and by and 20 November by 20 November 2020, more2020, than more 380 than aftershocks 380 aftershocks have been have recorded been recorded (National (National Observatory Observatory of Athens; of Seismo- Athens; logicalSeismological Laboratory Laboratory of NKUA) of NKUA) (Figure (Figure 2). 2).

Figure 2.2. TheThe mainmain earthquakeearthquake atat 30/10/20 30/10/20 and the aftershocks untiluntil 20/11/20,20/11/20, from from the the National National Observatory of Athens and the Seismological LaboratoryLaboratory ofof NKUA.NKUA.

Evidence of uplift as a result of past earthquakes has been noted in the past mainly from tidal notches and benches [15,24] [15,25] at the northwestern coast of of the island (Figure 33).). Conversely, onon thethe southeasternsoutheastern coast, coast, subsidence subsidence has has been been noted noted based based on on the the presence presence of ofsubmerged submerged geological, geological, geomorphological geomorphological and an archaeologicald archaeological indicators indicators [15 [15,24–28].,25–29]. This research research aims aims to to re-examine re-examine various various sea sea level level indicators indicators in Samos in Samos island island by com- by paringcomparing past pastwith withnew measurements new measurements in order in orderto understand to understand and quantify and quantify the co-seismic the co- movementsseismic movements caused by caused the Mw by the= 7.0 Mw seismic = 7.0 seismicevent of event30th October of 30th October2020 and 2020 shed and light shed to thelight tectonic to the tectonicregime of regime the island. of the island.

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Figure 3. EvidenceFigure 3. Evidence of former of former uplifts uplifts in the in theform form of ofraised raised benche benchess and and a tidala tidal notch notch at Mikro at Mikro Seitani, Seitani, at the northwestern at the northwestern part of Samospart of(near Samos SA24). (near SA24).

2. Materials2. Materials and and Methods Methods ExtensiveExtensive fieldwork fieldwork took took place in in April April 2015 2015 and and November November 2020 along 2020 the along coastal the coastal zone zoneof Samos of Samos island, island, both both on on the coastcoast and and underwater. underwater. The underwater The underwater survey, in survey, both in both years,years, was wasaccomplished accomplished by by snorkeling snorkeling and and free free diving diving equipment, equipment, while a wh boatile was a boat used was used in order to facilitate access at all sites and establish their continuity. The sites examined in in order2015 to were facilitate re-visited access and re-mapped at all sites in and early establish November their 2020, continuity. along with additional The sites sites examined in 2015 aroundwere re-visited the island, and in order re-mapped to document in early possible November vertical changes 2020, afteralong the with earthquake additional sites aroundof 2020.the island, In addition, in order sites to with document evidence ofpossi formerble upliftvertical reported changes by Stiros after etthe al. earthquake [15], of 2020.were In addition, also measured sites in with order evidence to better quantify of former the new uplift vertical reported displacements. by Stiros et al. [15], were Former sea level positions were deduced from various sea level indicators, such as also measuredtidal notches, in benches order andto better biological quantify indicators. the Thenew profile vertical of the displacements. notches was recorded in Formerdetail during sea fieldlevel work positions and in particular were deduced their height, from inward various depth andsea vertexlevel depthindicators, from such as tidal seanotches, level were benches measured and according biological to [ 30indicators.] and [31]. TheThe inward profile depth of the of notch notches profiles was is recorded in detailconsidered during to field estimate work the durationand in particular of sea level stability their height, based on inward rates of intertidaldepth and erosion vertex depth for the Mediterranean region (0.2–1 mm/yr) [32], while the notch height was used to from sea level were measured according to [29] and [30]. The inward depth of notch pro- determine whether their profile is related to gradual sea level changes or co-seismic vertical files isdisplacements considered [to31, 33estimate]. Biological the indicatorsduration includedof sea level measurements stability based on freshly on rates exposed of intertidal erosionlimpets, for the vermetids Mediterranean and dead red region algae (0.2–1 of the midlittoral mm/yr) [31], zone [while34] or bythe the notch characteristic height was used to determinecolor belts whether of microbial their origin profile on coastal is related rocks [35 to]. gradual sea level changes or co-seismic vertical displacementsMeasurements were [30,32]. accomplished Biological with indi calmcators sea included conditions measurements and the accuracy on was freshly ex- improved by multiple measurements on each location. Measurements in tidal notches posedaccessible limpets, only vermetids through swimmingand dead were red carriedalgae of out the with midlittoral both a wrist zone depth [33] gauge or andby the a charac- teristicfolding color meter belts of of rigid microbial parts. Ten origin measurements on coastal were rocks taken [34]. at each site and the average Measurementsvalue was used, providing were accomplished a vertical accuracy with of calm±5 cm. sea Measurements conditions in and land-reached the accuracy was improved by multiple measurements on each location. Measurements in tidal notches ac- cessible only through swimming were carried out with both a wrist depth gauge and a folding meter of rigid parts. Ten measurements were taken at each site and the average value was used, providing a vertical accuracy of ±5 cm. Measurements in land-reached sites were accomplished using a DGPS-GNSS, providing a vertical accuracy of ±2 cm. DGPS-GNSS measurements in the land-reached sites were compared with the average of ten measurements with a folding meter of rigid parts, to assess the accuracy reported in our measurements. The supplementary table (Table S1) presents all measurements and the method used for each measurement. As shown in Table S1, in most cases the coeffi- cient of standard deviation is lower than 1, suggesting a distribution of low variance. For

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J. Mar. Sci. Eng. 2021, 9, x FOR PEER REVIEW 5 of 18 sites were accomplished using a DGPS-GNSS, providing a vertical accuracy of ±2 cm. DGPS-GNSS measurements in the land-reached sites were compared with the average of ten measurements with a folding meter of rigid parts, to assess the accuracy reported in our measurements. The supplementary table (Table S1) presents all measurements and the all themethod accomplished used for each measurements measurement. As using shown different in Table S1, tools, in most we casesconsider the coefﬁcient an error of range of ±5 cm. Geographicstandard deviation locations is lower of thanmeasured 1, suggesting sea leve a distributionl indicators of loware variance.reported For as all Long/Lat the coor- dinatesaccomplished with an average measurements accuracy using of different 80 cm using tools, we GPS. consider Depth an measurements error range of ±5 were cm. referred to theGeographic sea level locations at the time of measured of measurement sea level indicators and subsequently are reported as Long/Latcorrected coordinates using tidal records with an average accuracy of 80 cm using GPS. Depth measurements were referred to the fromsea a nearby level at the tidal time device, of measurement provided and by subsequently the Hellenic corrected Navy usingHydrographic tidal records Service from a (HNHS). nearby tidal device, provided by the Hellenic Navy Hydrographic Service (HNHS). 3. Results 3. Results Fieldwork results are summarized in Table 1, which includes the sites measured in Fieldwork results are summarized in Table1, which includes the sites measured in two twoperiods periods of offieldwork, ﬁeldwork, i.e.,i.e., April April 2015 2015 and and November November 2020 (Figure 2020 4(Figure). 4).

Figure 4. FigureMeasurement 4. Measurement results results map, map, which which shows shows thethe magnitude magnitude of uplift of uplift along thealong coastal the zone coas oftal Samos, zone from of Samos, comparative from comparative measurementsmeasurements between between 2015 2015 and and 2020, 2020, from from new measurementsnew measurements and from aand review from ofpositions a review by of Stiros positions et al. [15 by]. The Stiros red et al. [15]. The red dotsdots and SA1–SA29 SA1–SA29 indicate indicate the locations the locations discussed discussed in the text. in The the red text. numbers The correspond red numbers to the correspond magnitude of theto the seismic magnitude of the seismicuplift uplift in cm. in Wherecm. Where red numbers red number are absent,s are there absent, was no changethere was in elevation. no change The main in elev tectonication. features The main are modiﬁed tectonic after features are Roche et al. [10]. The lithology is based on the geological map of Samos [17]. modified after Roche et al. [10]. The lithology is based on the geological map of Samos [17].

3.1. Sykia3.1. Sykia 1 (SA1) 1 (SA1) SA1 site is located 3 km east of Sykia Village, in the southernmost part of Samos Island. MarksSA1 site of former is located sea levels 3 km were east found of on Sykia the carbonate Village, cliffs. in the In 2015, southernmost three submerged part tidal of Samos Is- land.notches Marks were of foundformer and sea measured levels atwere−80 ±found10 and on−250 the± 10carbonate cm (Figure cliffs.5a) , respectively, In 2015, three submerged tidal notches were found and measured at −80 ± 10 and −250 ± 10 cm (Figure 5a), respectively, along with a slightly submerged notch at −5 cm. In 2020, the latter was found raised at +18 ± 5 cm, suggesting an uplift of +23 ± 5cm.

3.2. Klima (SA9) Approximately 1 km west of Klima Village (SE Samos), on a carbonate headland, two submerged notches were identified in 2015, an upper one at −20 ± 5 cm and a lower one at −115 ± 5 cm. During the 2020 fieldwork, the upper notch was measured at −21 ± 5 cm and a lower one at −120 ± 5 cm, suggesting no vertical displacement of this site since 2015 (Figure 5b,c). Based on intertidal erosion rates (see materials and methods), the two submerged notches suggest a stable sea level for approximately 1–2 centuries to one millennium. The lower notch has been co-seismically submerged due to a former earthquake highlighting the complex vertical displacements of the island.

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along with a slightly submerged notch at −5 cm. In 2020, the latter was found raised at +18 ± 5 cm, suggesting an uplift of +23 ± 5cm.

3.2. Klima (SA9) Approximately 1 km west of Klima Village (SE Samos), on a carbonate headland, two submerged notches were identiﬁed in 2015, an upper one at −20 ± 5 cm and a lower one at −115 ± 5 cm. During the 2020 ﬁeldwork, the upper notch was measured at −21 ± 5 cm and a lower one at −120 ± 5 cm, suggesting no vertical displacement of this site since 2015 (Figure5b,c). Based on intertidal erosion rates (see materials and methods), the two submerged notches suggest a stable sea level for approximately 1–2 centuries to J. Mar. Sci. Eng. 2021, 9, x FOR PEER REVIEW 6 of 18 one millennium. The lower notch has been co-seismically submerged due to a former earthquake highlighting the complex vertical displacements of the island.

(a) (b) (c)

Figure 5. (aFigure) Two 5.continuous(a) Two continuous submerged submerged notches notches at Sykia at Sykia 1 (SA1) 1 (SA1) measur measureded in in 2015 2015 and 20202020 indicate indicate an an uplift uplift of +18 of ±+185 cm± 5. cm. Photo taken in 2015;Photo (b taken,c) Two in 2015; continuous (b,c) Two submerged continuous submerged notches at notches Klima at (SA9) Klima (SA9)measured measured in 2015 in 2015 (c) ( cand) and 2020 2020 ((bb),), suggestsuggest no no vertical vertical displacement. The upper one is indicated by an arrow, while the lower one by the diver. displacement. The upper one is indicated by an arrow, while the lower one by the diver.

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Table 1. Different types of sea level indicators testifying the tectonic uplift of 2020.

Field Trip Measured Vertex Measured Vertex Vertex Height 2020 Site Name Long. E Lat. N Date Sea Level Indicator Depth/Bench Depth/Bench from Inward Source (cm) Movement (Month/Year) from SL (cm) SL in 2020 (cm) Depth (cm) 04/2015 Tidal notch −5 +18 7 7 +23 uplift This paper SA1 Sykia 1 26◦50.6660 37◦38.2330 04/2015 Tidal notch −80 61 20 uplift This paper 04/2015 Tidal Notch −250 117 53 uplift This paper 04/2015 Tidal notch −20 −21 30 24 0 uplift This paper SA9 ◦ 0 ◦ 0 Klima 27 02.125 37 42.281 04/2015 Tidal notch −115 −120 34 18 0 uplift This paper SA10 Posidonio 27◦04.1920 37◦43.0460 04/2015 Tidal notch −30 −17 34 16 +13 uplift This paper SA15 Mourtia 27◦03.2120 37◦46.1520 04/2015 Tidal notch −40 −32 24 18 +8 uplift This paper SA16 Kokkari 26◦53.6060 37◦46.7900 11/2020 exposed midlittoral zone - +22 - - +22 uplift This paper White (St. Nicholas) Vermetids reef Notch SA18 26◦40.1960 37◦47.6000 11/2020 +50 - - +20 uplift [15] chapel at Potami beach Beachrock slab +20 White (St. Nicholas) SA19 26◦40.0050 37◦47.5210 11/2020 exposed midlittoral zone - +20 - - +20 uplift This paper chapel at Potami Beach Bench +60 +82 - - +22 uplift SA21 Punta Promontory 26◦39.5890 37◦47.3610 11/2020 bench +110 +132 - - +22 uplift [15] Tidal notch +232 - - uplift SA24 Megalo Seitani 26◦37.9920 37◦46.2140 11/2020 exposed midlittoral zone - +22 - - +22 uplift This paper 11/2020 Dendropoma bench +60 +88 - - uplift SA25 Agios Isidoros 26◦35.5940 37◦45.5010 11/2020 Tidal notch +50–70 - uplift [15] 11/2020 Tidal notch +110–130 +111 61 33 uplift SA26 Agios Isidoros 26◦35.4840 37◦45.1130 11/2020 Notch - +70 - - +35 uplift This paper Exposed SA27 Pithagoreio 26◦56.6390 37◦41.2480 11/2020 Midlittoral - +15 - - +15 uplift This paper zone SA28 Psili Ammos 27◦0.6730 37◦42.2050 11/2020 Exposed midlittoral zone - +13 - - +13 uplift This paper J. Mar. Sci. Eng. 2021, 9, x FOR PEER REVIEW 8 of 18

3.3. Posidonio (SA10) At this site, located about 1 km east of Posidonio Village (ESE Samos), in 2015 one submerged notch was measured at −30 ± 5 cm. Based on its profile characteristics, the sea level stood at the vertex level from one to eight centuries before it was drowned by a relative sea level rise. The same notch was recorded at −17 ± 5 cm in 2020, suggesting a J. Mar. Sci. Eng. 2021, 9, 40 +13 ± 5 cm uplift (Figure 6a,b). 8 of 17

3.4. Mourtia (SA15) 3.3. PosidonioOn the carbonate (SA10) cliffs, about 1.2 km east of Mourtia beach (NE Samos), a submerged fossilAt shoreline this site, through located a about tidal notch 1 km eastwas ofidentified Posidonio and Village measured (ESE at Samos), −40 ± 5 incm 2015 in 2015. one Thesubmerged same site notch was was revisited measured in 2020 at − and30 ± the5 cm.notch Based depth on of its − proﬁle32 ± 5 characteristics,cm was recorded the im- sea plyinglevel stood a slight at theemergence vertex level of 8 from± 5 cm one (Figur to eighte 6c). centuries The notch before is visible it was continuously drowned by for a morerelative than sea 1 levelkm on rise. the The coast. same Its inward notch was dept recordedh corresponds at −17 to± a5 sea cm level in 2020, stability suggesting for one a +13to nine± 5 centuries. cm uplift (Figure6a,b).

(a) (b)

(c)

Figure 6. (a(a) )SA10 SA10 site site in in Posidonio Posidonio area area indicates indicates a coastal a coastal uplift uplift of 13 of ± 13 5 ±cm.5 Photo cm. Photo taken takenin 2015; in ( 2015;b) Schematic (b) Schematic repre- sentationrepresentation of the oftidal the notch tidal notchin Posidonio in Posidonio comparing comparing its position its position in 2015 inand 2015 2020; and (c) 2020; Underwater (c) Underwater tidal notch tidal NE notch of Mourtia NE of beach, which was slightly raised by 8 ± 5 cm based on comparisons between 2015 and 2020. Photo taken in 2015. Mourtia beach, which was slightly raised by 8 ± 5 cm based on comparisons between 2015 and 2020. Photo taken in 2015.

3.5. Kokkari (SA16) 3.4. MourtiaKokkari (SA15) is located 8 km west of Vathy, at the northwestern coastal part of Mytilinii basin.On At the the carbonate port of the cliffs, town, about a +22 1.2 ± km 5 cm east uplift of Mourtia was measured beach (NE based Samos), on athe submerged exposed midlittoralfossil shoreline zone through (uplifted a midlittoral tidal notch color was identiﬁed belt of microbial and measured origin [34]) at − at40 the± 5 vertical cm in 2015. cliff ofThe a small same outcrop site was of revisited Vourliotes in 2020marbles. and the notch depth of −32 ± 5 cm was recorded implying a slight emergence of 8 ± 5 cm (Figure6c). The notch is visible continuously for more than 1 km on the coast. Its inward depth corresponds to a sea level stability for one to nine centuries.

3.5. Kokkari (SA16) Kokkari is located 8 km west of Vathy, at the northwestern coastal part of Mytilinii basin. At the port of the town, a +22 ± 5 cm uplift was measured based on the exposed midlittoral zone (uplifted midlittoral color belt of microbial origin [35]) at the vertical cliff of a small outcrop of Vourliotes marbles. J. Mar. Sci. Eng. 2021, 9, x FOR PEER REVIEW 9 of 18

3.6. White (St. Nicholas) Chapel at Potami Beach (SA18 and SA19) At the eastern part of the beach located east of White Chapel, there is evidence of J. Mar. Sci. Eng. 2021, 9, 40 three raised notches (SA18); however, their profiles are not well developed (Figure9 of7a). 17 An uplift of +20 ± 5 cm was deduced based on the position of the lower notch and the exposed midlittoral zone. 3.6. White (St. Nicholas) Chapel at Potami Beach (SA18 and SA19) At the western part of Potami Beach (west of White Chapel—site SA19), measure- mentsAt at thethe easternexposed part midlittoral of the beach zone were located performed, east of White supporting Chapel, an there uplift is of evidence +20 ± 5 cm of (Figurethree raised 7b). The notches former (SA18); midlittoral however, zone their with proﬁlesthe characteristic are not well vegetation developed belt (Figure consisting7a). ± ofAn limpets uplift ofand +20 brown5 cmalgae was is deducednow observed based above on the present position sea of level. the lower notch and the exposed midlittoral zone.

(a) (b)

Figure 7. ((a)) Evidence of of three uplifted tidal notches (SA18) howe howeverver their profiles proﬁles are not well developed. An uplift of +20 ± 55 cm cm waswas measured basedbased onon the the position position of of the the lower lowe notch,r notch, which which was was ascribed ascribed to the to 30ththe 30th October October 2020 2020 earthquake; earthquake;(b) SA19 (b site) SA19 at Potami site at Potami beach indicates beach indicates an uplift an of uplift +20 ± of5 +20 cm ± based 5 cm onbased exposed on exposed vegetation vegetation belt rich belt in rich limpets in limpets and brown and brown algae. Photos taken in 2020. algae. Photos taken in 2020.

3.7. PuntaAt the (SA21) western part of Potami Beach (west of White Chapel—site SA19), measurements at thePunta exposed Cape midlittoral is located on zone the were western performed, side of Potami supporting Beach an and uplift hosts of +20three± raised5 cm fossil(Figure shorelines7b) . The formercorresponding midlittoral to zonetwo benc withhes the characteristicand one tidal vegetation notch [15]. belt The consisting cape is formedof limpets onand Kerketeas brown algaemarbles is now dipping observed seaw aboveard. presentThe November sea level. 2020 measurements showed a clear uplift of the area after the recent earthquake. The lower and upper benches were3.7. Punta measured (SA21) at +82 ± 5 and +132 ± 5 cm above present sea level (apsl), respectively, supportingPunta an Cape uplift is locatedof +22 cm on in the comparison western side with of Stiros Potami et al. Beach [15] values and hosts (Figure three 8a,b). raised A well-developedfossil shorelines tidal corresponding notch is also to twosituated benches at +232 and ± one 5 cm. tidal notch [15]. The cape is formed on KerketeasAt the western marbles part dipping of Potami seaward. Beach The and November close to Punta 2020 Cape, measurements there is a showedwave-cut a cave clear withuplift no of speleothems, the area after thejust recent next to earthquake. the coastal The road lower (Figure and upper8c). The benches cave develops were measured along tectonicat +82 ± discontinuities,5 and +132 ± 5resulting cm above in a present triangular sea levelshape (apsl), of its respectively,passage. The supportingcave length anis aboutuplift 100 of +22 m and cm in it comparisonprogressively with narrows Stiros ettowa al. [rds15] its values inner (Figure part. The8a,b). latter A well-developed bears signs of notchtidal notchprofiles is alsoat the situated bottom at of +232 both± walls.5 cm. The altitude of the entrance lies conspicuously, at theAt same the altitude western of part the ofreported Potami notch Beach (+232 and cm) close at to Punta Punta by Cape, Stirosthere et al. is[15]. a wave-cut The two sitescave are with only no separated speleothems, by 150 just m nextand they to the share coastal a common road (Figure uplift 8history.c). The The cave cave develops devel- opedalong by tectonic the wave discontinuities, action when the resulting sea stood in aat triangular the position shape of the of notch its passage. vertex. The The max- cave imumlength width is about value 100 of m the and cave it progressivelyis observed at its narrows current towards bottom, its the inner altitude part. of which The latter co- incidesbears signs withof the notch notch proﬁles vertex atsuggesting the bottom a st ofable both sea walls. level Theposition altitude at that of the level. entrance lies conspicuously, at the same altitude of the reported notch (+232 cm) at Punta by Stiros et al. [15]. The two sites are only separated by 150 m and they share a common uplift history. The cave developed by the wave action when the sea stood at the position of the notch vertex. The maximum width value of the cave is observed at its current bottom, the altitude of which coincides with the notch vertex suggesting a stable sea level position at that level.

J. Mar. Sci. Eng. 2021, 9, x FOR PEER REVIEW 10 of 18 J. Mar. Sci. Eng. 2021, 9, 40 10 of 17

(a)

(b)

(c)

Figure 8. (a) TwoFigure benches 8. (a and) Two one benches tidal notch and oneat Punta tidal Cape, notch su atpport Punta an Cape, uplift support of +22 ± an 5 upliftcm. Photo of +22 taken± 5 in cm. 2020; (b) Schematic presentationPhoto taken of the in uplift 2020; at ( bPunt) Schematica Cape. Ages presentation in red letters of the correspond uplift at to Punta the dates Cape. of Agesuplift inof redformer letters shorelines [15]; (c) Wave-cutcorrespond cave, at the to thewestern dates part of uplift of Potami of former Beach, shorelines uplifted [by15]; the (c) same Wave-cut event cave, that uplifted at the western the tidal part notch of +2.32 m at Punta Cape. Potami Beach, uplifted by the same event that uplifted the tidal notch +2.32 m at Punta Cape.

J. Mar. Sci. Eng. 2021, 9, x FOR PEER REVIEW 11 of 18

3.8. Megalo Seitani (SA24) At the western coastal cliffs of Megalo Seitani beach, signs of a +22 ± 5 cm uplift were identified, where the former midlittoral zone has been left exposed above the present sea level (white strip of dead algae) (Figure 9a). The site is comprised of Kerketeas marbles overlaid by conglomerates. J. Mar. Sci. Eng. 2021, 9, 40 11 of 17 3.9. Aghios Isidoros (SA25 and SA26) At the cape consisting of Kerketeas marbles where the traditional shipyard is located, evidence3.8. Megalo of former Seitani palaeo-shorelines (SA24) is visible [15]. In 2020, the team measured one bench at +88 At± 5 thecm and western one tidal coastal notch cliffs at +111 of Megalo ± 5 cm Seitaniapsl (SA25) beach, (Figure signs 9b). of aAdditionally, +22 ± 5 cm at uplift were theidentiﬁed, center of Aghios where theIsidoros former bay midlittoral (SA26), a co zonelony of has Cirripedia, been left freshly exposed exposed above at the+35 present± sea 5level cm at (whitethe edge strip of a oftidal dead notch algae) base (Figurewith the9 notcha). The vertex site lying is comprised at +70 apsl, of suggests Kerketeas an marbles uplift of +35 ± 5 cm. overlaid by conglomerates.

J. Mar. Sci. Eng. 2021, 9, x FOR PEER REVIEW 12 of 18

(a)

(b)

FigureFigure 9. 9.(a)( Thea) The former former midlittoral midlittoral zone zonetestifies testiﬁes to an uplift to an of uplift +22 cm of at +22 Megalo cm at Seitani; Megalo (b) Seitani; Ag- (b) Agios ios Isidoros: Tidal notch and bench already uplifted in former stage and a colony of Cirripedia are Isidoros: Tidal notch and bench already uplifted in former stage and a colony of Cirripedia are indicative of a 35 ± 5 cm uplift due to the seismic event of 30th October 2020. Photos taken in 2020. indicative of a 35 ± 5 cm uplift due to the seismic event of 30th October 2020. Photos taken in 2020. 3.10. Pithagoreio (SA27) At the southeast part of Samos, at Pithagoreio town, the contemporary breakwater appears to have recorded the uplift, which took place as a result of the 2020 earthquake. Measurements of the former midlittoral zone that is exposed above mean sea level suggest +15 ± 5 cm of uplift (Figure 10a).

3.11. Psili Ammos (SA28) At Psili Ammos, marks of an uplifted shoreline at 10 ± 5 cm apsl lie at the eastern part of the beach, which did not exist in 2015. The rocks consist of Vourliotes marbles. The exposed limpets, vermetids and dead red algae of the former midlittoral zone [33] are characteristic of the 2020 earthquake uplift. On the other side of the beach and about 1 km to the west, a military facility is located next to the shoreline. At this site we measured marks of an uplifted shoreline at +13 ± 5 cm apsl on Zoodochos Pigi marbles (Figure 10b).

3.12. Springs at Mytilinii Village (SA29) The village of Mytilinii is located 6.5 km NW of Vathy. One week after the main earthquake, high discharge activity at the springs of Mytilinii Village emerged.

J. Mar. Sci. Eng. 2021, 9, 40 12 of 17

3.9. Aghios Isidoros (SA25 and SA26) At the cape consisting of Kerketeas marbles where the traditional shipyard is located, evidence of former palaeo-shorelines is visible [15]. In 2020, the team measured one bench at +88 ± 5 cm and one tidal notch at +111 ± 5 cm apsl (SA25) (Figure9b). Additionally, at the center of Aghios Isidoros bay (SA26), a colony of Cirripedia, freshly exposed at +35 ± 5 cm at the edge of a tidal notch base with the notch vertex lying at +70 apsl, suggests an uplift of +35 ± 5 cm.

3.10. Pithagoreio (SA27) At the southeast part of Samos, at Pithagoreio town, the contemporary breakwater appears to have recorded the uplift, which took place as a result of the 2020 earthquake. J. Mar. Sci. Eng. 2021, 9, x FOR PEER REVIEW 13 of 18 Measurements of the former midlittoral zone that is exposed above mean sea level suggest +15 ± 5 cm of uplift (Figure 10a).

(a) (b)

FigureFigure 10. 10. (a(a) )Exposed Exposed midlittoral midlittoral zone zone at at Pithagoreio Pithagoreio suggests suggests +15 +15 ±± 5 5cm cm of of uplift uplift because because of of the the 30th 30th October October 2020 2020 earthquake;earthquake; (b (b) )Uplift Uplift of of +10–13 +10–13 ±± 5 5cm cm in in the the coastal coastal zone zone of of Psili Psili ammos ammos increasing increasing from from the the site site west west of of the the lagoon lagoon towardstowards the the military military station. station. Photos Photos taken taken in in 2020. 2020.

4. Discussion 3.11.In Psili tectonically Ammos (SA28) active coastal areas, abrupt relative sea-level changes take place before, duringAt Psili and Ammos, after marksearthquake of an events uplifted [35–4 shoreline0]. When at 10the± origin5 cm apslof vertical lie at the displace- eastern mentspart of is theco-seismic, beach, whichthey are did generally not exist related in 2015. to earthquakes The rocks consist with magnitude of Vourliotes larger marbles. than 6.0,The often exposed associated limpets, with vermetids morphogenic and dead faults, red and algae therefore of the former result midlittoral in direct surface zone [34 fault-] are ingcharacteristic [41]. of the 2020 earthquake uplift. On the other side of the beach and about 1 km to theThe west, carbonate a military rocks facility along the is located coasts of next Samos to the (Figure shoreline. 4) favour At thisthe development site we measured and preservationmarks of an upliftedof tidal notches. shoreline The at +13 value± 5 of cm tidal apsl notches on Zoodochos for coastal Pigi tectonics marbles (Figureis often 10 ex-b). pressed in the literature, especially in the Eastern Mediterranean [15,29,37,42–49]. In par- 3.12. Springs at Mytilinii Village (SA29) ticular, notches, mainly tidal, are often used to deduce relative sea level changes for the late PleistoceneThe village [50] of and Mytilinii Holocene is located [51] and 6.5 for km elucidating NW of Vathy. vertical One tectonic week displacements after the main [35,52].earthquake, high discharge activity at the springs of Mytilinii Village emerged. Uplifted tidal notches and other sea level indicators in Samos island have been stud- 4. Discussion ied in the past by Mourtzas and Stavropoulos [24] and Stiros et al. [15], proving that tectonic Inmovements tectonically of activeco-seismic coastal origin areas, have abrupt uplifted relative the sea-level northwestern changes coast take of place Samos before, is- landduring during and the after late earthquake Holocene. events Submerged [36–41 sea]. When level theindicators origin ofat verticalthe southeastern displacements part of is the island were studied by the authors in 2015, but have remained unpublished until today. In this paper, we discuss seven sites (SA16–SA26) of the NW part of Samos island (Table 1), and based on our findings it is clear that the area has been co-seismically uplifted during the 2020 event. Although we have measured additional sea level indicators in the NW part of Samos, we focus here on the best evidence, which comes from the re-visited sites and the comparative measurements. Based on our findings, the NW part of Samos island from Vathy to Agios Isidoros has been co-seismically uplifted by 20 ± 5 cm to 35 ± 5 cm, with maximum uplift of +35 ± 5 cm at Agios Isidoros (SA25, Figure 10), which fades out towards the northeast at Kokkari, with +22 ± 5 cm uplift (SA16). This part of Samos was uplifted at least three times in the late Holocene (Figure 8a) [15]. Specifically, Stiros et al. [15] identified three raised palaeo-shorelines corresponding to three earthquakes, dated approximately 500, possibly 1500, and 3600–3900 years ago.

J. Mar. Sci. Eng. 2021, 9, 40 13 of 17

co-seismic, they are generally related to earthquakes with magnitude larger than 6.0, often associated with morphogenic faults, and therefore result in direct surface faulting [42]. The carbonate rocks along the coasts of Samos (Figure4) favour the development and preservation of tidal notches. The value of tidal notches for coastal tectonics is often expressed in the literature, especially in the Eastern Mediterranean [15,30,38,43–50]. In particular, notches, mainly tidal, are often used to deduce relative sea level changes for the late Pleistocene [51] and Holocene [52] and for elucidating vertical tectonic displacements [36,53]. Uplifted tidal notches and other sea level indicators in Samos island have been studied in the past by Mourtzas and Stavropoulos [25] and Stiros et al. [15], proving that tectonic movements of co-seismic origin have uplifted the northwestern coast of Samos island during the late Holocene. Submerged sea level indicators at the southeastern part of the island were studied by the authors in 2015, but have remained unpublished until today. In this paper, we discuss seven sites (SA16–SA26) of the NW part of Samos island (Table1), and based on our findings it is clear that the area has been co-seismically uplifted during the 2020 event. Although we have measured additional sea level indicators in the NW part of Samos, we focus here on the best evidence, which comes from the re-visited sites and the comparative measurements. Based on our findings, the NW part of Samos island from Vathy to Agios Isidoros has been co-seismically uplifted by 20 ± 5 cm to 35 ± 5 cm, with maximum uplift of +35 ± 5 cm at Agios Isidoros (SA25, Figure 10), which fades out towards the northeast at Kokkari, with +22 ± 5 cm uplift (SA16). This part of Samos was uplifted at least three times in the late Holocene (Figure8a) [ 15]. Specifically, Stiros et al. [15] identified three raised palaeo-shorelines corresponding to three earthquakes, dated approximately 500, possibly 1500, and 3600–3900 years ago. In the southeastern part of Samos, six sites were studied (SA1–SA15) in this work, mainly through submerged tidal notches and biological indicators. Based on the submerged features four palaeo-shorelines were identified. The upper notch has only recently been drowned due to global sea-level rise of about 20–30 cm that took place during the 19th and 20th century [54]. The profile of the tidal notch at +115 ± 5 cm indicates its co-seismic subsidence in the past (SA9, Figure5b), while the profile of the other two tidal notches at −80 ± 10 and −250 ± 10 cm probably corresponds to a period of relative sea level rise (SA1, Figure5a). The re-examination of the same submerged tidal notches in November 2020, revealed that have been uplifted, but they remain drowned. Based on the comparisons of their depth values between 2015 and 2020, it is clear that the uplift is higher in the west (e.g., SA1) and progressively lowers towards the east (e.g., SA15). It is interesting to note the southeastern part of the island is mostly characterized by a subsidence regime, while periods of uplift are less expressed in the north and northwest parts of the island. The results of submerged tidal notches at the southeastern part of Samos island studied in 2015 and their uplift due to the seismic event of 30th October 2020, reveal the complex tectonics of the area. This is also represented in the sedimentary records of Mesokampos and Psili Ammos discussed by Evelpidou et al. [29]. The corings are located approximately 2.5 km northeast of the footwall of Pithagoreio fault, a structure defining the morphology in this part of the island [12,29]. According to Pavlides et al. [55], the Pithagoreio fault has earthquake potential of the order of 6.6. In fact, two active normal faults, namely Pithagoreio and Vathy [12], are the most significant tectonic features in this area, striking WNW-ESE, which may define the main vertical displacement trend in the area but other local faults dipping in the opposite direction may cancel out part of this trend [29]. The measured uplift values in the field are consistent with the geophysically modelled displacements of the earthquake of October 2020. We are reporting a +35 ± 5 cm maximum vertical displacement at the northwestern part of Samos and a vertical displacement ranging between +23 ± 5 and +8 ± 5 cm at the south and southeastern part, which fit very well with the announced model approaches [22,56]. Our data imply a fading of the uplift produced by the earthquake towards the east. J. Mar. Sci. Eng. 2021, 9, 40 14 of 17

The preliminary slip distribution map produced by the USGS [56] depicts the largest slip areas located at the northern offshore part of Samos and more particularly at and northwest of the epicentre. This region coincides with the northwestern onshore locations of large uplift. Although there is no modelled fault slip towards the east, a small uplift did occur according to our findings, resulting in the +8±5 cm vertical displacement of the Mourtia beach area. Most probably, the magnitude of this displacement was such that the Finite Fault model was unable to detect it. Moreover, the macroseismic intensity (MMI) predicted by the ShakeMap model [56] had the highest values (6.5–7.0) at the areas of the northern part of Samos, whereas the eastern and southeastern part of the island accommodating the smaller uplift was not included in the high MMI sector. The MMI is indicative of the fault geometry. The GNSS observed displacements also support our findings for differential uplift during this seismic event. The GPS co-seismic deformation as well as the GPS modelled co-seismic deformation display a large difference in horizontal movement between the northwestern (almost 20–25 cm) and eastern (5 cm) parts of the island indicating a different uplift along a normal fault of a 37◦ dip-angle [22]. The overall differential uplift of Samos with higher values at the west and gradually lower ones at the east, indicates the complex geological setting of the island. The strong earthquake of October 2020 displaced the footwall of the ruptured fault where Samos lies but an unevenly uplifting pattern took place. This pattern distinguishes two discrete sectors at the island, the western and the eastern one (Figure4). The border among the two is located along the NNE-SSW trending tectonic contact between the Vourliotes nappe and the Mytilini basin. On both north and south sides of this contact, the authors measured a +22 ± 5 and +23 ± 5 cm uplift of the coast, whereas the respective values decrease towards the east of this zone. Most probably, the aforementioned tectonic contact that emerges east of the Vourliotes thrust represents a back-thrust fault, outcropping partially at the contact between the southeastern part of Vourliotes nappe and Selçuk nappe (Figure4) . Its continuation to the north probably runs along the Mytilini Neogene sediments. The same case is observed for the tectonic contact between Ampelos nappe and Karlovasi basin to the west. This NNE-SSW tectonic feature can only be justified under the current NNE-SSW extension as being an older structure of compressional regime. According to Ring et al. [16], evidence of a short-lived E-W compressional phase between 9 and 8.6 Ma interrupted the NNE extension. This phase is also observed in Samos through several reverse faults affecting the Miocene basin as well as its margins and the presence of folds in the Miocene deposits [10]. Such a structure can act as a seismotectonic barrier preventing the equal uplift of western and eastern sectors of Samos island, thus resulting in lower uplift values for the eastern part. The observed high discharge of springs at Mytilinii Village was most probably triggered by the eastward tilting of Samos eastern sector due to the M7.0 earthquake, which is also supported by the findings of our work. The Mytilinii Village lies in the Mytilinii basin consisting of fluvial-lacustrine deposits and is dissected by WNW-ESE faults that represent the main tectonic directions on the island [12]. These tectonic discontinuities were probably activated by the October 2020 earthquake, disturbing the underground water flow and directing it towards the Mytilinii springs.

5. Conclusions The comparative study of various sea level indicators along the coastal zone of Samos island was accomplished through measurements taken by the authors in 2015 and 2020 and the published measurements by Stiros et al. [15]. Based on our ﬁndings, we concluded that the island has been co-seismically uplifted but with different magnitude. In fact, the largest uplift was noted at the northern part of the coast, with the highest value at the northwestern tip of the island. Although the southern part of Samos has experienced many submergence events in the past, during the earthquake of 30th October 2020, it has been uplifted by up to 23 ± 5 cm, while the uplift fades out towards the east-northeast. We believe that J. Mar. Sci. Eng. 2021, 9, 40 15 of 17

the tectonic contact between the Vourliotes nappe and the Mytilinii basin has acted as a seismotectonic barrier, preventing the south east part of the island from the high uplift rates noticed at the north.

Supplementary Materials: The following are available online at https://www.mdpi.com/2077-1 312/9/1/40/s1, Table S1: Measurements performed on the different sea level indicators and the method used for each site. Author Contributions: Conceptualization, N.E.; investigation, N.E., A.K., I.K.; writing—original draft preparation, N.E., A.K., I.K.; writing—review and editing N.E., A.K., I.K. All authors have read and agreed to the published version of the manuscript. Funding: This research received no external funding. Institutional Review Board Statement: “Not applicable” for studies not involving human or animals. Informed Consent Statement: “Not applicable” for studies not involving human. Data Availability Statement: The data presented in this study are available in Table S1. Acknowledgments: Special thanks to East Samos municipality and specifically to mayor George Stanzos and vice mayor Despina Kaila. We would also wish to thank Manolis Karlovassitis for his support during all fieldwork activities, and Nikos Tsoumakis and Dimitris Siganos for escorting the team with their vessel in submarine field work in 2020 and Archipelagos for accompanying the team by boat in 2015. The authors would also like to thank Evangelos Kamperis for his fruitful discussion. We also thank four anonymous reviewers and the academic editor, whose comments improved an earlier version of this manuscript. Conflicts of Interest: The authors declare no conflict of interest.

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