The 30 October 2020 (11:51 Utc) Izmir-Samos Earthquake and Tsunami; Post-Tsunami Field Survey Preliminary Results

THE 30 OCTOBER 2020 (11:51 UTC) IZMIR-SAMOS EARTHQUAKE AND TSUNAMI; POST-TSUNAMI FIELD SURVEY PRELIMINARY RESULTS

Ahmet Cevdet Yalcinera, Gozde Guney Dogana, Ergin Ulutaşb, Orhan Polatc, Ahmet Tarihd, Evrens Rıza Yapard, Evrim Yavuzd

aMiddle East Technical University, Department of Civil Engineering, Ocean Engineering Research Center, Turkey b Kocaeli University, Department of Geophysical Engineering, Seismology Division, Turkey cDokuz Eylul University, Department of Geophysical Engineering, Seismology Division, Turkey dIstanbul Metropolitan Municipality, Directorate of Earthquake and Ground Investigation

Correspondence: [email protected] and [email protected]

November 03, 2020

TABLE OF CONTENTS

ABSTRACT ...... 1

1. INTRODUCTION ...... 2

2. FIELD OBSERVATIONS ON TSUNAMI SUMMARY ...... 3

2.1. FIELD OBSERVATIONS IN ALACATI AND ZEYTINELI REGION ...... 6

2.1.1 Zeytineli Locality ...... 7 2.1.2 Alacati Locality ...... 9

2.2. FIELD OBSERVATIONS IN DEMIRCILI AND ALTINKOY REGION ...... 12

2.2.1 Demircili Locality ...... 12 2.2.2 Altinkoy Locality ...... 15 2.3. FIELD OBSERVATIONS IN SIGACIK AND AKARCA REGION ...... 15

2.3.1 Sigacik Locality ...... 15 2.3.2 Akarca Locality ...... 21 2.4. FIELD OBSERVATIONS IN TEPECIK AND GUMULDUR REGION ...... 25

2.4.1 Tepecik Locality ...... 25 2.4.2 Gumuldur Locality ...... 26

3. DISCUSSIONS AND CONCLUSIONS ...... 27

4. ACKNOWLEDGEMENTS ...... 28

LIST OF FIGURES AND TABLES

Figure 1.1 Bathymetric map around Kusadasi, Sigacik Bays and Samos Island ...... 2

Figure 2.1 Post-tsunami field survey area where observations of tsunami waves were obtained from locals, debris or traces identified ...... 3

Figure 2.2 Location map showing the distribution of the observations of the tsunami waves, obtained from locals, debris or traces identified in Zeytineli (Urla) and Alacati (Cesme) towns of Izmir city, Turkey ...... 6

Figure 2.3 View of the stream bed (green line) and the tsunami inundation zone (blue line) as of GPS records for Zeytineli. Main roads (black line) are located at the E and W part of the valley heights. Gray lines denote track records...... 7

i Figure 2.4 View of the stream bed and the tsunami inundation zone in Zeytineli (photo view from E to W) ...... 7

Figure 2.5: (Left) Wave traces on the palm tree (1.90 m) near the coastline (N38.19600 E26.48859), and (Right) trace of debris materials accumulated at the outer wall (1.50 m) of a house (N38.19587 E26.49027 and N38.19587 E26.49027, respectively) ...... 8

Figure 2.6 Damage observation in the fisher shelter (N38.19336 E26.49233), and rescue operation of a car which was dragged into due to tsunami ...... 9

Figure 2.7 View of the stream bed (green line) and the tsunami inundation zone (blue line) as of GPS records for Alacati. Gray lines denote track records ...... 9

Figure 2.8 View of the stream bed and the tsunami inundation zone in Alacati (photo view from W to E). Alacati fisher shelter is 1.1 km far from the boat and slightly visible at the right extremity of the photo ...... 10

Figure 2.9 Fisher boat on Alacati Azmak is dragged 430 m away from the shoreline (at 14:22 Local Time on 31 October 2020) ...... 10

Figure 2.10 Water level increase at the garden wall of Alacati Port Houses according to house owner (N38.26370 E26.37427) ...... 11

Figure 2.11 (Top) Wave trace was visible on Alacati Azmak bridge (~30 cm height from the bottom of the bridge wall) located at the North, 1.0 km away from the coastline (N38.27061 E26.37684), and (Bottom) near the Izmir-Cesme highway viaduct. Looking directions are from N to S for the top, and reverse for the bottom pictures ...... 12

Figure 2.12 Demircili locality, small inundation in the Northwestern part ...... 13

Figure 2.13 Demircili Beach, highly damaged boats ...... 14

Figure 2.14 Denizkizi Beach inundation extent ...... 14

Figure 2.15 Inundated areas in Altinkoy ...... 15

Figure 2.16 Summary of tsunami parameters measured in Sigacik ...... 16

Figure 2.17 Photo of Teos Marina before the event taken on 07.09.2020 ...... 16

Figure 2.18 Photo of Teos Marina after the event taken from a local newspaper (https://www.sabah.com.tr/video/yasam/depremin-merkez-ussu-seferisar-sigaciktaki-tsunami- felaketi-havadan-boyle-goruntulendi-video) ...... 17

Figure 2.19 Photo of Teos Marina after the event taken by a drone ...... 17

Figure 2.20 Tsunami traces on the garden fence of Teos Marina ...... 18

Figure 2.21 Azmak river in the East direction from Teos Marina where the tsunami overflowed the small bridge ...... 19

Figure 2.22 Dragged paddleboat in Sigacik ...... 20

ii Figure 2.23 Damage and tsunami traces in cafes and shops in Sigacik ...... 20

Figure 2.24 The white house damaged due to tsunami at 38.195600N 26.787424E ...... 21

Figure 2.25 Surveyed locations in Akarca ...... 22

Figure 2.26 Damaged fishery port piers, boats and small structures in Akarca due to tsunami ...... 22

Figure 2.27 Dragged boat in Akarca ...... 23

Figure 2.28 The white house where 1.9 m splash height was measured in Akarca ...... 23

Figure 2.29 Tsunami damage in Seferihisar Diving Center located in Akarca region ...... 24

Figure 2.30 Tsunami inundation near Seferihisar Diving Center ...... 24

Figure 2.31 Surveyed locations in Tepecik locality ...... 25

Figure 2.32 Tsunami inundation along a stream in Orsal Bay in Tepecik locality ...... 26

Figure 2.33 Surveyed locations in Gumuldur region ...... 26

Figure 2.34 25 m inundation in Gumuldur ...... 27

iii

FOREWORD

Tsunamis leave different types of traces in the inundation zone after the event. These traces may disappear in a short time because of natural processes and human activities. Therefore, quick post tsunami field surveys are important to obtain undisturbed data of tsunami parameters. Measurements, eyewitness interviews and questionnaires are the main tools and methods to collect data and determine the tsunami parameters at the coastal and inundation zones. However, these surveys can reach fresh data when performed soon after the event.

The 30 October 2020 Izmir - Samos earthquake and tsunami reminded the tsunami threat in the Eastern Mediterranean to the coastal communities, scientists and decision makers. A quick tsunami field survey was performed on the day after the 30 October 2020 event in the tsunami hit areas in Turkey from Kusadasi to Alacati coast. This report is prepared to present the collected data obtained from the post tsunami field survey conveyed on 30 and 31 October 2020 on the coast from Alacati to Gumuldur regions. It is important to note that the ground elevation was not measured at the survey locations except a few points where the ground elevation was already known or could be interpreted. However, in the next days and surveys, the ground elevation will also be measured to obtain tsunami runup at the surveyed location. The report will be updated when new survey(s) are performed.

The survey has been performed by Prof. Dr. Ahmet Cevdet Yalciner (METU), PhD Candidate Gozde Guney Dogan (METU), Assoc. Prof. Dr. Ergin Ulutas (Kocaeli University), Prof. Dr. Orhan Polat (Dokuz Eylul University), Ahmet Tarih, Evrens Rıza Yapar and Evrim Yavuz (Istanbul Metropolitan Municipality). In the survey, UNESCO International Tsunami Survey Team (ITST) Post -Tsunami Survey Field Guide 2nd Edition, UNESCO-ITST, (2014) has been used. The report is completely written by Gozde Guney Dogan.

iv ABSTRACT

A strong earthquake (Mw=6.6 AFAD*, Mw=6.9** KOERI, Mw=7.0 USGS***) of normal faulting striking about E-W occurred on October 30, 2020 (11:51 UTC) in between offshore Seferihisar (Izmir, Turkey) and Samos Island (Greece). The earthquake generated a tsunami that affected an area in the Aegean Coast of Turkey from Cesme Alacati in the northwestern part to Gumuldur coast in the southeastern part. Immediately after the event, a post-event field survey was performed on 31 October and 1 November 2020 by a team of seven people (A.C. Yalciner, G.G. Dogan, E. Ulutas and O. Polat, A. Tarih, E. R. Yapar and E. Yavuz) from METU, Kocaeli University, Dokuz Eylul University and Istanbul Metropolitan Municipality. The Turkey coast survey area covers mainly three parts: i) Alacati and Zeytineli regions in the Northwestern, ii) Sigacik Bay and Akarca region in Seferihisar coast in the North, and iii) Tepecik and Gumuldur regions in the Northeastern with respect to the earthquake epicenter. The team feels deep sorrow and express their condolences to the people for the loss of life and property in Izmir, Turkey and Greece.

Unfortunately, the tsunami was not recorded by any tide gauge located along the Turkish Coast of the Aegean Sea. Therefore, findings from the post-event survey have gained much more importance as the main documentation of sea level variations. The main objectives of this survey are to document the tsunami effects along the coast, obtain any available data on the observed coastal amplitudes and inundation extent, take pictures and audiovisual recording before they were cleaned, interview the eyewitnesses and to understand and explain the event in detail.

According to the findings in this field survey and eyewitness reports, the most impacted areas were Sigacik Marina, Sigacik Bay and Akarca region located in a 30 km distance to the epicenter in the northern direction. The maximum inundation distance reached 320 m in Akarca, where 20 boats were sunk in a small fishery port, as reported by the head of the port. The flow depth at this location was measured as 1.86 m. There was a splash height of 1.9 m recorded on a vertical wall of a highly damaged house just near the shore. The more to the southeastern coast after Akarca region, the less impacts were observed. There was almost no significant inundation water motion after Gumuldur. The tsunami impacts highly decreased after the cape of v shape peninsula between Tepecik and Gumuldur.

In the northeastern part, Alacati and Zeytineli, the maximum inundation was observed along Alacati Azmak measured as 1300 m. The maximum runup was measured as 1.9 m on the palm trees 50 m away from the coastline in Zeytineli region.

To summarize, our findings show that in small bays with narrow entrances, the tsunami was much amplified and the impacts on these coast were more severe. The region contains many streams (called Azmak in the local language) in the bays, which increases the potential of tsunami inundation and damage as also experienced in this event. Another important point is the remarkable increase in the awareness of the people who mostly moved away from the shore after noticing the sea withdrawal. However, unfortunately, a victim, who could not resist the strong current generated and died, was reported. After the 2017 Bodrum-Kos tsunami, the Aegean Sea with its high seismic mobility and this event once more reminded considerable tsunami potential in the eastern Mediterranean.

*https://deprem.afad.gov.tr/downloadDocument?id=2064 **http://www.koeri.boun.edu.tr/sismo/2/30-ekim-2020-mw6-9-ege-denizi-izmir-depremi/ ***https://earthquake.usgs.gov/earthquakes/eventpage/us7000c7y0/region-info

1. INTRODUCTION

A strong earthquake (Mw=6.6 AFAD*, Mw=6.9** KOERI, Mw=7.0 USGS***) of normal faulting striking about E-W occurred on October 30, 2020 (11:51 UTC) in between offshore Seferihisar (Izmir, Turkey) and Samos Island (Greece). The earthquake generated a tsunami, which affected an area in the Aegean Coast of Turkey from Cesme Alacati in the northwestern part to the Gumuldur coast in the southeastern part. Immediately after the event, a post-event field survey was performed on 31 October and 1 November 2020 by a team of seven people (A.C. Yalciner, G.G. Dogan, E. Ulutas and O. Polat, Ahmet Tarih, Evrens Rıza Yapar and Evrim Yavuz) from METU, Kocaeli University, Dokuz Eylul University and Istanbul Metropolitan Municipality Earthquake. The Turkey coast survey area covers mainly three parts: i) Alacati and Zeytineli regions in the Northwestern, ii) Sigacik Bay and Akarca region in the North and iii) Tepecik and Gumuldur regions in the Northeastern with respect to the earthquake epicenter. The team feels deep sorrow and express their condolences to the people for the loss of life and property in Izmir, Turkey and Greece.

Figure 1.1 Bathymetric map around Kusadasi, Sigacik Bays and Samos Island

2. FIELD OBSERVATIONS ON TSUNAMI SUMMARY

The field survey was performed on October 31 and November 1, 2020 along the coast from Alacati (26.389E 38.258N) to Gumuldur region (26.9961E 38.0675N). The survey area has been split into three parts as the northeastern (Alacati and Zeytineli), North (Demircili, Altinkoy, Sigacik, Akarca) and the northwestern regions (Tepecik and Gumuldur) with respect to the earthquake location and the field survey observations are given in the following sections respectively. Figure 2.1 shows the survey area covered by the team, where the survey locations eyewitnesses were inquired, local authorities were contacted, measurements were taken, and observations on the tsunami waves and audiovisual recording were performed. Table 2.1 presents a complete list of these coastal sites as well as measurements and important notes.

Figure 2.1 Post-tsunami field survey area where observations of tsunami waves were obtained from locals, debris or traces identified

Table 2.1 List of locations where the team performed the post-tsunami survey and measurements

Measurement ID Label/Place Region Lon. E Lat. N Notes Flow Depth (m) Z1 Palm Tree-1 Zeytineli 26.48859 38.19600 Traces on the palm tree 1.9 Traces on the wall of a Z2 Summer House Zeytineli 26.49027 38.19587 1.5 house Maximum inundation Z3 House-3 Zeytineli 26.49296 38.201206 700 m Severe damage on Z4 Fisher Shelter Zeytineli 26.49233 38.19336 boats and port. A car was dragged. A boat was dragged to A1 Boat Alacati 26.37770 38.26550 this point along the stream ~430 m water level increased Port Alacati A2 Alacati 26.37427 38.26370 and overtopped the Houses-1 garden wall up to 1.7 m A3 Azmak Bridge Alacati 26.37684 38.27061 1.0 km far from coast 0.3 water level increased Port Alacati A4 Alacati 26.37304 38.26346 and overtopped the Houses-2 garden wall up 1.7 m 1.3 km inundation A5 Alacati Azmak Alacati 26.37654 38.26320 along Alacati Azmak stream No severe damage with A6 Fisher Shelter Alacati 26.38443 38.25651 few exceptions D1 Beach Demircili 26.676901 38.211628 3m inundation Significant damage, 1.8m sea receded. Southeastern D2 Demircili 26.686378 38.207508 More than 1m water narrow beach level increase inside the port Denizyildizi D3 Demircili 26.694419 38.210438 15 m inundation 0.7m* Beach AL1 Altinkoy Beach Altinkoy 26.721817 38.212994 230 m inundation - AL2 Streambed Altinkoy 26.721487 38.214794 650 m inundation 0.15 Keyf-i Kahya S1 Sigacik 26.785155 38.191387 0.22 Lounge Cafe S2 Local park Sigacik 26.784490 38.191601 A wall in the local park 0.8 a garden fence S3 Teos Marina Sigacik 26.783164 38.191170 0.86 surrounding the port FD @ entrance: 0.6 S4 Kumsal Cafe Sigacik 26.786701 38.195445 1.22 FD @ inside: 0.86 trace on a wall of a S5 House Sigacik 26.787424 38.19560 0.88 white colored house a trace on a house wall, S6 House Sigacik 26.79003 38.19578 0.1 max inundation 320m trace on the walls of S7 Shop Sigacik 26.78609 38.19488 shops - local name 0.4 "kale ici" trace on the walls of S8 Shop Sigacik 26.786443 38.195027 shops - local name 0.4 "kale ici"

Vuslat trace on the windows S9 Sigacik 26.785967 38.201305 1.5 Restaurant of the restaurant trace on the garden S10 Building Sigacik 26.788412 38.195615 0.6 wall of a building a wire fence next to A1 Fishery port Akarca 38.1647 26.8146 1.3 coast trace on the walls of A2 House Akarca 38.164393 26.814826 the closest house to the 1.9** shoreline Diving center maximum inundation A3 Akarca 38.168305 26.813498 area 320 m Southeastern Traces on the wall, A4 Akarca 26.825079 38.155888 0.8 part sweeps on the road trace on the steps of a A5 Cafe Akarca 26.821295 38.161486 0.2 cafe Okeanos Beach A6 Akarca 26.821212 38.161753 100 m inundation Bungalows A7 Stream Akarca 26.821461 38.162223 150 m inundation trace on the wall of a Fishery Port A8 Akarca 26.814925 38.164035 house at 40 m distance 0.5 Area from shore trace on the wall of a A9 Garden Akarca 26.810972 38.166476 garden 0.55

Diving Center A10 Akarca 26.811804 38.166841 112 m inundation 0.2 Area the eyewitness cleaned the wall; he said that it House/Diving A11 Akarca 26.812036 38.166436 was 1 meter, the 0.8 Center Area veranda was all covered by sweeps Northwestern A12 Akarca 26.807888 38.168139 80 m inundation part Northwestern A13 Akarca 26.803827 38.171062 20 m inundation part Northwestern A14 Akarca 26.811287 38.168131 250 m inundation part Northeastern A15 Akarca 26.820431 38.16152 45 m inundation part Northeastern A16 Akarca 26.818972 38.162938 80 m inundation part only traces on the G1 Beach Gumuldur 27.013597 38.056631 beach Yali Resort G2 Gumuldur 26.999167 38.065173 25 m inundation Beach Yali Resort G3 Gumuldur 26.998755 38.065219 Trace on an object. 0.5 Beach Minor damage on the G4 Harbour Gumuldur 26.995283 38.067702 boats. No trace of water on walls, etc. Rafael 25 m inundation only at G5 Gumuldur 26.949292 38.075673 Boutique Hotel the beach 17 m inundation, G6 Beach Gumuldur 26.949218 38.075688 sweeps next to beach

valley line, inundation only at the beach Inundation 12 m, only T1 Central part Tepecik 38.1458290 26.8200730 sweeps Inundation 120 m along T2 Stream Tepecik 38.1395390 26.8314440 a small stream Inundation 20 m No T2a Cafe Tepecik 38.138961 26.83055 flow into the cafe. Café next to the stream Beach T3 area/summer Tepecik 38.1355660 26.8330510 1.5 houses 24 m inundation, only T4 Tepecik 38.1113740 26.8444360 sweeps *Tsunami runup. The ground elevation was approximately determined at this location. ** Splash Height

2.1. FIELD OBSERVATIONS IN ALACATI AND ZEYTINELI REGION

Post-event tsunami field surveys were performed along the coast of Zeytineli and Alacati towns at 11:00 am and 14:00 am on October 31, 2020 (Figure 2.2). Extension of inundation and wave heights have been traced and mapped by GPS in detail in both observation areas.

2.1.1 Zeytineli Locality

In this locality, the maximum inundation distance was measured as ~700 m along the NNE-SSW direction from the sea coast. The tsunami effects mainly followed the stream bed (Zeytineli Azmak). According to the findings in this field survey and eyewitness reports, the width of the inundation zone (parallel to the shoreline) was measured as ~400 m near to coastal area while it decreases down to 80 m towards the inner part (Figure 2.3, blue line). This finding clearly shows that the tsunami inundation behavior directly followed the topographic features as there are steep slopes on both sides (mountainside). The tsunami impact areas were mostly observable in an area limited between two main roads at the beginning of the valley heights in the East and West (Figure 2.3, Figure 2.4).

Figure 2.4 View of the stream bed and the tsunami inundation zone in Zeytineli (photo view from E to W)

The flow depth was measured as 1.9 m on the palm trees, which were 50 m away from the coastline (N38.19600 E26.48859 and N38.19602 E26.48936) and from debris materials accumulated at the outer wall of a house (N38.19587 E26.49027) (Figure 2.5). We also observed severe damage in the fisher shelter located in the eastern part of the gulf at N38.19336 E26.49233. In addition to the damages in fishing boats, a car was also dragged into the sea by the wave (Figure 2.6).

Figure 2.6 Damage observation in the fisher shelter (N38.19336 E26.49233), and rescue operation of a car which was dragged into due to tsunami

2.1.2 Alacati Locality

The maximum inundation distance was measured as ~1.3 km on the N-S direction of the stream bed (Alacati Azmak) from the sea coast. According to the observations and eyewitness reports, the width of the inundation zone was measured as ~280 m near to Alacati Azmak bridge located in the northern part and 1 km away from the coastline (N38.27061 E26.37684), again the inundation following the topographical features. The tsunami effects mainly followed the stream bed across a 130m wide band zone. The tsunami impact areas were mostly observable, starting from the beginning of the river, Alacati Azmak (Figure 2.7-Figure 2.9).

Figure 2.7 View of the stream bed (green line) and the tsunami inundation zone (blue line) as of GPS records for Alacati. Gray lines denote track records

Figure 2.9 Fisher boat on Alacati Azmak is dragged 430 m away from the shoreline (at 14:22 Local Time on 31 October 2020)

The water level increased and overtopped the garden wall of Port Alacati Houses up to a point at 1.7 m (N38.26346 E26.37304 and N38.26320 E26.37654) (Figure 2.10). We observed no severe damage in the fisher shelter except two locations at N38.25651 E26.38443. We also measured a 0.3 m flow depth in the Alacati Azmak bridge located at the North (near the Izmir-Cesme highway viaduct) and 1.0 km far from the coast (N38.27061 E26.37684, Figure 2.11).

Figure 2.10 Water level increase at the garden wall of Alacati Port Houses according to house owner (N38.26370 E26.37427)

2.2. FIELD OBSERVATIONS IN DEMIRCILI AND ALTINKOY REGION

2.2.1 Demircili Locality

In Demircili locality, there was a small inundation in the beach at 38.211628N 26.676901E, which was measured as 3m on the northwestern side of the bay. However, significant damage was observed by the local people and fishermen in a narrow beach site in the southeastern part of the bay (38.207508N 26.686378E). According to the eyewitness statements, the sea receded almost 20 min after the earthquake and came back in 3-4 minutes. They observed this recede-inundation for 5 hours. A boat

12 moored at a depth of 1.8 m was grounded when the sea receded during the depression wave. The water level increased more than 1 m inside the port.

Figure 2.12 Demircili locality, small inundation in the Northwestern part

Figure 2.13 Demircili Beach, highly damaged boats

In Denizyildizi Beach, next bay to Demircili Beach in the eastern direction, the runup was measured as 0.7 m, and the inundation distance was 15 m (38.210438N 26.694419E, Figure 2.14).

Figure 2.14 Denizkizi Beach inundation extent

2.2.2 Altinkoy Locality

In Altinkoy locality, the tsunami inundated up to 230 m in the bay (38.212994N, 26.721817E). On the other hand, the inundation at the streambed was measured as 650 m with a 0.15 m flow depth at 38.214794N 26.721487E (Figure 2.15).

Figure 2.15 Inundated areas in Altinkoy

2.3. FIELD OBSERVATIONS IN SIGACIK AND AKARCA REGION

2.3.1 Sigacik Locality

In Sigacik Bay, there was severe damage due to the tsunami. Figure 2.16 shows the locations where maximum tsunami parameters were measured and severe damage was observed. Teos Marina inside the bay was highly damaged by experiencing 4-5 hours lasting large period oscillations with an amplitude of 0.7 m according to eyewitness statements. 4 pantons were replaced from their locations and many boats were damaged. Figure 2.17 is a photo taken before the event showing the layout of Teos Marina the boats and Figure 2.18 shows the situation in Teos Marina after the event (taken by a drone).

Figure 2.16 Summary of tsunami parameters measured in Sigacik

Figure 2.17 Photo of Teos Marina before the event taken on 07.09.2020

Figure 2.19 Photo of Teos Marina after the event taken by a drone

Near the pedestrian entrance of Teos Marina (38.191379N 26.783131E), the flow depth was measured as 0.86 m on the garden fence of the port (Figure 2.20). In Teos Park, the recreation area of the marina, the flow depth was measured as 0.8 m at 38.191601N 26.784490E.

Figure 2.20 Tsunami traces on the garden fence of Teos Marina

The sea level increased 1.35 m from the stream level overflowing the small bridge according to the eyewitnesses at a stream located towards the East direction from Teos Marina (38.192722N 26.784206E). The inundation distance here reached up to 260 m (Figure 2.21).

Figure 2.21 Azmak river in the East direction from Teos Marina where the tsunami overflowed the small bridge

In the land part in the ESE direction of Teos Marina, the tsunami reached 210 m inland, where a flow depth of 0.4 m was measured at 38.191436N 26.785063E.

All of the café and restaurants located along the beachside in Sığacık Bay experienced high damage from tsunami waves (Figure 2.23). The flow depth was measured as 0.6 m at the entrance of Kumsal Café (38.195445N 26.786701E), increased to 0.86 m on the walls inside and 1.22 m at the back garden (landside) of the café since there is a reverse slope (the elevation is decreasing) from the entrance to the landside. The inundation distance in this part of Sigacik Bay was measured as 70 m as 38.195248N 26.787168E being the inundation end.

When moving to the northern part inside Sigacik Bay, the flow depth was measured as 0.88 m from the trace on the wall of a white house (38.195600N 26.787424E, Figure 2.24). The maximum inundation distance in this part of the bay was measured as 320 m along a stream bad at 38.195706N 26.789995E. A paddleboat was found dragged to the land at 38.196150N 26.789420E (Figure 2.22).

Figure 2.22 Dragged paddleboat in Sigacik

Figure 2.23 Damage and tsunami traces in cafes and shops in Sigacik

Figure 2.24 The white house damaged due to tsunami at 38.195600N 26.787424E

In the northern part of Sigacik Bay, the flow depth was measured in a restaurant near the shore (38.201147N 26.785744E) as 1.50 m and the flow depth decreased to 0.2 m at the inner land part inside a room of Dag Butik Hotel (38.201566N 26.785765E). The inundation distance here was measured as 60 m.

2.3.2 Akarca Locality

The coast in Akarca region from 38.171062N, 26.803827E to 38.168131N, 26.811287E (points A3- A17) was highly impacted by the tsunami waves, whereas a significant change (reduction) of tsunami impact was observed in the region after the small V shape cape in the northwestern direction (Figure 2.25). Therefore, we have collected many points in this region with flow depth and inundation distance measurements as well as eyewitness interviews. The first part was a small fishery port in the small cape (38.164666N, 26.814649E) in Figure 2.25. 20 boats were sunk and damaged in this port (Figure 2.26). A boat was dragged by the strong currents about 150-200 m towards inland (Figure 2.27). A water storage tank (half full) and a car were also dragged towards land at 38.164526N, 26.814808E. There was a 1.9 m splash height measured on a vertical wall of a house located just near the shore (38.1646660N 26.8146490E, Figure 2.28).

Figure 2.25 Surveyed locations in Akarca

Figure 2.26 Damaged fishery port piers, boats and small structures in Akarca due to tsunami

Figure 2.27 Dragged boat in Akarca

Figure 2.28 The white house where 1.9 m splash height was measured in Akarca

In Seferihisar Diving Center (38.165560N 26.813708E) located in this locality, the sea was receded up to a depth of 4m and ~180m in the horizontal direction. The arrival time of the first wave receded 10 minutes after the earthquake, according to the owner of Seferihisar Diving Center, Aydin Tunca, who was a survivor at the time of the event. The first wave arrival was between 10-15 minutes, according to him. He stated that he stayed on a sofa bed and he was dragged ~300m on this bed towards inland until the foot of the sofa was locked on the land. He observed 4-5 waves, of which the time between successive waves was observed around 8-10 minutes. The flow depth at this diving center was measured as 1.86 m. The maximum inundation distance was obtained as 320 m according to the first

23 observations, but this value may be larger and will be updated with new survey findings and measurements.

Figure 2.29 Tsunami damage in Seferihisar Diving Center located in Akarca region

Figure 2.30 Tsunami inundation near Seferihisar Diving Center

2.4. FIELD OBSERVATIONS IN TEPECIK AND GUMULDUR REGION

2.4.1 Tepecik Locality

In Tepecik locality, 1.5 m flow depth was measured at 38.135566N 26.833051E, where the ground elevation was about 0.5m above the sea level (i.e. inundation height is 2.0m). According to an eyewitness, the sea first receded ~25 m in the horizontal direction. At Orsal Bay in Tepecik locality, the inundation distance reached up to 120 m along a small stream (Figure 2.32), where 20 m inundation was measured in another cafe in this bay. Further distance to the North direction, Zumrut Houses in local name, the inundation was only 12 m where there was some sweep at 38.145829N 26.820073E. Figure 2.31 shows the surveyed locations in Tepecik locality.

Figure 2.31 Surveyed locations in Tepecik locality

Figure 2.32 Tsunami inundation along a stream in Orsal Bay in Tepecik locality

2.4.2 Gumuldur Locality

The maximum inundation was measured as 25 m in Gumuldur region at an area limited to only Rafael Boutique Hotel beach (38.0756730N, 26.9492920E). At another location, 38.065219N 26.998755E, there was a 0.5 m trace. The tsunami effects were mainly limited to beach areas where the inundation ranges between 17-25 m at different locations (Figure 2.33, Figure 2.34).

Figure 2.33 Surveyed locations in Gumuldur region

Figure 2.34 25 m inundation in Gumuldur

3. DISCUSSIONS AND CONCLUSIONS

The 30 October 2020 Izmir - Samos earthquake and tsunami reminded the tsunami threat in the Eastern Mediterranean to the coastal communities, scientists and decision-makers. Considering the importance of collecting tsunami data in the affected coastal areas, it is essential to perform field surveys as soon as possible to be able to observe the tsunami traces and deposits before they are cleaned/removed. The next day of the event, a team arrived in the affected area and performed a two-day field survey. The team attempted to cover a large area as conditions and time limitations allowed in this Covid-19 pandemic.

It is important to note that the ground elevation was not measured at the survey locations except a few points where the ground elevation was already known or could be interpreted. However, in the next days and surveys, the ground elevation will also be measured to obtain tsunami runup at the surveyed location. Therefore, the inundation distances can also be updated if necessary at some locations. Regarding the measurements, the team followed the UNESCO International Tsunami Survey Team (ITST) Post -Tsunami Survey Field Guide 2nd Edition, UNESCO-ITST, (2014). In addition to the flow depth and inundation distance measurements, the team tried to understand the time evolution of the event through eyewitnesses to obtain a picture of the phenomenon. There is a lack of data along some bays of the covered coast due to the fact that there is no settlement in these areas.

Regarding the collected information, Sigacik Bay and Akarca are the most hit and damaged regions of the surveyed area by the tsunami with 1.5 m and 1.86 m of flow depths, respectively. The maximum inundation distances measured in both areas are 320 m, but new findings/higher inundation distances may be expected in the next surveys. In Teos Marina in Sigacik and in the fishery port in Akarca, there 27 were many boats highly damaged and there were boats and cars dragged to the land by the waves. Strong currents and several vortexes were also observed by the survivors. The eyewitness statements reveal that the arrival time of the wave is between 10-15 minutes. Tsunami penetration has been observed much higher wherever any stream beds exist in the bays and the region contains many streams/streambeds (called Azmak in local language), which increases the potential of tsunami inundation and damage as also experienced in this event. The maximum inundation distance was measured along with one of these Azmak streams in Alacati as 1300 m. The tsunami impact highly decreases after the cape of V shape peninsula between Tepecik and Gumuldur.

4. ACKNOWLEDGEMENTS

Middle East Technical University, Department of Civil Engineering, Kocaeli University, Istanbul Metropolitan Municipality, Dokuz Eylul University, TUBITAK 119Y419 Project are acknowledged for their kind support to the post-tsunami field survey, which contributed to obtain the data for this report. Satellite images are taken from Google Earth 7.3.3.7786 (64-bit), image on 21 July 2020, server kh.google.com. Thanks are extended to Assoc. Prof. Dr. Ersen Aksoy and PhD Candidate Ozlem Aksoy (Mugla Sıtkı Kocman University) for their companion in the survey in Sigacik.