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On January 24, 2020, Sivrice–Elazig–Turkey earthquake occurred along the East Anatolian Fault Zone. The moment magnitude of the event was reported as 6.8. This paper documents reconnaissance findings performed immediately after the event. Investigated sites namely, Lake Hazar shores, Karakaya Dam Reservoir–Euphrates River shores, Malatya–Battalgazi district and its villages, and Elazig Downtown are predicted to be shaken by rock peak ground acceleration, PGAVS30=1100 m/s, levels of 0.12–0.42 g, 0.05–0.11 g, 0.05 g, and 0.08 g respectively. The documented geotechnical field performances vary from widespread liquefaction-induced sand boils and lateral spreading, to no signs of surface manifestations of permanent ground deformations or soil liquefaction. In Battalgazi district and Elazig Downtown, the foundation performances vary from no signs of permanent ground deformations to 1–3 cm settlements, and 1–2 cm lateral movements. Additionally, the hydraulic structures inspected are estimated to be shaken by PGAVS30=1100 m/s levels of 0.03–0.23 g. Other than a minor longitudinal cracking along a limited section along the crest of a homogeneous earthfill dam, no apparent signs of permanent ground deformations were reported. Last but not least, a number of rock falls were mapped, based on back analyses of which probable peak ground velocities at these rockfall sites were speculated.

Due to the unique soil and morphological conditions prevailing in Izmir Bay basin, structural damage has been governed by site effects. Consistently, during October 30, 2020 M7.0 Samos Earthquake, which took place offshore of Samos Island, structural damage and life losses were observed to be concentrated in Bayrakli region of Izmir Bay, despite the fact that the fault rupture was at a distance of 65-75 km from the city of Izmir. Additionally, strong ground motions recorded in Izmir Bay showed unique site amplifications that were observed surprisingly at both rock and soil sites. Soil amplifications and duration elongations were mostly due to site effects governed by the response of very deep alluvial deposits of low plasticity. Similarly, due to very extensive faulting-induced fracturing and unusually stratified nature of rock sub-layers, unexpected long period amplifications were also observed at rock sites. These earthquake and site resonance effects were more pronounced in the period range of 0.5-1.5 s. When they were superposed with relatively coinciding natural period of 7-9 story residential buildings of Izmir City, it was concluded that the triple resonance effects among incoming rock ground motions, soil deposits, and the damaged buildings, amplified and prolonged the overall system response. Within the confines of this manuscript, the governing role of site effects leading to increased seismic demand was assessed, through a series of 1D equivalent linear, total stress-based site response assessments, the results of which clearly highlighted the variation of seismic demand in Izmir Bay., Middle East Technical University, The earthquake reconnaissance studies were supported by Middle East Technical University. The authors would also like to thank the undergraduate students, who collaborated on field campaigns and data processing.

On October 30, 2020 14:51 (UTC), a moment magnitude (M-w) of 7.0 (USGS, EMSC) earthquake occurred in the Aegean Sea north of the island of Samos, Greece. Turkish and Hellenic geotechnical reconnaissance teams were deployed immediately after the event and their findings are documented herein. The predominantly observed failure mechanism was that of earthquake-induced liquefaction and its associated impacts. Such failures are presented and discussed together with a preliminary assessment of the performance of building foundations, slopes and deep excavations, retaining structures and quay walls. On the Anatolian side (Turkey), and with the exception of the Izmir-Bayrakli region where significant site effects were observed, no major geotechnical effects were observed in the form of foundation failures, surface manifestation of liquefaction and lateral soil spreading, rock falls/landslides, failures of deep excavations, retaining structures, quay walls, and subway tunnels. In Samos (Greece), evidence of liquefaction, lateral spreading and damage to quay walls in ports were observed on the northern side of the island. Despite the proximity to the fault (about 10 km), the amplitude and the duration of shaking, the associated liquefaction phenomena were not pervasive. It is further unclear whether the damage to quay walls was due to liquefaction of the underlying soil, or merely due to the inertia of those structures, in conjunction with the presence of soft (yet not necessarily liquefied) foundation soil. A number of rockfalls/landslides were observed but the relevant phenomena were not particularly severe. Similar to the Anatolian side, no failures of engineered retaining structures and major infrastructure such as dams, bridges, viaducts, tunnels were observed in the island of Samos which can be mostly attributed to the lack of such infrastructure., METU; HAEE/ETAM; NSF; National Science Foundation [CMMI-1826118], The authors are indebted to Professor George Bouckovalas of the National Technical University of Athens, Prof. Dr. Atilla Ansal of Ozyegin University, Istanbul, Prof. Dr. Ayfer Erkin of Istanbul Technical University, Prof. Dr. Bilge Siyahi of Gebze Technical University, Istanbul for their valuable review of this work, and their insightful comments that significantly improved many of the discussions presented herein, particularly those pertaining to the seismic performance of foundation systems and seismic response of port facilities. The authors would also like to deeply thank external contributors who kindly provided data and assistance with carrying out field measurements included in this paper. In this regard, George Milionis, Geologist, provided the boreholes log data for BH1, BH2, BH3 and BH4 shown in Figure 33 while the borehole log data for BH5 shown in the same figure was provided by Peggy Sechioti, employee of the Hellenic Ministry of Infrastructure and Transport. MASW field measurements by Prof. P. Pelekis were supported by Vasilis Christopoulos, laboratory member, and Paraskevi Paliatsa, postgraduate student, Civil Engineering Department, University of Patras. The members of Middle East Technical University, Ankara were partially funded by reconnaissance funds of METU, which is greatly appreciated. The authors are also thankful to Professor K. Antonopoulos and Gurel Ozdemir for sharing photographs from local earthquake damages, and to Dr. Prodromos Psarropoulos, who did reconnaissance work as member of the HAEE/ETAM geotechnical team, for sharing information. Their valuable contribution is gratefully acknowledged. Financial support to the U-Patras team was provided by HAEE/ETAM. Prof Katerina Ziotopoulou's field reconnaissance and participation was supported by the NSF-sponsored Geotechnical Extreme Events Reconnaissance (GEER) association. The work of the GEER Association, in general, is based upon work supported in part by the National Science Foundation through the Geotechnical Engineering Program under Grant No. CMMI-1826118. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the NSF. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. The GEER Association is made possible by the vision and support of the NSF Geotechnical Engineering Program Directors: Dr. Richard Fragaszy and the late Dr. Cliff Astill. Last but not least, the authors are grateful to the anonymous reviewers who provided constructive feedback that improved the work.

On October 30, 2020 14:51 (UTC), a moment magnitude (M) 7.0 (USGS, EMSC) earthquake occurred in the Aegean Sea. This paper presents the reconnaissance findings regarding the site effects on recorded strong ground motion intensities and duration, along with the resulting induced-structural damage in Izmir Bay and Samos Island, respectively. In all rock records, relatively high intensity long period rock spectral accelerations were observed in the mid to long period range of 0.5-1.5 s, which are attributed to the source, more specifically, to the slower rupture-mechanism of the event. These rich spectral intensities were further amplified by soil site effects and soil-superstructure resonance, leading to two to six times amplified overall responses and prolonged seismic shaking durations, more pronounced in Bayrakli and other Izmir Bay sites in Turkey. However, these amplified and prolonged excitations are still below design basis earthquake levels, which addresses the lack of proper structural design and construction deficiencies, as the underlying causes for the collapse to heavy damage performance of 795 buildings. On the other hand, although located only about 10 km from the rupture (22 km from the epicenter) and within the near fault zone, the town of Vathy on Samos Island (Greece) was rather lightly affected by the earthquake, with relatively few collapsed or heavily damaged buildings, partially attributed to the low height/low weight of structures in the area. However, a concentration of damage in low-rise buildings in Ano Vathy hill is considered indicative of a combination of coupled valley and topography effects on the strong motion. This event once again addressed the need to develop region-specific zonation and provisions, when more general code practices are proven to be inadequate to assess these extreme site effects., METU; HAEE/ETAM; NSF; National Science Foundation through the Geotechnical Engineering Program [CMMI-1826118], The authors are indebted to Professor George Bouckovalas of the National Technical University of Athens, Prof. Dr. Atilla Ansal of Ozyegin University, Istanbul, Prof. Dr. Ayfer Erkin of Istanbul Technical University, Prof. Dr. Bilge Siyahi of Gebze Technical University, Istanbul for their valuable review of the paper, and their insightful comments that significantly improved many of the discussions presented herein, particularly those pertaining to site effects in the town of Vathy and city Izmir. The authors would also like to deeply thank external contributors who kindly provided data and assistance with carrying out field measurements included in this paper. In this regard, George Milionis, Geologist, provided the boreholes log data for BH1, BH2, BH3 and BH4 shown in Fig. 20 and Fig. 24, while the borehole log data for BH5 shown in Fig. 20 was provided by Peggy Sechioti, employee of the Greek Ministry of Infrastructure and Transport. A number of photographs and information about structural damage in Ano Vathy were provided by HAEE/ETAM members Christos Giarlelis and Prof. A. Sextos, respectively. Information about the orientation and polarity of the strong motion instruments at Vathy was provided by Drs Ioannis Kalogeras, Vassilis Margaris and Nikos Theodulidis of NOA and ITSAK-EPPO. MASW and HVSR field measurements by Prof. P. Pelekis were supported by Vasilis Christopoulos, laboratory member, and Paraskevi Paliatsa, postgraduate student, of the Civil Engineering Department, University of Patras. Additionally, a number of photographs and information about structural damage in Izmir Bayrakli were provided by Ali Aksoyer. Their valuable contribution is gratefully acknowledged. The members of Middle East Technical University, Ankara, were partially funded by reconnaissance funds of METU, which is greatly appreciated. Financial support to the U-Patras team was provided by HAEE/ETAM. Prof Katerina Ziotopoulou's field reconnaissance and participation was supported by the NSF-sponsored Geotechnical Extreme Events Reconnaissance (GEER) association. The work of the GEER Association, in general, is based upon work supported in part by the National Science Foundation through the Geotechnical Engineering Program under Grant No. CMMI-1826118. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the NSF. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. The GEER Association is made possible by the vision and support of the NSF Geotechnical Engineering Program Directors: Dr. Richard Fragaszy and the late Dr. Cliff Astill. GEER members also donate their time, talent, and resources to collect time-sensitive field observations of the effects of extreme events. Last but not least, thanks to EduPro Civil Systems Inc., the ProShake software license was freely provided for assessing site response analyses, which is acknowledged.

This study serves as an update to the Cetin et al. (2000, 2004) [1,2] databases and presents new liquefaction triggering curves. Compared with these studies from over a decade ago, the resulting new Standard Penetration Test (SPT)-based triggering curves have shifted to slightly higher CSR-levels for a given N1,60,CS for values of N1,60,CS greater than 15 blows/ft, but the correlation curves remain essentially unchanged at N1,60,CS values less than 15 blows/ft. This paper addresses the improved database and the methodologies used for the development of the updated triggering relationships. A companion paper addresses the principal issues that cause differences among three widely used SPT-based liquefaction triggering relationships.

The 2020 M7.0 Samos earthquake had occurred on the north of Samos Island; however, structural damage was observed in Izmir-Bayrakli, which is located approximately 65 km away from the epicenter. Strong ground motions recorded in Izmir Bay showed unique site amplifications, mostly due to the interaction between the basin and deep alluvial deposit response. The objective of this study is to evaluate the predictive performance of current ground motion models (GMMs) for estimating the recorded strong motions, especially the recordings over or near the Bayrakli-Bornova basin. 66 strong motion stations from Turkey with rupture distance (RRUP) < 200 km are used in the residual analysis, considering the ambiguities in the magnitude and depth to the top of the rupture estimations. Event terms of the earthquake for tested GMMs are found to be small and lie within the expected scatter, except for T = 0.5-1.5 s spectral accelerations. Event-specific distance attenuation for RRUP

The preceding companion paper presented the updating of the seismic soil liquefaction triggering relationship of Cetin et al. [1], and compared the resulting updated relationship with the earlier version. In this second paper, a detailed cross-comparison is made between three triggering relationships: (1) Seed et al. [2], as slightly updated by the NCEER Working Group (Youd et al. [3]), (2) Boulanger and Idriss [4], and (3) Cetin et al. [5]. Differences between these three triggering relationships, and the apparent causes of them are examined. Also studied are the impacts of these differences on levels of conservatism with regard to evaluation of liquefaction triggering hazard, and the resulting risks for engineering projects.

This data article provides a summary of seismic soil liquefaction triggering and non-triggering case histories, which were compiled, screened for data completeness and quality, and then processed for the development of triggering relationships proposed in “SPT-based probabilistic and deterministic assessment of seismic soil liquefaction triggering hazard” [1]. The database is composed of 113 liquefaction, 95 non-liquefaction, and 2 marginal liquefaction case histories, from seismic events with moment magnitude Mw values varying in the range of 5.9 to 8.3. A spreadsheet summary of these case histories are included along with a separate spreadsheet, by which maximum likelihood assessment was performed. These data transparently enable researchers to access case history input parameters and processing details, and to compare the case history processing protocols with the ones of different researchers (e.g.: “The influence of SPT procedures in soil liquefaction resistance evaluations.” [2], “SPT-based liquefaction triggering procedures.” [3]).

Graphical abstract, Probabilistic and deterministic seismic soil liquefaction triggering methodologies are proposed in Cetin et al. [1]. This manuscript: i) presents the protocols, which need to be followed for the correct use of this methodology for forward engineering (design) assessments, ii) guides the engineers through the procedure, and iii) discusses the “tricks” alongside the protocol. An illustrative soil profile shaken by a scenario earthquake is presented, through which consistent estimations of representative SPT blow-counts along with fines content are discussed. Additionally, the estimation of CSR input parameters are illustrated. Last but not least the uncertainty estimations of these input parameters are presented along with the probability and factory of safety for the assessment of liquefaction triggering. • A simplified methodology and its use to assess liquefaction triggering hazard of a soil site under an earthquake scenario event. • The consistent and unbiased mean estimates of input parameters of SPT blow-counts(N1,60), fines content (FC), vertical effective (σ'v) and total (σv) stresses, maximum ground acceleration (amax), stress reduction (or non-linear shear mass participation) factor (rd) and moment magnitude (Mw) along with their uncertainties are discussed. • Outlined methodology enables engineers to estimate the probability of- and factor of safety against- seismic soil liquefaction triggering for design problems.

A database, which consists of maximum and minimum void ratio limits and their range, particle size, distribution and shape characteristics, is compiled. More specifically, minimum and maximum void ratios (emin and emax) along with their range (emax-emin), particle roundness (R) and spherecity (S), fines content (FC), coefficient of uniformity (Cu), mean grain size (D50) data are compiled from natural cohesionless soils and reconstituted grained material (e.g.: rice, glass beads, mica) mixtures. The final dataset is composed of 636, mostly soil samples. Out of 636 samples, 496, 474 and 603 of them have emax, emin or emax-emin data, respectively. Similarly, for 593, 419, 171, 126 and 93 soils, D50, Cu, R, S and FC data exists, respectively. Not for every sample, USCS based soil classification designation is available, hence for the missing ones, soil classification is performed based on mean particle diameter-based classification as suggested by ASTM D2487 – 17: Standard Practice for Classification of Soils for Engineering Purposes (Unified Soil Classification System) [1]. The dataset consists of 19 silts and clays, 527 sands (357 fine sands, 153 medium sands, 17 coarse sands) and 47 gravels (44 fine gravels, 3 coarse gravels). A spreadsheet summary of the dataset is provided. This dataset is later used for the development of probability-based void ratio predictive models. Keywords: Void ratio, Mean grain size, Coefficient of uniformity

The void ratio limits and their range are mostly governed by their grain size, distribution, particle shape and fabric for cohesionless soils. For the purpose of developing a probability-based predictive model, a database, which consists of minimum and maximum void ratios, their range, as well as particle morphology (roundness, sphericity), size and distribution (mean grain size, fines content and coefficient of uniformity) parameters, is compiled. A set of predictive models, which use the combinations of Cu, D50, FC, R, and S parameters, is proposed. The models with Cu and/or D50, R and S, produce the most precise predictions. The probabilistic forward use of the proposed models is illustrated by a practical example. They are also presented in the form of deterministic chart solutions, illustrating the variation of in-situ void ratios for varying density states as functions of uniformity coefficient or mean grain size.