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Seismological and Engineering Effects of the M 7.0 Samos Island (Aegean Sea) Earthquake
Abstract
On 30 October 2020, an M 7.0 earthquake occurred north of Samos Island. The fault rupture caused sudden lowering of the seafloor, which produced a tsunami that mainly impacted nearby Samos Island as well as a series of Anatolian cities along the coast of Seferihisar Bay, with maximum runup and inundation lengths of about 3.8 m and 2500 m, resulting in substantial property losses. The mainshock was recorded by > 200 accelerometers from Turkish and Greek national networks for rupture distances up to 600 km. Overall levels of ground shaking, and their variation with distance, are consistent with expectation from regionally-adjusted global ground motion models. The intensity of ground shaking was near design levels in Samos Island, but well below design levels for reference rock conditions in the Anatolian coastal regions due to large source-site distances (30 to 70 km). Where site conditions were favorable (rock or shallow stiff soils), these ground motions did not damage structures. However, pronounced site effects locally amplified ground shaking at site frequencies near 0.7-1.6 Hz throughout the Izmir Bay region for both stiff and soft soil sites. This amplification was particularly pronounced on soft soils in the Bayrakli district, which led to significant structural damage. The earthquake produced isolated incidents of rockfalls and landslides, mainly in the northern part of Samos Island. We document these ground failures, as well as several “no-ground failure” case histories in Anatolia. Liquefaction was observed in different parts of Samos island, including ports. The emergency responses in Greece and Turkey provided support to residents displaced from their homes. In both regions, educational efforts with local government officials and residents had been undertaken prior to the event that were helpful.
... Meanwhile the Aegean plate advances rapidly to the south overriding the almost stalled African slab, causing N-S extension in parts of upper plate of Anatolia and Aegean Sea (Taymaz et al. 1990 ;Papazachos et al. 1998 ;Ganas & Parsons 2009 ;Yolsal-C ¸evikbilen & Taymaz 2012 ;Meng et al. 2021 ). These complex tectonic interplays create active seismicity, so the Aegean Sea and western T ürkiye regions have a history of moderate to large earthquakes (Benetatos et al. 2006 ;Yolsal-C ¸evikbilen et al. 2014 ;Kassaras et al. 2020 ;Papadimitriou et al. 2020 ;Cetin et al. 2020 and references therein). In addition, due to the oceanic environment, the Aegean Sea region is at significant risk of tsunamis generated by earthquakes. ...
... In this tectonic setting, on 30 October 2020 11:51 UTC, a M w 7.0 earthquake occurred in the eastern Aegean Sea nearby Samos Island, affecting Samos Island in Greece and Ku s ¸adası Bay surrounding nearby İ zmir Province in T ürkiye (Papadimitriou et al. 2020 ;Ganas et al. 2021 ;Taymaz et al. 2022 ; Fig. 1 ). The Samos earthquake caused a total of 119 deaths, more than 1000 injuries, and some structural damage and building collapses in both areas (Cetin et al. 2020 ;Mavroulis et al. 2022 ). The ensuing tsunami impacted and flooded the southern coastal area of İ zmir and Samos Island and affected other eastern Aegean Sea islands (Cetin et al. 2020 ;Dogan et al. 2021 ;Kalligeris et al. 2021 ;Triantafyllou et al. 2021 ). ...
... The Samos earthquake caused a total of 119 deaths, more than 1000 injuries, and some structural damage and building collapses in both areas (Cetin et al. 2020 ;Mavroulis et al. 2022 ). The ensuing tsunami impacted and flooded the southern coastal area of İ zmir and Samos Island and affected other eastern Aegean Sea islands (Cetin et al. 2020 ;Dogan et al. 2021 ;Kalligeris et al. 2021 ;Triantafyllou et al. 2021 ). Dogan et al. ( 2021 ) measured and investigated tsunami runup and inundation, focusing on a ∼110-km-long stretch of coastline in T ürkiye and found that the largest tsunami run-up was 3.8 m at an inundation distance of 91 m at Akarca (Seferihisar, İ zmir). ...
We present a kinematic slip model and a simulation of the ensuing tsunami for the 2020 Mw 7.0 Néon Karlovásion (Samos, Eastern Aegean Sea) earthquake, generated from a joint inversion of high-rate GNSS, strong ground motion and InSAR data. From the inversion, we find that the source time function has a total duration of ∼20 s with three peaks at ∼4, 7.5 and 15 s corresponding to the development of three asperities. Most of the slip occurs at the west of the hypocenter and ends at the northwest down-dip edge. The peak slip is ∼3.3 m, and the inverted rake angles indicate predominantly normal faulting motion. Compared with previous studies, these slip patterns have essentially similar asperity location, rupture dimension and anti-correlation with aftershocks. Consistent with our study, most published papers show the source duration of ∼20 s with three episodes of increased moment releases. For the ensuing tsunami, the eight available gauge records indicate that the tsunami waves last ∼18-30 hours depending on location, and the response period of tsunami is ∼10-35 min. The initial waves in the observed records and synthetic simulations show good agreement, which indirectly validates the performance of the inverted slip model. However, the synthetic waveforms struggle to generate long-duration tsunami behavior in simulations. Our tests suggest that the resolution of the bathymetry may be a potential factor affecting the simulated tsunami duration and amplitude. It should be noted that the maximum wave height in the records may occur after the decay of synthetic wave amplitudes. This implies that the inability to model long-duration tsunamis could result in underestimation in future tsunami hazard assessments.
... It is well known that high damage levels were observed in some Izmir areas (e.g., Bayrakli district) due to the joint influence of site-effects and poor construction quality. More specifically, the observed high spectral accelerations in Izmir, particularly within the mid-to-long period (0.6 s-1.5 s) range due to soft soil amplification, the different structural typologies and the height of structures, contributed to the heavy damage locally observed (Cetin et al. 2020). ...
We investigate the possibility of combined interpretation of macroseismic and strong-motion data for recent large earthquakes in the Aegean area. We employ macroseismic information derived from EMSC testimonies, as well as strong-motion information extracted from online sources provided by two Greek institutes (ITSAK and GEIN-NOA). The EMSC testimonies database (https://www.seismicportal.eu/testimonies-ws/) is a widely used inventory for the damage distribution of significant earthquakes. The collected data were first compared with the predicted macroseismic intensities using the empirical relation of Papazachos and Papaioannou (J Seismol 1:181–201, 1997) While the correlation between the observed and modeled data was found to be satisfactory, a systematic bias is evident for very high and very low values intensities derived from the reported EMSC testimonies. A Monte Carlo simulation approach was employed to identify the source of this bias, suggesting that it is a result of the large scatter of the EMSC data and the limits of the macroseismic scale used. To minimize this effect, a spatial grouping and smoothing approach was adopted for the EMSC dataset, resulting in significantly improved correlations with the available independent strong motion estimates, such as PGA and PGV. Using this correlation, we demonstrate through several examples that it is possible to reconstruct the main features of the damage pattern for strong earthquakes in the Aegean. This is achieved by jointly analyzing rapidly crowdsourced EMSC data and strong motion information, after appropriate processing of the raw macroseismic dataset.
... Recently, an M w 7 off-shore normal earthquake occurred in the Aegean Sea, close to the shores of Samos Island and Izmir in Western Türkiye (also known as the Samos earthquake, Cetin et al., 2020). This well-recorded earthquake with 30 recordings within R RUP < 100 km (Askan et al., 2021) provided a rare opportunity to test the applicability of the global and regional GMMs for large-magnitude normal events. ...
Complex fault geometries with multiple sets of inclined active faults pose a challenge to the accurate representation of fault-based seismic sources in probabilistic seismic hazard assessment (PSHA). In the absence of slip rates associated with fault segments and the presence of sparse seismic and geodetic data, the estimation of segment-specific activity rate includes significant uncertainty. This study proposes a comprehensive procedure for defining the segment-specific activity rates and associated uncertainties in fault-based PSHA for extensional tectonic regimes and applies the procedure in the northern margin of Western Anatolian Extensional Province. The seismic sources are modeled as rupture systems with individual fault segments using the connections between available active fault traces, first-order geological complexities, earthquake catalog, and focal mechanism solutions. Alternatives to estimate and partition segment-specific activity rates based on annual slip rate, seismicity rate, and moment rate are explored. Each alternative is implemented in PSHA, and the results are compared in terms of peak ground acceleration (PGA) maps for a 475-year return period. A comparison of the 475 yr PGA maps showed that the activity rates based on annual slip rates translate into higher hazard estimates and a more uniform distribution of PGA; whereas, the activity rates based on seismicity and moment rate result in a PGA distribution that is more sensitive to the occurrence and location of previous large-magnitude events. The approach utilized to partition activity rates among parallel segments has a noticeable effect in the areas where highly asymmetric fault activity is inferred from morphology. Hence, alternative approaches for estimation and partition of activity rates are combined to model the epistemic uncertainty in segment-specific activity rates, and a repeatable procedure is developed to build fault-based seismic source models in the presence of complex fault geometries.
... The North Anatolian and the East Anatolian Fault Zones are major earthquake tectonic structures that are responsible for the generation of many damaging earthquakes not only during antiquity and the historical period but also during the period of instrumental recordings [23,24]. The high level of seismic hazard in Turkey could be highlighted by the recent generation of destructive earthquakes with Mw ≥ 6.0, namely the 24 January 2020 Mw = 6.8 Elazıg earthquake [25,26], the 30 October 2020, Mw = 7.0 Samos earthquake [27][28][29][30] and the 23 November 2022 Mw = 6.1 Düzce earthquake [31]. Many other seismic events have occurred in the past and are among the largest and most destructive earthquakes worldwide such as the 17 August 1999, Mw = 7.6 Izmit earthquake [32,33], among others. ...
On 6 February 2023, southeastern Turkey was struck by two major earthquakes that devastated 11 provinces. Tens of thousands of buildings collapsed and more were later demolished. During post-event field surveys conducted by the authors, several disposal sites set up in the most affected provinces were detected and checked for suitability. Based on field observations on the properties of sites and their surrounding areas as well as on the implemented debris management activities, it is concluded that all sites had characteristics that did not allow them to be classified as safe for earthquake debris management. This inadequacy is mainly attributed to their proximity to areas, where thousands of people reside. As regards the environmental impact, these sites were operating within or close to surface water bodies. This situation reveals a rush for rapid recovery resulting in serious errors in the preparation and implementation of disaster management plans. In this context, measures for effective debris management are proposed based on the existing scientific knowledge and operational experience. This paper aims to highlight challenges during earthquakes debris management and related threats posed to public health and the environment in order to be avoided in future destructive events.
Bu çalışmada İzmir ili ve yakın çevresinde (37.70-39.28 kuzey enlemleri ve 26.00-28.00 doğu boylamları arasında kalan bölge) aletsel dönemde meydana gelen (M=5.8 ve daha büyük) depremler şiddet, büyüklük ve odak mekanizma çözümleri açısından bir aletsel deprem kataloğu oluşturacak şekilde düzenlenmiş ve elde edilen veriler analiz edilerek değerlendirilmiştir. Elde edilen verilere göre, aletsel dönem süresince İzmir ili ve yakın çevresinde, yaklaşık 54 bin adet deprem kaydı vardır. Bölgede aletsel dönemde kayıt altına alınmış olan en büyük depremin şiddeti IX, büyüklüğü ise Mw=6.9’dur. Büyüklüğü 5.8’den fazla olan depremlerin ortalama oluşma sıklığı 8 yıldır. Depremlerin odak mekanizma çözümleri İzmir ve yakın civarında meydana gelen depremlerin eğim atımlı normal/oblik faylar ve doğrultu atımlı faylar tarafından üretildiğini göstermektedir. 11 Ağustos 1904 Sisam Depremi (Mw:6.1), 18 Ağustos 1904 Kuşadası Körfezi Depremi (Mw:6.0) ve 10 Ekim 1904 Buca Depremi (Mw:5.8) birbirini tetikleyecek şekilde gelişmiş olmalıdır. Benzer benzer tetiklenme mekanizması 30 Ekim 2020 Sisam depremi (Mw: 6.9) sonrasında 14 Ağustos 2022 Kuşadası Körfezi depremi (Mw:4.9) ve 04 Kasım 2022 Buca depremi (Mw:4.9) ile tekrar etmiştir. Bu da normal faylarla üretilen depremlerden sonra stres boşalımının komşu segmentlerdeki faylar boyunca transfer edildiğini göstermektedir. Tarihsel dönem deprem kayıtlarında yüzey faylanmasıyla sonuçlanmış ve X şiddetine varan depremler olduğu düşünüldüğünde, Aletsel dönemde İzmir il sınırları içindeki fayların yüzey faylanması geliştirecek düzeyde henüz kırılmadığı anlaşılmaktadır. Bu nedenle, il düzeyindeki mevcut yapı stoğunun depreme dirençli hale getirilmesi ve olası bir yıkıcı depreme hazır olma anlamında toplumun bilinçlendirilmesi gerekmektedir.
An earthquake of Mw = 7.0 occurred on October 30, 2020, in the Aegean Sea near Samos Island, which caused severe structural damage in Bayraklı, Izmir (Türkiye), located around 70 km from the epicenter. To investigate the source, path, and site effects, ground motions recorded in Western Anatolia are simulated using the stochastic finite-fault method based on a dynamic corner frequency approach. The input model parameters are calibrated using the recorded motions at selected 10 stations within an epicentral distance of less than 100 km. The soil amplifications are modeled using horizontal-to-vertical spectral ratios and generic amplification factors. At most stations, including a few within Izmir Bay, amplitudes and frequency contents are modeled closely. Minor discrepancies within particular frequency bands can be attributed to insufficient representation of the local site effects. Finally, distributions of observed and simulated felt intensities are found to be consistent.
The role of soil saturation condition on the liquefaction occurrence highlights the need for a tool to track the ground-truth soil moisture content involved in this seismic phenomenon. Soil Moisture Active Passive (SMAP) satellite estimates near-real time surface and root zone soil moisture measurements with global coverage. Typical proxies for soil saturation in liquefaction analysis include average water table depth patterns, mean annual precipitation measurements, and topographic conditions. As an alternative to these proxies, this paper incorporates satellite-based soil moisture data to enhance the understanding of the interrelation between saturation conditions and liquefaction events. Proposing a new approach for sampling non-liquefaction cases, a liquefaction/non-liquefaction database was developed in this paper based on reconnaissance reports of eleven target earthquakes. Well-known geospatial explanatory variables as well as new SMAP-based soil moisture parameters , affecting soil liquefaction, are used to develop a new soil moisture-based global liquefaction model (SMGLM), which is compared with an existing global liquefaction model. Considering the ongoing advancement of earth observing satellites, the results of this paper can build a basis for developing fully satellite-based models that could identify liquefied sites using high resolution near-real time soil moisture data.
Due to the unique soil, morphological, and subsurface topographical conditions, amplified and prolonged seismic demand traces were observed in historical strong ground motion records from Bayrakli-Izmir-Turkiye. A vivid example of this response was recorded during the Mw 7.0 Samos event on October 30, 2020. After the event, structural damage and loss of life were unexpectedly concentrated in Bayrakli-Izmir, even though the fault rupture was located 70 km away. The presence of strong ground motion stations (SGMS) located on rock (#3514) and soil (#3513) sites enabled a quantitative assessment of the amplified and prolonged seismic demand traces. The seismic response of SGMS #3513 site was assessed by using 1-D equivalent linear and analytical methods. The idealized 1-D soil profile and input parameters were calibrated and fine-tuned by using the 2020 Samos earthquake accelerograms. Then, the calibrated equivalent linear site response model was further validated by the recordings from historical events. Alternatively, an analytical wave propagation-based model was proposed, the input parameters of which were probabilistically estimated based on, again, historical recordings. Finally, the seismic responses of the site during future earthquakes were predicted based on the calibrated and validated site response models. The predicted intensity-dependent amplification spectral responses were compared with the provisions of the TEC (2018). Even though limited in number in all five future seismic scenario events, amplification ratios suggested by TEC were exceeded by a factor of 2–4 at periods falling in the range of 0.5 to 1.2 s. This clearly suggested the need to further quantify the Bayrakli seismic basin responses with basin-specific models, rather than code-based, intensity-dependent generalized amplification factors.
On 30 October 2020 11:51 UTC, a Mw=6.9 earthquake struck the offshore region north of Samos Island, Greece, in the Gulf of Ephesos/Kuşadasi, causing two fatalities and 19 minor injuries at Samos Island, as well as 115 casualties and over 1,030 injuries in Western Turkey. Preliminary results indicate that the mainshock occurred on a north-dipping normal fault, with a focal mechanism of 270º/50º/-81º. The selection of the fault plane is supported by evidence of uplift at western Samos and over 10 cm of subsidence at the northernmost edge of the central part of the island. The distribution of relocated hypocenters shows clustering of events, east of the mainshock's epicenter, where most major aftershocks have occurred. To the west, a smaller group of aftershocks is observed, separated by a spatial gap in seismicity. The latter is likely related to the region of the fault plane where most of the co-seismic slip occurred, with Coulomb stress-transfer towards the western and eastern margins of the rupture triggering aftershock activity. The apparent complexity of the mainshock's source time function, supported by preliminary results, could indicate the rupture of more than one structures. This could explain the relatively weak magnitude of the largest aftershock (Mw=5.0). The mainshock caused damage mainly to non-engineered constructions, i.e. old residential buildings, churches and monuments in Samos Island, and minor damage to the majority of the building stock of the island built according to the National Seismic Code. On the other hand, it caused severe damage at Izmir, especially to high-rise
On the role of basin effects for the case of strong ground motions recorded in Izmir (Turkey) during the October 30th, 2020 M 7.0 Aegean Sea earthquake. Along these lines, the herein presented short note is a first attempt to understand the reasons of heavy damages in Izmir by investigating the possible basin effects on the recorded ground motions (TK network). Moreover, having obtained some preliminary indications and insights on the site response topic using spectral ratios techniques, the elastic response spectra of the recorded motions are compared to the elastic design spectrum specified in old and modern Turkish seismic codes for those stations that are located in heavily-damaged areas of Izmir, in order to provide some further explanations of the damages and the associated heavy fatalities.
Technical report of the Hellenic Association for Earthquake Engineering (ΗΑΕΕ/ΕΤΑΜ) on the seismological, structural and geotechnical aspects of the 30/10/2020 Samos Earthquake.
Muğla Milas ilçesinde Söke Milas Karayolu Derince Çayı köprüsünün 3,5 km kuzeyinde Derince Çayı üzerinde yer alan Derince Barajı, önyüzü beton kaplı kum çakıl dolgu tipinde olup temelden yüksekliği 67 m’dir. Baraj 2014 yılında hizmete açılmış olup, 2015 yılında barajın deprem altındaki yapısal durum ve performansını izlemek üzere bir adet gövde üzerine bir adet ana kayaya olmak üzere 2 adet ivmeölçer cihazı yerleştirilmiştir. Bu istasyonlar ile bir deprem anında barajın depremlere karşı vermiş olduğu tepki gözlenmiş olacaktır. 2017-2018 yıllarında Ege bölgesinde meydana gelen depremlerden anakaya ve baraj gövdesinde kurulu bulunan ivmeölçerler tarafından kaydedilen; lokasyonları farklı Mw>4.4 olan 9 adet deprem kaydı kullanılmıştır. Barajın dinamik özelliklerinin belirlemek amacıyla kaydedilen deprem sinyallerine referans yöntemine göre standart spektral oran (SSR) ve yatay/düşey spektral oran (HVSR) yöntemleri uygulanmıştır. Bu iki yöntemin analizleri sonucunda baraj gövdesine ait büyütmeler, baskın frekanslar belirlenmiştir. Bu yöntemin analizi sonucunda barajın hakim frekansı 2.36 Hz bulunmuş ve iki yöntem karşılaştırılmıştır.
Evaluating the damage state of buildings has always been one of the major challenges that both engineers and authorities face after catastrophic earthquakes in seismic regions. After such events, considering the number of buildings in need of inspection and the insufficient number of qualified inspectors, the availability of a thorough but rapidly applicable damage assessment method is vitally important. An assessment system serving this purpose was developed for the Turkish Catastrophe Insurance Pool (TCIP, known as DASK in Turkey) at the beginning of the new millennia to evaluate the damages in reinforced concrete (RC) and masonry structures. The assessment system assigns a damage state (related with a damage modifier for the capacity loss) to each vertical structural member (columns and shear walls) based on the observed residual damages, such as crack width, concrete crushing, cover spalling and buckling of reinforcement. Beam damages are also taken into account in a similar way. After that, the weighted damage percentage (WDP) is calculated by taking into account the damage state and the cross-sectional area of each vertical member and the number of heavily damaged horizontal members. Since its development, this assessment method has been used by TCIP to decide the indemnities (and somehow future) of damaged structures to be either ‘repaired’ (partial indemnity) or ‘demolished’ (full indemnity) after earthquakes that took place in Turkey.
In recent years, the number of scientific studies in regard to the concept of reparability of damaged structures, which is a determining parameter in buildings’ future decisions after seismic events, is increased. Consequently, TCIP initiated a research project to adjust the damage assessment method with the conclusions of up-to-date state-of-the-art scientific research. This paper presents the followed methodology and brief results of different phases of the project.
In order to propose modifications for the current method, firstly, an experimental database was established focusing on the performance of damaged structural members. The database was used to validate/revise the member damage modifier parameters. Secondly, in order to define a reparability limit in terms of the building WDP value, a literature survey investigating the fundamental mechanical characteristics (such as stiffness, strength and ductility) that can be used to define the seismic behavior of damaged, and damaged-and-repaired structural members was performed. These mechanical characteristics were then used in a series of nonlinear structural analyses on typical buildings representing the common typologies of buildings in Turkey. The analyses covered the undamaged, damaged and damaged-and-repaired cases in order to determine the damage state/level where the cost of the repair applications become unfeasible or the seismic performance of the repaired structure deviates considerably from that of its undamaged state. Finally, by comparing the seismic performances of undamaged, and damaged-and-repaired cases together with the repair costs, new threshold values were proposed for WDP for different damage levels (and indemnity decisions).
We present a Hellenic database of intensity measures from uniformly processed strong ground motion recordings, together with metadata on earthquake source attributes and recording site conditions. The database consists of information from 471 earthquakes between 1973 and 2015 that produced 2993 usable recordings from 333 sites. A key element of this work is a unified presentation of data from two major data providers that operate in Greece (Institute of Engineering Seismology and Earthquake Engineering and the Institute of Geodynamics, National Observatory of Athens) along with a university-operated local urban array (University of Patras). Consistent procedures were applied to develop source parameters that include hypocenter locations, moment magnitudes (directly estimated or derived using a conversion procedure), fault-plane solutions, and finite-fault parameters (generally, for events with M>6.0). The time-averaged shear-wave velocity in the upper 30 m parameter is provided for all 333 recording sites based on geophysical measurements where available (102) and proxy-based estimates otherwise. Most events are in the magnitude range of 3.8–7, occurred at shallow hypocentral depths (<30 km), and provide data for rupture distances generally between 10 and 300 km. The combined ground motion, seismic source, and site database is anticipated to be useful for engineering applications, including ground-motion model development and time series selection for response-history analyses.
Using a recently completed database of uniformly processed strong-motion data recorded in Greece, we derive a ground-motion prediction model (GMPM) for horizontal-component peak ground velocity, peak ground acceleration, and 5% damped pseudoacceleration response spectra, at 105 periods ranging from 0.01 to 10 s. The equations were developed by modifying a global GMPM, to account for more rapid attenuation and weaker magnitude scaling in the Greek ground motions than in the global GMPM. Our GMPM is calibrated using the Greek data for distances up to 300 km, magnitudes from 4.0 to 7.0, and time-averaged 30 m shear-wave velocities from 150 to 1200 m/s. The GMPM has important attributes for hazard applications including magnitude scaling that extends the range of applicability to M 8.0 and nonlinear site response. These features are possible because they are well constrained by data in the global GMPM from which our model is derived. An interesting feature of the Greek data, also observed previously in studies of mid-magnitude events (6.1–6.5) in Italy, is that they are substantially overpredicted by the global GMPM, which may be a repeatable regional feature, but may also be influenced by soil–structure interaction. This bias is an important source of epistemic uncertainty that should be considered in hazard analysis.
Two of the most important parameters in any dynamic analysis involving soils are the shear modulus and damping ratio. Based on lab tests on gravels from 18 investigations, simplified equations to define G/Gmax and the damping ratio as a function of shear strain, γ, have been developed. The G/Gmax versus γ equations rely on two parameters that can be defined in terms of confining pressure and uniformity coefficient. Increasing confining pressure leads to a more linear curve, while increasing the uniformity coefficient leads to a more nonlinear curve shape. G/Gmax versus γ curves for gravels tend to plot somewhat below curves for sands under similar conditions. Estimates of the standard deviation in G/Gmax versus γ curves are provided to consider scatter about the mean. The damping ratio versus γ equation employs the modified Masing approach with a minimum damping ratio of 1%. In addition, about 67% of the damping data points fall within an error band of ±33% from the computed value. The damping ratio of gravel specimens also decreases as the confining pressure increases, whereas it increases for higher uniformity coefficients. Other direct correlations between damping ratio and factors such as shear strain, uniformity coefficient, and confining pressure did not provide significant improvements in predictive capacity.
