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The city of Iznik, called Nikaia or Nicaea in ancient times, is located in northwest Anatolia, Turkey. Nicaea is renowned especially for the first Council of Nicaea convened by the Roman emperor Constantine in ad 325 in an attempt to unify the Church. During an international field course on the geophysical exploration of archaeological targets we detected the remains of a small previously unknown Byzantine church on a fallow lot of land inside the city. The church is oriented parallel to the ancient Hippodamian street grid that deviates from the modern street system of the quarter by ~45°. We found the contours of the nave, two aisles and three apses as well as evidence of a partly refilled grave. The geophysical measurements indicate that the foundations of the church consist of low-porosity hard rock with a low magnetic susceptibility, probably limestone or sandstone embedded in fluvial sediments. The field study is based on ground-penetrating radar (GPR), magnetics, electric resistivity tomography (ERT) and microgravimetry. It highlights the strength and necessity of combining different geophysical methods in exploring and characterizing archaeological sites. In fact, the foundation walls of the church do not show any magnetic anomaly but could be delineated clearly only by GPR. The wall remains appear as highly resistive spots in ERT. By converting the three-dimensional GPR image into an electric resistivity model we could verify that the ERT results fully correspond to the ruins found by GPR. The structure interpreted as a loosely refilled grave is indicated mainly by a weak gravity anomaly (~9 μGal) and a diffuse reflection pattern in GPR. Electric forward modelling shows that this structure leads to an additional increase of a high resistivity anomaly, which is primarily caused by foundation rocks, but it cannot be resolved within the ERT pattern a priori. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

SUMMARY We investigate different aspects concerning the application of swarm intelligence optimization to the inversion of Scholte-wave phase-slowness frequency ( p- f) spectra with respect to shear wave velocity structure. Besides human influence due to the dependence on a priori information for starting models and interpretation of p- f spectra as well as noise, the model resolution of the inversion problem is strongly influenced by the multimodality of the misfit function. We thus tested the efficiency of global, stochastic optimization approaches with focus on swarm intelligence methods that can explore the multiple minima of the misfit function. A comparison among different PSO schemes by applying them to synthetic Scholte-wave spectra led to a hybrid of Particle Swarm Optimization and Downhill Simplex providing the best resolution of inverted shear wave velocity depth models. The results showed a very low spread of best fitting solutions of 7 per cent in shear wave velocity and an average of 9 per cent for noisy synthetic data and a very good fit to the true synthetic model used for computation of the input data. To classify this method we also compared the probability of finding a good fit in synthetic spectra inversion with that of Evolutionary Algorithm, Simulated Annealing, Neighbourhood Algorithm and Artificial Bee Colony algorithm. Again the hybrid optimization scheme showed its predominance. The usage of stochastic algorithms furthermore allowed a new way of misfit definition in terms of dispersion curve slowness residuals making the inversion scheme independent on Scholte-wave mode identification and allowing joint inversion of fundamental mode and higher mode information. Finally we used the hybrid optimization scheme and the misfit calculation for the inversion of 2-D shear wave velocity profiles from two locations in the North- and Baltic Sea. The models show acceptable resolution and a very good structural correlation to high resolution reflection seismic data. [ABSTRACT FROM AUTHOR]

SUMMARY Azimuthal P-receiver functions are influenced by crustal anisotropy and heterogeneity. To study these effects we created a catalogue of 30 crustal models and corresponding azimuthal P-receiver functions. The crustal models are grouped in five classes of anisotropic and isotropic horizontal and dipping plane layers. The model design was motivated by geological structure found by deep seismic reflection profiling and deep drilling. In the synthetic seismogram catalogue, we identified 14 azimuthal waveform features that could be used to narrow the range of possible crustal model for seismic inversion or interactive forward modelling. Based on a hierarchical classification of these waveform features 80 per cent of the input models could be uniquely identified. In case of field data the hierarchical classification can be used to find a starting model for forward modelling or non-linear inversion. To test the applicability of the method we applied it to records of four permanent stations of the German Regional Seismic Network. In two cases the procedure led to a satisfactory agreement of observed and modelled azimuthal data in both R and T components. The obtained subsurface models are plausible because they correspond to anisotropy values and structures found for similar settings by deep drilling and deep seismic profiling. In the other two cases only partial agreement of real and synthetic data could be obtained. These stations are located in a complicated tectonic setting that cannot be modelled satisfactorily by an approach based on plane dipping layers. [ABSTRACT FROM AUTHOR]

Examines the correlation between rock fabric and elastic anisotropy of crystalline rock. Factors influencing anisotropy in situ; Formation of microcracks in crystalline basement rocks; Classification of crystalline rock cracks.

Seismoelectric (SE) signals, accompanying seismic wave fields radiated from earthquakes, can be observed on records of magnetotelluric stations. Assuming that these SE signals are generated by electrokinetic coupling we investigate whether they can be used as a 'pore-space monitoring'-tool. Regarding future field experiments we analyse synthetic SE waveforms calculated for a fully saturated base model consisting of five layers overlying a half-space, resembling the conditions of the Armutlu Peninsula (Turkey). This example site stands for a location with near-surface thermal aquifers exposed to tectonic stress and significant microseismicity. As expected, coseismic SE waves arrive simultaneously with the seismic onsets whereas interface response (IRs) SE waves arrive (shortly) before the generating seismic onsets. Therein, so-called evanescent IRs show a similar moveout as seismic phases and so-called radiation IRs travel with zero slowness. We found that the influence of IRs on the overall SE signal can be identified by envelope analysis of SE time series and by seismoelectric spectral ratios (SESRs) in the frequency domain. For a sensitivity analysis we added an extra layer to the base model with differing porosity, porefluid salinity and permeability values. At near-epicentral distances both trace-envelopes and SESRs are sensitive to the porosity and porefluid salinity changes in the simulated near-surface aquifer. The SESRs' and SE envelopes' amplitudes vary in the order of up to some 10 per cent in response to porosity and salinity increases of factor 2 and 100, respectively. In contrast, a decrease of the permeability value by the factor 100 leads to an SESR amplitude variation of less than 1–10 per cent. In the Armutlu model the largest relative changes of SE signals occur near the epicentre where the ratio between coseismic and IR amplitudes is close to 1. For 1–6 km deep source depth the SE detection swell at the earth surface is in the order of magnitude 2–3, depending on the ambient electromagnetic noise and hypocentral distance. This estimate assumes that SE signals are recorded with standard magnetotelluric stations. It can improve if array methods are applied. [ABSTRACT FROM AUTHOR]

We investigate seismoelectric (SE) signals accompanying seismic waves radiated from earthquake sources. SE signals are mostly generated from compressional portions of seismic waves by electrokinetic coupling. They contain coseismic electric fields travelling with seismic wave velocity and interface response (IR) waves, which originate at layer interfaces and travel with electromagnetic wave speed. IR wave amplitudes are sensitive to contrasts in poroelastic and electric rock parameters. We introduce SE spectral ratios (SESRs) as a tool to evaluate the influence of IRs on the overall SE signal independently of the earthquake source–time function. Based on data from Northern Chile we show that SESRs show a site specific frequency dependence with a trend of decreasing amplitudes towards increasing frequency. Modelling results reveal that the specific frequency dependence of the SESRs is caused by IRs excited at depths of some hundred metres underneath the recording stations. We analyse the SESR sensitivity towards porosity, permeability, fluid salinity and the depth of the interfaces. We verify that observed SESRs can be reproduced through forward modelling and linearized inversion based on realistic subsurface parameters. [ABSTRACT FROM AUTHOR]

After more than a decade of multidisciplinary studies of the Central American subduction zone mainly in the framework of two large research programmes, the US MARGINS program and the German Collaborative Research Center SFB 574, we here review and interpret the data pertinent to quantify the cycling of mineral-bound volatiles (HO, CO, Cl, S) through this subduction system. For input-flux calculations, we divide the Middle America Trench into four segments differing in convergence rate and slab lithological profiles, use the latest evidence for mantle serpentinization of the Cocos slab approaching the trench, and for the first time explicitly include subduction erosion of forearc basement. Resulting input fluxes are 40-62 (53) Tg/Ma/m HO, 7.8-11.4 (9.3) Tg/Ma/m CO, 1.3-1.9 (1.6) Tg/Ma/m Cl, and 1.3-2.1 (1.6) Tg/Ma/m S (bracketed are mean values for entire trench length). Output by cold seeps on the forearc amounts to 0.625-1.25 Tg/Ma/m HO partly derived from the slab sediments as determined by geochemical analyses of fluids and carbonates. The major volatile output occurs at the Central American volcanic arc that is divided into ten arc segments by dextral strike-slip tectonics. Based on volcanic edifice and widespread tephra volumes as well as calculated parental magma masses needed to form observed evolved compositions, we determine long-term (10 years) average magma and KO fluxes for each of the ten segments as 32-242 (106) Tg/Ma/m magma and 0.28-2.91 (1.38) Tg/Ma/m KO (bracketed are mean values for entire Central American volcanic arc length). Volatile/KO concentration ratios derived from melt inclusion analyses and petrologic modelling then allow to calculate volatile fluxes as 1.02-14.3 (6.2) Tg/Ma/m HO, 0.02-0.45 (0.17) Tg/Ma/m CO, and 0.07-0.34 (0.22) Tg/Ma/m Cl. The same approach yields long-term sulfur fluxes of 0.12-1.08 (0.54) Tg/Ma/m while present-day open-vent SO-flux monitoring yields 0.06-2.37 (0.83) Tg/Ma/m S. Input-output comparisons show that the arc water fluxes only account for up to 40 % of the input even if we include an 'invisible' plutonic component constrained by crustal growth. With 20-30 % of the HO input transferred into the deeper mantle as suggested by petrologic modeling, there remains a deficiency of, say, 30-40 % in the water budget. At least some of this water is transferred into two upper-plate regions of low seismic velocity and electrical resistivity whose sizes vary along arc: one region widely envelopes the melt ascent paths from slab top to arc and the other extends obliquely from the slab below the forearc to below the arc. Whether these reservoirs are transient or steady remains unknown. [ABSTRACT FROM AUTHOR]

Abstract: The maximum slip area of the 1960 Mw 9.5 Valdivia (Chile) earthquake has been investigated down to 100km depth by a receiver function survey along two trench-perpendicular profiles at 39.3° and 39.5°S. The data are compared with seismicity and local earthquake tomography. We find a slab of ca. 35° dip at depths similar to what is observed to the north and south of the study area. The slab and the overlying mantle wedge show a local decrease in seismic velocities possibly caused by hydration or underplating of sediments. The presence of hydrated or sedimentary rocks would reduce plate coupling in this region in agreement with recent GPS measurements. The Moho is found at depths of 30 to 40km deepening from the coast to the Andes. The Moho topography is close to isostatic equilibrium. Under the volcanic centre of Villarrica, Quetrupillán and Lanín the Moho conversion occurs about 10km shallower than expected for a standard isostatic model. This can be explained by a density reduction in the lower crust due to magmatic processes or by non-compensated stress. [Copyright &y& Elsevier]

Seismic and volcanic activities in Central Java, Indonesia, the area of interest of this study, are directly or indirectly related to the subduction of the Indo-Australian plate. In the framework of the MERapi AMphibious EXperiments (MERAMEX), a network consisting of about 130 seismographic stations was installed onshore and offshore in Central Java and operated for more than 150 days. In addition, 3-D active seismic experiments were carried out offshore. In this paper, we present the results of processing combined active and passive seismic data, which contain traveltimes from 292 local earthquakes and additional airgun shots along three offshore profiles. The inversion was performed using the updated LOTOS-06 code that allows processing for active and passive source data. The joint inversion of the active and passive data set considerably improves the resolution of the upper crust, especially in the offshore area in comparison to only passive data. The inversion results are verified using a series of synthetic tests. The resulting images show an exceptionally strong low-velocity anomaly (−30 per cent) in the backarc crust northward of the active volcanoes. In the upper mantle beneath the volcanoes, we observe a low-velocity anomaly inclined towards the slab, which probably reflects the paths of fluids and partially melted materials in the mantle wedge. The crust in the forearc appears to be strongly heterogeneous. The onshore part consists of two high-velocity blocks separated by a narrow low-velocity anomaly, which can be interpreted as a weakened contact zone between two rigid crustal bodies. The recent Java Mw= 6.3 earthquake (2006/05/26-UTC) occurred at the lower edge of this zone. Its focal strike slip mechanism is consistent with the orientation of this contact. [ABSTRACT FROM AUTHOR]

Integration of multiple geophysical data is a key practice to reduce model uncertainties and enhance geological interpretations. Electrical resistivity models resulting from inversion of marine magnetotelluric (MT) data, often lack depth resolution of lithological boundaries and distinct information for shallow model parts. This is due to the diffusive nature of electromagnetic fields, enhanced by deficient data sampling and model regularization during inversion. Thus, integrating data or models to constrain layer thicknesses or structural boundaries is an effective approach to derive better constrained and more detailed resistivity models. We investigate the different impacts of three cross‐gradient coupled constraints on 3D MT inversion of data from the Namibian passive continental margin. The three constraints are (a) coupling with a fixed structural density model; (b) coupling with satellite gravity data; (c) coupling with a fixed gradient velocity model. Here, we show that coupling with a fixed model (a and c) improves the resistivity model the most. Shallow conductors imaging sediment cover are confined to a thinner layer in the resulting resistivity models compared to the MT‐only model. Additionally, these constraints help to suppress vertical smearing of a conductive anomaly attributed to a fracture zone, and clearly show that the seismically imaged Moho is not accompanied by a change in electrical resistivity. All of these observations help to derive an Earth model, which will form the basis for future interpretation of the processes that lead to continental break‐up during the early Cretaceous. Plain Language Summary: Jointly evaluating different geophysical measurements may improve geological interpretation. Methods measuring electromagnetic properties of the earth often have issues to resolve geological boundaries and may not provide sufficient information about the shallow subsurface. We therefore investigate three different ways to improve the interpretation of measurements conducted at the Namibian coast by integrating electromagnetic with additional information from gravity and acoustic measurements. Within this processes, we enhance the identification of geological boundaries that are compatible with both electromagnetic and gravity or alternatively with electromagnetic and acoustic observations. In our study, we were able to improve interpretation most by the combination of electromagnetic measurements with a fixed model, that is, definition of subsurface geological structures derived from gravity and acoustic measurements. The combination allows the identification of deceptive structures arising from the interpretation of electromagnetic measurements, only. Additionally, the sharpness of geological boundaries was improved by the suppression of excessive blurring. All of these findings may help to understand the mechanisms leading to the formation of the South Atlantic Ocean circa 130 million years ago. Key Points: Imaging of rift related volcanic processes at the Namibian margin through joint analysis of magnetotelluric, gravity, and seismic dataComparing the impact of three different inversion constraints on 3D inversion of marine magnetotelluric data3D inversion of marine magnetotelluric data is most improved by cross‐gradient coupling with fixed structural density model [ABSTRACT FROM AUTHOR]

Abstract Measuring rock elastic constants and anisotropy parameters and understanding their changes in response to changes in pressure and temperature is crucial for modeling and interpreting seismic measurements. The rapid advance in seismic exploration and characterization of conventional and unconventional reservoirs requires a thorough understanding of variations in seismic velocities in response to variations of the rock elastic constants and anisotropy parameters. In attempt to develop this understanding, we measured variations in the elastic constants of three rock samples in the lab as a function of temperature (up to 600 ∘C) and pressure (up to 150 MPa) to simulate the in-situ conditions using a triaxial ultrasonic pulse transmission method. The rock samples used in this study came from a metamorphic rock core sample collected from a geothermal reservoir at the Larderello Geothermal Field in Italy. The rock samples have different chemical and structural composition and inherently contain both vertical transverse isotropy (VTI) and orthorhombic isotropy. We used two different methods to calculate the elastic stiffness constants and corresponding anisotropic parameters including VTI and orthorhombic isotropy. Our results showed that increasing the pressure leads to an increase in the orthorhombic constants while increasing the temperature leads to a decrease in these constants. The lagging decrease of the elastic constants with respect to the decrease in the pressure is explained by the hysteresis phenomenon. These observations and results will promote a better understanding and interpretation of reservoirs within the seismic domain. Highlights • Pressure and temperature effects on elastic constants a key factor in reservoir rock • Relation between the seismic wave velocity and elastic constants variation is addresses • Anisotropy as a function of pressure and temperature is quantify by estimating Thomesn parameters VTI media and Orthorhombic media from elastic constant • Elastic constants and anisotropic parameters trend as a function pf pressure is vice versa as a function of temperature [ABSTRACT FROM AUTHOR]

ABSTRACT: We develop a two‐dimensional full waveform inversion approach for the simultaneous determination of S‐wave velocity and density models from SH ‐ and Love‐wave data. We illustrate the advantages of the SH/Love full waveform inversion with a simple synthetic example and demonstrate the method's applicability to a near‐surface dataset, recorded in the village Čachtice in Northwestern Slovakia. Goal of the survey was to map remains of historical building foundations in a highly heterogeneous subsurface. The seismic survey comprises two parallel SH‐profiles with maximum offsets of 24 m and covers a frequency range from 5 Hz to 80 Hz with high signal‐to‐noise ratio well suited for full waveform inversion. Using the Wiechert–Herglotz method, we determined a one‐dimensional gradient velocity model as a starting model for full waveform inversion. The two‐dimensional waveform inversion approach uses the global correlation norm as objective function in combination with a sequential inversion of low‐pass filtered field data. This mitigates the non‐linearity of the multi‐parameter inverse problem. Test computations show that the influence of visco‐elastic effects on the waveform inversion result is rather small. Further tests using a mono‐parameter shear modulus inversion reveal that the inversion of the density model has no significant impact on the final data fit. The final full waveform inversion S‐wave velocity and density models show a prominent low‐velocity weathering layer. Below this layer, the subsurface is highly heterogeneous. Minimum anomaly sizes correspond to approximately half of the dominant Love‐wavelength. The results demonstrate the ability of two‐dimensional SH waveform inversion to image shallow small‐scale soil structure. However, they do not show any evidence of foundation walls. [ABSTRACT FROM AUTHOR]

ABSTRACT We develop a two-dimensional full waveform inversion approach for the simultaneous determination of S-wave velocity and density models from SH - and Love-wave data. We illustrate the advantages of the SH/Love full waveform inversion with a simple synthetic example and demonstrate the method's applicability to a near-surface dataset, recorded in the village Čachtice in Northwestern Slovakia. Goal of the survey was to map remains of historical building foundations in a highly heterogeneous subsurface. The seismic survey comprises two parallel SH-profiles with maximum offsets of 24 m and covers a frequency range from 5 Hz to 80 Hz with high signal-to-noise ratio well suited for full waveform inversion. Using the Wiechert-Herglotz method, we determined a one-dimensional gradient velocity model as a starting model for full waveform inversion. The two-dimensional waveform inversion approach uses the global correlation norm as objective function in combination with a sequential inversion of low-pass filtered field data. This mitigates the non-linearity of the multi-parameter inverse problem. Test computations show that the influence of visco-elastic effects on the waveform inversion result is rather small. Further tests using a mono-parameter shear modulus inversion reveal that the inversion of the density model has no significant impact on the final data fit. The final full waveform inversion S-wave velocity and density models show a prominent low-velocity weathering layer. Below this layer, the subsurface is highly heterogeneous. Minimum anomaly sizes correspond to approximately half of the dominant Love-wavelength. The results demonstrate the ability of two-dimensional SH waveform inversion to image shallow small-scale soil structure. However, they do not show any evidence of foundation walls. [ABSTRACT FROM AUTHOR]

Seismic full waveform inversion (FWI) has been applied to simple elastic problems with certain symmetries, such as isotropic, transverse isotropic or vertical transversely isotropic media. In this study, the FWI concept is extended to the most general anisotropic case with 21 independent elastic material parameters and no symmetry plane (triclinic). Beside a short description of the 3-D finite-difference scheme to solve the forward problem and the FWI optimization algorithm, we present a sensitivity study for a simple anisotropic medium. This test problem consists of a homogenous triclinic anisotropic full space, which contains 21 spatially separated spheres. In each sphere one component of the elastic tensor deviates by 5 per cent from the background medium. The resolution of the different spheres, ambiguities between the different elastic parameters, as well as the effect of the acquisition geometry can be systematically investigated. Due to the high computational costs of the triclinic forward problem a few compromises have to be made regarding the acquisition geometries. Point sources are replaced by plane wave sources which lead to a limitation of incidence angles and therefore a strong decrease in resolution of the nondiagonal elastic tensor components. It is shown that, despite these limitations, a tomographic acquisition geometry would be able to resolve to some extent a monoclinic symmetry via FWI. Restricting the acquisition geometries (e.g. VSP combined with reflection seismic or reflection seismic only) significantly reduces the number of resolvable tensor elements in strict dependence of the covered incidence angles. [ABSTRACT FROM AUTHOR]

Abstract: Soil compaction not only reduces available pore volume in which fluids are stored, but it alters the arrangement of soil constituents and pore geometry, thereby adversely impacting fluid transport and a range of soil ecological functions. Quantitative understanding of stress transmission and deformation processes in arable soils remains limited. Yet such knowledge is essential for better predictions of effects of soil management practices such as agricultural field traffic on soil functioning. Concepts and theory used in agricultural soil mechanics (soil compaction and soil tillage) are often adopted from conventional soil mechanics (e.g. foundation engineering). However, in contrast with standard geotechnical applications, undesired stresses applied by agricultural tyres/tracks are highly dynamic and last for very short times. Moreover, arable soils are typically unsaturated and contain important secondary structures (e.g. aggregates), factors important for affecting their soil mechanical behaviour. Mechanical processes in porous media are not only of concern in soil mechanics, but also in other fields including geophysics and granular material science. Despite similarity of basic mechanical processes, theoretical frameworks often differ and reflect disciplinary focus. We review concepts from different but complementary fields concerned with porous media mechanics and highlight opportunities for synergistic advances in understanding deformation and compaction of arable soils. We highlight the important role of technological advances in non-destructive measurement methods at pore (X-ray tomography) and soil profile (seismic) scales that not only offer new insights into soil architecture and enable visualization of soil deformation, but are becoming instrumental in the development and validation of new soil compaction models. The integration of concepts underlying dynamic processes that modify soil pore spaces and bulk properties will improve the understanding of how soil management affect vital soil mechanical, hydraulic and ecological functions supporting plant growth. [Copyright &y& Elsevier]

Abstract: Within Project Tor, which is about Teleseismic Tomography across the Tornquist Zone in Germany–Denmark–Sweden, we have confirmed very significant deep lithosphere differences. And modeling is substantiated via completely independent methods. In 1996–1997 our 130 seismographs constituted the largest seismic antenna ever in Europe. The Tor area was chosen along a well studied crustal profile of an earlier project, and the modeling efforts were concentrated on the deep lithosphere and asthenosphere differences to depths around 300 km. The Tor data have been subjected to P-wave travel time tomography, surface wave and receiver function analysis as well as anisotropy and scattering measurements. An important goal of the project was to make several independent inversions of the tomography data, and compare the results in an attempt to evaluate uniqueness, resolution and accuracy of these inversions. The comparisons of this paper involve more diversity in methods than any previous comparison. The geological outcome is a substantiation of earlier statements that: “The transition is interpreted to be sharp and steep in two places. It goes all through the lithosphere at the northern rim of the Tornquist Zone near the border between Sweden and Denmark, and here the lithosphere difference is large to depths more than 200 km. The other lithosphere difference, of smaller scale, is found near the southern edge of the Ringkøbing-Fyn High near the border between Denmark and Germany. Also this transition is sharp and steep, and goes all through the lithosphere to depths around 120 km. These two sharp transitions divide the Tor region into 3 different lithosphere structures distinguishable in P-wave travel time tomography, surface wave dispersion, P- and S-wave anisotropy and partly in P-wave scattering”. The mentioned broad-scale features are judged to be unambiguously determined, with well-described resolution and accuracy. Unfortunately a detail like the slope of the subcrustal lithosphere transition right under the Tornquist Zone cannot be constrained even if this is where the resolution is best, and the curiosity largest. [Copyright &y& Elsevier]

Abstract: 2D and 3D high-resolution seismic investigations were performed on submerged coastal archaeological sites at Iskele and near to Karantina Island in the Bay of Izmir in western Turkey. Tectonic subsidence of the coastline has submerged a number of archaeological features associated with an important Early Bronze Archaic settlement (Liman Tepe) and the classical Ionian city of Clazomenae. Seismic surveys were focused on imaging of an Archaic harbour structure and other submerged Hellenistic and Roman architectural features. Seismic data were acquired with the SEAMAP-3D ultra-high-resolution 3D marine seismic acquisition system developed for detailed archaeological site investigation. A 2D reconnaissance survey was performed over a 2 km2 area around Karantina Island to evaluate the seismic penetrability and to locate sites for further 3D investigation. This survey predominantly revealed marine sediment layers covering the local bedrock, which is characterized by scattering of seismic energy showing its rocky nature. Two ultra-high-resolution 3D seismic surveys were performed. The first covered a 350 m×30 m area in the modern harbour targeting a prominent Archaic harbour structure. The second was acquired across a 120 m×40 m area on the southeast shore of the Karantina Island close to a Roman architectural feature. The 3D surveys were acquired with nominal line spacings of 1 m, using a 8×4 pseudo-rigid hydrophone array and a Boomer source firing at 3 Hz shot frequency. Automated processing of the seismic data using a portable Linux cluster provided stacked 3D seismic volumes with 25 cm×25 cm bin size on-site. The 3D seismic survey of the harbour clearly imaged the submerged Archaic structure and the underlying sediment sequence. The seismic time slices reveal two seismic anomalies (2–3 m in diameter) in the harbour basin sediments. The 3D surveys southeast of Karantina identified a thicker marine sediment sequence overlying steeply dipping bedrock reflectors. The sediment sequence records the rapid accumulation and progradation of the coastline following the construction the Alexander causeway linking the mainland with the island in 334 B.C. [Copyright &y& Elsevier]