Description: This dataset contains subaquatic passive seismic recordings taken in September 2021 at 88 locations off Tuktoyaktuk Island as well as in a small lake (“Lake 3”) between the villages of Tuktoyaktuk and Inuvik, Northwest Territories, Canada. The measurements were part of the “Mackenzie Delta Permafrost Field Campaign” (mCan2021) within the “Modular Observation solutions for Earth Systems” (MOSES) program. Data is from a seismic intermediate-bandwidth seismic sensor lowered for few minutes to the bottom of the sea and lake, respectively, and from underwater short-period sensors deployed for a few days. The aim of the study was to determine the depth of the subaquatic permafrost (local lake and oceanic locations). Raw data is provided in proprietary “Cube” format and standard mseed format.

Description: The Walvis Ridge (WR) is the most prominent hotspot track related to the opening in the South Atlantic Ocean. Several hypotheses have been developed to explain its origin and evolution. The presence of a massive magmatic structure at the landfall of the WR in Northwest Namibia raised speculation about the role of a hotspot during the opening of the South Atlantic ocean. To investigate its deeper velocity structure at the junction of the WR with the African continent was the focus of the amphibious seismological WALPASS experiment. In total 12 ocean-bottom seismometers and 28 broad-band land stations were installed between 2010 and 2012 to acquire seismological data. Here, we present the results of seismic ambient noise tomography to investigate to which extent the Tristan hotspot modified the crustal structure in the landward prolongation of the ridge and in the adjacent oceanic basins. For the tomography, vertical and hydrophone component cross correlations for 〉300 d for OBS stations and between 1 and 2 yr for land stations data were analysed. More than 49 000 velocity measurements (742 dispersion curves) were inverted for group velocity maps at 75 individual signal periods, which then had been inverted for a regional 3-D shear wave velocity model. The resulting 3-D model reveals structural features of the crust related to the continent–ocean transition and its disturbance caused by the initial formation of the WR ∼130 Ma. We found relatively thick continental crust below Northwest Namibia and below the near-shore part of the WR, a strong asymmetry offshore with typical, thin oceanic crust in the Namibe Basin (crossing over into the Angola Basin further offshore) to the North and a wide zone of transitional crust towards the Walvis Basin south of the WR.

Description: Ambient seismic noise tomography is a novel, low-impact method for investigating the earth's structure. Although most passive seismic studies focus on structures on crustal scales, there are only a few examples of this technique being applied in a mineral exploration context. In this study, we performed an ambient seismic experiment to ascertain the relationship between the shallow shear wave velocity and mineralized zones in the Erzgebirge in Germany, one of the most important metal provinces in Europe. Late Variscan mineralized greisen and veins occurring in the Geyer-Ehrenfriedersdorf mining district of the Central Erzgebirge were mined from medieval times until the end of the 19th century. These occurrences represent a significant resource for commodities of high economic importance, such as tin, tungsten, zinc, indium, bismuth and lithium. Based on ambient noise data from a dense “LARGE-N” network comprising 400 low-power, short-period seismic stations, we applied an innovative tomographic inversion technique based on Bayesian statistics (transdimensional, hierarchical Monte Carlo search with Markov Chains using a Metropolis/Hastings sampler) to derive a three-dimensional shear wave velocity model. An auxiliary 3D airborne time-domain electromagnetic dataset is used to provide additional insight into the subsurface architecture of the area. The velocity model shows distinct anomalies down to approximately 500 m depth that correspond to known geological features of the study area, such as (a) gneiss intercalations in the mica schist-dominated host rock, imaged by a SW–NE striking low-velocity zone with a moderately steep northerly dip, and (b) a NW-trending strike-slip fault, imaged as a subvertical linear zone cross-cutting and offsetting this low-velocity domain. Similar to the velocity data, the electromagnetic data exhibit north-dipping (high-conductivity) structures in the mica schists, corresponding to the strike and dip of the predominant metamorphic fabric. An unsupervised classification performed on the bivariate 3D dataset yielded nine spatially coherent classes, one of which shows a high correspondence with drilled greisen occurrences in the roof zone of a granite pluton. The relatively high mean shear velocity and resistivity values of this class could be explained by changes in density and composition during greisen formation, as observed in other areas of the Erzgebirge. Our study demonstrates the great potential of the cost-efficient and low-impact ambient noise technology for mineral exploration, especially when combined with other independent geophysical datasets.

Description: Imaging the critical zone at depth, where intact bedrock transforms into regolith, is critical in understanding the interaction between geological and biological processes. We acquired a 500 m long near-surface seismic to investigate the weathering structure in the Santa Gracia National Reserve, Chile which is located in a granitic environment in an arid climate. Data processing comprised the combination of two seismic approaches: 1) body wave tomography, and 2) Multichannel Analysis of Surface Wave (MASW) with Bayesian inversion. This allowed us to derive P-wave and S-wave velocity models down to 90 and 70 m depth, respectively. By callibrating of the seismic results with those from an 87-m deep borehole that is crossed by the profile. We identified the boundaries of saprolite, weathered bedrock, bedrock. These divisions are indicated in the seismic velocity variations and refer to weathering effects at depth. The thereby determined weathering front in borehole location can be traced down to 30 m depth. The modelled lateral extent of the weathering front, however, cannot be described by established weathering front model. The discrepancies suggest more a more complex interaction between different aspects such as precipitation and topography in controlling the weathering front depth.

Description: This dataset contains over 30 marine Electrical Resistivity Tomography (ERT) profiles taken in September 2021 around Tuktoyaktuk Island (NWT / Beaufort Sea, Canada). The measurements were part of the “Mackenzie Delta Permafrost Field Campaign” (mCan2021) within the “Modular Observation solutions for Earth Systems” (MOSES) program. The collected profiles consist of numerous adjacent vertical soundings in a (quasi-symmetric) reciprocal Wenner-Schlumberger array, using a floating cable towed behind a boat. GPS records along the electrode streamer were taken, enabling the improvement of pre- processing by excluding measurements for which the cable was curved and electrode positions deviated too widely. The aim of the study was to determine the depth of the submarine permafrost. Cleaned data is provided in csv format.

Description: This collection contains permafrost related measurements in the Mackenzie Delta, NWT, Canada from the MOSES (Modular Observation Solutions for Earth Systems) field campaign in September 2021. The field campaign was focused on three subaquatic sites: a small thermokarst lake along the ITH just south of Trail Valley Creek, "Lake 3", an elongated lake with known methane occurence in the outer Mackenzie Delta, "Swiss Cheese Lake", and north and south of Tuktoyaktuk Island. At "Swiss Cheese Lake", we measured methane and CO2 concentrations in surface water and in the air above the lake, lake bed temperatures and detailed bathymetry. At "Lake 3" we measured active layer thickness on the lake banks, lake bed temperatures, and detailed bathymetry, as well as an ERT survey to estimate the talik depth below the lake. North and south of Tuktoyaktuk Island, we measured active layer thickness and sea bed temperatures and did an extensive ERT survey to obtain the depth of the subsea permafrost table. An additional passive seismic survey was carried out and the data is available at https://doi.org/10.5880/GIPP.202199.1.

Description: This dataset contains seven Electrical Resistivity Tomography (ERT) profiles taken in September 2021 at “Lake 3”, a thermokarst lake near the Inuvik-Tuktoyaktuk-Highway (ITH), about 50 km north of Inuvik (NWT, Canada). The measurements were part of the “Mackenzie Delta Permafrost Field Campaign” (mCan2021) within the “Modular Observation solutions for Earth Systems” (MOSES) program. The collected profiles consist of numerous adjacent vertical soundings in a (quasi-symmetric) reciprocal Wenner-Schlumberger array. In addition to surveys on the lake, using a floating cable towed behind a boat, two “amphibian” profiles were taken. Starting as purely terrestrial surveys using metal spike electrodes, the cable was then moved towards the lake with some of the electrodes floating on the water surface, and some still on land. The aim of the study was to determine permafrost properties on the land, to detect a possible talik beneath the lake and to especially be able to infer the transition between the two below the shoreline.

Description: We provide new results from a controlled-source seismic experiment on the deepest part of the Val Sesia crust–mantle section of the Ivrea–Verbano zone (IVZ) in the Italian Alps. The IVZ is a tilted, almost complete section through the continental crust and exposes gabbros and peridotites in the structurally deepest level, coinciding with high-resolution gravity anomalies imaging the Ivrea geophysical body. The seismic experiment SEIZE (SEismic imaging of the Ivrea ZonE) was conducted along two crossing profiles: an NNE-SSW profile of ∼11 km length and an E-W profile of ∼16 km length. 432 vibration points were recorded with 110 receivers resulting in 24 392 traveltime picks. Inversion methods using Markov chain Monte Carlo techniques have been used to derive an isotropic 3-D P-wave velocity model based on first break traveltimes (refracted phases) from controlled source seismic data. Resulting seismic P-wave velocities (Vp ) range from 4.5 to 7.5 km s−1, with an expected general trend of increasing velocities with depth. A sharp velocity change from low Vp in the West to high Vp in the East marks the Insubric Zone (ISZ), the Europe–Adria plate boundary. The most prominent feature of the 3-D tomography model is a high-velocity body (Vp increases from 6 to 7.5 km s−1) that broadens downwards. Its pointy shape peaks the surface East of Balmuccia at a location coincident with the exposed Balmuccia peridotite. Considering rock physics, high-resolution gravity and other geophysical data, we interpret this high-velocity body as dominantly composed of peridotite. The dimension of this seismically imaged peridotite material is far bigger than interpreted from geological cross-sections and requires a revision of previous models. The interpretation of ultramafic bodies in the IVZ as fragments of mantle peridotites interfingered in the crust during pre-Permian accretion is not supported by the new data. Instead, we revive a model that the contact between the Balmuccia peridotite and the Permian mafic magmas might represent a fossil continental crust–mantle transition zone.