The question of the structure of the Wind River uplift, a Laramide foreland structure in Wyoming, has been answered by Consortium for Continental Reflection Profiling (Cocorp) deep crustal reflection profiling and by gravity interpretation. Wyoming uplifts are asymmetrical anticlines whose steep limb is commonly cut by a reverse fault or thrust. If the thrust continues into the crust with low dip, the uplift is caused by horizontal movements; and if the fault steepens into a high‐angle reverse fault in depth, the uplifts are caused by vertical movement. The Wind River uplift is the largest of the Laramide structures in Wyoming, and the thrust fault has 14 km of vertical separation and 26 km of horizontal separation. About 168 km of crustal reflection profiling has been completed by Cocorp across the uplift. The Wind River thrust fault generates a continuous reflection from near the surface to a depth of about 24 km, and the thrust appears as a complex zone of faults. Apparent dip of the thrust is 30°–38°, and true dip may be up to 48°. Interpretation of deep crustal reflections is complicated by the presence of multiple reflections. A structure whose complexity approaches that of basement outcrops is found in the deep crust. Gravity modeling also suggests that the fault dips moderately and that dense rocks are uplifted in the deep crust. The Moho does not seem to be presently displaced by faulting. The crust in the Wind River uplift began to deform by large‐scale folding and then broke and faulted as a rigid slab. Faulting is caused by crustal shortening from compression that is related to plate movements.

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The Hardangerfjord Shear Zone is a more than 600 km long low-angle extensional structure that affects the South Norway and North Sea Caledonides. The ductile shear zone, which shows total maximum onshore displacement of the order of 10–15 km, is primarily a basement structure with an associated passive, monoclinal fold structure of the overlying Caledonian nappes. Deep seismic data indicate that the shear zone continues down to the lower crust (20–25 km) at a dip of 22–23°, where it appears to flatten and merge with the general lower-crustal deformation fabric. Onshore, the Hardangerfjord Shear Zone consists of a system of hard-linked ductile shear-zone segments. Brittle faults (the Lœrdal–Gjende fault system) occur in the folded Caledonian allochthons in the NE part of the Hardangerfjord Shear Zone, and reappear in the North Sea. These may represent a high-level brittle response to the Devonian development of the Hardangerfjord Shear Zone, but were reactivated during Permo-Triassic and late Jurassic extensional events. A c . 5 km thick package of seismic reflectors along the Hardangerfjord Shear Zone is presumed to represent a mylonite zone, which is too thick to be formed entirely by 10–15 km of Devonian displacement. Hence the Hardangerfjord Shear Zone is likely to be a Proterozoic shear zone, reactivated during Devonian extension.

Seismic methods continue to receive interest for use in mineral exploration due to the much higher resolution potential of seismic data compared to the techniques traditionally used, namely gravity, magnetics, resistivity and electromagnetics. However, the complicated geology often encountered in hard-rock exploration can make data processing and interpretation difficult. Inverting seismic data jointly with a complimentary dataset can help overcome these difficulties and facilitate the construction of a common Earth model. We consider the joint inversion of seismic traveltimes and gravity data. Our joint inversion approach incorporates measures of model similarity (i.e. slowness versus density) that are both compositional and structural in nature and follow naturally from this specific data combination. We perform the inversions on unstructured grids comprised of triangular cells in 2D, or tetrahedral cells in 3D. We present our joint inversion method on a scenario inspired by the Voisey's Bay massive sulphide deposit in Labrador, Canada.

Seismic methods continue to receive interest for use in mineral exploration due to the much higher resolution potential of seismic data compared to the techniques traditionally used, namely, gravity, magnetics, resistivity, and electromagnetics. However, the complicated geology often encountered in hard-rock exploration can make data processing and interpretation difficult. Inverting seismic data jointly with a complementary data set can help overcome these difficulties and facilitate the construction of a common earth model. We considered the joint inversion of seismic first-arrival traveltimes and gravity data to recover causative slowness and density distributions. Our joint inversion algorithm differs from previous work by (1) incorporating a large suite of measures for coupling the two physical property models, (2) slowly increasing the effect of the coupling to help avoid potential convergence issues, and (3) automatically adjusting two Tikhonov tradeoff parameters to achieve a desired fit to both data sets. The coupling measures used are both compositional and structural in nature and allow the inclusion of explicitly known or implicitly assumed empirical relationships, physical property distribution information, and cross-gradient structural coupling. For any particular exploration scenario, the combination of coupling measures used should be guided by the geologic knowledge available. We performed our inversions on unstructured grids comprised of triangular cells in 2D, or tetrahedral cells in 3D, but the joint inversion methods are equally applicable to rectilinear grids. We tested our joint inversion methodology on scenarios based on the Voisey’s Bay massive sulfide deposit in Labrador, Canada. These scenarios present a challenge to the inversion of first-arrival traveltimes and we show how joint inversion with gravity data can improve recovery of the subsurface features.