Models for the evolution of the Carolina trough and their limitations

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric and Planetary Sciences, 1986.Microfiche copy available in Archives and Science.Bibliography: leaves 162-172.by Bernard Celerier.Ph.D

Bedrock geology of DFDP-2B, central Alpine Fault, New Zealand

<p>During the second phase of the Alpine Fault, Deep Fault Drilling Project (DFDP) in the Whataroa River, South Westland, New Zealand, bedrock was encountered in the DFDP-2B borehole from 238.5–893.2 m Measured Depth (MD). Continuous sampling and meso- to microscale characterisation of whole rock cuttings established that, in sequence, the borehole sampled amphibolite facies, Torlesse Composite Terrane-derived schists, protomylonites and mylonites, terminating 200–400 m above an Alpine Fault Principal Slip Zone (PSZ) with a maximum dip of 62°. The most diagnostic structural features of increasing PSZ proximity were the occurrence of shear bands and reduction in mean quartz grain sizes. A change in composition to greater mica:quartz + feldspar, most markedly below c. 700 m MD, is inferred to result from either heterogeneous sampling or a change in lithology related to alteration. Major oxide variations suggest the fault-proximal Alpine Fault alteration zone, as previously defined in DFDP-1 core, was not sampled.</p

Constraint on Stress Tensor from Slip on a Single Fault Plane

Given a fault plane and its slip vector, the stress tensor which caused the displacement is sought. Two constraints are considered: first, a geometrical constraint that the shear stress applied to the fault plane is parallel to the slip [Wallace, 1951; Bott, 1959]; second, a frictional constraint that the shear to normal stress ratio equals tan?0 [Coulomb, 1776]. This is done in two steps. In a first step, the stress tensors that satisfy the geometrical constraint are sought. For tensors belonging to the vectorial space of solutions, shear and normal stress magnitudes become a function of the principal stress orientation s1, s2, s3 and are mapped, extending a study by McKenzie [1969]. The relationship between Mohr's [1882] (?nt) plane and these maps is described. In a second step, it is investigated which among these tensors also satisfy the frictional constraint. Within this more restricted vectorial space, there is a relationship between principal stress magnitudes, represented ?= (?1-?2)/( ?1 – ?3) and s = (?1 – ?3)/ ?1, and the principal stress orientation s1, s2, s3. Both the range of s and the spatial distribution of s1, s2, s3 are more restricted than when the geometrical constraint alone is considered. As when the geometrical constraint is solely considered [McKenzie, 1969], the principal stress orientations s1, s2, s3 may lie significantly away from and up to right angle to the P, B, T axis. However, this can happen only in two cases: (1) either the effective stress difference, s, has reached a high value, which is unlikely to happen if enough pre-existing fractures are available to release the stress, or (2) ?2 becomes close to either ?1 or ?3 and therefore barely distinguishable from it; in that case the delocalisation of the principal stress orientations is best described by a tendency for s2 to exchange role with either s1 or s3. When the stress difference remains small and ?2 reasonably away from ?1 and ?3, sf, s2, s3 approach positions that we define as the Pf, B, Tf axis and that are obtained from the P, B, T axis by a rotation of angle ?0/2 around B and towards the slip vector. This explains why the P, B, T axis gives reasonable estimates of the principal stress orientations [Scheidegger, 1964] despite objections [McKenzie, 1969]. However, whenever the fault plane can be distinguished from the auxiliary plane, Pf, B, Tf should give a better estimate [Raleigh et al., 1972]. In an area where many fault planes are available and a uniform tensor is assumed, the scatter in the plane orientations contains information about both the relative position of ?2, represented by ?, and the relative stress difference, s: the higher s or the closer ? to either 0 or 1, the more scatter. This information could then be extracted by inverse methods. Because a friction law would constrain these inverse methods more tightly, it may show the necessity of non-uniform tensor to explain scattered fault planes.Institute for Geophysic

Remarks on the relationship between the tectonic regime, the rake of the slip vectors, the dip of the nodal planes, and the plunges of the P, B, and T axes of earthquake focal mechanisms

We use a triangular representation of the plunges of P, B, and Taxes to compare the different ways tectonic regime is inferred from earthquake focal mechanisms in recent works. We argue that P, B, and Taxes provide a reasonable estimate of principal stress directions when faulting is close to Andersonian conditions, and that this can be estimated from the location on a triangular diagram. We analyze the geometrical relationship between the plunges of P, B, and Taxes on one hand, and the rake of slip and dip of nodal planes on the other hand. We show that the rake and dip level curves correspond to trajectories of the vertical direction along great and small circles with respect to the frame of the P, B. and Taxes. This shows that dip-slip faulting is compatible with vertical P or Taxes, but does not require it, and instead requires horizontal B axes. It also shows that strike-slip faulting does not require vertical B axes, but P and Taxes with equal plunges. This also reveals that focal mechanisms where P, B, and Taxes all have moderate plunge correspond to two very different types of nodal planes: a steeply dipping one with oblique slip and a moderately dipping one with strike-slip. Seismically active and moderately dipping strike-slip faults are to be found among these events

In situ formation of non-noble metal nanoparticles in a polymer-derived high specific surface area Si-C-N-O(H) support to promote electrocatalytic water oxidation

International audienc

Structure of the hydrothermal root zone of the sheeted dikes in fast-spread oceanic crust : a core-log integration study of ODP hole 1256D, Eastern Equatorial Pacific

Ocean Drilling Program Hole 1256D reached for the first time the transition zone between the sheeted dike complex and the uppermost gabbros. The recovered crustal section offers a unique opportunity to study the deepest part of the hydrothermal system in present-day oceanic crust. We present a structural analysis of electrical borehole wall images. We identified, and measured the orientations of four categories of structures: major faults, minor fractures, possibly hydrothermal veins, and dikes. All structures tend to strike parallel to the paleo-ridge axis. Three major fault zones (meter thick) and dikes are steeply dipping (~ 75° on average) outward the ridge. Centimeter-thick moderately conductive planar features are interpreted as hydrothermal veins, are organized in arrays of consistent spacing, thickness, and orientation, and are dipping about 15-20° toward the ridge. This structural pattern is interpreted as an on-axis paleohydrothermal circulation system, with vertical, dike-parallel fractures, and sub-horizontal high-temperature hydrothermal veins at the base of the sheeted dike, which was subsequently rotated ~ 15° westward around a ridge-parallel, sub-horizontal axis. This rotation can be caused by upper-crustal block rotation along a listric normal fault, and/or subsidence at the ridge axis

Formation in situ de nanoparticules de Ni dans une céramique Si-N-C-O(H) obtenue par voie PDC pour applications en RDO

International audienc

In situ formation of Ni nanoparticles inside a Si-C-N-O(H) ceramics obtained by PDC road with high specific area: Applications for OER (VIRTUAL)

International audienc

Formation in situ de nanoparticules de Ni dans une céramique de type Si-C-N-O(H) obtenue par voie PDC : Applications à l’électrolyse de l’eau

International audienc