Papers by Christopher Scholz
Geological Society of America Bulletin, 1973
Pure and Applied Geophysics PAGEOPH, 1974
A technique is described for measuring strains in rock deformation experiments by means of hologr... more A technique is described for measuring strains in rock deformation experiments by means of holographic interferometry. The method allows the entire surface displacement field of the sample to be mapped to within one-tenth the wavelength of light. Several illustrative experiments show that inhomogeneous strain, in particular bending and torsion, is commonly present in uniaxial compression experiments, and that some of this strain can be caused by the testing machine. In a creep experiment in uniaxial compression, a concentration of dilatancy was observed very early in the experiment that was spatially related to the location of the ultimate failure plane.
Planetary and Space Science, 2002
... Tobias Karp Corresponding Author Contact Information , E-mail The Corresponding Author , a , ... more ... Tobias Karp Corresponding Author Contact Information , E-mail The Corresponding Author , a , Bernd Milkereit a , 1 , Peter Janle a , Sylvester K ... A portable modular research catamaran, the R/V Kilindi, operated by the Syracuse University, was used to deploy and recover OBH ...
Natural faults generally have wavy geometry in a wide spectrum of scale from mesoscopic to macros... more Natural faults generally have wavy geometry in a wide spectrum of scale from mesoscopic to macroscopic scales. Since the kinks in wavy faults cause the intensified concentration of stresses, the nucleation of secondary faults or branches are expected at there. This geometrical evolution of faults may interact with dynamic process of individual earthquake events. We use a boundary integral equation method (BIEM) that can unify the dynamic and static analyses to evaluate the local stress state along the wavy faults and the nucleation of the branches at the kinks during a seismic cycle. We assume a wavy main fault and surrounding medium, which is much stronger than the preexisting weak plane but still breakable. We confirm that off-fault shear and normal stresses can be accumulated around the kinks associated with recurrent slip events on the faults, and then the concentrated stress causes newly formation of branches cutting through a preexisting wavy main fault triggered by the dynamic rupture on the main fault. The stress concentrated at kinks after a dynamic slip event explains the observed occurrence of off-fault aftershocks. The branch nucleation also explains a geologic empirical law that states some faults tend to be planar with increasing cumulative slip; this model is applicable to dip slip faults as well as strike slip faults. The cutting-through branches avoid kinks pinning slip that courses slip-hardening, therefore slip weakening is shown during ruptures instead. The simulated evolution of stress heterogeneity further contributes to the occurrence of different rupture process between each earthquake event even in a cycle within a single fault system including rupture path, directivity, spatial distribution and entire value of moment release.
We propose a new approach to quantifying fault system geometry, using an objective fit of the fau... more We propose a new approach to quantifying fault system geometry, using an objective fit of the fault geometry to a test function, specifically here a fault branch. Fitting a "Y" shaped object using a cost function to dextral faults in California, we find a number of significant results arising from using a systematic, objective, quantitative approach. (1) The largest angle of the branch structure is generally very close to 180°, implying the branch is a splay fault off the primary throughgoing fault. (2) The distribution of the smallest angle, the splay angle, has a peak near ± 17°, symmetric about the primary fault. (3) These features appear independent of scale. These results are not yet explained by any theory, and pose new questions and constraints for the physics of fault system formation and behavior.
ABSTRACT Tectonic controls on the localization of high-temperature (>250°C) fluid flow are... more ABSTRACT Tectonic controls on the localization of high-temperature (>250°C) fluid flow are evaluated for geothermal systems of the Taupo Volcanic Zone (TVZ), New Zealand. Most geothermal systems occur within an actively rifting arc (~150 km-long) dominated by silicic volcanism and they occur in association with major faults near caldera bounding structures or within accommodation zones that transfer extension between rift segments. Geothermal systems are hosted in a thick sequence (1 to >3 km) of Quaternary volcanic deposits that rest unconformably on weakly metamorphosed Mesozoic argillite and sandstone (termed greywacke). Permeability controls in selected geothermal systems, including Kawerau, Rotokawa, and Wairakei-Tauhara, can be summarized as follows: 1) intergranular host-rock porosity and permeability; 2) fault-fracture network permeability produced by tectonism, volcanism, and/or dike injection (magmatism); 3) pipe-like vertical conduits produced by volcanic and hydrothermal eruptions; and 4) hydrothermal alteration, mineral deposition and dissolution that may cause heterogeneity in the porosity and permeability of a fluid reservoir. Such controls influence fluid flow within three distinctive depth zones: 1) a feed zone (>2000 m depth), 2) a reservoir zone
Scientific Drilling, 2005
... back row (lr): Donald Bagley, James Addo, Sylvester Blay, Dave Altman, Kevin Loveland, Chris ... more ... back row (lr): Donald Bagley, James Addo, Sylvester Blay, Dave Altman, Kevin Loveland, Chris Walters (far back), Doug Schnurrenberger, Adam Carey, Tim Shanahan; middle row (lr): Jannadi Lapukenu, Daniel Somuah, Eric Boahen, Bernard Worlanyo, Anna Henderson ...
Journal of Paleolimnology, 2003
New sediment core data from a unique slow-sedimentation rate site in Lake Tanganyika contain a mu... more New sediment core data from a unique slow-sedimentation rate site in Lake Tanganyika contain a much longer and continuous record of limnological response to climate change than have been previously observed in equatorial regions of central Africa. The new core site was first located through an extensive seismic reflection survey over the Kavala Island Ridge (KIR), a sedimented basement high that separates the Kigoma and Kalemie Basins in Lake Tanganyika. Proxy analyses of paleoclimate response carried out on core T97-52V include paleomagnetic and index properties, TOC and isotopic analyses of organic carbon, and diatom and biogenic silica analyses. A robust age model based on 11 radiocarbon (AMS) dates indicates a linear, continuous sedimentation rate nearly an order of magnitude slower here compared to other core sites around the lake. This age model indicates continuous sedimentation over the past 79 k yr, and a basal age in excess of 100 k yr. The results of the proxy analyses for the past ~ 20 k yr are comparable to previous studies focused on that interval in Lake Tanganyika, and show that the lake was about 350 m lower than present at the Last Glacial Maximum (LGM). Repetitive peaks in TOC and corresponding drops in δ 13 C over the past 79 k yr indicate periods of high productivity and mixing above the T97-52V core site, probably due to cooler and perhaps windier conditions. From 80 through ~ 58 k yr the δ 13 C values are relatively negative (-26 to-28‰) suggesting predominance of algal contributions to bottom sediments at this site during this time. Following this interval there is a shift to higher values of δ 13 C, indicating a possible shift to C-4 pathway-dominated grassland-type vegetation in the catchment, and indicating cooler, dryer conditions from ~ 55 k yr through the LGM. Two seismic sequence boundaries are observed at shallow stratigraphic levels in the seismic reflection data, and the upper boundary correlates to a major discontinuity near the base of T97-52V. We interpret these discontinuities to reflect major, prolonged drops in lake level below the core site (393 m), with the lower boundary correlating to marine oxygen isotope Stage 6. This suggests that the previous glacial period was considerably cooler and more arid in the equatorial tropics than was the last glacial period. *This is the third in a series of four papers published in this issue collected from the 2000 GSA Technical Session 'Lake basins as archives of continental tectonics and paleoclimate' in Reno, Nevada. This collection is dedicated to Dr.
Scientific Drilling, 2006
Science, 1996
Lake Victoria is the largest lake in Africa and harbors more than 300 endemic species of haplochr... more Lake Victoria is the largest lake in Africa and harbors more than 300 endemic species of haplochromine cichlid fish. Seismic reflection profiles and piston cores show that the lake not only was at a low stand but dried up completely during the Late Pleistocene, before 12,400 carbon-14 years before the present. These results imply that the rate of speciation of cichlid fish in this tropical lake has been extremely rapid.
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Papers by Christopher Scholz