Lithospheric deformation beneath the San Gabriel Mountains in the Southern California Transverse Ranges

High-resolution tomographic images from Los Angeles Region Seismic Experiment (LARSE) array and southern California Seismic Network (SCSN) teleseismic data suggest that the entire lithosphere below the San Gabriel Mountains and San Andreas fault in the Transverse Ranges has thickened in a narrow, vertical sheet. P wave travel time inversions of the combined data support the presence of the well-documented upper mantle high-velocity anomaly that extends ∼200 km into the mantle under the northernmost Los Angeles basin and Transverse Ranges, and is associated with mantle downwelling due to oblique convergence. We find that the high-velocity, high-density upper mantle anomaly comprises a 60–80 km wide sheet of mantle material that lies directly below a substantial crustal root in the San Gabriel Mountains. The velocity perturbations are as large as 3% in the anomaly, corresponding to a ∼2% density increase. The tomographic images suggest that deformation in the ductile lower crust and mantle lithosphere may be partially coupled mechanically and thermally if the thickening is occurring together in response to convergence and that it may be a local compressional feature

Ohio and the World

Commencement address given by the Honorable Foy David Kohler, Appointed Ambassador to the U. S. S. R., to the Summer 1962 graduating class of The Ohio State University, St. John Arena, Columbus, Ohio, August 24, 1962

Group and phase velocity mismatch fringes in triple sum-frequency spectroscopy

The effects of group and phase velocity mismatch are well-known in optical harmonic generation, but the non-degenerate cases remain unexplored. In this work we develop an analytic model which predicts velocity mismatch effects in non-degenerate triple sum-frequency mixing, TSF. We verify this model experimentally using two tunable, ultrafast, short-wave-IR lasers to demonstrate spectral fringes in the TSF output from a 500 $\mu$m thick sapphire plate. We find the spectral dependence of the TSF depends strongly on both the phase velocity and the group velocity differences between the input and output fields. We define practical strategies for mitigating the impact of velocity mismatches

On the minimization of Dirichlet eigenvalues of the Laplace operator

We study the variational problem \inf \{\lambda_k(\Omega): \Omega\ \textup{open in}\ \R^m,\ |\Omega| < \infty, \ \h(\partial \Omega) \le 1 \}, where $\lambda_k(\Omega)$ is the $k$'th eigenvalue of the Dirichlet Laplacian acting in $L^2(\Omega)$, \h(\partial \Omega) is the $(m-1)$- dimensional Hausdorff measure of the boundary of $\Omega$, and $|\Omega|$ is the Lebesgue measure of $\Omega$. If $m=2$, and $k=2,3, \cdots$, then there exists a convex minimiser $\Omega_{2,k}$. If $m \ge 2$, and if $\Omega_{m,k}$ is a minimiser, then $\Omega_{m,k}^*:= \textup{int}(\overline{\Omega_{m,k}})$ is also a minimiser, and $\R^m\setminus \Omega_{m,k}^*$ is connected. Upper bounds are obtained for the number of components of $\Omega_{m,k}$. It is shown that if $m\ge 3$, and $k\le m+1$ then $\Omega_{m,k}$ has at most $4$ components. Furthermore $\Omega_{m,k}$ is connected in the following cases : (i) $m\ge 2, k=2,$ (ii) $m=3,4,5,$ and $k=3,4,$ (iii) $m=4,5,$ and $k=5,$ (iv) $m=5$ and $k=6$. Finally, upper bounds on the number of components are obtained for minimisers for other constraints such as the Lebesgue measure and the torsional rigidity.Comment: 16 page

Parametric correlations versus fidelity decay: the symmetry breaking case

We derive fidelity decay and parametric energy correlations for random matrix ensembles where time--reversal invariance of the original Hamiltonian is broken by the perturbation. Like in the case of a symmetry conserving perturbation a simple relation between both quantities can be established.Comment: 8 pages, 8 figure

Report for passive data acquired in the 1998-1999 Los Angeles Region Seismic Experiment II: a transect from Santa Monica Bay to the Westernmost Mojave Desert

Between October, 1998 and April, 1999, 83 seismic stations were installed in the greater western Los Angeles, California area to record teleseismic, regional, and local earthquakes. The near-linear 93-km long array extended between Santa Monica Bay and the western Mojave Desert, through the epicentral region of the Northridge earthquake. The goals of the experiment were to determine crustal thickness below the western Transverse Ranges, San Fernando Valley basin, and western Mojave Desert, measure anistropy along the line with special emphasis on the San Andreas fault region, evaluate the potential for future strong ground shaking at sites in the basins, and determine the kinematic relationship between crustal and uppermost mantle deformation by three-dimensional tomographic inversion using regional network data combined with the array data. The stations consisted of three-component, broadband and short-period seismometers, and timing was controlled by Global Positioning System (GPS) receivers. The array recorded 165 Gb of raw waveform data in continuous (25 sps) and triggered (50 sps) streams. Approximately 144 teleseismic earthquakes with magnitudes ≥ 5.5, and 2025 local earthquakes with magnitude ≥ 2.0 were recorded. Preliminary results from three-dimensional teleseismic traveltime inversion tomography indicate that uppermost mantle seismic anomalies strongly correlate with thickened crust in the Transverse Ranges suggesting that the width of the compressional region and convergence rate control the location of deformation more than the San Andreas shear zone does

Three-dimensional lithospheric structure below the New Zealand Southern Alps

Uppermost mantle seismic structure below the Southern Alps in South Island, New Zealand, is investigated by teleseismic P wave travel time residual inversion. The three-dimensional tomographic images show a near-vertical, high-velocity (2–4%) structure in the uppermost mantle that directly underlies thickened crust along the NNESSW axis of the Southern Alps. The center of the high-velocity anomaly lies to the east of the Alpine fault which bounds Pacific and Australian plate rocks. The oblique collision of these plates resulted in the uplift of the Southern Alps during the past 5–7 m.y. Also, a high-velocity anomaly (3–5%) corresponding to the Hikurangi subduction zone lies to the northeast of the Southern Alps anomaly, and low-velocity anomalies (-3%) underlying parts of northwestern and southern South Island may be signatures of late Tertiary extension and volcanism. The data consist of teleseismic arrival times from the New Zealand National Seismograph Network and arrival times recorded during the 1995–1996 Southern Alps Passive Seismic Experiment. Crustal heterogeneity was accounted for by back projecting the rays through an independently obtained three-dimensional crustal velocity and Moho depth model. The Southern Alps uppermost mantle velocity anomalies are most simply explained by lithospheric thickening below the center of convergence accompanied by thinning and asthenospheric upwelling adjacent to the region of convergence

Managing weeds by integrating smother plants, cover crops and alternative soil management

Any serious attempt to reduce pesticide use must focus on weed management. This project looks at practices to suppress weeds before crop planting, which will improve the effectiveness of other weed control tactics

Vibrational coherence in electron spin resonance in nanoscale oscillators

We study a scheme for electrical detection, using electron spin resonance, of coherent vibrations in a molecular single electron level trapped near a conduction channel. Both equilibrium spin-currents and non-equilibrium spin- and charge currents are investigated. Inelastic side-band anti-resonances corresponding to the vibrational modes appear in the electron spin resonance spectrum.Comment: 4 pages, 3 figures: Published versio

Argent, religion et pouvoir en Nouvelle-Calédonie : A. Ballande et les évêques, 1885-1935

Kohler Jean-Marie, Shineberg Dorothy. Argent, religion et pouvoir en Nouvelle-Calédonie. A.Ballande et les évêques, 1885-1935. In: Journal de la Société des océanistes, 95, 1992-2. pp. 151-183