Russ Evans

Neotectonics of the Marmara Sea region of Turkey

Seismological investigations in Western Anatolia, NW Turkey have identified linear patterns of earthquake epicentres outlining a wedge-shaped block in the area of the Marmara Sea. This block shows different seismic characteristics from the rest of Western Anatolia and appears to act as a separate tectonic unit. Earthquake fault-plane mechanisms show that the Marmara block is being rotated and sheared in order to accommodate the right-lateral motion of the north Anatolian Fault and the extensional tectonics of the southwestern Anatolia. Investigations of the behaviour of seismic shear-waves suggest that neotectonic stress aligns water-filled microcracks throughout the upper (brittle) 10–20 km of the crust and that in situ stress directions can be monitored by analysis of shear waves recorded on three-component instuments.

The Dental Health and Caries-Related Microflora in Children With Craniosynostosis

OBJECTIVE To compare levels of dental caries, bacterial dental plaque, gingivitis, enamel defects, and caries-related microflora in children with and without craniosynostosis. STUDY GROUP Fifty-seven children with craniosynostosis and their matched controls. OUTCOME MEASURES The decayed, missing, and filled teeth and surfaces in both the deciduous (dmfs and dmft) and the permanent dentition (DMFS and DMFT). The plaque and gingivitis scores and developmental enamel defects were also recorded. The caries-related microflora was sampled using an alginate swab and the prevalence of Streptococcus mutans and Lactobacillus and Candida species were recorded. RESULTS The dmfs (p <.02) and dmft (p <.01) were significantly greater in the control children. The plaque score for the deciduous dentition only (p <.02) and also the gingivitis score for the permanent teeth only (p <.008) in the craniosynostosis group were significantly greater. The total aerobic bacterial count (p <.004), anaerobic count (p <.002), and Candida count (p <.05) were significantly greater in the control group. The proportion of S. mutans both as a percentage of the total anaerobic count (p <.04) and the total streptococcal count (p <.05) was significantly greater in the control group.

Inversion of arrival-times in a region of dilatancy anisotropy

Shear-wave splitting has been identified in many three-component seismograms from two separate field experiments on a section of the North Anatolian Fault in North-West Turkey. These observations are consistent with shear-wave propagation through a zone of extensive-dilitancy anisotropy. A preliminary attempt has been made to confirm this interpretation by simultaneously inverting suites of arrival-times for hypocentral locations and for parameters describing an anisotropic halfspace. Although the inversion procedure is not globally convergent, it is possible to recognize the true solution by systematically varying the initial conditions. Applied to selected data sets, the inversion defines several anisotropic models that fit the data significantly better than a simple isotropic model, and display the anisotropy required by the shear-wave splitting. However, most of these anisotropic models are not superior when they are used to individually locate events in a much larger data set. However, for each experiment, there is a single model that produces clearly superior locations for the larger data sets than those of other anisotropic or simple isotropic models. Both models display similar velocity variations which are characteristic of propagation through distributions of biplanar cracks displaying orthorhombic symmetry. The principal axes of the two models are oriented in similar directions and are within 20° of the principal axis of regional stress derived from fault-plane solutions. The solutions indicate low velocities close to the tensional axis, as would be expected in extensive-dilatancy anisotropy.

Regularized inversion of 3D full tensor gradient (FTG) data for dynamic reservoir monitoring

Summary Three-Dimensional Full Tensor Gradiometry (3D FTG) acquires ultra-sensitive measurements of the Earth’s (vector) gravity gradient field. Departures from simple weakening of the field in the vertical direction are due to subsurface variations in density. We have undertaken a numerical examination of the feasibility of using this system for detecting lateral density contrasts in subsurface layers during reservoir monitoring. Our gravity modeling focuses on the additional value added by taking account of the horizontal components of gravity gradient in imaging local targets. A regularized inversion algorithm that can describe and predict the dynamic behavior of a hydrocarbon reservoir has been developed and tested on synthetic FTG data based on realistic petrophysical models. Our approach also yields estimates of uncertainty in hydrocarbon production data. Results show that the technique is particularly useful for direct monitoring of gas-oil contact or temperature front expansion during CO2 injection in heavy-oil reservoirs at shallow or moderate depths.

Feasibility of FTG reservoir monitoring

Three-Dimensional Full Tensor Gradiometry (3-D FTG) acquisition system takes ultra sensitive real-time measurements of small gravity changes (gradients) caused by density differences in all directions. We have undertaken a numerical examination of the feasibility of using this system for reservoir monitoring. Special gravity modeling and inversion algorithms that can describe and predict the dynamic behavior of a hydrocarbon reservoir have been developed and tested on synthetic FTG data based on realistic 4-D petrophysical models. Our inversion yields estimates of uncertainty in hydrocarbon production data. Results show that the technique is robust and is particularly useful for direct GOC monitoring and CO2 injection in heavy-oil reservoirs at moderate depths.

Multi‐scale fracture characterization using fractal frequency‐power‐law attenuation models

We have investigated wave scattering by chaotic fractured systems of fractal geometry with random spatial variation. Specifically, we have examined simple closed-form solutions in fractal poroelastic media. These solutions may be characterized by their frequency-power-law (FPL) signature caused by wave dispersion and attenuation. Numerical results show that the fractal dimension can be estimated from the FPL dependence of the scattered wavefield. It appears that finite-bandwidth signals are delayed with respect to the wavefront in comparable elastic media. Applications to fracture characterization are considered.

Predicting the unpredictable

Predicting the unpredictable Welcome The potential for corporate fraud and misconduct to easily spread from a small brush fire into a full-blown firestorm has garnered the attention of regulators, with the United States Securities and Exchange Commission, the Public Company Accounting Oversight Board and the Federal Sentencing Commission all having recently addressed this topic. While it may not be possible to eliminate the risk of fraud altogether, a company can at least identify it early and minimize its damage with proper planning, policies and procedures. This report provides step-by-step guidance on how to develop an effective antifraud program that addresses not only financial statement risk, but also reputation, operational, legal and strategic risks. In addition, it provides a summary of fraud schemes that are common to the transportation & logistics industry. Fraud management makes good business sense. A company that establishes an effective antifraud program will go a long way toward maintaining or restoring investor confidence in the integrity of its financial results. Equally important, reducing fraud will help a company to lower costs, improve profitability, protect its reputation and mitigate liability. We believe this report is a valuable blueprint to help transportation & logistics companies achieve these goals.

An Experiment to Investigate Polarization Anomalies in North Anatolia

A three-component seismometer network, 15 km in aperture, was set up over some swarm activity just East of the Sea of Marmara. In an eight week period several hundred small earthquakes were recorded beneath or immediately adjacent to the network. Almost all the shear wave trains of these earthquakes display polarization anomalies indicative of dilatancy anisotropy.