Direct monitoring of active geohazards: emerging geophysical tools for deep-water assessments

Seafloor networks of cables, pipelines, and other infrastructure underpin our daily lives, providing communication links, information, and energy supplies. Despite their global importance, these networks are vulnerable to damage by a number of natural seafloor hazards, including landslides, turbidity currents, fluid flow, and scour. Conventional geophysical techniques, such as high-resolution reflection seismic and side-scan sonar, are commonly employed in geohazard assessments. These conventional tools provide essential information for route planning and design; however, such surveys provide only indirect evidence of past processes and do not observe or measure the geohazard itself. As such, many numerical-based impact models lack field-scale calibration, and much uncertainty exists about the triggers, nature, and frequency of deep-water geohazards. Recent advances in technology now enable a step change in their understanding through direct monitoring. We outline some emerging monitoring tools and how they can quantify key parameters for deepwater geohazard assessment. Repeat seafloor surveys in dynamic areas show that solely relying on evidence from past deposits can lead to an under-representation of the geohazard events. Acoustic Doppler current profiling provides new insights into the structure of turbidity currents, whereas instrumented mobile sensors record the nature of movement at the base of those flows for the first time. Existing and bespoke cabled networks enable high bandwidth, low power, and distributed measurements of parameters such as strain across large areas of seafloor. These techniques provide valuable new measurements that will improve geohazard assessments and should be deployed in a complementary manner alongside conventional geophysical tools

Detecting tip mining Olethreutinae (Torticidae) moths in the northern and central Great Plains with synthetic attractants.

RM-RN-44

Seismic inversion for site characterization: When, where and why should we use it?

The application of seismic inversion techniques to the foundation and drilling top hole zones has garnered significant interest in recent years. The shift towards more geologically complex and deeper water sites, combined with the global economic climate, has driven a requirement for more cost-effective site characterisation. More often used by the exploration industry, seismic inversion has been touted as a potentially valuable tool for quantifying the spatial and depth variability in sediment properties. In doing so, this approach can reduce the risk of encountering unforeseen ground conditions and the need for excessive over-design. Despite its potential, the inversion of high-resolution seismic data has yet to see widespread use, leaving unanswered questions regarding how and where this tool can best fit into the site characterization work flow. We test the potential usefulness of seismic inversion using a range of existing site investigation data sets. We apply several different inversion methods, including acoustic impedance and seismic quality factor inversion, as well as artificial neural network multi-attribute regression, to tackle end-member potential uses. First, explore early-phase potential uses, showing how seismic quality factor and acoustic impedance inversion can be used to capture the spatial variability in facies architecture and bulk sediment properties that could be used in appraisal and pre-FEED studies to optimize borehole and penetrometer (CPT) depths/locations and to ensure effective site-wide characterization. Second, we apply a combined acoustic impedance and artificial neural network workflow to link seismic properties with CPT profiles. These results demonstrate the potential late-phase use of seismic inversion for short-range interpolation/extrapolation of more complex geotechnical properties through the generation of synthetic CPT profiles useful for infrastructure design and micro-siting late in the development cycle. While not a comprehensive list of applications, together these examples illustrate how seismic inversion can be utilized throughout the development cycle. If the required objectives are clearly defined and an appropriate inversion workflow developed, seismic inversion can help to reduce uncertainty in site-wide characterization and drive efficiencies in layout and design studies throughout a project lifetime

NSC968

This articles discusses the logic, or logic-based, languages required for a full deployment of the SemanticWeb. It presents ten theses addressing 1. the kinds of logic languages needed, 2. data and data processing, 3. semantics, and 4. engineering and rendering issues. The views reported about in this article have been presented at the W3C Workshop on Rule Languages for Interoperability (27-28 April 2005,Washington, D.C., USA, http://www.w3.org/2004/12/rules-ws/)