Volcano monitoring in NZ and links to SW Pacific via the Wellington VAAC

Monitoring for natural hazards like earthquakes, volcanic eruptions and landslides in New Zealand is under taken by GNS Science through the GeoNet project, funded by the Earthquake Commission (EQC). The volcano monitoring function, which includes seismograph and GPS networks, visual observations, webcams, deformation, gas and chemical measurements, assesses the status of New Zealand’s 12 active volcanoes and disseminates warnings as necessary. Interaction with the Wellington VAAC addresses aviation concerns. Near-real-time data is obtained from the monitoring networks and processed via two data centres, with two Duty Officers who respond to pager alerts. Through the National Civil Defence Plan, the volcano monitoring function is delegated to GNS Science, which is responsible for setting the volcanic alert level at each volcano. The Alert level is then used by responding agencies, industries, utility providers and the public to set their response. The New Zealand alert level system is based on the current status of the volcano, and is not necessarily predictive. The aviation industry is one of these responding industries. As a consequence of the 1995 and 1996 eruptions of Ruapehu volcano, it became apparent that the aviation industry required more information than the standard VAAC data and an additional service known as VAAS (NZ Volcanic Ash Advisory System) was established by MetService NZ and GNS Science. This arrangement provides enhanced services to the airlines and ensures rapid dissemination and quantification of information like SIGMET and NOTAM. GNS Science has informal relationships with similar geological based organisations in SW Pacific countries, especially Vanuatu and the Solomon Islands, and is able to quantify information about eruptions in those countries. Similarly, MetService NZ has relationships and is able to obtain pilot reports and updates from the meteorological and air traffic control organisations.     

Antithethic and homothetic faults

Antithetic faults are dip slip faults that displace rocks so as to prevent or reduce structural relief, typically producing tilted fault blocks. They may or may not occur in conjugate systems with their opposites, homothetic faults, which serve to increase structural relief. Several examples serve to illustrate the concept and to correct current misunderstandings.

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Zusammenfassung Die Arbeit soll die Begriffe antithetisch und homothetisch klären helfen. Antithetische Verschiebungen wirken dem tektonischen Relief entgegen, homothetische Verwerfungen unterstützen es. Die Begriffe werden an einigen Beispielen erläutert.

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Résumé Ce travail constitue une tentative d'élucider les termes »antithétique« et »homothétique«. Le rejet des failles antithétiques s'oppose à la création d'un relief tectonique. Le rejet des failles homothétiques augmente ce relief. Quelques exemples sont discutés.

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A comparison of TRMM to other basin-scale estimates of rainfall during the 1999 Hurricane Floyd flood

The volumetric rainfall attributed to Hurricane Floyd in 1999 was computed for the bulk of the Tar, Neuse, and Cape Fear River Basins in eastern North Carolina, USA from the Tropical Rainfall Measuring Mission (TRMM) Multi-Satellite Precipitation Analysis (TMPA) research product, and compared with volumes computed using kriged gauge data and one centrally located radar. TMPA showed similar features in the band of heaviest rainfall with kriged and radar data, but was higher in the basin-scale integrations. Furthermore, Floyd’s direct runoff volumes were computed and divided by the volumetric rainfall estimates to give runoff coefficients for the three basins. The TMPA, having the larger storm totals, would suggest greater infiltration during Floyd than the gauge and radar estimates would. Finally, we discuss a concept for adjusting the United States Department of Agriculture Natural Resources Conservation Service rainfall-runoff model when predicting discharge values from real-time TMPA in ungauged river basins.

Blast Induced Damage and Dynamic Behaviour of Hangingwalls in Bench Stoping

This paper presents the results of a comprehensive monitoring program designed to investigate the extent of blast induced damage experienced by rock masses extracted by bench stoping methods. An array of triaxial geophones and extensometers were used to monitor blast vibration attenuation and measure hangingwall deformations during stope extraction. In addition, pre and post surveys of the hangingwall rock mass were conducted using a TV borehole camera and cavity survey instrumentation. These surveys were later used to calibrate damage profiles into the stope hangingwalls.

Peak particle velocity, hangingwall deformation measurements and stope surveys were used to develop a site specific damage model that allowed engineers to asses drilling and blasting configurations to minimise the extent of pre-conditioning and damage. In addition the study included the analysis of the frequency response, displacements and accelerations experienced by the excavation as extraction and mine filling progressed. This work aimed at improving our understanding of the influence of blasting on the dynamic behaviour of stope hangingwalls.

The study demonstrated that estimates of the maximum extent of rock mass pre-conditioning and/or damage made through the application of the Holmberg-Persson approach compared well with measured results. In addition, the study found that dynamic loading imparted on an exposed hangingwall from subsequent stope blasting was also expected to contribute to rock mass weakening and that mine filling was crucial to arrest further deterioration. Hangingwall accelerations were used to demonstrate that larger openings may be more susceptible to dynamic loading.     

High latitude river runoff in a doubled CO2 climate

A global atmospheric model is used to calculate the monthly river flow for nine of the world's major high latitude rivers for the present climate and for a doubled CO₂ climate. The model has a horizontal resolution of 4° × 5°, but the model's runoff from each grid box is quartered and added to the appropriate river drainage basin on a 2° × 2.5° resolution. A routing scheme is used to move runoff from a grid box to its neighboring downstream grid box and ultimately to the mouth of the river. In a model simulation in which atmospheric carbon dioxide is doubled, mean annual precipitation and river flow increase for all of these rivers, increased outflow at the river mouths begins earlier in the spring, and the maximum outflow occurs approximately one month sooner due to an earlier snow melt season. In the doubled CO₂ climate, snow mass decreases for the Yukon and Mackenzie rivers in North America and for rivers in northwestern Asia, but snow mass increases for rivers in northeastern Asia.     

A non-hydrostatic model for the numerical study of landslide-generated waves

This paper proposes and demonstrates a two-layer depth-averaged model with non-hydrostatic pressure correction to simulate landslide-generated waves. Landslide (lower layer) and water (upper layer) motions are governed by the general shallow water equations derived from mass and momentum conservation laws. The landslide motion and wave generation/propagation are separately formulated, but they form a coupled system. Our model combines some features of the landslide analysis model DAN3D and the tsunami analysis model COMCOT and adds a non-hydrostatic pressure correction. We use the new model to simulate a 2007 rock avalanche-generated wave event at Chehalis Lake, British Columbia, Canada. The model results match both the observed distribution of the rock avalanche deposit in the lake and the wave run-up trimline along the shoreline. Sensitivity analyses demonstrate the importance of accounting for the non-hydrostatic dynamic pressure at the landslide-water interface, as well as the influence of the internal strength of the landslide on the size of the generated waves. Finally, we compare the numerical results of landslide-generated waves simulated with frictional and Voellmy rheologies. Similar maximum wave run-ups can be obtained using the two different rheologies, but the frictional model better reproduces the known limit of the rock avalanche deposit and is thus considered to yield the best overall results in this particular case.     

The essex earthquake of 1884

The largest British earthquake to occur in several hundred years took place in Essex, in the south east of England, in 1884. From contemporary accounts and a recent visit to the area affected by the earthquake, the intensity of the earthquake was assessed. It is estimated that the peak accelerations generated may have been as much as 0.1 g. This would be of consequence to some modern structures, designed without earthquake provisions.