How can the ISC location procedures be improved?

For many decades the International Seismological Centre (ISC) has used a well defined procedure to locate seismic events using first P-onsets and the Jeffreys-Bullen tables ([Jeffreys, H., Bullen, K.E., 1940. Seismological Tables. British Association for the Advancement of Science, Gray Milne Trust, London, 50 pp]) as the travel-time reference. However, during the last two decades, more accurate spherical Earth models have been published and enhanced computer capabilities make it easier to implement more sophisticated data inversion schemes. Several features that may improve the location procedure at the ISC were systematically tested using the location program HYPOSAT. The investigated features were the influence of

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the usage of the spherical Earth models JB, PREM, IASP91, SP6, and AK135;

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the usage of later onsets;

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travel-time corrections for local crustal structure based on CRUST 5.1;

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different weighting of the residuals;

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reducing the amount of defining data at a late stage of the inversion process.

Application of different combinations of these factors led to a reduction of the location errors for the 156 test events, of which the epicenter is known with an accuracy of less than 5 km. However, no clear rule of common factors to achieve this result could be defined. Most promising is the application of AK135 as model for travel-time calculations, applying crust specific station corrections and corrections for the reflection points of surface reflections, a combined usage of surface and core reflections, and removing data which have large residuals or do not much contribute to the solution for the last iterations.     

Potential for remediation of acidic mining lakes evaluated by hydrogeochemical modelling: Case study Grünewalder Lauch (Plessa 117, Lusatia/Germany)

About one third of several hundred mining lakes in Eastern Germany are highly acidified, and there is a need to restore them to neutral conditions because they constitute an environmental hazard for water resources and downstream environments. The aim of this study is to evaluate the efficiency of three different acid pit lake water remediation treatments: dilution with alkaline (river) water, limestone treatment and biological neutralization by organic carbon-driven alkalinity generation. The efficiency is evaluated for the acidic mining lake Grünewalder Lauch by adjusting input values into a geochemical model and making future projections. Current approaches, such as flooding with neutral surface water or extensive liming, are not suitable for many lakes because of a limited supply of alkaline water or high lime immobilizing potential of Fe- and Al-rich water in acidic lakes, respectively. Further treatment methods are, therefore, designed to combine water supply and biological measures with the management of water quality by the application of in-lake microbial processes. These processes are focused on the metabolic response of aquatic ecosystems to nutrient enrichment (enhancement of primary production and thereby organic carbon supply) and the microbial decomposition of organic matter and their effects on the gain or loss of alkalinity.The results and comparisons of different neutralization measures will be generalized by the application of hydrogeochemical models for alkalinity production showing

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the long term efficiency of the measures, depending on carbon turnover at the sediment/water interface,

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the development of bicarbonate buffering capacity as a consequence of biological measures,

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the importance of pyrite formation instead of FeS.

     

Hydrologic effects of a bushfire in a catchment in south-eastern New South Wales

An opportunity to study the effect of a bushfire on the hydrology of a forested catchment was presented when a bushfire burned through an area of approximately 280 square miles in the Snowy Mountains region of south-eastern New South Wales, Australia, in March 1965. The effect of the fire upon the hydrologic characteristics of two catchments for which streamflow records were available before and after the fire was examined and it was shown that:

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(i) there were pronounced changes in the shape of the flood hydrographs of one catchment,