Integration of micro-gravity and geodetic data to constrain shallow system mass changes at Krafla Volcano, N Iceland

New and previously published micro-gravity data are combined with InSAR data, precise levelling and GPS measurements to produce a model for the processes operating at Krafla volcano, 20 years after its most recent eruption. The data have been divided into two periods: from 1990 to 1995 and from 1996 to 2003 and show that the rate of deflation at Krafla is decaying exponentially. The net micro-gravity change at the centre of the caldera is shown, using the measured Free Air Gradient, to be -85 μGal for the first and -100 μGal for the second period. After consideration of the effects of water extraction by the geothermal power station within the caldera, the net gravity decreases are -73 ± 17 μGal for the first and -65 ± 17 μGal for the second period. These decreases are interpreted in terms of magma drainage. Following a Mogi point source model we calculate the mass decrease to be ~2 x 1010 kg/yr reflecting a drainage rate of ~0.23 m3/s, similar to the ~0.13 m3/s drainage rate previously found at Askja volcano, N-Iceland. Based on the evidence for deeper magma reservoirs and the similarity between the two volcanic systems, we suggest a pressure-link between Askja and Krafla at deeper levels (at the lower crust or the crust-mantle boundary). After the Krafla fires, co-rifting pressure decrease of a deep source at Krafla stimulated the subsequent inflow of magma, eventually affecting conditions along the plate boundary in N-Iceland, as far away as Askja. We anticipate that the pressure of the deeper reservoir at Krafla will reach a critical value and eventually magma will rise from there to the shallow magma chamber, possibly initiating a new rifting episode. We have demonstrated that by examining micro-gravity and geodetic data, our knowledge of active volcanic systems can be significantly improved

The potential of social indicators: Minimum conditions for impact at the national level as suggested by a study of the use of ‘social indicators’ 73

Empirical evidence is presented which suggests that the use of social indicators among upper level government officials in the United States is minimal at present. Further, the level of use is not likely to be increased by improved measurement procedures, aesthetically improved packaging, or more widespread dissemination of such information among persons who influence policy decisions. The power of such information can be expected to be no greater than that of ‘mere’ statistics unless deliberate effort is made to institutionalize the importance of social indicators into government operations in conjunction with policy planning, goal setting, and commitment to the use of indicators as a system of national evaluation of progress toward the achievement of societal objectives. Several recommendations are made to develop the potential of social indicators and to increase their creative and useful application in matters of public policy at the national level.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43692/1/11205_2004_Article_BF00352942.pd

Use of Advanced Tools for the Analysis of Gasoline Direct Injection Engines

A methodology that uses simultaneously three dimensional (3D) calculations and advanced experimental tools has been developed in order to characterize air/fuel mixing and combustion of gasoline direct injection (GDI) engines at every stage of development. The experimental tools used in this analysis underline the great cycle-to-cycle variability and show that the air/fuel ratio variations at spark plug are closely linked to the fluctuations of combustion starting and development. Despite this variability, average measurements are reproducible and in good agreement with 3D computational results obtained with KIVA-MB code. The common use of both kinds of tools allows getting a very fine understanding of GDI engine concepts. This approach has been first applied to the analysis of wall-guided direct injection engine concept, through the analysis of Mitsubishi GDI engine. It has also been used for the analysis of the spray-guided direct injection engine concept. In both cases the robustness of the air/fuel ratio control at spark plug is clearly the greatest challenge for GDI stratified engines