23 research outputs found
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Ground Truth Collection for Mining Explosions in Northern Fennoscandia and Northwestern Russia
We concluded comprehensive ground truth collection at the Khibiny, Olenegorsk, Kovdor, and Zapolyarnyi mines, and have basic information on 2,052 explosions. In the past two years we used this ground truth information to extract waveform data from the ARCES array and a number of regional stations (KEV, LVZ, APA) as well as from six stations that we deployed along two lines stretching between the Khibiny Massif mines and the region around the ARCES array. We calculated P/S ratios using the ARCES array data for many of these events comprising several source types (compact underground explosions, underground ripple-fired explosions, surface ripple-fired explosions). We found that the P/S ratios of small compact underground explosions in mines of the Khibiny Massif are systematically lower than the P/S ratios of large ripple-fired surface explosions. We had anticipated that smaller underground shots would appear more like single well-coupled explosions, thus having higher P/S ratios than large ripple-fired explosions. A possible explanation for this phenomenon is that the compact underground explosions in these mines are designed to fracture and drop a large quantity of ore from the ceiling of a horizontal shaft. The potential energy released by the falling ore may express as shear wave energy, which may be considerably greater than the (P wave) energy released directly by the explosive. We concluded the deployment of the six stations along the Khibiny-ARCES lines this past summer; this year we are examining the data from these stations to see how P/S ratios vary with range from the source. We have an update on the P/S ratio analysis contrasting different source types, with the addition of an analysis of range dependence using data from the temporary stations. The portable stations were redeployed in the fall of 2004 to the Kiruna and Malmberget underground mines in northern Sweden. The stations deployed in Malmberget also record events from the surface mining operations at the Aitik mine, located some 15 km from Malmberget mine. The data from these stations will allow comparisons of seismic waveforms resulting from different types of shooting practices at different locations within the mines. These stations will provide ground truth on a large number of explosions at these mines allowing future analyses of the dependence of discriminants on source type, possibly assessing the portability of results obtained with the Khibiny explosion observations
Low Frequency Gravitational Wave Detection With Ground Based Atom Interferometer Arrays
We propose a new detection strategy for gravitational waves (GWs) below few Hertz based on a correlated array of atom interferometers (AIs).Our proposal allows to reject the Newtonian Noise (NN) which limits all ground based GW detectors below few Hertz, including previous atom interferometry-based concepts.Using an array of long baseline AI gradiometers yields several estimations of the NN, whose effect can thus be reduced via statistical averaging.Considering the km baseline of current optical detectors, a NN rejection of factor 2 could be achieved, and tested with existing AI array geometries.Exploiting the correlation properties of the gravity acceleration noise, we show that a 10-fold or more NN rejection is possible with a dedicated configuration.Considering a conservative NN model and the current developments in cold atom technology, we show that strain sensitivities below in the frequency band can be within reach, with a peak sensitivity of at .Our proposed configuration could extend the observation window of current detectors by a decade and fill the gap betweenground-based and space-based instruments