Ground Truth collection for mining explosions in northern Fennoscandia
and northwestern Russia
27th Seismic Research Review: Ground-based nuclear explosion monitoring
technologies, page 31--41. Rancho Mirage, California, (September 2005)Abstract
We concluded comprehensive ground truth collection at the Khibiny,
Olenegorsk, Kovdor and Zapolyarnyi mines, and have basic information
on 2052 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 expect to have an update on the P/S
ratio analysis contrasting different source types for this years
SRR meeting, 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.