SEISMIC MONITORING OF LARGE-SCALE KARST PROCESSES
IN A POTASH MINE
A.B. Ivanov, C. Petrov
Mining Institute, Perm, Russia
A. Johnson
Mining Constultants Ltd., Stellenbosch, Republic of South Africa
In October 2006 a serious accident happened in Berezniki-1 mine of the world’s second largest Verkhnekamskoye potash
deposit. The integrity of the waterproof stratum which separates mine workings from aquifers was broken and an uncontrolled
flooding of the mine had begun. The accident resulted in the appearance of several potential problems associated with karst
processes in the rock mass above the mine, i.e. hazardous subsidence of the earth’s surface and formation of a sinkhole. The
exact position of the water inflow zone was unknown due the inaccessibility of the excavations within the problematic part of
the mine. The applied complex of geophysical and geotechnical methods made it possible to localise the inflow zone, to
estimate the size of the expected sinkhole and to monitor its development in time. Seismic monitoring played an essential role
in these investigations. This paper summarises the details of the seismological observations in Berezniki-1 mine and the main
results thereof.
INTRODUCTION
Mining in the Verkhnekamskoye Potash Deposit
The Verkhnekamskoye potash deposit is situated in the
northern part of Perm region (Russia) and comprises of
seven minefields six of which were in development in
2006. Productive layers in sylvinite and carnallite zones
(Figure 1) are 140-420 m below the earth’s surface. The
room-and-pillar mining method is used in all mines.
or brines from the upper horizons. Penetration of the brines
through the waterproof stratum may cause unavoidable
mine flooding and forming of a karst depression or sinkhole
on the surface. Such situation had already taken place in the
Verkhnekamskoye deposit previously - in Berezniki-3 mine
in 1986.
An Emergency Situation in Berezniki-1 Mine in 2006
On 18 October 2006 a loss of integrity of the
waterproof stratum and penetration of brines from upper
layers to the mining excavations were identified according
to indirect indicators (dynamics and chemical composition
of brines in mine) in the western part of Berezniki-1 mine.
This area was mined out in the sixties-seventies and most of
the excavations there were partially backfilled or collapsed
which restricted the access to the area. For this reason the
place of brines inflow was unknown within the area of
800x1000 m size. The problem of localizing the inflow
zone was solved promptly by applying a complex of surface
geophysical and geotechnical methods (including
seismological observations). As the result, a 400x500 m socalled risk zone was contoured.
The following techniques were applied:
 Active surface seismic survey to track the changes in
elastic properties of the near-surface layers.
 Passive seismic monitoring to detect any dynamic
processes within the risk area.
Figure 1. Schematic geological section of the
Verkhnekamskoye deposit
The main requirement for safe mining in the
Verkhnekamskoye deposit is the keeping of integrity of the
waterproof stratum. This stratum consists of salt-clay rocks
which are laid above the productive layers (Figure 1) and
prevent them against solving by weakly mineralized water
 Borehole
and
surface
hydrodynamical
and
hydrochemical observations to monitor the flow of brines
and groundwater in different horizons.

Land-surveying to measure surface subsidence.
From October 2006 to July 2007 the karst processes
had no visible manifestations. However, the application of
several techniques pointed to significant variations of the
-1-
controlled characteristics and properties (i.e. gradual
decrease of seismic wave velocity for different horizons
within the risk area, anomalous subsidence (with rates up to
270 mm/month) in the eastern part of the risk zone,
formation of local areas with high concentration of methane
in soils).
At 3 PM of 28 July 2007 a sinkhole had appeared on
the earth’s surface 150 m to south-west from the centre of
the risk zone1. The initial size of the sinkhole was 55 x 80
m. A huge gas and rock blowout had happened next
morning.
During the following several months the sinkhole had
actively grown mostly in the northern and north-eastern
directions toward the federal railway (Figure 2a-b). The
growth decelerated significantly during the winter months,
but nevertheless the eastern slope of the sinkhole reached
the old federal railway in December. During February and
April 2008, a short-time increase in the rate of the sinkhole
expansion was noted in the eastern and south-eastern
directions (Figure 2c).
At the end of 2008 the flooding of Berezniki-1 mine
was completed and the growth of the sinkhole virtually
stopped. Its size had stabilized at approximately 440 x 320
m (Figure 2d).
The Use of Seismic Monitoring for the Study of Karst
Processes
It is plausible that the fracture of waterproof stratum
and karst cave(s) development may be accompanied by
dynamic events leading to the radiation of seismic waves in
the ambient rockmass. We may assume two possible types
of such events:
1)
Rupture of tensile and shear cracks.
2)
Rock falls from roof and walls of the cave(s).
Registration and processing of seismic signals from
such events may provide information about their basic
source parameters such as: location, time and radiated
seismic energy. An analysis of the spatial and temporal
characteristics of the events may lead to conclusion about
the current state and tendencies of the karst processes. This
is the traditional way of using seismic monitoring for the
study of karst processes (Wust-Bloch and Joswig2006).
DATA
Regional Seismic Network
km apart from each other. The network allowed to reliably
detect all events with seismic energy above 1000 J within
the whole area of the mine (about 50 km2) (Table I).
Table I Characteristics of the regional and the local
seismic networks used in Berezniki-1 mine
Regional
network
50
Local
network
0.5
1000-2000
150
1000
10
0.5-100
10-1000
Characteristics
Controlled area [km2]
Average distance between
sensors [m]
Minimal seismic energy of
events [J]
Frequency range [Hz]
The system registered several dozens of events per
year. The largest ones had seismic energy of about 105 J.
The analysis of the source mechanisms showed that most of
the events could be associated with the falls of ground (rock
falls) in the excavations (Ivanov2005).
The regional seismic network of Berezniki-1 mine has
been in operation until 28 October 2006, when the minewide power supply system was switched off and the access
to the mine was restricted.
It was the termination of the regional monitoring and
the need of more detailed seismic information which
initiated the organization of local seismic monitoring in the
risk zone (Malovichko et al.2009).
RESULTS
A time lag ( T , days) between the periods of
increased seismic activity and the moments of accelerated
growth of the sinkhole was found. The delay was
proportional to the square of the sinkhole diameter L and it
depended on the direction of the growth (N, E, S or W):

L2

T

+ 10  4,
 E , N 150

2
TW , S  L + 20  10.

220
(1)
ACKNOWLEDGEMENTS
The authors would like to thank Alexander Zverev and
Alexander Peresypkin for help in carrying out of the
seismic monitoring in Berezniki-1 mine. We wish to
acknowledge the support of the leading specialists of JSC
”Uralkali” Alexander Shumaher and Nikolay Kuznetsov.
A regional seismic network was in operation in
Berezniki-1 mine since 1998. The network consisted of 6
underground and 1 surface vertical geophones installed 1-2
1
Risk zone is an area where sinkhole appearance had been
anticipated.
SEISMIC MONITORING OF LARGE-SCALE KARST PROCESSES IN A POTASH MINE
-2-
Figure 2. Evolution of the sinkhole
REFERENCES
AS2294.2 Earth-moving machinery – protective structures.
Part 2: laboratory test and performance requirements
for roll-over protective structures, Standards
Association of Australia, 1997.
GIBOWICZ, S.L. and KIJKO, A. An introduction to mining
seismology, Academic Press, San Diego, 1994. 399 p.
IVANOV, A.B. Seismicity in the potash mines of the
Verkhnekamskoye deposit, PhD thesis, Perm State
University, Perm, 2005. 155 p.
MALOVICHKO, D.A., DYAGILEV, R.A., SHULAKOV,
D.Y., BUTYRIN, P.G. and GLEBOV, S.V. Seismic
monitoring of large-scale karst processes in a potash
mine, in Proc. 7th Int. Symp. on Rockbursts and
Seismicity in Mines: Controlling Seismic Hazard and
Sustainable Development of Deep Mines (ed. Tang,
C.A.), Rinton Press, New York, 2009. pp. 989-1002.
ORTLEPP, W.D. Rock fracture and rockbursts: an
illustrative study, Monograph series M9, S. Afr. Inst. of
Min. Metall., Johannesburg, 1997. 98 p.
ORTLEPP, W.D. RaSiM comes of age – A review of the
contribution to the understanding and control of mine
rockbursts, in Proc. 6th Int. Symp. on Rockbursts and
Seismicity in Mines: Controlling Seismic Risk (eds.
Potvin, Y. and Hudyma, M.), Australian Centre for
Geomechanics, Perth, 2005. pp. 3-20.
PETROV, C. Forecasting seismicity in the Western Urals,
RFBR project № 04-05-96048 report, 2006. 90 p.
RICHARDSON, E. and JORDAN, T.H. Some properties of
gold-mine seismicity and implications for tectonic
earthquakes, in Proc. 5th Int. Symp. on Rockbursts and
Seismicity in Mines: Dynamic Rock Mass Response to
Mining (eds. van Aswegen, G., Durrheim, R.J. and
Ortlepp, W.D.), S. Afr. Inst. of Min. Metall., 2005. pp.
149-156.
SALAMON, M.D.G., Keynote address: Some applications
of geomechanical modelling in rockburst and related
research, in Proc. 3rd Int. Symp. on Rockbursts and
Seismicity in Mines (ed. Young, P.), Balkema,
Rotterdam, 1993. pp. 297-309.
WUST-BLOCH, G.H. and JOSWIG, M. Pre-collapse
identification of sinkholes in unconsolidated media at
Dead Sea area by `nanoseismic monitoring' (graphical
jackknife location of weak sources by few, low-SNR
records), Geophys. J. Int., vol. 167 (3), 2006. pp. 12201232.
-3-