GEOLOGICA CARPATHICA, 49, 2, BRATISLAVA, APRIL 1998
8598
DYNAMICS AND KINEMATICS OF THE CIROCHA, TRANGOKA
AND ZÁZRIVÁ STRIKE-SLIP FAULTS, WESTERN CARPATHIANS
MICHAL
ΝΕΜ
È
ΟΚ
and JÁN NEMÈOK
Slovak Geological Survey, Mlynská dolina 1, 817 04 Bratislava, Slovak Republic
(Manuscript received January 9, 1997; accepted in revised form December 11, 1997)
Abstract: The Cirocha, Trangoka and Zázrivá fault zones have dominant structures developed during the transtensional
strike-slip stage of their movement histories. It is indicated by the negative flower structure on the cross-cutting reflec-
tion seismic profile and the calculated paleostress pattern from one of the three stress patterns in the case of the Zázrivá
fault zone. Rotated paleocurrent sets in undefined blocks indicate the existence of flats somewhere in depht accommo-
dating the separate block movements in the dextral strike-slip system. The most prominent structures of the Trangoka
fault zone, large shear planes with striation having a significant divergent dip-slip component, were also developed during
the transtensional strike-slip reactivation. It is indicated by the slickenside lineations. This sinistral reactivation did not
develope shallow flats, as shown by the lack of rotations. The Cirocha fault zone acted as a dextral transtensional strike-
slip during its activity. This is indicated by the calculated paleostress pattern which did not undergo significant changes.
Presence of the flat at about 2.53 km depth is constrained by the reconstruction of the 3 km wide and 10 km long Ve¾ká
Po¾ana flake. This flake dextrally rotated about 90
o
, as indicated by the rotation of Cretaceous, Eocene and Oligocene
paleocurrent patterns and paleostress patterns. This rotation was not accommodated by the formation of new faults in-
side the flake. These observations are compared with the shear stress/reactivation modelling. The presence of the very
low friction flake boundaries would explain the fact that no new faults were formed until the flake rotated about 90
o
. The
flat underneath the flake was developed along the flat of the pre-existing thrust fault.
Key words: Western Carpathians, strike-slip faults, fault dynamics.
Methods
All chosen parts of the strike-slip fault zones described be-
low (Fig. 2), except the area in Fig. 2c, have been mapped in
detail. Cave systems formed along various shear planes of
the Trangoka fault zone and a strike-parallel reflection seis-
mic profile (Kadleèík et al. 1988) through the Zázrivá fault
zone allowed direct 3D study. The 3rd dimension in the Ciro-
cha fault zone study is constructed from surface data. All
available features including folds, faults, extensional veins,
Introduction
Three-dimensional strain compatibility in upper crustal lev-
els requires steep strike-slip faults to be associated with
shallow-dipping faults (Fig. 1), allowing various levels in
the system to move separately (Dewey 1982; Woodcock &
Fischer 1986). Such flats, together with various steeply
dipping faults in a strike-slip zone, can create fault-bounded
blocks, which, under certain circumstances, could undergo
uplift, subsidence and rotation. Such uplift, subsidence and
rotation have been demonstrated by high resolution seismic
data (Ben Avraham et al. 1979; Ben Avraham 1985), sedi-
mentological data (Segall & Pollard 1980; Ballance &
Reading 1980; Biddle & Christie-Blick 1985), earthquake
data (Nabelek et al. 1987), analogue material modelling
(Emmons 1969; Bartlett et al. 1981; Naylor et al. 1986), pa-
leomagnetic studies (e.g. Luyendyk et al. 1980, 1985; Bo-
gen & Seeber 1986; Kamerling & Luyendyk 1979, 1985;
Terres & Luyendyk 1985; Hornafius et al. 1986) and de-
scribed by various models (e.g. Freund 1971, 1974; Gar-
funkel 1974; Greenhause & Cox 1979; Lamb 1987, 1988).
Our paper aims to study the 3D strain compatibility mani-
festation along the strike-slip fault zones, related vertical
movements and rotation, the internal deformation of rotated
blocks, the origin of flats and controlling stress pattern.
We evaluate the Cirocha strike-slip fault zone involving
block rotation, localized in the Flysch Belt of the eastern part of
the Western Carpathians. The two other strike-slip fault zones,
the Zázrivá and Trangoka zone, are evaluated for comparison.
Fig. 1. Dextral strike-slip fault with a flat fault accommodating its
3D deformation at Trwyn-y-Witch in the Bristol Channel region,
UK. The flat is contoured in white, with reverse fault movement,
dextral strike-slip is contoured in black.
86 NEMÈOK and NEMÈOK
bedding planes and sediment paleotransport vectors have
been measured where possible.
Folds and extensional veins provided a rough estimate of
the stress configuration which caused their origin. Fault pop-
ulations outside and inside strike-slip zones have been used
as input for the inversion stress routines. The methods used
include the Carey & Brunier (1974) routine, Reches (1987)
based method of Hardcastle (1989) and BRUTE3 software of
Hardcastle & Hills (1991), providing the orientations of all
three principal stresses and their ratio defined in related pa-
pers. Readers interested in details of these inversion methods
are referred to Carey & Brunier (1974), Hardcastle (1989)
and Hardcastle & Hills (1991).
In order to understand what happened inside the rotated
block in the strike-slip zone, a field analysis was combined
with fault reactivation calculations. Reactivation under ap-
plied stress configuration was simulated, in order to test what
amount of rotation of the fault pattern inside the rotating
block would result in new slip vectors the overprinting origi-
nal ones. A set of faults measured along part of the Cirocha
strike-slip fault zone was chosen arbitrarily as the test00 file.
The stress configuration which controlled their displacement
was computed by BRUTE3 (Hardcastle & Hills 1991). Then
the same fault population was rotated about a vertical axis in
30
o
increments. The same stress configuration was applied to
these artificially made fault populations (test30, test60,
test90) to calculate related shear stress vectors and compare
them with measured ones using available approaches (e.g.
Guiraud et al. 1989; Hardcastle & Hills 1991; Simon-Gomez
1986).
This procedure resulted in a set of slip vectors calculated
for each of the three artificial populations formed by rotation
of the original ones. All three new sets of slip vectors were
matched against rotated original ones. Tests were done to find
out, whether such a rotation of the original faults and their
subsequent reactivation by the same regional stress field
would be identifiable either in the field or by paleostress in-
version for polyphase fault/striae data sets.
Data
The Cirocha strike-slip fault zone
The sediments affected by the Cirocha strike-slip fault
zone, studied in detail, belong to the Dukla Unit (Koráb &
Ïurkoviè 1978) of the Flysch Belt (Fig. 2a,d, 3). The Dukla
Unit in the surroundings of the Ve¾ká Po¾ana flake (Fig. 3),
consists of a turbiditic sequence of sandstone and clay shale
of Cretaceous to Early Oligocene age (Nemèok 1970, 1978;
Fig. 2). This sequence, being part of the Outer Carpathian
accretionary wedge, was deformed by folding and thrusting
(Fig. 4ad) with no evidence for ductile deformation in the
outcrops. The strike-slip faulting, contemporaneous with,
and post-dating the thrust shortening, also has a brittle char-
acter at outcrops. The Paleogene-Sarmatian age of faulting
(Nemèok 1993), our estimates of the amount of shortening
and far-field evaluations of erosion (Francù & Müller 1983)
suggest that the mapped faults formed at depths of 25 km
and host rock temperatures of 60150
o
C.
The Ve¾ká Po¾ana flake is 3 km wide and 10 km long. It
has been mapped in detail by Nemèok (1970; Fig. 3). The
Cirocha strike-slip fault zone extends at least 25 km to the
NE (Mahe¾ et al. 1973) and 45 km to the SW (Mahe¾ et al.
1984) of the flake. The fault zone contains Y shears trend-
ing 044048
o
in the Ve¾ká Po¾ana area. The dextral dis-
placement of about 56 km has been described by Nemèok
(1970) and Koráb (1983). The strike-slip fault cuts through
the thrust and fold structures in a direction roughly perpen-
dicular to the fold axes and thrust fault strikes. Adjacent
blocks show slightly different structures. The western block
has fold axial surfaces and thrusts dipping SW to vertical,
while the eastern block has NE dipping axial surfaces and
thrust planes (Fig. 5). Based on the slickensides formed on
the bedding planes, both sets of folds are formed by bending
with flexural slip. The flake itself has an irregular shape and
no distinct offsets made by internal cross faults have been
observed. Uniform paleocurrent patterns measured in three
various formations inside the flake also rule out internal
cross faults. A cross section through the north-eastern half
of the Ve¾ká Po¾ana flake gives a roughly estimated thick-
ness for the rotated flake of about 2.53 km.
Collected mesoscale shear plane populations from several
dozen localities can be divided into two sets. One set is re-
lated to the thrust plane pattern, which formed prior to, and
contemporaneously with the strike-slip faulting along the
Cirocha strike-slip fault zone. On the basis of the inversion
stress computations from the thrust plane pattern made by
methods of Carey & Brunier (1974), Hardcastle (1989) and
Hardcastle & Hills (1991), the shortening had a NESW di-
rection during the Paleogene to Sarmatian (Nemèok 1993).
No significant stress rotations have been detected from the
thrust pattern localized around the Cirocha strike-slip fault
zone. The basic characteristics of the thrust plane pattern
from the Ve¾ká Po¾ana area are shown on Figs. 4ad.
The basic characteristics of the strike-slip plane pattern
along the Slovak part of the Cirocha strike-slip fault zone
(Fig. 2d) are shown on Fig. 6be. The stress tensors com-
puted from the rocks of various ages deformed by the Ciro-
cha strike-slip fault zone are shown in Table 1. In addition
to the shear plane populations connected with strike-slip
faulting, measurements of the calcite tension veins have
been collected (Fig. 7).
A more complicated situation was observed in the rotated
Ve¾ká Po¾ana flake. The stress tensors computed from the
shear planes present at locations 2 and 5 comprise two gen-
erations. An earlier
σ
1
, oriented NWSE, is perpendicular to
the regional NESW oriented
σ
1
. The NESW oriented
σ
1
Fig. 2. a Major regional geological elements of the Western
Carpathians. White European Platform; rectangles: Zázrivá
strike-slip fault zone, Trangoka strike-slip fault zone, Cirocha
strike-slip fault zone. b Trangoka strike-slip fault zone. c
Zázrivá strike-slip fault zone. d Cirocha strike-slip fault zone.
e Zázrivá strike-slip fault zone northern continuation.
→
DYNAMICS AND KINEMATICS OF THE STRIKE-SLIP FAULTS 87
88 NEMÈOK and NEMÈOK
is present inside the flake as the younger event, re-
corded by cross-cutting slickenside striations (Ta-
ble 1). A similar sequence is indicated by the ten-
sion veins measured by Nemèok & Nemèok (1990).
Independent evidence for block rotation has been
determined by comparing paleocurrent directions
from the Cretaceous, Eocene and Oligocene turbid-
itic sediments within the Ve¾ká Po¾ana flake with
those outside (Fig. 3). Paleocurrent directions have
been determined by using a variety of turbiditic
sole structures. Outside the flake the results show a
regionally homogeneous direction, characteristic
for each of the three mapped formations. The pale-
ocurrents of each of these formations within the ro-
tated block are also locally homogeneous, but dex-
trally rotated 90
o
(Fig. 3).
Fig. 3. Map of the Ve¾ká Po¾ana surroundings, localized in Fig. 2. horizontal hachure Cretaceous sediments; white Eocene sedi-
ments; diagonal hachure Oligocene sediments; straight lines profile locations; thick lines faults without kinematic description;
thick lines with triangles thrusts; arrows paleocurrents; short lines crossed 3 times by shorter ones paleocurrents without sense of
transport; numbers in circles localities; short lines with perpendicular shorter ones plus number strike and dip of bedding planes,
the normal stratigraphy of which is indicated by a little bend on the strike indicator towards the dip indicator, opposite bending indicates
overturned stratigraphy.
Site
Age
Rock
type
Stress
sigma 1
Tensor
sigma 2
sigma 3
Stress
ratio
Method
CZ-02 O
fl
302/27
205/14
090/59
-0.087
CB
CZ-05 Cr
fl
155/56
023/30
055/07
257/45
321/33
123/30
-4.478
0.100
CB
HB
CZ-06 Cr
fl
237/23
061/67
328/01
-2.768
CB
CZ-07 O
fl
196/24
020/10
295/20
148/74
060/58
288/12
-0.829
-0.750
CB
HH
CZ-8 Eo
fl
060/50
060/50
240/40
263/38
330/00
164/11
0.100
0.250
HH
HH
CZ-11 Ec
fl
008/73
165/15
256/06
0.147
Hard
CZ-12 Eo
fl
226/40
006/24
240/50
247/30
247/30
356/37
243/50
044/39
100/56
043/58
109/28
111/29
140/08
347/15
151/11
-3.468
-0.733
0.150
0.100
0.100
CB
CB
HB
HB
HB
CZ-13 Ti-Ne
li
000/30
096/10
202/58
0.100
HH
CZ-15 LBa
tu
023/30
020/10
203/60
200/80
113/00
110/00
0.700
0.700
HH
HH
CZ-16 LBa
tu
094/71
284/19
193/03
0.103
Hard
CZ-17 LBa
tu
002/03
270/33
096/56
0.138
Hard
CZ-18 USa
an
010/25
130/47
263/33
0.621
Hard
CZ-22 MSa
an
080/10
322/70
173/17
0.250
HH
CZ-24 M-UTr
do
203/30
220/10
055/56
116/53
302/15
317/35
0.850
0.700
HH
HH
CZ-25 Ne-AL
li
004/17
102/23
241/61
0.193
Hard
CZ-26 UTr
do
023/30
225/30
220/10
235/56
355/48
348/74
122/15
199/26
128/12
0.200
0.150
0.250
HH
HH
HH
CZ-27 M-UEo
con
010/67
079/42
221/20
291/44
127/11
184/17
0.223
0.904
Hard
Hard
CZ-28 UBa
an
045/30
060/10
240/10
225/60
188/74
122/70
315/00
328/12
333/17
0.600
0.450
0.200
HH
HH
HH
CZ-29 M-UTr
do
154/70
255/04
346/20
0.100
HH
Table 1: List of stress tensors computed from the fault
populations along the Cirocha strike-slip fault zone. M-
UTr indicate Middle to Upper Triassic, UTr Upper Tri-
assic, Ti-Ne Tithonian to Neocomian, Ne-Al Neoco-
mian to Albian, Cr Cretaceous, Eo Eocene, M-UEo
Middle to Upper Eocene, O Oligocene, LBa Low-
er Badenian, UBa Upper Badenian, MSa Middle Sar-
matian, USa Upper Sarmatian. Abreviation fl means
flysch rocks, con conglomerate, li limestone, do
dolomite, tu tuff and an andesite. Hardcastle & Hills
(1991) and Carey & Brunier (1974) stress inversion rou-
tines have been used. Stress axes are indicated by azimuth
and dip.
←
Table 1
DYNAMICS AND KINEMATICS OF THE STRIKE-SLIP FAULTS 89
The Zázrivá strike-slip fault zone
The Zázrivá strike-slip fault zone (Fig. 2a,c,e) was first de-
scribed by Andrusov (1925), who called it the Zázrivá sig-
moidal structure which he interpreted as the dextral offset of
the Pieniny Klippen Belt in the northern part of the Western
Carpathians (Fig. 2c). The Flysch Belt to the north of the Pi-
eniny Klippen Belt in this area is deformed by SW-NE strik-
ing thrusts and folds. Most of the NW-SE shortening in
this zone was accommodated by platform-vergent thrusting;
back thrusting was only subordinate (Roth et al. 1963). The
Zázrivá strike-slip fault zone was probably initiated as a lat-
eral ramp during variable transport associated with thrusting
of sediments of both the Flysch and Pieniny Klippen Belt.
The horizontal component of the displacement along the
Zázrivá strike-slip fault zone is about 10 km (Hako & Pot-
faj 1976). The dextral displacement is indicated by the off-
set of the Pieniny Klippen Belt (Fig. 2c), and also by the
dextral rotation of the paleocurrent system in the flysch sed-
iments of the Flysch Belt (Hako & Potfaj 1976). The dex-
tral displacement during the earlier stages of the activity of
this fault is also indicated by structural data (e.g. Kováè &
Hók 1993; Nemèok 1994). Rotations indicated by paleocur-
rents determined by Hako & Potfaj (1976) vary from place
Fig. 4. Thrust planes in surrounding of the Ve¾ká Po¾ana flake. a) Contoured diagram of the fault plane poles. Kamb contour method, counting
area 0.158, expected No. 7.58 point per area, sigma 2.53, contour interval 3 sigma, vertical hachure 13, horizontal hachure
46, cross-cutting hachure 79, thick cross-cutting hachure 1012, number of points 48. b) Contoured diagram of the striation vectors.
Kamb contour method, counting area 0.158, expected No. 7.58 point per area, sigma 2.53, contour interval 3 sigma, vertical ha-
chure 13, horizontal hachure 46, cross-cutting hachure 79, thick cross-cutting hachure 1012, number of points 48. c) Rose
diagrams: a) fault plane strikes, b) azimuths of striations, c) fault plane dips, d) striation plunges, number of thrusts 48. d) Fault plane dip ver-
sus striation plunge diagram. Vertical axis striation plunge, horizontal axis fault plane dip, number of thrusts 48.
90 NEMÈOK and NEMÈOK
to place and poor outcrops do not allow the definition of the
rotated blocks and their boundary faults.
The north continuation of the Zázrivá strike-slip fault
zone can be studied in the reflection seismic profile 315/85
(Fig. 2e) made and interpreted by Kadleèík et al. (1988). It
indicates a negative flower structure suggesting a transten-
sional strike-slip regime (Fig. 8). Flat lying reflectors indi-
cate strike sections through bedding planes and thrust
planes. Some of the shears forming elements of the flower
structure in the profile have been studied at outcrop, where
most of the related mesoscale faults indicate a strike-slip to
oblique-slip movement (see Nemèok 1994). Outcrop-scale
data similar to those of the Cirocha fault zone have been
collected at 119 locations (Fig. 2e; Nemèok 1994) from
more than 600 visited ones. Most of the fold axes are SW
NE oriented, with shallow to moderate plunge, and are relat-
ed to thrusting. Smaller fold sets in the area have W-E and
NW-SE striking axes. In addition, there is a significant num-
ber of vertical fold axes connected with the strike-slip fault-
ing. Mesoscale fault populations have been used to compute
stress tensors (Nemèok 1994). Extension veins have provided
an additional rough check of these computations. Finally,
stress trajectory maps have been constructed for the area
(Figs. 9, 10; Nemèok 1994). One of maps was made assum-
ing that the
σ
1
trajectories were perpendicular to the fold axes
related to the fault bend folding (Fig. 9). The other map
shows the
σ
1
trajectories computed from the shear plane pop-
ulations. Both maps (Figs. 9, 10) demonstrate that this area
was affected by three successive tectonic events. Measured
paleocurrents corrected by tilt correction do not provide the
regionally homogeneous pattern characteristic for certain for-
mations. The most variable pattern is present in the Bystrica
Formation of the Bystrica Unit (localized in Fig. 2e), com-
prising north-, northeast- and southwest-vergent paleocur-
rents. It indicates a rather complex fan system in time and
space. A high mobility of the system is also indicated by
cross-cutting relationships of flute casts on the same bedding
planes, reaching a maximum difference angle of nearly 90
o
.
This cancels the possibility of using paleocurrents as an indi-
cator of block rotations in this area.
The Trangoka strike-slip fault zone
The Trangoka strike-slip fault zone (Kubíny 1956) strikes
WSW-ENE, and deforms the Mesozoic rocks of the Central
Western Carpathians in middle Slovakia (Fig. 2a,b). Our sur-
face studies at 60 localities indicate that this fault has under-
gone polyphase reactivation. The last event, which caused a
sinistral strike-slip displacement, created the present distinct
features. It completely overprinted the previous kinematic
record at some outcrops. The 3D structure of the strike-slip
zone was studied thanks to 70 localities on 4 levels in the
Trangoka cave system. Only 16 of them, allowed a measure-
ment of large fault planes. Fault dip and striation plunge dia-
grams indicate the distinct dip-slip component of the overall
movement (Fig. 11a,b), unlike the surface outcrops. The fault
and bedding plane pattern in a vertical section perpendicular
to the fault zone is shown in Fig. 11c and shows features sim-
ilar to the flower structure of Fig. 8. A study of the fault
planes utilized by the cave system shows that the majority of
the faults in the deeper levels have steeper oblique-slip stria-
tions while those in the upper levels have lower angle ob-
lique-slip or even strike-slip striations. A similar behaviour,
modelled under ideal conditions, was published by Naylor et
al. (1986), who have shown how the stress field controlling
strike-slip faulting rotates as a function of depth (Fig. 12).
This would cause a progressively more pronounced dip-slip
component of the displacement on local fault planes.
Results of numerical tests
After a certain amount of rotation a fault pattern inside a ro-
tating flake should be reactivated in order to be able to ac-
commodate further rotation (Nur et al. 1986; Scoti et al.
1991).
In order to test this behaviour in the Cirocha fault zone
case, one locality outside the fault zone cleaned from outli-
ers was selected as a test fault population called test00. Its
behaviour was investigated during simulated rotation in or-
der to compare computed results with observations of natu-
ral faults within the rotated Ve¾ká Po¾ana flake.
A stress tensor has been computed from this test00 file,
having
σ
1
= 195/15,
σ
2
= 295/33,
σ
3
= 84/53 and stress ratio
R = (
σ
2
-
σ
3
)/(
σ
1
-
σ
3
) = 0.1. This stress configuration has
similar parameters to other stress states computed from local-
ities adjacent to the Cirocha strike-slip fault zone. This com-
puted stress tensor was used to calculate a vector of maxi-
mum shear stress acting on each of the planes of our chosen
Fig. 5. Cross sections through the area of the Ve¾ká Po¾ana sur-
roundings. Horizontal hachure Cretaceous sediments, white
Eocene sediments, diagonal hachure Oligocene sediments, thick
lines thrusts. Localization of profiles is indicated in Fig. 3.
DYNAMICS AND KINEMATICS OF THE STRIKE-SLIP FAULTS 91
Fig. 6. Strike-slip faults of the Cirocha strike-slip fault zone. a) Contoured diagram of the fault plane poles. Kamb contour method, counting
area 0.055, expected No. 8.51 point per area, sigma 2.84, contour interval 3 sigma, vertical hachure 13, horizontal hachure
46, cross-cutting hachure 79, thick cross-cutting hachure 1012, square pattern 1315, right-dipping diagonal hachure 16
18, left-dipping diagonal hachure 1921, number of points 156. b) Contoured diagram of the striation vectors. Kamb contour method,
counting area 0.055, expected No. 8.51 point per area, sigma 2.84, contour interval 3 sigma, vertical hachure 13, horizontal
hachure 46, cross-cutting hachure 79, thick cross-cutting hachure 1012, square pattern 1315, right-dipping diagonal ha-
chure 1618, left-dipping diagonal hachure 1921, number of points 156. c) Rose diagrams: a) fault plane strikes, b) azimuths of
striation, c) fault plane dips, d) striation plunges, number of strike-slip faults 156. d) Fault plane dip versus striation plunge diagram. Ver-
tical axis striation plunge, horizontal axis fault plane dip, number of faults 156. e) Hoeppners (1955) projection of the faults. Num-
ber of faults 156.
92 NEMÈOK and NEMÈOK
Fig. 7. Calcite tension veins in the Cirocha fault area contoured
diagram of plane poles. Kamb contour method, counting area
0.164, expected No. 7.53 point per area, sigma 2.51, contour
interval 3 sigma, vertical hachure 13, horizontal hachure
46, cross-cutting hachure 79, thick cross-cutting hachure
1012, square pattern 1315, right-dipping diagonal hachure
1618, number of points 46.
Fig. 8. Zázrivá strike-slip fault zone-flower structure in the line
drawing of ENEWSV oriented reflection seismic profile 315/85
(modified after Kadleèík et al. 1988). Thick lines interpreted
faults. SW and NE indicate related intersections of the profile with
boundary of Fig. 2e. Profile is localized in Fig. 2e.
Fig. 9.
σ
1
stress trajectories derived from the fold pattern along the
Zázrivá strike-slip fault zone in the area of 1:25,000 map sheet M-
34-87-C-d Oravská Lesná (area of the Fig. 2e). Thin lines oldest
stress field, lines with dots younger stress field, thick lines
youngest stress field.
Fig. 10.
σ
1
stress trajectories derived from the fault pattern along the
Zázrivá strike-slip fault zone in the area of 1:25,000 map sheet M-
34-87-C-d Oravská Lesná (area of the Fig. 2e). Thin lines oldest
stress field, medium thick lines younger stress field, thick lines
youngest stress field, c stress ratio valid for older trajectory
(old) or for younger stress trajectory (y).
gular deviations of original maximum shear vectors (stria-
tions) from computed maximum shear stress vectors (Ta-
ble 3). Because the measured striations were used to compute
this stress tensor by an inversion technique BRUTE3 (Hard-
castle & Hills 1991), the average angular deviation listed in
Table 3 shows in fact the accuracy of this stress inversion.
Then we applied the same stress configuration to the fault
populations: test30, test60 and test90 to see what kind of re-
activation slip vector pattern is obtained in the case when
grid (Tables 2, 3). The vector orientation of maximum shear
stress was indicated by its pitch value (Table 2) showing
that the kinematics of each fault is a function of its orienta-
tion in relation to the applied stress tensor.
Then we rotated the fault planes of the test00 file clock-
wise in 30
o
increments. The fault positions in these stages
were recorded as files: test30, test60 and test90.
The faults of test00 file were also tested by direct stress
routine SELECT of Hardcastle & Hills (1991) to compute an-
DYNAMICS AND KINEMATICS OF THE STRIKE-SLIP FAULTS 93
Fig. 11. Trangoka strike-slip fault zone. a Map view of 4 floors of the Trangoka cave
system with fault dip rose diagrams. 1 1st floor at 1640 m altitude, 3 3rd floor at
1570 m altitude, 4 4th floor at 1520 m altitude, 6 6th floor at 1420 m altitude. b
Map view of 4 floors of the Trangoka cave system with striation plunge rose diagrams. c
Flower structure interpreted from the fracture pattern in the cave system of the Tran-
goka strike-slip fault zone in a S-N oriented profile. Thin lines bedding, thick lines
faults. Location of the cave is in Fig. 2b.
the stress tensor remains in the same orientation and the faults rotate. Tables 4,
5 and 6 show the angular deviations computed for the fault rotated about 30
o
,
60
o
and 90
o
increments. It is apparent that very large angular deviations are ob-
tained.
Similar test with the same results was carried out using the Simon-Gomez
(1986) routine, which uses an opposite approach: analysing the relation of fixed
fault planes and continuously rotating stress tensor. If the regional stress config-
uration reactivated a rotating fault pattern inside a rotating flake it would be in-
dicated by a new striation cross-cutting the original one on each of the faults.
Thus even 30
o
rotation of the Ve¾ká Po¾ana flake in the Cirocha fault zone
should be recognized in the field by cross-cutting relationships of striae.
94 NEMÈOK and NEMÈOK
Prior to the block rotation induced by strike-slip fault-
ing, a block which will be later rotated is deformed by a
pattern of mesoscale faults related to the activity of the
developing strike-slip fault zone. Thus, when tested by
stress inversion techniques, a pattern of mesoscale
faults from the rotated block provides the stress config-
uration synchronous with that determined from locali-
ties adjacent to the strike-slip fault zone, which did not
undergo a block rotation. Such a mesoscale fault pattern
rotates together with a rotated block controlled by the
regional stress field, which causes the displacement
along the strike-slip fault zone. Such an original mesos-
cale fault pattern dextrally rotated about 90
o
with the
Ve¾ká Po¾ana flake. This is the reason why the stress
configuration computed from the original fault pattern
indicates a stress configuration also dextrally rotated
about 90
o
at locations 2 and 5.
When a consistent regional stress field controls the
strike-slip fault zone kinematics and a randomly orient-
ed fault plane pattern rotated inside a rotating block,
each event of the internal fault reactivation should be re-
corded by specific cross-cutting striation on each of
them. However, there is no evidence of the transmission
of the stress to the rotating Ve¾ká Po¾ana flake, large
enough to reactivate internal faults, earlier than after 90
o
of dextral rotation.
Interpretation/discussion
We aim to discuss: 1) characteristic features of studied
natural cases of vertical block movements and block rota-
tion induced by strike-slip faulting, 2) the potential origin
of flats underneath the rotating block, 3) internal defor-
mation of rotated blocks, 4) when new sets of Coulombs
faults accommodating rotation have to be created and 5)
what kind of stress pattern controlled the studied cases of
a block rotation.
In order to discuss the first question we need to divide
our studied strike-slip fault zones into distinct groups;
those with and without rotated blocks.
The Trangoka strike-slip fault zone (Fig. 2b), unlike
the other two zones, does not provide any evidence for
block rotations. However, the Trangoka strike-slip
fault zone had a lot of features similar to the other
zones.
Table 2: Stress tensor (sigma 1 = 195/15, sigma 2 = 295/33, sigma 3 =
84/53, stress ratio
(σ
1
σ
2
/
σ
2
σ
3
) = 0.1). Pitch of maximum shear stress
vector reactivated on a grid of planes. 90 indicate pure reverse fault-
ing, 0 pure sinistral strike-slip faulting, 90 pure normal faulting
and 180 pure dextral strike-slip faulting.
Dip
Strike
0
10
20
30
40
50
60
70
80
90
000
154 -022 -018 -012 -006 179
171
165
158 153
015
169 -009 -006 -003 178 171
162
148
122 076
030
176 177 179 -003 -018 -130 -162 -169 -173 -175
045
161 165 -001 -078 -129 -142 -150 -156 -162 -168
060
146 155 -033 -111 -124 -131 -138 -145 -153 -162
075
131 144 -068 -104 -113 -118 -123 -130 -140 -153
090
116
133 -071 -093 -098 -102 -106 -111 -118 -133
105
101
119 -061 -079 -083 -085 -086 -087 -087 -087
120
086 102 -045 -065 -069 -069 -068 -065 -059 -047
135
071 083 -019 -051 -055 -055 -053 -048 -042 -031
150
056 064 122 -035 -042 -043 -041 -038 -033 -025
165
041 045 054 172 -032 -035 -035 -032 -029 -023
180
026
028
028 026 012 -061 -042 -037 -032 -027
195
011 011 011 009 007 002 -176 -165 -145 -104
210
004 -175 -175 -176 -177 -178 -179
001 002 005
225
019 -160 -160 -162 -165 -169 -174 -180 006 012
240
034 -144 -145 -148 -152 -159 -167 -177 007 018
255
049 -128 -129 -131 -136 -144 -156 -171 010 027
270
064 -112 -112 -113 -117 -123 -135 -160 018 047
285
079 -097 -095 -094 -093 -093 -093 093
092 093
300
094 -081 -078 -074 -069 -061 -046 -016 157 133
315
109 -066 -061 -056 -048 -037 -022 -003 164 149
330
124 -051 -045 -039 -031 -021 -009 176 165 155
345
139 -036 -031 -024 -017 -008 180 171 163 157
360
154 -022 -018 -012 -006 179 171
165
158 153
Table 3: Angular deviations of the measured and computed
shear stress vectors of the file test00.flt. Upper table princi-
pal stress axes positions and stress ratio of a tensor applied onto
a fault pattern of test00.flt file. Lower table each of the mea-
sured faults is characterized by its strike and dip of fault plane,
azimuth and plunge of shear stress vector and displacement
sense. RL indicates right lateral, R reverse, RLR right lat-
eral with reverse component, RLN right lateral with normal
component. Each fault has indicated computed values of shear
stress vector, displacement sense, acting normal and shear
stress magnitudes and angle of deviation betwen measured and
computed shear stress vector in the same line.
←
Faults are from file test00.flt
Sigma 1 Sigma 2 Sigma 3
Magnitudes
Ratio
Az
/Plunge
Az
/Plunge
Az
/Plunge
Sigma 1
Sigma 2 Sigma 3 Sig2-Sig3
/Sig1-Sig3
195/15
295/33
084/53
5.50
1.00
0.50
0.100
Fault
data:
Comp.
values:
Fault
Str/Dip
Slicks
Az/Plg
Fault
class
Displ.
sense
Slicks
Az/Plg
Fault
class
Ang.
dev.
Normal
stress
Shear
stress
354/86
174/09 RL
1
172/22 RL
14
1.44
1.60
004/76
173/39 RLN
1
178/20 RL
19
1.19
1.09
340/82
157/24 RL
1
157/17 RL
06
2.43
2.22
168/78
177/39 RLR
1
174/28 RL
11
1.35
1.69
188/75
203/42 RLR
1
251/60 R
20
0.71
0.33
179/78
180/08 RL
1
186/31 RLR
24
0.91
1.00
180/71
187/22 RL
1
193/34 RLR
13
0.76
0.76
170/74
182/36 RLR
1
179/29 RLR
07
1.15
1.49
152/67
168/34 RLR
1
169/34 RLR
01
1.81
2.17
183/67
199/33 RLR
1
205/41 RLR
10
0.66
0.46
171/41
205/25 RLR
1
196/20 RLR
10
0.52
0.31
168/51
186/25 RLR
1
191/26 RLR
05
0.67
0.88
154/32
190/18 RLR
1
183/17 RLR
06
0.58
0.58
145/42
187/32 RLR
1
183/29 RLR
04
0.97
1.44
170/46
189/21 RL
1
195/23 RLR
06
0.57
0.57
175/77
182/29 RL
1
182/29 RLR
01
1.02
1.25
156/58
183/41 RLR
1
178/31 RLR
10
1.23
1.75
176/62
182/11 RL
1
194/30 RLR
23
0.70
0.78
166/48
185/21 RL
1
190/25 RLR
07
0.66
0.86
178/49
202/28 RLR
1
213/33 RLR
11
0.53
0.24
172/58
199/33 RLR
1
192/28 RLR
07
0.71
0.90
175/61
211/36 RLR
1
193/30 RLR
08
0.70
0.81
157/49
202/25 RLR
1
184/28 RLR
16
0.89
1.34
N = 23 Average angular deviation = 10
Table 3
DYNAMICS AND KINEMATICS OF THE STRIKE-SLIP FAULTS 95
strike-slip fault zone as the tear fault, which accommodat-
ed inhomogeneous shortening and caused the dextral drag
in the Ve¾ká Po¾ana area. Thus the rotation happened only
after a large amount of shortening. That explains the pres-
ence of folds inside the rotated Ve¾ká Po¾ana block. Thus,
they do not indicate the deformation of rotated block dur-
ing the rotation. As a matter of fact, they underwent the
same rotation as both the paleocurrent indicators and the
original paleostress record. On the other hand, generations
of extension veins and normal faults indicate that they
formed either prior to or after the block rotation. The angle
between the fault strike and
σ
1
in certain cases (Table 1)
also indicates transtensional dynamics of this strike-slip
fault zone. However, these computations have been done
most probably from various stages of the long lasting activi-
ty of the Cirocha strike-slip fault zone. That is why the local
stress perturbations could change along the strike of the Cir-
ocha strike-slip fault zone due to the local geometry chang-
es through the time, once being transtensional, or pure
strike-slip, or even transpressional, while the Cirocha strike-
slip fault remained dextral from Paleogene to Sarmatian.
We would not like to rule out slight changes of local dy-
namics along this fault zone.
The question of characteristic features is closely con-
nected with the stress pattern controlling rotation. Know-
ing that the dynamics of the strike-slip fault zones was
transtensional, we need to evaluate whether the stress
fields controlling the displacements were regionally ho-
Table 4: Angular deviations of the measured and computed shear stress
vectors of the file test30.flt. Upper table principal stress axes posi-
tions and stress ratio of a tensor applied onto a fault pattern of test30.flt
file. Lower table each of the measured faults is characterized by its
strike and dip of fault plane, azimuth and plunge of shear stress vector
and displacement sense. RL indicates right lateral, R reverse, RLR
right lateral with reverse component, RLN right lateral with normal
component. Each fault has indicated computed values of shear stress
vector, displacement sense, acting normal and shear stress magnitudes
and angle of deviation between measured and computed shear stress
vector in the same line. Test30.flt file is the test00.flt file rotated about
30
0
around a vertical axis. Stress tensor is the same as in Table 5.
Faults are from test30.flt
Sigma 1 Sigma 2 Sigma 3
Magnitudes
Ratio
Az
/Plunge
Az
/Plunge
Az
/Plunge
Sigma 1 Sigma 2 Sigma 3
Sig2-Sig3
/Sig1-Sig3
195/15
295/33
084/53
5.50
1.00
0.50
0.100
Fault
data:
Comp. values:
Fault
Str/Dip
Slicks
Az/Plg
Fault
class
Displ.
sense
Slicks
Az/Plg
Fault
class
Ang.
dev.
Normal
stress
Shear
stress
024/86 204/09 RL
1
024/03 LL
168
0.97
0.64
034/76 203/39 RLN
1
210/12 LL
153
1.23
1.07
010/82 187/24 RL
1
184/34 RLN
011
0.96
0.58
198/78 207/39 RLR
1
015/12 LL
127
0.80
0.55
218/75 233/42 RLR
1
218/02 LL
139
1.64
1.86
209/78 210/08 RL
1
209/01 LL
174
1.15
1.30
210/71 217/22 RL
1
210/00 LL
158
1.20
1.47
200/74 212/36 RLR
1
018/05 LL
137
0.83
0.76
182/67 198/34 RLR
1
202/38 RLR
006
0.67
0.53
213/67 229/33 RLR
1
213/00 LL
144
1.36
1.69
201/41 235/25 RLR
1
202/01 LL
141
0.85
1.26
198/51 216/25 RLR
1
199/01 LL
151
0.75
0.99
184/32 220/18 RLR
1
200/10 LL
160
0.58
0.60
175/42 217/32 RLR
1
206/25 RLR
011
0.51
0.15
200/46 219/21 RL
1
201/01 LL
154
0.81
1.16
205/77 212/29 RL
1
024/00 LL
150
0.99
1.05
186/58 213/41 RLR
1
324/46 LLR
074
0.57
0.18
202/62 212/11 RL
1
025/00 LL
167
1.02
1.34
196/48 215/21 RL
1
198/02 LL
155
0.70
0.91
208/49 232/28 RLR
1
026/01 LL
142
1.09
1.56
202/58 229/33 RLR
1
021/00 LL
138
0.87
1.14
205/61 231/36 RLR
1
024/00 LL
136
0.98
1.29
187/49 232/25 RLR
1
005/02 LL
127
0.55
0.36
N = 23 Average angular deviation = 127
mogeneous. That is not the case of the Trangoka strike-
slip fault zone, which was found to be reactivated by a
few tectonic events. That is not the case with the Zázrivá
strike-slip fault zone either inspite of the fact that this
strike-slip fault zone was selected to be localized in the
accretionary wedge to avoid the multiple reactivation so
typical for the strike-slip faults inside orogenic belts (e.g.
Christie-Blick & Biddle 1985; Gronlie & Roberts 1989),
because of the following reasons. This part of the West-
ern Carpathians was affected by changes of the stress
field due to the changes in the trajectories of the orogen
advance towards the European Platform (Nemèok 1993).
The only strike-slip fault zone without the stress field
On the basis of Naylor et al.s (1986) analogue modelling
of flower structures, the one from Fig. 11c is indicative of
transtension, forming just two simple branches towards the
surface. This fact is also supported by the presence of a dis-
tinct amount of extensional veins and lack of the stylolites,
reverse fault and fold pattern. The pure strike-slip move-
ments combined with divergence are also indicated by a dis-
tinct dip-slip component of the displacement (Fig. 11a,b).
The Zázrivá strike-slip fault zone (Fig. 2c,e) also has also
a transtensional character as supported by the negative
flower structure in the reflection seismic profile (Fig. 7) and
mesoscale fault data.
The situation in the Cirocha strike-slip fault zone (Fig. 2d)
is rather complicated, because of mesoscale folds which are
present in the rotated Ve¾ká Po¾ana block, which were misin-
terpreted by Nemèok & Nemèok (1990) as indicative of
transpression. However, this block started to rotate when NE
shortening of the flysch sediments originated the Cirocha
changes is the Cirocha strike-slip fault zone. The stress con-
trolling both the thrust shortening and the strike-slip fault
zone acting as a tear fault was the same. Stress configura-
tions computed from different stratigraphic horizons from an
interval PaleogeneSarmatian listed in Table 1 do not indi-
cate any significant changes of orientation through time.
In order to discuss the origin of flats we will discuss a lit-
tle bit more the study of the Trangoka strike-slip fault zone.
There is a rough trend present, indicating the transition from
the strike-slip striations to fairly steeply dipping striations as
a function of depth. This situation was modelled by Naylor
et al. (1986) using the sheared sand box. Authors showed a
three dimensional picture of the stress field rotation which
can explain the possibility of the reactivation of the pre-ex-
isting flats, increased with depth. Caused by the shear stress-
es (drag) induced in the overburden by the strike-slip
movement,
σ
1
rotates towards being parallel with the strike
of the principal displacement zone and towards the steeper
96 NEMÈOK and NEMÈOK
dip angle in relation to the surface (Fig. 12). Thus, it can
reactivate pre-existing flats, e.g. flats of the thrust planes
present in the case of both the Zázrivá and Cirocha strike-
slip fault zone, at a certain depth. The problem of the in-
ternal deformation of the rotated block is difficult, espe-
cially when there is no good outcrop control as occurs in
the case of the Zázrivá strike-slip fault zone. The majori-
ty of studied outcrops are situated to the north of the Pi-
eniny Klippen Belt offset, in the area without evidence of
block rotations. However, this zone is not suitable for this
study, because of the regional stress changes interpreted
here (Figs. 9, 10). A similar outcrop situation exists in the
case of the Cirocha strike-slip fault zone. There is no way
to determine the exact positions of the internal faults de-
forming the rotated block. However, a sufficient number
of outcrops provides the paleocurrent readings for three
time levels: Cretaceous, Eocene and Oligocene. On the
basis of the data shown in Fig. 3 and data collected by
Nemèok (1970), one can see that there is a homogeneous
pattern of three paleocurrent systems which excludes a
possibility of more distinct deformations connected with
the activity of various shears inside the rotated block.
Otherwise, the internal deformation of the rotated block
would be indicated by locally rotated measured paleocur-
rent vectors. That is why we suggest a relatively rigid
block rotation here.
For the same reason we do not suggest that a new set
of cross faults has to be created to accommodate rota-
tion obeying Coulombs law. A three dimensional block
rotation model with irrotational stress directions
Faults are from file test60.flt
Sigma 1 Sigma 2 Sigma 3
Magnitudes
Ratio
Az
/Plunge
Az
/Plunge
Az
/Plunge
Sigma 1 Sigma 2 Sigma 3
Sig2-Sig3
/Sig 1-Sig3
195/15
295/33
84/53
5.50
1.00
0.50
0.100
Fault
data:
Comp. values:
Fault
Str/Dip
Slicks
Az/Plg
Fault
class
Displ.
sense
Slicks
Az/Plg
Fault
class
Ang.
dev.
Normal
stress
Shear
stress
054/86
234/09 RL
1
232/18
LL
170
2:53
2.17
064/76
233/39 RLN
1
234/32
LLR
174
2.87
2.22
040/82
217/24 RL
1
217/14
LL
170
1.56
1.57
228/78
237/39 RLR
1
229/04
LL
145
2.32
2.21
248/75
263/42 RLR
1
248/01
LL
137
3.90
2.23
239/78
240/08 RL
1
240/05
LL
177
3:18
2.34
240/71
247/22 RL
1
059/02
LL
155
3.28
2.38
230/74
242/36 RL
1
230/01
LL
144
2:49
2.29
212/67
228/34 RLR
1
212/00
LL
143
1.30
1.64
243/67
259/33 RLR
1
060/06
LL
136
3:48
2.38
231/41
265/25 RLR
1
036/12
LL
119
2.11
2.33
228/51
246/25 RLR
1
040/09
LL
137
2.17
2.33
214/32
250/18 RLR
1
027/04
LL
133
1.25
1.78
205/42
247/32 RLR
1
024/00
LL
129
0.98
1.45
230/46
249/21 RL
1
038/11
LL
136
2.19
2.35
235/77
242/29 RL
1
235/04
LL
154
2.87
2.34
216/58
243/41 RLR
1
034/02
LL
129
1.51
1.91
236/62
242/11 RL
1
051/08
LL
158
2.89
2.43
226/48
245/21 RL
1
037/09
LL
140
2.00
2.27
238/49
262/28 RLR
1
044/15
LL
123
2.74
2.74
232/58
259/33 RLR
1
046/08
LL
128
2.54
2.40
235/61
261/36 RLR
1
050/08
LL
127
2.80
2.43
217/49
262/25 RLR
1
032/04
LL
124
1.51
1.97
N= 23 Average angular deviation =143
Table 6: Angular deviations of the measured and computed
shears stress vectors of the file test90.flt. Upper table princi-
pal stress axes positions and stress ratio of a tensor applied onto
a fault pattern of test 90.flt file. Lower table each of the mea-
sured faults is characterized by its strike and dip of fault plane,
azimuth and plunge of shear stress vector and displacement
sense. RL indicates right lateral, R reverse, RLR right
lateral with reverse component, RLN right lateral with nor-
mal component. Each fault has indicated computed values of
shear stress vector, displacement sense, acting normal and shear
stress magnitudes and angle of deviation between measured and
computed shear stress vector in the same line. File test90.flt is
the test00.flt file rotated about the angle of 90
0
around a verti-
cal axis. Stress tensor is the same as in Table 5.
Faults are from file test 90.flt
Sigma 1 Sigma 2 Sigma 3
Magnitudes
Ratio
Az
/Plunge
Az
/Plunge
Az
/Plunge
Sigma 1 Sigma 2 Sigma 3 Sig2-Sig3
/Sig 1-Sig3
195/15
295/33
84/53
5.50
1.00
0.50
0.100
Fault
data:
Comp. values:
Fault
Str/Dip
Slicks
Az/Plg
Fault
class
Displ.
sense
Slicks
Az/Plg
Fault
class
Ang.
dev.
Normal
stress
Shear
stress
184/86 264/09 RL
1
260/43 LLR
145
4.50
1.88
094/76 263/39 RLN
1
236/67 R
148
4.27
2.06
070/82 247/24 RL
1
244/32 LLR
171
3.51
2.24
258/78 267/39 RL
1
259/06 LL
147
4.58
1.85
278/75 293/42 RLR
1
097/01 LL
134
5.44
0.55
269/78 270/08 RL
1
271/09 LL
178
5.16
1.21
270/71 277/22 RL
1
084/15 LL
141
5.18
1.20
260/74 272/36 RLR
1
079/02 LL
140
4.71
1.76
242/67 258/34 RLR
1
059/06 LL
136
3.40
2.39
273/67 289/33 RLR
1
077/31 LLR
109
5.22
1.15
261/41 295/25 RLR
1
038/30 LLR
088
3.50
2.44
258/51 276/25 RLR
1
051/28 LLR
111
3.96
2.31
244/32 280/18 RLR
1
032/18 LLR
105
2.34
2.41
235/42 277/32 RLR
1
038/14 LL
107
2.35
2.41
260/46 279/21 RL
1
044/30 LLR
106
3.78
2.38
265/77 272/29 RL
1
266/05 LL
156
4.98
1.46
246/58 273/41 RL
1
055/16 LL
113
3.52
2.42
266/62 272/11 RL
1
068/29 LLR
133
4.81
1.72
256/48 275/21 RL
1
047/27 LLR
113
3.71
2.40
268/49 292/28 RLR
1
045/37 LLR
089
4.26
2.16
262/58 289/33 RLR
1
061/29 LLR
103
4.48
2.01
265/61 291/36 RLR
1
066/29 LLR
102
4.73
1.80
247/49 292/25 RLR
1
047/20 LL
102
3.27
2.48
N = 23 Average angular deviation =125
Table 5: Angular deviations of the measured and computed
shears stress vectors of the file test60. flt. Upper table prin-
cipal stress axes positions and stress ratio of a tensor applied
onto a fault pattern of test60.flt file. Lower table each of the
measured faults is characterized by its strike and dip of fault
plane, azimuth and plunge of shear stress vector and displace-
ment sense. RL indicates right lateral, R reverse, RLR
right lateral with reverse component, RLN right lateral with
normal component. Each fault has indicated computed values
of shear stress vector, displacement sense, acting normal and
shear stress magnitudes and angle of deviation between mea-
sured and computed shear stress vector in the same line. File
test60.flt is the test00.flt file rotated about the angle of 60
0
around a vertical axis. Stress tensor is the same as in Table 5.
←
←
Table 5
Table 6
DYNAMICS AND KINEMATICS OF THE STRIKE-SLIP FAULTS 97
through time (Scoti et al. 1991) explaining the possible rota-
tions up to 75
o
can be one of the possible explanations. This
requires rotation about a generally oriented rotation axis.
However, this model is still unable to explain the rotations
greater than 75
o
, which were pointed out by Mandl (1987)
and indicated by our data from the Ve¾ká Po¾ana flake. As
noted by Mandl (1987) it seems likely in nature that, during
the rotation of the first set of fractures, marginal zones of
the shear band experience a reduction in shear strength
e.g. cataclasis and, hence, will allow easier slip along the
band (flake) margin. The 90
o
block rotation of the Ve¾ká
Po¾ana flake along the Cirocha strike-slip fault zone indi-
cates a similar explanation. It could be demonstrated by the
Lambs (1987) floating block model assuming a rigid inclu-
sion rotating in a highly viscous fluid. The case of the Ve¾ká
Po¾ana block rotation, in accordance with this model, is not
characterized by the presence of the cross faults pinned to
the strike-slip zone boundary faults. This case can be char-
acterized rather by presence of a wider highly deformed
zone bounding the rotated block which apparently allowed
unconstrained rotation (more than the amount suggested
by Nur et al. (1986) and Scoti et al. (1991)). Apart from the
paleocurrent measurements, further evidence is provided by
locations 2 and 5 inside the rotated block with computed
initial stress configurations passively rotated roughly 90
o
in
respect to the new stress configurations recorded as young-
er. This presence of new stress tensors recorded in the rotat-
ed Ve¾ká Po¾ana flake implies that the friction along the
boundaries of the rotated block increased up to the level
which allowed the transmission of a large enough stress
from the surrounding rocks to the rotating block, that is
large enough to cause this calculated new stress tensor to
be recorded. The new stress record has the same orienta-
tion as the regional stress in the adjacent blocks juxtaposed
along the Cirocha strike-slip fault zone in various time peri-
ods. On the basis of the results of the fault reactivation mod-
elling, each new fault motion inside the rotating Ve¾ká
Po¾ana flake would be recorded by newly developed cross-
cutting striation of specific orientation on each of the fault
planes if the large enough stress for reactivation was trans-
mitted. The fact that such an event happened only after 90
o
rotation suggests that the Ve¾ká Po¾ana flake rotated freely
without internal faults reaching the Coulomb-Mohr condi-
tions for reactivation. It lasted until 90
o
clockwise rotation,
when the internal faults of the rotated block were reactivat-
ed by the regional stress controlling the overall displace-
ment of the Cirocha strike-slip fault zone.
Summary
The transtensional character of the three cases of the strike-
slip fault zones has been found during their displacement
history.
Flats underneath the rotated block appear to be pre-existing
anisotropies reactivated by a suitable rotated stress configura-
tion as a function of depth.
An internal deformation of the rotated block may not occur
in specific cases. Thus, a new set of cross faults needs not be
created after 45
o
or 75
o
rotation to accommodate a rotation.
This accommodation can be inhibited by an easier slip along
the flake boundary. It can last until the boundary friction in-
creases enough to allow a transmission of enough stress for the
origin of new cross faults or reactivation of the older ones. The
Ve¾ká Po¾ana flake inside the Cirocha strike-slip fault zone in-
dicates a case of a 90
o
rotation prior to such a reactivation.
Acknowledgements: MN wishes to thank JN who cannot
see the final result, Rod Gayer whose help improved the pa-
per considerably and Gabriela Polákova who helped with
drafting. The final version of the paper was greatly im-
proved by constructive criticism from Duan Plaienka and
a second anonymous referee.
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