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Microseismicity and tectonics in the Granada Basin (Spain)
D. Munoz a, A. Cisternas b,*, A. Udıas a, J. Mezcua c, C. Sanz de Galdeano d,J. Morales e, M. Sanchez-Venero c, H. Haessler b, J. Ibanez e, E. Buforn a,
G. Pascual c, L. Rivera b
aDepartamento de Geofısica, U. Complutense de Madrid, Madrid, SpainbInstitut de Physique du Globe de Strasbourg, Ecole et Observatoire de Sciences de la Terre, 5 rue Rene Descartes, 67084 Strasbourg, France
cInstituto Geografico Nacional, Madrid, SpaindDepartamento de Geologıa, Universidad de Granada, Granada, Spain
eInstituto Andaluz de Geofisica, Universidad de Granada, Granada, Spain
Received 15 August 2001; accepted 21 June 2002
Abstract
A microseismic experiment carried out in 1994 in the Granada Basin (Spain) permitted the precise recording of more than 80
local earthquakes. The dense distribution of the local network, with 40 to 50 instrumental records for each event, enabled us to
have well-controlled hypocenters, and also 10 reliable focal mechanisms. The above observations are interpreted together with
topographic data, neotectonics, and sub-surface information. Microtectonic observations in Sierra Elvira, Padul and Zafarraya
gave a set of fault planes and striae, which were interpreted in terms of the recent regional stress tensor. The actual stress tensor
obtained from the microseismic campaign data gives a regime in radial extension, with r1 vertical and r3 oriented NS to NNE.
Microtectonic information is coherent with these orientations, but closer to 3-axial extension. A set of 64 mechanisms obtained
from the permanent Andalusian network favors a NS orientation for r3. This results are interpreted in terms of the general
model implying the lateral ejection of the Betic ranges towards the Atlantic.
D 2002 Elsevier Science B.V. All rights reserved.
Keywords: Granada Basin; Andalucia; Microseismicity; Stress tensor; Neotectonics
1. Introduction
The Granada Basin is located within the Betic
Cordillera in southern Spain (Fig. 1). It constitutes,
together with the Guadix and the Baza basins, a
sequence of pull-apart basins along the Cadix–Ali-
cante right-lateral fault system (Sanz de Galdeano,
1983). This fault system, together with the Lorca–
Palomares–Carboneras left-lateral system and the
Gibraltar arc, limit a triangular wedge being expulsed
westwards by the NS convergence between Africa and
the Spanish stable block. The Betics are located along
the northern side of the wedge, the southern side
corresponding to the Moroccan Riff.
Several models (Platt and Vissers, 1989; Calvert et
al., 2000) have been proposed to explain the geo-
dynamics of the wedge, in particular the existence of
an internal zone, formed by the Alboran Sea, parts of
0040-1951/02/$ - see front matter D 2002 Elsevier Science B.V. All rights reserved.
PII: S0040 -1951 (02 )00338 -4
* Corresponding author. Fax: +33-390-24-0125.
E-mail address: armando@eost.u-strasbg.fr (A. Cisternas).
www.elsevier.com/locate/tecto
Tectonophysics 356 (2002) 233–252
Fig. 1. General geodynamics of southern Spain and northern Maroc (modified after Sans de Galdeano et al., 1995). The wedge limited by the Cadix–Alicante fault, the Gibraltar Arc
and the Lorca–Palomares–Carboneras system is expulsed westwards (large arrow). The Granada Basin may be recognized near the center.
D.Munozet
al./Tecto
nophysics
356(2002)233–252
234
the Betics and parts of the Riff, which has been
subjected first to compression and thickening, then to
the lost of the lithospheric mantle under the Alboran
Sea either by subduction or delamination, with the
corresponding thinning and extension (Blanco and
Spakman, 1993; Serrano et al., 1998). The surrounding
external zone is characterized by thrusting and folding
(Santanach et al., 1980; Sanz de Galdeano et al., 1990;
Calvert et al., 2000). Volcanism is calc-alkaline in the
Alboran Sea and internal zones, but changes to alka-
line-basaltic during the Quaternary in the external
zones.
Several neotectonic studies of the Granada Basin
has been carried out by Rodrıguez-Fernandez et al.
(1991) and by Sanz de Galdeano and Vera (1992) with
a very detailed description of its geodynamic evolu-
tion since upper Miocene, of its depositional sequen-
ces and active faulting.
Seismicity is moderate in this region and the best
information is that given by the Instituto Geografico
Nacional Seismic Data Files (IGN) and by the Cartuja
Observatory of the Instituto Andaluz de Geofisica
(IAG). Most of the earthquakes are within the crust,
but there are intermediate events (down to 150 km
depth) and a remarkable deep activity at a depth of
about 650 km (Buforn et al., 1995, 1997). Several
focal mechanisms have been computed for shallow
and intermediate earthquakes in the region (Carreno et
al., 1991a; Coca and Buforn, 1994; Bezzeghoud and
Buforn, 1999).
The purpose of this paper is to discuss the results of
a detailed microseismic survey carried out from May
21 to July 21 1994, with a dense local network within
the Granada Basin. Similar surveys had been per-
formed already in the same region in 1978 and in
1988 (Carreno et al., 1991a,b). The 1994 experiment
allows us to increase the information concerning
active faulting, and to obtain well constrained focal
mechanisms, which may be interpreted in terms of the
present regional stress regime acting on the basin.
This study gives a more detailed local stress field than
that of a more general survey carried out for the whole
of Spain (Herraiz et al., 2000). A comparison will be
made with the results obtained from records of the
permanent seismic networks installed in the region.
Microtectonic observations in Sierra Elvira, Padul and
Zafarraya, provide an independent data set, which
permits additional control.
2. Neotectonics
Overall reviews of the seismotectonics of the
Granada Basin may be found in Rodrıguez-Fernandez
et al. (1991), and in Morales et al. (1990). A more
local study of the Zafarraya basin, SW of the Granada
Basin, is found in Morales et al. (1991). The tectonics
and earthquake hazard of the Sierra Nevada, in
particular the one related to the Padul fault, has been
studied by Sanz de Galdeano (1996) and by Keller et
al. (1996).
The units belonging to the Internal zone are: (i) the
Nevado–Filabrides, formed by deposits of Paleozoic
and Triassic age which have been subjected to meta-
morphism. (ii) The Alpujarride, of Paleozoic to Trias-
sic age, also showing some degree of metamorphism.
(iii) The Malaguide deposits, of Mesozoic and Tertiary
age. On the other hand, marine deposits of Mesozoic to
Tertiary age not being affected by metamorphism
characterize the External zone.
The Granada Basin extends some 60 km along the
EW direction, and 40 km in the NS direction (Fig.
2a) and it is filled with Neogene sedimentary depos-
its. The height of the sedimentary basin decreases
from south (1000 m) to north (500 to 600 m)
(Morales et al., 1990, 1997). Maximum sediment
thickness on top of the basement is about 2.5 km
according to seismic sections (1.5 s reflection time
for the basement, Rodrıguez-Fernandez et al., 1991).
The basin is surrounded by topographic heights.
Thus, we find clockwise: (a) the Sierra Arana
(1943 m) towards the NE, along the contact between
the external and internal zones; (b) the Sierra Nevada
(3482 m) towards the SE, which belong to the
internal zone; (c) then the Almijara (2025 m), also
within the internal zone; (d) the Sierra de Tejeda of
the internal zone along the southern border; (e) the
Sierra Gorda (1671 m) at the SW, which belongs to
the external zone, and finally, (f) the Parapanda hills
(1604 m) at the northern border, well within the
external zone.
The most significant active fault systems (Fig. 2b)
observed on the borders of the Granada Basin are: (I)
The Cadiz–Alicante fault system, which is a right-
lateral fault oriented N60–70E, located on the north-
ern border of the basin. (II) The EW trending Alhama
de Granada–Alpujarra right-lateral wrench, showing
kilometric cumulated displacements, at the southern
D. Munoz et al. / Tectonophysics 356 (2002) 233–252 235
border of the basin. The 1884 Alhama de Granada
large destructive earthquake occurred along this fault.
(III) An impressive NW oriented normal fault system,
the Sierra Elvira–Padul–Durcal system, with 1.5 km
of cumulated vertical slip, is located along the eastern
side of basin. (IV) A set of NNE–SSW oriented,
normal and left-lateral faults affecting the internal
zone, but also some sediments, is present at the
eastern and SE side of the basin across Sierra
Nevada.
Fig. 2. (a) Topographic map of the Granada Basin. Elevation difference between contours is 100 m. For topographic heights around the Basin
see the text, Section 2. The topography reflects well the Cadiz–Alicante fault system next to the northeastern corner. The Alpujarra corridor
fault is also well defined by the sharp change in topography at the southern border of the basin. (b) Active tectonics of the Granada Basin with
the main fault systems (I to IV). The scale is the same as that of (a). C.Z.I.Z.E. is the limit between internal (southeast) an external zones
(northwest). The main sites described in the text are: Zafarraya (Z), Alhama de Granada (AG), Padul (P), Durcal (Du), Sierra Elvira (SE) and the
Cadiz–Alicante fault. The Alpujarra corridor fault of EWorientation is the large one at the bottom of the figure (Alp-C). The triangles show the
sites of microtectonic measurements.
D. Munoz et al. / Tectonophysics 356 (2002) 233–252236
Fig.2(continued).
D. Munoz et al. / Tectonophysics 356 (2002) 233–252 237
3. Seismicity and the 1994 microseismic
experiment
The Granada Basin has a moderate permanent
activity with earthquakes of magnitude smaller than
5, nevertheless it has been the site of some large
earthquakes, or of seismic clusters. Historical earth-
quakes are shown in Fig. 3 according to their epicen-
tral intensity. They are spread all over the basin and
many affected the coastal region. The largest one
known is the big Alhama de Granada event of 1884,
which reached MKS intensity X (Udıas and Munoz,
1979). There is a concentration of historical activity
near Granada, though this may be an effect of the
density of population over there. Fig. 3 also shows the
instrumental seismicity previous to 1994, with mag-
nitudes larger than 4. Again the epicenters are spread
across the basin, and there is some concentration near
Granada. A large earthquake was registered in 1954
with epicenter at Padul and magnitude 7, but it was an
event at a depth of 645 km. A previous microseismic
experiment performed in 1978 (Carreno et al.,
1991a,b) registered events with magnitudes between
2 and 4. A seismicity cluster near Loja was the
dominant event during this experiment. A more
detailed microseismic campaign was carried on in
1988 with a dense network of 31 stations (Carreno
et al., 1991a,b), and it provided precise epicenters and
depths, though it lacked a reliable determination of
individual focal mechanisms.
Fig. 3. Historical seismicity and instrumental seismicity between 1900 and 1994. The 1884 Alhama de Granada earthquake had maximum
intensity X. The clustering of historical seismicity around Granada might be due to the large density of population over there. The largest
recorded event is the deep 1954 Padul earthquake (M=7.0, depth=657 km).
D. Munoz et al. / Tectonophysics 356 (2002) 233–252238
The 1994 campaign was designed to contribute
with another set of well-located events, which could
be correlated with tectonics, but also to obtain reli-
able individual focal mechanisms. About 49 stations
were distributed across the basin and its surround-
ings. Some were permanent stations of the Instituto
Andaluz de Geofisica (IAG), and of the Instituto
Geografico Nacional (IGN), and the rest were tem-
porary short period instruments (Fig. 4). Hypocen-
ters were determined through the HYPO 71 pro-
gram (Lee and Lahr, 1971), by using a three layered
crustal model over an homogeneous mantle (Layer
1: between 0 and 11 km with VP=6.1 km/s; Layer
2: between 11 and 24 km with VP=6.4 km/s; Layer
3: between 24 and 31 km with VP=6.9 km/s;
Mantle with VP=8.0 km/s). Only hypocenters with
Fig. 4. Station distribution during the 1994 campaign (May 21 to July 21). The triangles are the temporary stations, the inverted triangles belong
to the IGN National Network, and the crosses are the permanent stations of the Instituto Andaluz de Geofisica (IAG) network.
D. Munoz et al. / Tectonophysics 356 (2002) 233–252 239
an rms <0.35 s were accepted. Fig. 5a shows the
location of 60 well located microearthquakes distrib-
uted all over the basin. A NS linear alignment of
activity is observed between Huetor-Tajar and
Alhama. The depths of most of the events are located
within the upper 15 km of the crust (Fig. 5b).
4. Focal mechanisms
One of the main purposes of this study was to
obtain instead of composite mechanisms, individual
focal mechanisms having in common the regional
stress regime (Rivera and Cisternas, 1990). In this
Fig. 5. (a) Epicentral distribution during the 1994 campaign and tectonic features. Two clusters may be observed, one going from Huetor-Tajar
to Alhama, and the other near Arenas del Rey. Duration magnitudes are between 0 and 4. (b) Depth distribution. Most of the events are
shallower than 15 km.
D. Munoz et al. / Tectonophysics 356 (2002) 233–252240
method, a set of individual mechanisms, together with
an average regional stress tensor compatible with
them, are determined so as to minimize a likelihood
function. Fig. 6 shows 10 individual mechanisms
obtained in this way in 1994. The selected events
had between 7 and 20 polarities each, and their
magnitude varied between 1.2 and 3.1. Most were in
normal faulting, but there were also some strike–slip
events. Appendix A and Table 1 show the nodal
planes and polarities corresponding to each mecha-
nism.
On the other hand, the IAG maintains a permanent
seismic network, and there is an accumulated set of
observations which, though less constraining for each
individual mechanism, have the advantage of being
more numerous due to the longer total time period of
the recordings. Thus, there is an additional set of 64
new focal mechanisms of local earthquakes (Fig. 7)
with magnitudes between 2.4 and 4.2, recorded
between 1988 and 1994. They were also obtained
from polarities of P arrivals by simultaneous inversion
of individual mechanisms and the regional stress
tensor (Rivera and Cisternas, 1990) (see Appendix
B and Table 2).
5. Microtectonic measurements
Microtectonic observations, namely the determi-
nation of active fault planes and striae in a region,
give complementary, and independent, information to
that obtained from focal mechanisms (Philip et al.,
1992). Single microtectonic measurements were per-
formed at Sierra Elvira (three sites), Padul (two sites)
and Zafarraya basin (six sites) during the 1994
campaign (Fig. 2b). Each microtectonic observation
consisted in measuring the azimuth and plunge of the
fault plane together with the rake of the correspond-
ing striae or slip vector, which gives the displace-
ment of the block on top of the fault plane (Fig. 8,
Table 3). The measurements are not necessarily made
on major faults, but on well defined, small scale,
features with various orientations. The variety and
quality of the fault mirrors and of the striations
Fig. 5 (continued).
D. Munoz et al. / Tectonophysics 356 (2002) 233–252 241
permitted a reliable set of measurements. Moreover,
each site correspond to places of recent seismic
activity: Quaternary alluvial fans are cut by the fault
in Padul (Keller et al., 1996), the Zafarraya basin
was within the rupture zone of the large 1884,
Alhama de Granada earthquake and finally, the
Sierra Elvira fault is seismically active and, more-
over, shows perturbed Quaternary units (Santanach et
al., 1980). These observations are displayed in Fig. 8
with the same conventions used for focal mecha-
nisms, showing the fault plane, the auxiliary plane
and the slip vector. Most of the cases are normal
faults, but right-lateral or left-lateral strike–slips are
also present.
6. Regional stress tensor
From the above description of the main active
faults (Fig. 2b) we may obtain a qualitative idea about
the overall stress regime acting on the region: First,
since we have normal faults in different directions, we
may conclude that the stress regime is in extension
and that r1 is nearly vertical. Next, since the azimuth
of the Sierra Elvira fault is about NW, and its
character is purely normal without horizontal compo-
nent, we may assume that r2 is also oriented in a
direction close to NW, namely along the fault plane.
Finally, r3 should be oriented near a NE direction so
that the fault system IV (oriented NNE) might have a
Fig. 6. Focal mechanisms determined after the 1994 campaign (lower hemisphere equal area projection) and observed seismicity. Almost all of
the events are located within the basin.
D. Munoz et al. / Tectonophysics 356 (2002) 233–252242
left-lateral component, and that the Alhama de Gran-
ada fault and the Cadiz–Alicante fault system may
have a right-lateral component. We will show from
quantitative inversions of the stress tensor that this
picture is not unreasonable.
We made a comparison between (a) the stress
obtained from microtectonic measurements, (b) the
stress tensor calculated from local earthquakes
observed at 49 stations during the 1994 microseismic
experiment, and (c) from mechanisms obtained by the
permanent IAG network for the period 1986–1994
(Tables 1–3). We used a Monte Carlo method for the
three cases in order to have a common data processing
before comparison. We started with a randomly gen-
erated set of stress tensors and then selected the best 15
tensors which were compatible with both populations
of focal mechanisms, or with the set of microtectonic
Table 1
List of focal mechanisms (azimuth and dip of nodal planes) obtained
during the 1994 campaign
Focal mechanisms of the 1994 campaign
N First plan Second plan Sign
Azimj Dipj Azimj Dipj
1 339 33 162 57 +
2 198 79 290 80 +
3 86 46 192 75 +
4 357 18 194 72 +
5 276 10 112 80 +
6 343 32 149 58 +
7 58 8 165 88 �8 4 4 164 86 �9 195 85 92 21 +
10 113 54 341 47 +
The sign is positive for a normal fault and negative for a reverse
fault.
Fig. 7. Focal mechanisms (lower hemisphere, equal area projection) calculated from the polarities of 64 earthquakes recorded by the permanent
network of the IAG from 1988 to 1994.
D. Munoz et al. / Tectonophysics 356 (2002) 233–252 243
data. The results of the inversion of the stress tensors
are given in Fig. 9. The conventions are those of
Rivera and Cisternas (1990). The principal stresses
are r1, r2, r3 in decreasing order. From these, we call
rz the one that is closer to the vertical direction, and ry,
rx (with ry>rx) are the ones closer to the horizontal
plane. The orientation of the stress deviator is given by
the Euler angles /, h and w, while the regional stress
regime (extension, compression or strike–slip) is
given by the shape factor R=(rz�rx)/(ry�rx).
Fig. 9a gives the Monte Carlo inversion from
microtectonic data (Table 3). In this case, the score
of 0.81 is good, the shape factor R=2.1, which
corresponds to 3-axial extension, r1 is nearly ver-
tical and r3 approaches the N05jW direction. The
fault planes and the striae are precisely known
before inversion, and they do not change in char-
acter during the calculations. Fig. 9b shows the
Monte Carlo stress inversion from the 10 individual
focal mechanisms obtained during the 1994 cam-
paign (Table 1). The fault planes are automatically
chosen from the two nodal planes in order to be
compatible with the resulting tensor. This inversion
produces a regime near radial extension (R=15.6 is
very large). In this case, r1 is practically vertical,
and r2 and r3 are horizontal but it is difficult to
differentiate them, as shown by the dispersion of
the best 15 solutions. The score of the inversion is
0.96, which is quite high. In this output, r1 is
vertical and r3 is oriented N25jE. The Monte
Carlo stress tensor inversion obtained from 64 focal
Table 2
List of the 64 focal mechanisms obtained from the data of the IAG
Focal mechanisms of the IAG network (1988–1994)
N Azimj Dipj Rakej
1 147.96 67.35 �28.62
2 11.99 17.40 �139.19
3 125.51 79.21 96.34
4 235.00 39.58 �31.22
5 21.16 49.51 �122.83
6 124.22 73.47 �22.55
7 124.98 73.75 �1.89
8 77.69 47.67 �150.89
9 34.00 52.76 164.22
10 130.35 83.20 75.73
11 81.59 22.68 �104.68
12 235.34 68.35 �109.94
13 131.88 14.30 �51.46
14 227.56 45.13 �36.49
15 29.16 38.52 �138.82
16 21.28 56.06 10.12
17 357.13 75.20 �10.75
18 240.02 17.56 81.38
19 95.15 53.82 �141.67
20 216.89 61.79 �51.99
21 137.61 48.27 �52.72
22 25.42 60.05 81.49
23 313.15 86.76 �87.20
24 227.17 47.42 �48.82
25 22.37 55.20 153.66
26 235.03 39.56 159.73
27 224.07 42.45 �8.59
28 320.14 86.28 �67.11
29 235.23 39.80 �132.85
30 214.54 62.18 �47.01
31 309.00 71.34 �105.15
32 237.80 58.66 �114.56
33 351.05 59.86 �61.10
34 120.67 71.83 �161.77
35 123.96 73.64 113.33
36 321.46 77.61 �80.18
37 82.28 40.61 �128.14
38 247.20 13.52 90.96
39 94.12 36.89 �107.33
40 123.93 73.92 112.14
41 333.75 82.48 �40.07
42 122.92 71.17 �93.68
43 18.06 13.87 �139.13
44 32.02 81.52 74.82
45 183.23 1.30 14.92
46 115.51 69.46 �163.97
47 233.53 39.23 21.68
48 232.70 39.72 6.90
49 33.04 41.65 �147.89
50 254.73 27.13 145.78
51 229.02 68.22 �95.87
52 49.61 34.72 �140.36
Focal mechanisms of the IAG network (1988–1994)
N Azimj Dipj Rakej
53 335.03 55.51 �88.40
54 21.51 67.58 47.71
55 117.62 76.74 138.13
56 93.66 39.99 �112.24
57 78.33 39.32 �130.07
58 322.65 68.37 �89.05
59 288.82 62.03 �123.43
60 229.26 41.26 �8.59
61 126.76 81.04 91.58
62 263.91 44.81 �143.44
63 230.88 75.75 �103.58
64 230.40 40.43 �1.47
Azimuth, dip and rake are given in degrees, the fault plane being
identified during the inversion.
Table 2 (continued)
D. Munoz et al. / Tectonophysics 356 (2002) 233–252244
Fig. 8. Fault planes and striae obtained by microtectonic measurements. The measurements are presented as focal mechanisms but the fault
plane is known without ambiguity. The arrows indicate the slip vector.
D. Munoz et al. / Tectonophysics 356 (2002) 233–252 245
mechanisms (Table 2) is given in Fig. 9c. The focal
mechanisms were the result of applying the max-
imum likelihood inversion to the total set of polar-
ities from the data provided by the IAG. The data
set is larger than for Fig. 9b, but the number of
polarities per event is smaller. The result shows that
again r1 is near vertical. Nevertheless, it is even
more difficult to discriminate r2 from r3 since
R=51.4 is closer to radial extension. The smaller
stress r3 is oriented in a direction N10jW. The score
is 0.61, which is rather low, meaning that it is
difficult to fit all of the data.
7. Discussion and conclusions
The general tectonics of the Granada Basin is
characterized by a stress regime in extension, which
apparently differs from what might be expected
from the convergence between Africa and stable
Spain. Nevertheless, such a regime is compatible
with a pull-apart mechanism for the development of
the basin, and is consistent with the right-lateral
character of the Cadiz–Alicante fault system, and
the lateral ejection of the wedge limited by the
Cadiz–Alicante and Lorca–Palomares–Carboneras
fault systems.
Seismic activity in different periods shows a dis-
tributed character across the Granada Basin. Some
special events, like the 1985 Loja cluster (Carreno et
al., 1991b; Herraiz and Lazaro, 1991) or the 1884
Alhama de Granada earthquake (Munoz and Udias,
1981), are clearly related to active faulting.
The seismicity of the 1994 experiment is also
distributed over the basin, but there is one cluster
along a NS line from Huetor-Tajar to Alhama. Most of
the events are concentrated within the upper 15 km.
An overall qualitative picture may be obtained
from the main active faults, and other large geody-
namic elements. The pure normal faults oriented NW
at Sierra Elvira may be interpreted as an indication
that r2 is subparallel to the fault plane, and that the
motion is controlled by r1 and r3. The left-lateral
character of the fault system IV, oriented NNE, and
affecting the internal zones at the eastern border of the
Granada Basin, is compatible with a r3 direction
oriented NNE to NE. The right-lateral character of
the Alhama de Granada fault is also compatible with
such an orientation of r3.Microtectonic measurements at three key sites,
Sierra Elvira, Padul and Alhama de Granada, are
compatible with a 3-axial extension stress regime
having r3 oriented N05jW.
Ten well-determined individual focal mechanisms
obtained from the 1994 data set indicate a stress
regime close to radial extension, with r3 oriented
N25jE.A long-term seismic survey by the permanent
network of the IAG contributes with 64 individual
focal mechanisms, which are compatible with a stress
regime in radial extension. This data set is controlled
by a smaller number of stations than that of the 1994
experiment, but the large number of total polarities
used in the inversion compensates this.
A synthesis of the above results, based on three
independent data sets, and the larger active faults of
the region, confirms an overall extension stress pattern
in the Granada Basin with r1 vertical and r3 oriented
N25jE to N10jW.
Acknowledgements
This work received support from the Centre
Nationale de la Recherche Scientifique (CNRS,
France), the Instituto Geografico Nacional (IGN,
Spain), and the Instituto Andaluz de Geofisica
(IAG). We thank M. Bezzegoud for his careful
reading of the text and numerous suggestions.
Table 3
List of the microtectonic measurements (azimuth, dip, rake)
corresponding to the Sierra Elvira, Padul and Zafarraya regions
Neotectonic measurements
N Azimj Dipj Rakej
1 93.0 68.0 �130.0
2 45.0 75.0 �150.0
3 98.0 67.0 �101.0
4 87.0 84.0 �5.0
5 51.0 86.0 �167.0
6 103.0 90.0 �16.0
7 139.0 18.0 �83.0
8 110.0 90.0 �105.0
9 118.0 90.0 �50.0
10 155.0 45.0 �78.0
11 150.0 45.0 �83.0
The order corresponds to Fig. 8.
D. Munoz et al. / Tectonophysics 356 (2002) 233–252246
Fig. 9. Stress tensor inversions obtained from microtectonic measurements, the 1994 microseismicity experiment, and from 64 individual focal
mechanisms observed by the IAG. The orientation of the stress deviator, the shape factor R and the score are shown for each inversion. The best
15 solutions are shown in a lower hemisphere equal area projection. (a) Monte Carlo inversion from microtectonic measurements (neo2.out). (b)
Monte Carlo inversion of the 1994 individual mechanisms (mad.out). (c) The stress tensor obtained by Monte Carlo inversion from the 64 IAG
mechanisms obtained by maximum likelihood from polarities (iag0.out).
D. Munoz et al. / Tectonophysics 356 (2002) 233–252 247
Appendix A
Individual focal mechanisms of 1994 and polarities. P and T axes are indicated. Black dots are compressions,
and white dots are dilatations. The polarities are used to determine the nodal planes, which are compatible with a
single stress regime.
D. Munoz et al. / Tectonophysics 356 (2002) 233–252248
Appendix B
Individual focal mechanisms for 64 local earthquakes obtained from data of the IAG, not including those of
Appendix A. Nodal planes and the one standard deviation ellipse error of the pole of the fault plane are given,
together with the slip direction. Black dots indicate compression and white dots dilatations.
D. Munoz et al. / Tectonophysics 356 (2002) 233–252 249
D. Munoz et al. / Tectonophysics 356 (2002) 233–252250
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