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1 EOST—Institut de Physique du
Globe
5, rue René Descartes
67084 Strasbourg Cedex,
France
ziyadin.cakir{at}eost.u-strasbg.fr
(Z.C.,
M.M., S.B.)
2 Eurasian Institute of Earth Sciences
ITU
Istanbul, Turkey
(A.M.A.)
3 Laboratoire de
Geophysique
CNRST
Rabat, Morocco
(N.J.)
4 des Sciences de la
Terre
Universite Mohammed V
Morocco
(L.A.-B.)
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Abstract |
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 Top Abstract IntroductionModeling InterferogramsAcknowledgmentsReferences |
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Introduction |
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TopAbstractIntroductionModeling InterferogramsAcknowledgmentsReferences |
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Focal-mechanism solutions of the mainshock from various sources are in good agreement and indicate a strike-slip mechanism with either a north-northeast–south-southwest- trending left-lateral fault or a northwest–southeast-trending right-lateral fault (Table 1). Field observations following the earthquake did not reveal any clear surface faulting associated with the earthquake. Instead, widespread fissures, joints, and landslides trending subparallel to the northeast–southwest left-lateral nodal plane were observed between the Beni Abdellah village to the south and Ajdir village to the north (Fig. 2). Preliminary field interpretations suggest that the surface breaks may represent the fault rupture at depth, and thus the earthquake is presumably associated with a left- lateral strike-slip fault, a similar situation as for the 1994 event (Ait Brahim, Nakhcha, et al., 2004). However, distribution of aftershocks recorded by a temporary local seismic network (Dorbath et al., 2005) shows two lineations of seismicity in the directions northwest–southeast and north- northeast–south-southwest, suggesting that the event might have been associated with multiple fault breaks (Ait Brahim, Nakhcha, et al., 2004). Therefore, in the absence of clear coseismic faulting and related tectonic features within the epicentral area, neither aftershock distribution nor focal- mechanism solutions can resolve the geometry and earthquake rupture characteristics.
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In this article we use synthetic aperture radar interferometry (InSAR) in order to determine the fault characteristics and seismic parameters of the 24 February 2004 earthquake. The analysis of ascending and descending radar images provides two sets of interferograms with clearly visible deformation lobes in the epicentral area. Furthermore, a unique model of rupture dislocation defines the coseismic rupture and related seismic characteristics. Finally, we discuss the implications of coseismic strike-slip ruptures within the Africa–Eurasia plate-boundary deformation zone.
Tectonic Setting
The Rif region forms the westernmost mountain range of the
east–west-trending thrust-and-fold system of North Africa and results
mainly from the convergent movements of Africa toward Eurasia (Iberia) mainly
during the Tertiary. The tectonic structures and compression regime of the Rif
are comparable to the thrusts and nappes and related tectonic regime of the Tell
Atlas mountain range in Algeria and Tunisia. From a global model of plate
tectonics and GPS measurements combined with slip vectors of
moderate-to-large earthquakes,
DeMets et al. (1990),
Pondrelli et al. (2002),
McClusky et al. (2003), and Nocquet and Calais (2004)
predict a range of 2.3–6.3 mm/yr northwest–southeast to north-
northwest–south-southeast shortening between Africa and Eurasia in
northern Morocco and Algeria, the Euler pole ranging between 2.1 and 21.0 in
latitude and –20.0 and –18.3 in longitude. Although the driving
force responsible for the active deformation along the plate boundary is the
oblique convergence between the two plates, the pattern of seismicity is diffuse
and varies significantly from east to west. In the long term, the rate of
seismicity might be correlated with the rate of convergence along the plate
boundary, but this is not evident to establish with the short period of
instrumental seismic records. While the 1994 (Mw 6.0) and
2004 (Mw 6.4) moderate-to-large earthquakes and the recent
seismicity manifest that the –400-km-long and 100- km-wide Rif Mountain
range is being deformed under a strike-slip tectonic regime
(Bezzeghoud and Buforn, 1999),
adjacent regions in northern Algeria to the east and the Gulf of Cadiz to the
west are subject to thrust faulting deformation
(Grimison and Cheng, 1986). In
their seismotectonic analysis,
Meghraoui et al. (1996) suggest that the North African mountain ranges are the result of transpression
tectonics that correspond to the interaction of shortening and transcurrent
movements along the plate boundary. Paleoseismic investigations in northern
Algeria
(Meghraoui and Doumaz, 1996) and
in southern Spain
(Masana et al., 2004)
provide estimates of the total shortening ranging between 1.15 and 3.7 mm/yr
along a N315 transect across the Betics and the Tell Atlas at the level of the
El Asnam thrust-and-fold area. No such estimates of convergence rates have yet
been determined across the Alboran Sea region.
The Al Hoceima region belongs to the east–west- trending imbricated thrust-and-fold system of the Rif Mountain range that results from the Tertiary tectonic regime (mostly Late Miocene and Lower Pliocene; Morel and Meghraoui, 1996). The neotectonic features of the Rif consist of the major Nekor and Jebha left-lateral strike-slip faults (Fig. 1), trending northeast–southwest, accompanied by north–south-trending normal faults that form a graben-like structure east of Al Hoceima and a conjugate network of relatively small (10–20 km long) northwest–southeast and northeast–southwest strike-slip faults (Fig. 2). The transpressive tectonics and existence of a complex fault network with thrust, normal, and strike-slip faulting in the Rif probably reflect the rapidly changing local tectonic regime with block rotations during the Neogene and Quaternary (Meghraoui et al., 1996). Evidence of late Pleistocene and Holocene activity with typical prominent geomorphological features of seismogenic faulting is undocumented along the Rif neotectonic faults. Therefore, the identification of active and seismogenic faults in the Rif Mountains remains a difficult task that needs the contribution of new methods, including InSAR.
Interferometric Data and Analysis
Over the last decade, InSAR has been proved to be a powerful tool for mapping
crustal deformation due to earthquakes at a high spatial resolution with
subcentimeter precision
(Massonnet et al., 1993); in addition, the InSAR methodology allows the measurements of postseismic
relaxation, interseismic loading, and aseismic surface creep
(Bürgmann et al., 2000;
Wright et al., 2001; Fialko, 2004;
Cakir et al., 2005).
We use the European Space Agency’s Envisat Advanced Synthetic Aperture Radar (ASAR) (Beam Mode 2) data acquired during ascending and descending passes of the satellite over the earthquake area in order to map the surface- deformation field (Fig. 1). Interferograms were calculated from ASAR Level-1 data (single look) using Doris InSAR processing software (Kampes et al., 2003) with 1 range 5 azimuth looks (i.e., averaged to 20 x 20 m of ground pixel size) and precise satellite orbits from Delft University (Scharoo and Visser, 1998). Effects of topography were removed from the interferograms using the Shuttle Radar Topography Mission (SRTM) 3-arcsec posting digital elevation model (Farr and Kobrick, 2000).
We formed two ascending (track 230) and four descending (track 280)
interferograms using nine ASAR images
(Fig. 3). The best four
interferograms are shown in
Figure 4. Having the shortest
temporal and spatial baseline, the ascending interferogram has the best
coherence (Fig. 4a);
decorrelation occurs due to large baselines, agricultural activities within the
time span between image pairs (mainly descending pairs), and the steep slopes in
the ragged terrain, particularly along the valley between Beni Abdellah and
Einzorene (Figs. 2 and
4). The fact that there is no
significant difference between the descending interferograms suggests that the
atmospheric effects and orbital errors are negligible. The ascending
interferograms show two asymmetric lobes of deformation with a peak-to-peak
line-of-sight (LOS) displacement of about 23 cm (eight fringes),
whereas three lobes of deformation can be seen in the descending interferograms
with a maximum of five fringes (
12 cm) in the eastern lobe. While the two
lobes in the coastal regions are clearly visible in all the interferograms, the
southern lobe is somewhat obscured due to the poor coherence. The only common
lobe between the ascending and descending interferograms is the one located
immediately west of Al Hoceima.
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Approximately 40% of east–west and 90% of vertical changes can be measured by synthetic aperture radar (SAR) interferometry with a steep look angle (–23° for Envisat Beam Mode 2 and European Remote Sensing [ERS] in the image center), whereas horizontal motion along the satellite flight direction that is approximately north–south but varies with latitude cannot be detected. Furthermore, a combination of horizontal and vertical displacement may lead to signal cancellation. Therefore, the striking difference in the fringe pattern between the ascending and descending interferograms mostly results from the change in the viewing geometry and the nature of surface deformation associated with a strike-slip fault trending oblique to the satellite flight direction. In the ascending and descending geometry, Earth surface is imaged from nearly opposite directions, and any changes in shape of the deformation reflect differences in the vertical versus horizontal deformation; the sum of ascending and descending interferograms is largely up motion, with about 10% of north motion, and the difference between the two phases (descending minus ascending) is approximately the east motion (Fielding et al., 2005). Therefore, the surface displacement in the region where there is a common lobe between the ascending and descending interferograms must be overwhelmingly vertical (i.e., subsidence as it shows range increase).
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Modeling Interferograms |
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TopAbstractIntroductionModeling InterferogramsAcknowledgmentsReferences |
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Since the fault rupture apparently did not reach the surface and the LOS component of the surface deformation captured by SAR interferometry is not quite unambiguous, we tested both northeast–southwest- and northwest–southeast- trending fault planes with varying dip and segmentation (i.e., single and multiple faults) (Table 2; Fig. 5). All the modeled faults used in our tests are discretized into triangular elements both along strike and azimuth (minimum 8 x 7 quadrangles, i.e., 112 triangles) so that realistic slip distribution can be obtained. Since the faults must not crosscut the visible fringes, northeast–southwest-trending left-lateral faults are placed only in areas of low coherence to the south of the earthquake area. The northwest–southeast-trending right- lateral strike-slip faults are placed along the fringe of zero LOS deformation between the two lobes of the ascending interferograms.
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Modeling results indicate that the best fit to the ascending and descending
interferograms can be achieved only by using a right-lateral strike-slip fault
(Table 2, model 4B). As shown
in Figure 5 and
Table 2, each type of
interferogram can presumably be modeled to some extent with left-lateral
strike-slip faults, but with a significant difference in dip and
strike—that is N15–20°E strike with near-vertical dip for the
descending (model 1F) and N30–35°E with 60° NW dip for the
ascending interferograms (model 2E). While left- lateral faulting can adequately
explain the descending interferograms, a satisfactory fit could not be obtained
for the ascending ones, even with multiple faults of varying strike (model 3).
This is because the ascending interferograms require unrealistically high (>5
m) slip on very short (5– 10 km) faults located 7–10 km away
from the lobe centers (i.e., areas of maximum LOS deformation;
Fig. 4a). Therefore, a single
or one type of interferogram (i.e., ascending or descending) should be
interpreted with caution when deducing earthquake source parameters, especially
in the absence of a clearly visible surface rupture.
Our best model fault is a curved right-lateral strike-slip fault about 21 km long and 16.5 km wide, dipping 87–88° eastward with a strike changing from N85°W in the south to N50°W in the north (Fig. 6; Table 2). The excellent fit between the modeled and observed interferograms can be seen from the residual interferograms (i.e., models minus data) and profiles shown in Figure 6. The curved fault plane necessarily forms a restraining bend as the fault is associated with a right-lateral strike-slip movement. The location and the azimuth of the northwest–southeast-trending portion of the fault are well constrained, as we are forced to place the fault along the fringe of zero LOS deformation between the two lobes of the ascending interferograms (Fig. 4a). A change in the rupture strike along the southern fault section is required by both ascending and descending interferograms (Fig. 5d; Table 2). However, the presence of the poor coherence does not allow us to better constrain the location of the west-northwest–east-southeast-trending fault or to infer how the two rupture planes of different strikes are connected. We assume a continuous fault rupture with a bend, as it is a common feature along strike-slip faults.
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The fault surface of the best model is composed of 14 and 8 quadrangles formed with a pair of triangles along azimuth and dip directions, respectively. Since the resolution of slip decreases with increasing depth, the size of the triangles is gradually increased (from 1 to 3 km) toward the bottom of the fault. The slip distribution on the fault was then inverted with a right-lateral constraint on the strike-slip component and zero displacement on the fault edges; no sign constraints were imposed on the dip-slip component. A smoothing operator is also applied to the inverted slip distribution; models with a less smoothing factor (<0.3) better predict the data but with unrealistically high and localized slips.
Our best slip model is shown in Figure 7. A large asperity with a predominant right-lateral displacement of up to 2.7 meters is present at a depth of 6–8 km on the west- northwest–east-southeast-trending portion of the fault to the south. The northwest–southeast-trending part of the fault to the north is dominated by oblique to normal slip, explaining the range increase indicated by the common lobe between the ascending and descending interferograms. The geodetic moment of 6.8 x 1018 N m (equivalent of Mw 6.5) determined from modeling is in good agreement with those obtained from seismological observations (Table 1).
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The continuity of fringes across the northwest–southeast-trending
portion of the fault in the ascending interferograms implies that the coseismic
rupture did not reach the surface. Modeling suggests that the slip is
practically absent in the uppermost 2 km of the fault, which is also
confirmed by the absence of aftershocks above 3 km of depth
(Dorbath et al., 2005).
The depth of the coseismic slip along the west-
northwest–east-southeast-trending part of the fault could not be well
constrained owing to the poor coherence in this region. Therefore, the rupture
could be shallower and thus some of the fissures of similar strike observed in
the field might be directly linked with the earthquake rupture below
(Ait Brahim, Nakheha, et al., 2004).
The presence of deep coseismic slip with large amplitudes suggests that the
earthquake probably nucleated at depths below 8–10 km, which in turn may
explain why the rupture did not break the surface. Another possible explanation
for the superficial seismic slip is that the uppermost part of the brittle crust
is detached as a result of imbricated thrust-and-nappes and thus has different
mechanical properties. As proposed by
Fialko et al. (2005),
surface slip deficit may also result from a distributed inelastic deformation
within the uppermost few kilometers of the Earth’s crust, occurring
predominantly during the interseismic period.
Discussion and Conclusions
Based on a detailed examination of Envisat radar data and subsequent modeling
of the observed LOS surface deformation, we were able to determine
the earthquake rupture parameters of the 24 February 2004
(Mw 6.4) Al Hoceima earthquake. In the absence of surface
faulting and complex aftershock distribution in a region like northern Morocco
where morphology does not provide clear signals of active strike-slip faults,
InSAR appears to be the appropriate methodology to characterize the seismic
source parameters accurately and in detail.
The preferred northeast–southwest-trending left-lateral fault planes from seismologic studies based on regional and teleseismic waveform modeling (Buforn et al., 2005) and apparent source time functions (ASTFs) (Stich et al., 2005) are incompatible with the observed LOS surface deformation as they run north–south and N10°E. The InSAR near-field data analysis, particularly with both ascending and descending geometry, provides powerful constraints on the location and kinematics of the earthquake rupture. Any fault plane with a reasonable length and strike of north–south to N15°E cannot explain any of the coseismic interferograms, as it would crosscut the fringes through the deformation lobes. The waveform modeling or ASTF cannot distinguish between the two nodal planes of the double-couple source where both fault planes are plausible solutions. In the Al Hoceima case, taking into account the local tectonics and seismicity of the region, the left-lateral fault plane is preferred even though the right-lateral nodal plane fits ASTFs almost equally well (D. Stich, personal comm. 2005).
Previous studies of the aftershocks and intensity distribution (Calvert et al., 1997; El Alami et al., 1998; Bezzeghoud and Buforn, 1999) suggest that the May 1994 Mw 6.0 earthquake took place on a north-northeast–south-southwest-trending left-lateral strike-slip fault. If this is correct, then the two earthquakes did not occur along the same fault but on conjugate faults.
Strike-slip earthquakes and related aftershocks with left- and right-lateral kinematics support the assumption that the Rif is subject to distributed strike-slip deformation via northwest–southeast- and northeast–southwest-trending conjugate faults. The Rif Mountain range can be considered a different and individual tectonic block along the plate boundary with respect to the Tell Atlas of Algeria that manifests earthquakes with noteworthy thrust kinematics (Meghraoui et al. 1996; Bezzeghoud and Buforn, 1999). That the active tectonics and related geomorphological features associated with strike-slip faults are not well developed on the landscape suggests that the Rif tectonic block is under the early stages of a new strike-slip regime. This observation is supported by the total absence of seismicity along (1) the graben-like structure and related prominent normal faults southeast of Al Hoceima, and (2) along the major Nekor strike-slip fault (Hatzfeld et al., 1993). The relatively newly formed seismogenic strike-slip faults may explain the occurrence of moderate-sized earthquakes with Mw <6.5. However, the northwest–southeast right-lateral faulting identified with InSAR is consistent with the oblique convergence and transpressive movements along the plate boundary and illustrates the complex rupture pattern and related seismicity of the Rif region.
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Acknowledgments |
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TopAbstractIntroductionModeling InterferogramsAcknowledgmentsReferences |
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Manuscript received May 27, 2005
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References |
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TopAbstractIntroductionModeling InterferogramsAcknowledgmentsReferences |
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Ait Brahim, L., C. Nakhcha, B. Tadili, A. El Mrabet, and N. Jabour (2004). Structural analysis and interpretation of the surface deformations of the February 24th, 2004 Al Hoceima earthquake, EMSC-Newsletter21 ,10 –12.
Ait Brahim, L., B. Tadili, C. Nakhcha, I. Mouayn, M. Ramdani, M. Limouri, A. El Qadi, F. Sossey Alaoui, and M. Benhalima (2004). Modeling in the eastern Rif (northern Morocco) using active faults and seismicity for the strong motion, Pure Appl. Geophys. 161,1081 – 1091, 0033-4553/04/061081-11, doi10.1007/s00024-003-2487-9 .[CrossRef]
Bezzeghoud, M., and E. Buforn (1999). Source parameters
of the 1992 Melilla (Spain, Mw 4.8), 1994 Alhoceima
(Morocco, Mw 5.8) and 1994 Mascara (Algeria, Mw 5.7)
earthquakes and seismotectonic implications, Bull. Seism. Soc.
Am. 89,359
-372.
Buforn, E., M. Bezzeghoud, C. del Fresno, J. F. Borges, R. Madariaga, and A. Udías (2005). Study of the fracture process of Al Hoceima earthquake (24/02/2004, Mw = 6.2) from regional and teleseismic data, Geophys. Res. Abst.7 , 05301, SRef-ID 1607-7962/gra/EGU05-A- 05301.
Bürgmann, R., D. Schmidt, R. M. Nadeau, M. d’Alessio, E. Fielding, D. Manaker, T. V. McEvilly, and M. H. Murray
(2000). Earthquake potential along the northern Hayward fault,
California, Science289
,1178
–1181.
Cakir, Z., A. M. Akoglu, S. Belabbes, S. Ergintav, and M. Meghraoui (2005). Creeping along the North Anatolian fault at Ismetpasa (western Turkey): rate and extent from InSAR, Earth Planet. Sci. Lett. 238,225 –234.[CrossRef]
Calvert, A., F. Gomez, D. Seber, M. Barazangi, N. Jabour, L. Ait Brahim, and A. Demnati
(1997). An integrate geophysical investigation of recent seismicity
in the Al-Hoceima region of north Morocco, Bull. Seism. Soc.
Am. 87,637
–651.
DeMets, C., R. G. Gordon, D. F. Argus, and S. Stein (1990). Current plate motions, Geophys. J. Int. 101,425 –478.[CrossRef]
Dorbath, L., Y. Hahou, B. Delouis, C. Dorbath, J. Van Der Woerd, S. Bardrane, M. Frogneux, H. Haessler, E. Jacques, M. Menzhi, and P. Tapponnier (2005). Études sismologiques sur le séisme D’al Hoceima: localisation, et mécanisme du choc principal et des répliques, contraintes et structure de la zone epicentrale. Presented at Colloque Intenational Seisme d’Al Hoceima: bilan et perspectives, 24–26 February 2005, Al Hoceima, Morocco.
El Alami, S. O., B. Tadili, T. E. Cherkaoui, F. Medina, M. Ramdani, L. Ait Brahim, and M. Harnafi (1998). The Al Hoceima earthquake of May 26, 1994 and its aftershocks: a seismotectonic study, Annali di Geofisica41 , no. 4,519 –537.[GeoRef]
Farr, T., and M. Kobrick (2000). Shuttle radar topography mission produces a wealth of data, EOS Trans. AGU 81,583 –585.
Fialko, Y. (2004). Evidence of fluid-filled upper crust from observations of postseismic deformation due to the 1992 Mw 7.3 Landers earthquake, J. Geophys. Res.109 , B08401, doi10.1029/2004JB002985 .[CrossRef]
Fialko, Y., D. Sandwell, M. Simons, and P. Rosen (2005). Three-dimensional deformation caused by the Bam, Iran, earthquake and the origin of shallow slip deficit, Nature435 , doi10.1038/nature03425 .[CrossRef][Medline]
Fielding, E. J., M. Talebian, P. A. Rosen, H. Nazari, J. A. Jackson, M. Ghorashi, and R. Walker (2005). Surface ruptures and building damage of the 2003 Bam, Iran, earthquake mapped by satellite synthetic aperture radar interferometric correlation, J. Geophys. Res.110 , B03302, doi10.1029/2004JB003299 .[CrossRef]
Grimison, N., and W. Cheng (1986). The Azores–Gibraltar plate boundary: focal mechanisms, depths of earthquakes and their tectonic implications, J. Geophys. Res.91 ,2029 –2047.[CrossRef]
Hatzfeld, D., V. Caillot, T.-E. Cherkaoui, H. Jebli, and F. Medina, (1993). Microearthquake seismicity and fault plane solutions around the Nekor strike-slip fault, Morocco, Earth Planet. Sci. Lett. 120,31 –41.[CrossRef]
Kampes, B., R. Hanssen, and Z. Perski (2003). Radar interferometry with public domain tools, in Proceedings of FRINGE 2003, 1–5 December, Frascati, Italy.
Maerten, F., P. G. Resor, D. D. Pollard, and L. Maerten
(2005). Inverting for slip on three-dimensional fault surfaces
using angular dislocations, Bull. Seism. Soc. Am.95
,1654
–1665.
Masana, E., J. J. Martínez-Díaz, J. L. Hernández-Enrile, and P. Santanach (2004). The Alhama de Murcia fault (SE Spain), a seismogenic fault in a diffuse plate boundary: seismotectonic implications for the Ibero- Magrebian region, J. Geophys. Res.109 , B01301, doi10.1029/ 2002JB002359 .[CrossRef]
Massonnet, D., M. Rossi, C. Carmona, F. Adragna, G. Peltzer, K. Feigl, and T. Rabaute (1993). The displacement field of the Landers earthquake mapped by radar interferometry, Nature364 ,138 –142.[CrossRef][GeoRef]
McClusky, S., R. Reilinger, S. Mahmoud, D. Ben Sari, and A. Tealeb (2003). GPS constraints on Africa (Nubia) and Arabia plate motions, Geophys. J. Int.155 ,126 –138, doi10.1046/j.1365-246X.2003.02023 .[CrossRef]
Meghraoui, M., and F. Doumaz (1996). Earthquake-induced flooding and paleoseismicity of the El Asnam (Algeria) fault-related fold, J. Geophys. Res.101 ,17,617 –17,644.[CrossRef]
Meghraoui, M., J. L. Morel, J. Andrieux, and M. Dahmani (1996). Tectonique plioquaternaire de la chaîne tello-rifaine et de la mer d’Alboran; Une zone complexe de convergence continent, Bulletin Societe Geologique de France167 , no. 1,141 –157.[Abstract]
Morel, J. L., and M. Meghraoui (1996). The
Goringe-Alboran-Tell (GALTEL) tectonic zone, a transpression system along the
Africa-Eurasia plate boundary, Geology24
,755
–758.
Nocquet, J.-M., and E. Calais (2004). Geodetic measurements of crustal deformation in the western Mediterranean and Europe, Pure Appl. Geophys.161 ,661 –681, 0033-4553/04/030661-21, doi10.1007/ s00024-003-2468 .[CrossRef]
Pondrelli, S., A. Morelli, G. Ekström, S. Mazza, E. Boschi, and A. M. Dzlewonski (2002). European-Mediterranean regional centroid- moment tensors: 1997–2000, Phys. Earth Planet. Interiors130 , 71– 101.[CrossRef]
Scharoo, R., and P. Visser (1998). Precise orbit determination and gravity field improvement for the ERS satellites, J. Geophys. Res.103 , 8113– 8127.[CrossRef][Web of Science]
Stich, D., F. de Lis Mancilla, D. Baumont, and J. Morales (2005). Source analysis of the 6.3, 2004, Al Hoceima earthquake (Morocco) using regional apparent source time functions, J. Geophys. Res. 110, B6, B06306, doi10.1029/2004JB003381 .
Thomas, A. L. (1995). Poly3D: a three-dimensional, polygonal element, displacement discontinuity boundary element computer program with applications to fractures, faults, and cavities in the earth’s crust, Master’s Thesis, Stanford University, 221 pp.
Wessel, P., and W. H. F. Smith (1991). Free software helps map and display data, EOS Trans. AGU72 , 441, doi10.1029/90EO00319 , 1991.[CrossRef]
Wright, T. J., B. Parsons, and E. J. Fielding (2001). Measurement of interseismic strain accumulation across the North Anatolian fault by satellite radar interferometry, Geophys. Res. Lett.28 ,2117 –2120.[CrossRef][Web of Science][GeoRef]
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