Int J Earth Sci (Geol Rundsch) (2003) 92:912–922 DOI 10.1007/s00531-003-0366-3

ORIGINAL PAPER

K. R. Reicherter · A. Jabaloy · J. Galindo-Zaldvar · P. Ruano · P. Becker-Heidmann · J. Morales · S. Reiss · F. Gonzlez-Lodeiro Repeated palaeoseismic activity of the Ventas de fault (S ) and its relation with the 1884 Andalusian earthquake

Received: 10 December 2002 / Accepted: 2 September 2003 / Published online: 14 November 2003 Springer-Verlag 2003

Abstract One of the most destructive historical earth- reported. The epicentre was probably located in the quakes (M 6.7) in Spain occurred in 1884 along the triangle between , Alhama de and normal Fault located in the Central Ventas de Zafarraya according to the macroseismic Betic Cordilleras. Palaeoseismic and radiocarbon data pre- information (Fig. 1). The maximum intensity was X sented in this study are the first to constrain the timing of (MSK scale) from which a magnitude of between 6.1 the pre-1884 fault history in the last 10 ka. These data (Lpez Casado et al. 2000) and 7 (Muoz and Udas yield a recurrence interval of between 2 and 3 ka for major 1980) has been calculated. European commissions studied earthquakes, under the assumption of uniform return pe- the geology of the region and the effects generated during riods along the normal fault. The Holocene slip rate is or after the earthquake (Orueta and Duarte 1885; estimated to be in the order of 0.35€0.05 mm/year, which Taramelli and Mercalli 1886; Kilian 1889; Muoz and is significantly higher than the mean slip rate of 0.17€ Udas 1980 and references herein). They described an 0.03 mm/year since the Tortonian. Several of the most area of a complex pattern of surface cracks (Fig. 2), important deformations and secondary features, such as landslides, rock falls, liquefaction, and the change of landslides and liquefaction, are related to strong ground spring-water chemistry associated with the seismic event. motion and document the Holocene activity of the Ventas The international collaboration resulted in the reconstruc- de Zafarraya Fault. tion of the new village of Arenas del Rey with one of the first earthquake-safe city designs. Although no unambiguous fault-related rupture at the Introduction surface or coseismic movements along the fault plane were recognized, Muoz and Udas (1980) and Sanz de The most destructive earthquake of the Iberian Peninsula Galdeano (1985) concluded that the earthquake has during the last 150 years occurred on 25 December 1884 possibly been associated with several faults and tectonic at 21:08 h (‘Terremoto de Andaluca’, Fernndez de blocks along the northern margin of the Sierra Tejeda Castro et al. 1885, in: Muoz and Udas 1980). More than (Fig. 3). 800 casualties and several destroyed villages were Here we characterize, palaeoseismologically, the Ven- tas de Zafarraya Fault (VZF) in order to establish its K. R. Reicherter ()) · S. Reiss relationship with the 1884 earthquake and with previous Institut fr Geophysik, Universitt Hamburg, coseismic events along the same normal fault. Our Bundesstraße 55, Hamburg, Germany investigations include sedimentology, microstratigraphy, e-mail: [email protected] radiocarbon dating, as well as an evaluation of aerial and Fax: +49-40-428385441 satellite photos, and an assessment of the recent and A. Jabaloy · J. Galindo-Zaldvar · P. Ruano · F. Gonzlez-Lodeiro historical seismicity. We applied high-resolution ground- Departamento de Geodinmica, penetrating radar (GPR), to describe and characterize the Universidad de Granada, sub-surface expression of the VFZ in the hanging wall. Campus Fuentenueva, Granada, Espaa The Betic Cordilleras in southern Spain are located within the Eurasian–African Convergence Zone in an P. Becker-Heidmann Institut fr Bodenkunde, Universitt Hamburg, approximately 500-km-wide region with a disperse seis- Allende-Platz 1, Hamburg, Germany micity. In the last few years, intense work on the palaeoseismicity of individual faults in the Betic Cordil- J. Morales leras started. Several structures along active fault zones in Instituto Andaluz de Geofsica, Universidad de Granada, the Betic Cordilleras are related to coseismic surface Granada, Espaa 913

Fig. 1 a Geological setting. General map of the Betic Cordillera plexes; 8 Alpujrride Complex; 9 Nevado-Filbride Complex; 10 (legend see b). b Map of study area. 1 Upper Miocene–Quaternary Iberian Massif with cover rocks; 11 isoseists of the 1884- sedimentary rocks; 2 Subbetic unit (the entire subbetic zone in a); 3 earthquake; 12 macroseismic intensity of the 1884-earthquake Internal subbetic; 4 Prebetic; 5 Oligocene–Lower Miocene sedi- source; 13 unconformity; 14 fault; 15 normal fault; 16 reverse fault; mentary rocks including flysch and olistostroms; 6 Campo de 17 syncline, 18 anticline. Inset shows locality of Fig. 2 Gibraltar Flysch; 7 Predorsalian, Dorsalian and Malguide Com-

Fig. 2 Topographic map of the scarp of the Ventas de Zafarraya cemetery of Ventas de Zafarraya, locality 2 Cortjo del Barranco, Fault. Topographic lines every 50 m; master topographic lines locality 3 Pilas de Algaida every 250 m. Note locality of radar-lines in Fig. 6. Locality 1 914 Fig. 3 Digital elevation model of the study area showing the 1884 rupture (Fig. 2). AD Al- born Domain; IEZB internal external zone boundary; ZP Zafarraya Polje; SID South Iberian Domain. Note landslide of Pilas de Algaida and locality of Fig. 8. The trace of the IEBZ is covered by Quaternary de- posits and projected, hence, it seems not to be displaced by the VZF

rupturing (see summary in Masana and Santanch 2001). Zone is locally overlain by nappes of the Campo de The Alhama de Murcia fault zone was investigated by Gibraltar Flysch units (Fig. 1). The Internal–External Silva et al. (1997), Martnez-Daz et al. (2001), and Zone Boundary (IEZB) separates the Internal Zones from Masana et al. (2003). The Carboneras Fault Zone in the the External Zones. The IEZB forms a low angle province of Almera has been studied by Bell et al. (1997) detachment (N50E strike and 25 dip to NW) in the and Reicherter and Reiss (2001). A description of active studied area with a top-to-the-W sense of movement faults in the Granada depression was provided by (Galindo-Zaldvar et al. 2000). Towards the west it bends Reicherter et al. (1999), Alfaro et al. (2001) Reicherter into an E–W direction. In the studied area, the VZF cuts (2001) and, recently, by Galindo-Zaldvar et al. (2003). the Internal–External Zone Boundary (IEZB) of the Betic The stratigraphic relationships along the active VZF Cordilleras (Lonergan et al. 1994). permit the reconstruction of the faulting history, including The normal VZF strikes WNW–ESE and dips towards the number and relative size of faulting events, and the NNE at an angle of 60 and is associated with a prominent determination of recurrence intervals (e.g. Wallace 1986; scarp in Jurassic limestones. The fault can be divided into McCalpin 1996). two E–W-oriented sectors separated by a central NW–SE- oriented sector. The striations on the fault plane indicate a main normal slip component with a minor dextral strike- Geological setting slip component (superposed striae with a rake of 12E and 27E). The present-day stress field indicates a NW–SE- The South Iberian Domain or External Zone is made up of directed maximum horizontal compression direction almost 1,000 m of Liassic white limestones and grey (Herraiz et al. 2000), and a SW–NE-directed extension, dolostones, followed by approximately 500 m of marly which is in concordance to the observed kinematic limestones and limestones of Middle Jurassic to Late indicators on the fault plane. Cretaceous age (Garca-Hernndez et al. 1980). The karstified Zafarraya Polje (Figs. 1, 2 and 3) is filled with alluvial and colluvial deposits of Quaternary age; under- Seismological setting lying Tortonian calcarenites have been drilled. The area of subsidence within the Zafarraya Polje is asymmetric The present-day stresses in the studied area and the (Ollero and Garca 1984). The small basin is bound to the Granada depression (Fig. 1) were determined by focal south by the normal VZF and forms a half-graben mechanism solutions. It is characterized by a NE–SW associated with an extensional roll-over structure, as extension (Galindo-Zaldvar et al. 1993, 1999). However, indicated by seismic and gravimetric data (unpublished the stress field in the area is heterogeneous as documented data of Galindo-Zaldvar). by permutations of the stress axes. Essentially, radial The Alborn Domain or Internal Zone, is deformed by extension, NE–SW extension, and NW–SE subhorizontal extensional detachments during the Mid-Miocene (Fer- compression are observed; the latter is parallel to the nndez-Fernndez et al. 1992; Martnez-Martnez and shortening direction active under the regional tectonic Azan 2002). Low- to high-grade metamorphosed stress field (Buforn et al. 1988; DeMets et al. 1990; schists and marbles form the Alpujrride Complex, Galindo-Zaldvar et al. 1999). whereas the Malaguide Complex includes Variscan The seismic activity in the Granada depression and basement covered by Mesozoic sediments. The Internal surrounding areas is characterized by frequent micro- 915 Fig. 4 Historical seismicity in Andalucia (after Reicherter 2001). Recent seismicity from NEIC data (http://neic.usgs.gov/ neis/epic/epic.html)

earthquake activity (MW 3.0, Fig. 4). The occurrence of series and seismic swarms is frequently observed, affect- ing the depression (Vidal 1986; Posadas et al. 1993; Serrano 1999; Saccorotti et al. 2001). The depth of this shallow activity ranges between 5 and 15 km to a maximum of 20 km and includes earthquakes with MW 5 or more. The last moderate event occurred to the south of the Granada depression with MW =5.0 in 1984 (Morales et al. 1996). The lower cut-off of seismic activity in 15–20-km depth has been interpreted by Morales et al. (1997) as the brittle–ductile transition in the crust. The Andalusian earthquake of 1884 is the most recent destructive major event in southern Spain, followed by several aftershocks with intensities of up to MSK=VIII during 1 year (Muoz and Udas 1980). Depending on the mode of calculation, magnitudes for this event ranges significantly between 6.1 (Lpez-Casado et al. 2000) and Fig. 5 Historical drawing of the 1884-earthquake in Zafarraya. 6.5. to 7.0 (Muoz and Udas 1980, 1982); recently, Note ground failure with open cracks, which are probably drawn exaggerated (Courtesy National Information Service for Earth- Ibaez et al. (2003) have estimated a MS of between 6.3 quake Engineering, University of California, Berkeley; see gallery and 6.8 based on intensity/magnitude relations. During of pictures at http://www.nisee.berkeley.edu/kozak/index.html) the EC-project FAUST (faust.ingv.it) a magnitude of 6.2, a length of 17.5 km and a strike of 89 were calculated for the VZF and the 1884 event. and Arenas del Rey (Fig. 5). The described cracks clearly delineate the WNW–ESE-trend- ing VZF and its prolongation towards the east (Lpez- Palaeoseismological analysis Arroyo et al. 1980; Muoz and Udas 1980; Figs. 2 and 5). The total rupture length observed was ~16 km, Although coseismic surface ruptures or cracks were not partitioned into two individual segments (Douville 1906). likely to survive human activity, we searched for evidence The rupture area, with a complicated system of fractures, of strong ground motion in the geological record. extends in an E–W-elongated area of approximately Contemporaneous historical drawings and etchings of 20 km length and 4 km width (Udas and Muoz 1979). unknown authors (Courtesy National Information Service Partly, the ‘cracks’ indicate normal displacement of the for Earthquake Engineering, University of California, Quaternary sediments with respect to the Jurassic lime- Berkeley, USA; see gallery of pictures at http:// stones. On the other side, cracks formed in the Polje area nisee.berkeley.edu/kozak/index.html) show the damage, (Fig. 5). This and other features related to the earthquake destruction and ground failures in the areas of Zafarraya, 916 Fig. 6 Radar sections and line interpretation of the Ventas de Zafarraya Fault (locality see Fig. 2). All radar lines obtained with 200-MHz antennae. Thick lines normal faults; thin lines bedding (B) and cracks (C), (L) liquefaction; dashed line ground water table; arrows counter- clockwise rotation of the hang- ing wall block; TWT two-travel time; ns nanoseconds; orienta- tion left side is south, right side is north 917 of 1884 have been described by Taramelli and Mercalli normal fault within the hanging wall: the reflectors are (1886) and Douville (1906, see summary in Reicherter interrupted and an apparent change in dip is observable 2001).The length of the rupture displays approximately and, again, a concave filling is related with the fault. We the mapped fault length. also suggest a coseismic origin of the scarplet in 1884, because of its topographic expression. Apart from this, secondary features have also been GPR visualization of the Ventas de Zafarraya Fault investigated to distinguish between mass movements (landslides), liquefaction and aseismic fault creep. Ap- Ground penetrating radar (GPR) is applied here to proximately 200 m N of the major scarp, within in the visualize sedimentary structures related to coseismic plane of the Polje (Fig. 2), a radar line exhibits vertical deformation (SIR 10B GPR system by Geophysical cracks and completely distorted layers within horizontal Survey Systems Inc. with antenna model 5106). Several beds (Fig. 6c). We interpret these observations as 200-MHz GPR-profiles perpendicular to the VZF were coseismically induced cracks, as documented in historical analysed, allowing a resolution of objects, discontinuities drawings (Fig. 5), and as liquefaction. The characteristic or strata in a dm/cm range (200 MHz approx. 20 cm). A peculiarities observed in high-resolution GPR images variety of filter tools were applied during processing with (Reiss et al. 2003) help to distinguish fault-related REFLEX-software (Sandmeier 2000): background re- sedimentary hanging-wall patterns from fluvial channel moval, Butterworth bandpass, energy decay and fk-filters fills or anthropogenic filling, which may produce similar as well as migration based on diffraction stack. The relief concave patterns. of the section can be modelled with the 3-D topography correction later (Fig. 6a, b). Maximum interpretable penetration was around 5 m in the present study. Palaeoseismic evidence In mainly arid regions, fault-related displacements in alluvial fans were mapped successfully with GPR (Basson The Ventas de Zafarraya Fault exhibits several typical et al. 1994; Cai et al. 1996; Marco et al. 1997). High- indicators of coseismic displacement. Sedimentological resolution GPR-profiling provides not only the possibility criteria are constrained by a series of radiocarbon data, in to trace active normal faults (Meschede et al. 1997; order to reconstruct the Holocene faulting history of the Reicherter and Reiss 2001), but also to visualize the fault. Along the fault, a set of 15 palaeosol samples, associated sedimentary hanging-wall patterns such as which are displaced or cover displaced Quaternary heterogeneous grabens and half-grabens including coarse- colluvial deposits, were sampled for 14C soil dating grained clastic wedges. Quantitative and qualitative GPR (Table 1). 14C activity was estimated by liquid scintilla- evaluation of these wedges yield the possibility of tion spectrometry (LCS). Low-carbon-containing palaeo- estimation of palaeomagnitudes and slip rates on active sols were dated with accelerator mass spectrometry normal faults (Reiss et al. 2003). This study showed, (AMS). To avoid isotopic effects, all 14C ages were however, that application of the georadar method in corrected with the 13C/12C ratios, which lie in the range coarse-grained sediments and caliche covered fans is between 19.5 and 25.9 d13C. limited due to weak penetration and diffraction hyperbo- At the cemetery of Ventas de Zafarraya (36570500N, lae. Along the selected profiles, Quaternary unlithified 04070500W, Fig. 2) the normal fault plane is exposed in sediments and palaeosols provide good contrasts against an artificial wall cut. Anthropogenic terracing destroyed well-bedded Jurassic limestone of the footwall (Fig. 6). partly the coseismic scarp, the uppermost layer contains The hanging wall of the VZF forms half-grabens that plastic material. The hanging wall contains three coarse- are generally characterized by internal asymmetric con- grained wedge-like deposits that thicken towards the fault cave, displaced reflectors or wedge-like features compa- plane (Fig. 7a). The formation of colluvial wedges is rable to sedimentary structures observed in adjacent generally considered as typical for coseismic ruptures outcrops (Fig. 7a). A GPR section was obtained perpen- (McCalpin 1996). Fine-grained, relict, reddish-yellowish dicular to the main scarp of the VZF where both foot and palaeosols and wash-off sediments rich in carbonates, hanging wall consist of Jurassic limestones (Fig. 6a). The eroded from the Jurassic substratum, separate the wedges. main fault trace in the central part of the radargram can be Older beds generally dip steeper towards the N than projected approximately 40 m E into the outcrop section younger strata. The main fault bifurcates and the two (Fig. 7a). Reflectors are interrupted and displaced by the lower wedges are displaced by a syn-1884 minor normal fault. Within the upper part of the hanging wall, fault (Fig. 7a). The distances between the wedges are in continuous reflectors show a significant change into the order of ~1 m for each and the inferred individual concave patterns, which are interpreted as dragged, fault- coseismic slip rates are approximately in the same order. related sediments of Holocene age (Fig. 6a). Pinching- The two lower wedges are ~70 cm thick, the upper wedge out features are interpreted as coarse-grained colluvial ca. 50 cm. With McCalpin’s rule of thumb (1986): double wedges. colluvial wedge thickness is approximately coseismic A second GPR line was obtained about 80 m N of the slip, and we end up at similar coseimic slip rates. Age major scarp (Figs. 6b and 8). The interpretation of radar dating of the wedge bases resulted in 8,800€130 years b.p. pattern revealed significant evidence for a secondary for the lower and 2,315€30 years b.p. for the middle base, 918 Fig. 7 a Outcrop sketch of the Ventas de Zafarraya Fault at the cemetery. Three colluvial wedges are intercalated by wash-off colluvium and pa- laeosols. Sample strategy, partly at the base of the wedges, and ages of 14C-dating in years b.p. Topmost colluvial wedge is supposed to be generated im- mediately after the 1884-earth- quake, probably modified by human activity.

Fig. 7 b Outcrop sketch of the Llanos de la Dona Fault. Note three rockfall wedges, and re- duced palaeosol formation and wash-off colluvium, including 14C-age dating results. Topmost pile of rocks is supposed to be generated by ground shaking during the 1884-earthquake

whereas the uppermost base is related to the 1884 event. strand developed approximately 50 m north of the main The cumulative offset is 2.96 m in 8,800€130 years b.p., fault contact associated with a 0.5-m-high scarplet and includes two 1884-like rupture events during the (Fig. 8), the hanging wall of which also shows concave Holocene. However, age dating of intercalated strata is colluvial filling in GPR (Fig. 6b). inconsistent and suggests a complex mixture of wash-off Near the Cortjo del Barranco (36570436N, sediments of the slope and palaeosols (Fig. 7a). Hence, 04070868W) approx. 300 m west of the cemetery we obtained not significant and palaeoseismically rele- (Fig. 2), the coseismic displacement of the 1884-rupturing vant 14C-ages. is between 1.2 and 1.5 m, resulting in a vertical slip of Both, coseismic displacement and wedge thickness between 1.0 and 1.3 m on a polished fault plane of suggest earthquakes with M >6.5. Liquefaction, such as Jurassic limestone that is not karstified. In the outcrop, the sand blows, clastic dikes and deformed beds, shear planes fault surface is exposed and a palaeosol covers approx- and ruptured or aligned pebbles, reveal further evidence imately 1.2 m of a coarse-grained breccia of Jurassic for repeated strong ground shaking. A secondary fault limestone fragments. Below this, a reddish-yellowish 919 Table 1 Radiocarbon data of Ventas de Zafarraya and Llanos de la Allende-Platz 2, 20146 Hamburg, Germany; KIA-yyyy dates of Dona. n.d. Not determined due to method of AMS radiocarbon Leibniz Laboratory for Radiometric Dating and Isotope Research, measurement; age b.p. conventional radiocarbon age (Stuiver and Christian-Albrechts-University Kiel, Max-Eyth-Str. 11-13, 24118 Polach 1977), i.e. half life 5,568 years, calibrated for isotope effects Kiel, Germany; HAM-xxxx/KIA-yyyy samples prepared in Hamburg to d13C of 25‰, (this is no calibration to calender years); error lab and measured in Leibniz Lab, Color according to Rock Color b.p. 1s standard deviation (2s=double deviation value); HAM-xxxx Chart, GSA Dates of Hamburg Radiocarbon Laboratory, Hamburg University, Lab. no. Sample no. d13C Age b.p. Error b.p. Colour (‰PDB) HAM-3711.1 Z1 20.0 8,800 €130 2.5Y 8/4 HAM-3712.1 Z2 21.2 10,070 €70 7.5YR 4/6 HAM-3713.1 Z3 20.9 13,540 €100 10R 4/6 HAM-3714.1 Z4 19.5 15,990 €120 7.5YR 4/4 HAM-3715.1 Z5 20.8 11,540 €70 7.5YR 4/6 HAM-3716.1 Z6 23.4 8,730 €70 5YR 4/8 HAM-3751.1 ZAF A 25.9 50 €30 7.5YR 4/4 HAM-3752.1 ZAF B 25.1 1,775 €35 10YR 5/6 HAM-3753.1 ZAF C 24.5 7,370 €60 5YR 4/8 HAM-3698/KIA9669 ZAF 1 n.d. 2,315 €30 7.5YR 4/6 HAM-3699/KIA9670 ZAF 2 n.d. 2,940 €140 10R 4/6 HAM-3717.1 Llanos 1 22.2 9,610 €90 5YR 6/8 HAM-3718.1 Llanos 2 25.2 2,960 €45 5YR 3/2 HAM-3749.1 Llanos A (3) 24.7 1,110 €40 5YR 5/3 HAM-3750.1 Llanos B (4) 24.9 1,650 €35 5YR 2/3

Fig. 8 Sketch model of the Ventas de Zafarraya Fault with associated roll-over structure. Note three different deforma- tion styles with respect to the distance of the major fault plane and locality of the radar-lines in Fig. 6. Not to scale

palaeosol overlying a fine-grained sand and clay yielded The Jurassic/Quaternary fault scarp, including a 2-m-thick 14C ages of 7,370€60 years b.p. We interpret this breccia cataclastic zone, slid en-block downslope (Fig. 3). An as a result of the rupture that triggered the formation of intensely folded and deformed palaeosol on top of the 14 b.p. the intermediate colluvial wedge dated at the cemetery landslide yielded C-ages of 1,775€30 years , this b.p. outcrop as 2,315€30 years b.p. The anatomy of the entire horizon is covered by a recent soil (50€30 years ). fault zone with its minor faults and the internal structure Approximately 8 km NE of the VZF, a minor scarp of of the hanging wall is depicted in the model displayed in approx. 1–2 m height is developed along a 4-km-long Fig. 8, where also the effects of liquefaction and refilled normal E–W-trending fault (Llanos de la Dona, 0 0 vertical fractures are represented, which have historically 3701 401N, 0403 490W, Fig. 1), juxtaposing Jurassic been observed. limestones against Quaternary colluvial sediments. In East of Pilas de Algaida (36570432N, 04050852W), a contrast to the VZF, the hill behind the scarp consists of small village 2 km East of Ventas de Zafarraya, evidence intensely karstified Jurassic limestones of only ~50 m for a 1884-coseismic landslide have been found (Fig. 2). altitude. Almost no soil and vegetation cover is developed 920 Discussion and conclusions

The palaeoseismological investigations along this seg- ment of the VZF demonstrate that not only during, but also prior to the destructive 1884 earthquake, coseismic displacements occurred. Repeated colluvial wedges along the bases of fault scarps and their stratigraphic relation with wash-off sediments and palaeosols preserved within the half-graben prove evidence for earthquake-related faulting. Several of the most important deformations and secondary features, such as landslides and liquefaction, are related to the activity of the VZF. Palaeoseismic and radiocarbon data indicate at least two pre-1884 ruptures along the fault during the last 10 ka. If we take into account the relationship for normal faults by Wells and Coppersmith (1994), the estimated 1884-rupture length (16 km) is typical of earthquakes with M=6.4€0.6. Taking the relationship using the maximum vertical displacement for normal faults (Wells and Coppersmith 1994), which is max. 1.3 m at the Cortijo del Barranco, magnitude estimates are M=6.7€0.1. Considering afterslip, which Fig. 9 Comparison of the dating methods colluvial vs rockfall wedges (see text for an explanation) seems likely on hardrock–softrock fault scarps, and calculating with a reduced coseismic displacement of 1 m, we end up at M=6.6€0.1. Our calculations, after on the mountain flank, which could provide wash-off Wells and Coppersmith (1994), agree with the magnitude sediments as observed along the VZF. Sediment accu- proposed by Lpez-Arroyo et al. (1980) based on palaeo- mulation rates are higher along the VZF because the intensity maps ranging between 6.5 and 7. Palaeoseismic hinterland of the Llanos foot wall is of smaller extent, field data favour a magnitude of around 6.5 for the 1884 hence providing lesser or no wash-off sediments. Trench event. The two former events are apparently in the same logging allows identification of three coarse-grained order of M 6.5, with respect to maximum displacement clastic wedges intercalated by relict palaeosols relationships and wedge-thickness vs scarp-height rela- (Fig. 7b). The origin of the clastic wedges is interpreted tions (McCalpin 1996). differently, as along the VZF, as ‘rockfall wedges’, Our data yield supplementary information accord induced by coseismic shaking. Dating of intercalated earthquake recurrence intervals along the VZF of between palaeosols bracket the timing of the rockfalls. In contrast 2 and 3 ka for major earthquakes of M>6.5, under the to the VZF scarp, where we dated the faulting episodes, assumption of uniform return periods. Taking into account here the phase of seismic quiescence has been dated, i.e. that the total slip of the fault is ~1,500 m, and considering the soil formation intervals. Reddish palaeosols yield 14C that the fault system is probably post-Tortonian in age, it is ages from the base to top of 9,610€90, 2,960€45 and possible to estimate that the minimum mean slip rate of 1,650€35 years b.p. (Fig. 7b). Parts of the recent soil the fault is 0.17€0.03 mm/year. The Holocene slip rate column directly at the fault scarp are ~1,110 years old. was estimated at ~0.35€0.05 mm/year along the VZF, This soil was affected by slip-faulting, but is not overlain including s1 error of the 14C-data (Table 1). The smaller by boulders of the 1884-rock fall deposits. Those were Llanos de la Dona fault is characterized by Holocene slip deposited at some distance from the scarp toe due to rates of 0.25€0.03 mm/year. This is typical for a moderate downhill rolling of lose limestone debris and jumping activity rate along both faults. In contrast to this, Pelez across the scarp (see Fig. 9). Instabilities along steep Montilla et al. (2001) calculated a slip rate 0.125 mm/year topographic slopes, like slides, slumps and falls, can be for the long-term slip without palaeoseismic data. If we triggered by strong earthquakes with magnitudes of M>5 consider the Slemmons and DePolo (1986) relationship, (Keefer 1984). Other slope-failure effects such as frost or these data suggest a mean recurrence interval of exceptional precipitation events happen spontaneously. ~2,000 years along the Ventas de Zafarraya Fault, which Radiocarbon dating support earthquake triggering of the is therefore one of the main active faults in southern Spain. rockfalls during the palaeoearthquakes along the VZF, rather than fault reactivation along the Llanos de la Dona Acknowledgements We are thankful to both anonymous reviewers scarp, although slip along the fault plane is observed. The and to the associate editor for helpful and in-depth comments on the paper. The German Science Foundation, DFG-project Re 1361/3-1, clastic ‘rockfall wedges’ possibly provide a new palaeo- and the Spanish CICYT, projects BET2000-1490-C02-01 and seimic indicator. In conclusion, the three major events REN2001-3378/RIES, REN2001-2418C04-04/RIES, are thanked detected along the VZF can surprisingly also be found for financial support. 14C-dating was partly carried out at the along the Llanos scarp (Fig. 9). Leibniz Labor (Univ. of Kiel). 921 References Marco S, Agnon A, Ellenblum R, Eidelman A, Basson U, Boas A (1997) 817-year-old walls offset sinistrally 2.1 m by the Dead Alfaro P, Galindo-Zaldvar J, Jabaloy A, Lpez-Garrido AC, Sanz Sea transform, Israel. J Geodynam 24:11–20 de Galdeano C (2001) Evidence for the activity and paleoseis- Martnez-Daz JJ, Masana E, Hernndez-Enrile JL, Santanach P micity of the Padul fault (Betic Cordillera, southern Spain). (2001) Evidence for coseismic events of recurrent prehistoric Acta Geol Hisp 36:283–295 deformation along the Alhama de Murcia fault, southeastern Basson U, Enzel Y, Amit R, Ben-Avraham Z (1994) Detecting and Spain. Acta Geol Hisp 36:315–327 mapping recent faults with a ground penetrating radar in the Martnez-Martnez JM, Anazn JM (2002) Orthogonal extension in alluvial fans of the Arava valley, Israel. In: Proc 5th Conference the hinterland of the Gibraltar Arc (Betics, SE Spain). In: on Ground Water Penetrating Radar. Waterloo Centre for Rosenbaum G, Lister GS (eds) Reconstruction of the Alpine– Groundwater Research; Kitchener, Ontario, pp 777–788 Himalayan orogeny. J Virtual Explorer 8 (as pdf-file) Bell JW, Amelung F, King GCP (1997) Preliminary Late Quater- Masana E, Santanach P (eds) (2001) Paleoseismology in Spain. nary slip history of the Carboneras Fault, southeastern Spain. J Acta Geol Hisp 36 Geodynamics 24:51–66 Masana E, Martnez-Daz JJ, Hernndez-Enrile JL, Santanch P Buforn E, Udias A, Colombas MA (1988) Seismicity, source (2003) The Alhama de Murcia fault (SE Spain), a seismogenic mechanisms and tectonics of the Azores–Gibraltar plate fault in a diffuse plate boundary. Seismotectonic implications in boundary. Tectonophysics 152:89–118 the Ibero-Maghrebian region. J Geophys Res (in press) Cai J, McMechan GA, Fisher MA (1996) Application of ground- McCalpin JP (1996) Paleoseismology. International Geophysics penetrating radar to investigation of near-surface fault proper- Series vol 62, Academic Press, New York ties in the San Francisco Bay region. Bull Seism Soc Am Meschede M, Asprion U, Reicherter K (1997) Visualization of 86:1459–1470 tectonic structures in shallow-depth high-resolution ground- DeMets C, Gordon RG, Argus DF, Stein S (1990) Current plate penetrating radar (GPR) profiles. Terra Nova 9:167–170 motions. Geophys J Int 101:425–478 Morales J, Singh SK, Ordaz M (1996) Analysis of the Granada Douvill R (1906) La Pninsule Iberque. III(3):pp 1–175 (Spain) earthquake of 24 June, 1984 (M=5) with emphasis on Fernndez-Fernndez E, Campos J, Gonzlez-Lodeiro F (1992) seismic hazard in the Granada Basin. Tectonophysics 257:253– Estructuras extensionales en las rocas alpujrrides al E de 262 Mlaga (Sierra Tejeda, Cordilleras Bticas). Geogaceta 12:13– Morales J, Serrano I, Vidal F, Torcal F (1997) The depth of the 16 earthquake activity in the Central Betics (Southern Spain). Galindo-Zaldvar J, Gonzlez-Lodeiro F, Jabaloy A (1993) Stress Geophys Res Lett 24:3289–3292 and palaeostress in the Betic-Rif cordilleras (Miocene to the Muoz M, Udias A (1980) Estudio de los Parmetros y Serie de present). Tectonophysics 227:105–126 Rplicas del Terremoto de Andaluca del 25 de Diciembre de Galindo-Zaldvar J, Jabaloy A, Serrano I, Morales J, Gonzlez- 1884 y de la Sismicidad de la Regin Mlaga-Granada. In: Lodeiro F, Torcal F (1999) Recent and present-day stresses in Instituto Geografico Nacional (ed) El Terremoto de Andaluca the Granada Basin (Betic Cordilleras): example of a late de 1884, Madrid, pp 95–139 Miocene–present-day extensional basin in a convergent plate Muoz M, Udias A (1982) Historical development of Spain’s boundary. Tectonics 18:686–702 catalogue of earthquakes. Bull Seism Soc Am 72:1039–1042 Galindo-Zaldvar J, Ruano P, Jabaloy A, Lpez-Chicano M (2000) Ollero E, Garca JL (1984) Morfologa del sustrato y geometra del Kinematics of faults between Subbetic Units during the acufero aluvial del Polje de Zafarraya. Ist Congreso Espaol Miocene (central sector of the Betic Cordillera). CR Acad Sci Geol 4:307–315 Paris 331:811–816 Orueta and Duarte D (1885) Informe de los terremotos ocurridos en Galindo-Zaldvar J, Gil AJ, Borque MJ, Gonzlez-Lodeiro F, el sur de Espaa en diciembre de 1884 y enero de 1885. Tip Marn-Lechado C, Jabaloy A, Ruano P, Sanz de Galdeano C Fausto Muoz, Mlaga, pp 1–51 (2003) Active faulting in the internal zones of the central Betic Pelez Montilla JA, Sanz de Galdeano C, Lpez Casado C (2001) Cordillera (SE Spain). J Geodynam 36:239–250 Potencialidad ssmica de las Fallas de la Cuenca de Granada. Garca-Hernndez M, Lopez-Garrido AC, Rivas P, Sanz de In: Sanz de Galdeano C, Pelez Montilla JA Lpez-Garrido AC Galdeano C, Vera JA (1980) Mesozoic palaeogeographic (eds) La Cuenca de Granada. Spain, pp 158–174 evolution of the external zones of the Betic Cordillera. Geol Posadas AM, Vidal F, De Miguel F, Pea J, Alguacil G, Ibaez JM, Mijnb 59:155–168 Morales J (1993) Spatial–temporal analysis of a seismic swarm Herraiz M, De Vicente G, Lindo-aupari R, Giner J, Simn JL, using the principal component analysis. The Antequera swarm Gonzlez-Casado JM, Vadillo O, Rodrguez-Pascua MA, (Spain), 1989. J Geophys Res 98 B2:1923–1932 Cicundez JI, Casas A, Cabaas L, Rincn P, Corts AL, Reicherter K (2001) Paleoseismological advances in the Granada Ramrez M, Lucini M (2000) The recent (upper Miocene to Basin (Betic Cordilleras, southern Spain). Acta Geol Hisp Quaternary) and present tectonic stress distributions in the 36(3–4):267–281 (Paleoseismology of Spain volume) Iberian Peninsula. Tectonics 19:762–786 Reicherter K, Reiss S (2001) The Carboneras Fault Zone (south- Ibaez JM, Bottari C, Esquivel JA, Morales J, Alguacil AG (2003) eastern Spain) revisited with ground penetrating radar—Qua- Magnitude-intensity relations for instrumental and historical ternary structural styles from high-resolution images. Nether J (IX–XIX century) earthquakes in south Spain. Tectonical and Earth Sci/Geol Mijnbouw 80:129–138 seismic hazard implications. Bull Seism Soc Am ( in press) Reicherter K, Jabaloy A., Galindo-Zaldvar J, Ruano P (1999) Keefer DK (1984) Landslides caused by earthquakes. Geol Soc Am Active faults in the Granada Depression and Zafarraya areas Bull 95:406–421 (Betic Cordilleras). Geogaceta 27:193–196 Kilian W (1889) Mission d’ Andalousie. Mem Ac Soc 30:1–582 Reiss S, Reicherter K, Reuther CD (2003) Visualization and Lonergan L, Platt JP, Gallagher L (1994) The internal–external characterization of active normal faults and associated sedi- zone boundary in the eastern Betic Cordillera, SE Spain. J mentary structures by high-resolution GPR. J Geol Soc Lond Struct Geol 16:175–188 Spec Publ 211:247–255 Lpez-Arroyo A, Martn-Martn AJ, Mezcua Rodrguez J (1980) Saccorotti G, Carmona E, Ibez JM, del Pezzo E (2001) Spatial Terremoto de Andaluca. Influencia en sus efectos de las characterization of Agron, southern Spain, 1988–1989 seismic condiciones del terreno y del tipo de construccin. In: Instituto series. Phys Earth Planet Interior 3983:1–17 Geografico Nacional (ed) El Terremoto de Andaluca del 25 de Sandmeier KJ (2000) ReflexW version 2.1.2, user manual. diciembre de 1884. Madrid Karlsruhe, Germany Lpez-Casado C, Molina-Palacios S, Delgado J, Pelez JA (2000) Sanz de Galdeano C (1985) La fracturacin del borde sur de la Attenuation of intensity with epicentral distance in the Iberian Depresin de Granada (discusin acerca del ecenario del Peninsula. Bull Seism Soc Am 90:34–47 terremoto del 25-XII-1884). Estud Geol 41:59–68 922 Serrano I (1999) Distribucin espacial de la sismicidad en las Taramelli T, Mercalli G (1886) I terrimoti andalusi cominciati il 25 Cordilleras Bticas-Mar de Alborn. PhD Thesis, University of dicembre 1884. Atti de la R Accad dei Lincei 83 Roma Granada Udas A, Muoz D (1979) The Andalusian earthquake of 25 Silva, PG, Goy JL, Zazo C, Lario J, Bardaj T (1997) Paleoseismic December 1884. Tectonophysics 53:291–297 indications along ‘aseismic’ fault segments in the Guadalentn Vidal F (1986) Sismotectnica de la regin Btica-Mar de Alborn. Depression (SE Spain). J Geodynam 24:105–115 PhD Thesis, University of Granada Slemmons DB, DePolo CM (1986) Evaluation of active faulting Wallace RE (ed) (1986) Active tectonics. Studies in geophysics. and related hazards. In: Wallace RE (ed) Active tectonics. National Academy of Sciences, Washington, DC Studies in geophysics. National Academy of Sciences, Wash- Wells DL, Coppersmith KL (1994) New empirical relationships ington, DC, pp 45–62 among magnitude, rupture length, rupture width, rupture area, Stuiver M, Polach HA (1977) Discussion: reporting of 14C data. and surface displacement. Bull Seismol Soc Am 84:974–1002 Radiocarbon 19(3):355–563