Fractal characteristics of active normal faults

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ELSEVIER Tectonophysics 308 (1999) 263274www.elsevier.com/locate/tecto

Fractal characteristics of active normal faults:an example of the eastern Gulf of Corinth, Greece

Ioannis K. Koukouvelas a,, Marios Asimakopoulos a, Theodoros T. Doutsos a

a Department of Geology, PhysicalMarine Geology and Geodynamics Division, University of Patras, 26 500 Patras, Greece

Received 27 March 1998; accepted 22 October 1998

Abstract

We present a model proposing the evolution of segmented normal faults in a currently extended area, allowing an

explanation of strong earthquakes hosted by short faults. Active normal faults accommodating the current extension in the

Gulf of Corinth result from the linkage of smaller-component faults. Well exposed fault zones in the Sofiko range are

arranged as pairs of graben-bounding faults and thus our structural analysis has implications for the evolution of active

normal faults as well as graben evolution. A basal strip of fresh bedrock at the base of fault scarps suggests continuous

seismic or aseismic creep. Thus the structural analysis of component faults, that show a power-law length distribution,

describes an evolved fault zone. Of particular interest is that faulting in this region is self similar between limits.

Distribution is characterized by a fractal dimension of D 1, and the limits in our study are between 10 m (mapping

resolution) and double the maximum displacement of each fault zone. Component segments of any compartmentalized

fault show a length-to-maximum displacement ratio of two. Basin architecture and structural analysis suggest that thenucleation points of faults are detectable over the entire evolution of the fault zone. All analyzed faults evolved by an

independent nucleation model. Morphotectonic and kinematic data, as well as fractal dimension of trace length population

plots, all suggest that fault zones defining north- and south-dipping conjugates are active at least over the late stages of

basin evolution. Although this study was focused on a relatively small area, this pattern of fault growth appears to be

applicable to the entire fault population in the Gulf of Corinth and is thus an important model for normal faults. 1999

Elsevier Science B.V. All rights reserved.

Keywords: fault linkage; faults nucleation points; basins; fractal analysis; Greece

1. Introduction

Since the first recognition that fault arrays showa fractal geometry (Tchalenko, 1970) recent workhas demonstrated that fractal properties of fault areimportant for understanding fault formation, growthand strain. In the simplest sense, fractal properties of

Corresponding author: Fax: C30 61 994485; E-mail:

[email protected]

a fault array suggest that geometrical properties arescale-independent between fractal limits. Thus in arecent spate of publications, scaling properties haveattracted much attention, and this rapidly growinginterest in the distribution of fault attributes such aslength, displacement etc., is based on the inferencethat self-similarity over a wide range of observa-

tions suggests that interpolation and extrapolationof fault populations out of the scale of observa-tion may be feasible (Childs et al., 1990; Marrett

0040-1951/99/$ see front matter 1999 Elsevier Science B.V. All rights reserved.

P I I : S 0 0 4 0 - 1 9 5 1 ( 9 9 ) 0 0 0 8 7 - 6


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264 I.K. Koukouvelas et al. / Tectonophysics 308 (1999) 263274

and Allmendinger, 1991; Cowie and Scholz, 1992;Needham et al., 1996; Watterson et al., 1996; Dout-sos and Koukouvelas, 1998). Of particular interestis the effect of the propagation or the linkage of

fault segments on the scaling properties (Carter andWinter, 1995; Dawers and Anders, 1995; Cladouhosand Marrett, 1996; Cartwright et al., 1996; Wojtal,1996). Linkage of faults is a critical mechanismfor fault propagation in the Hellenic peninsula, af-fecting both basin evolution and hazard assessment(Gawthorpe and Hurst, 1993; Koukouvelas et al.,1996; Koukouvelas and Doutsos, 1996).

Although the description of fault population interms of fractals is a useful tool of structural anal-ysis, geologists remain skeptical about the value offractals due to the small total database. The smalldatabase is due to the difficulty of collecting high-quality fault geometry data from deformed rocks.

Our contribution is an example of an activelyextended and excellently exposed onshore basin, thesouth flank of the Corinthian Gulf. In this areawe carried out a three-year program including fieldmapping, mesoscopic analysis and interpretation ofaerial photography.

In order to elicit and understand the physical pro-cesses during fault growth in an active basin, wepresent analyses of an array of active normal faults

from the southern half of a continental rift, andcharacterize the relationships between fault dimen-sions and displacements. We apply fractal measuresto fault traces with lengths between 10 m and 104

m and fault displacements with throws between 1 mand 600 m. Since fault segmentation is important, weaddress the implication of fault overlap zones withinthe actively extending east Corinthian Gulf and thesignificance of segmentation on the scaling proper-ties. Finally, a series of four well exposed basins is

shown to have developed by variably scaled overlap

relationships.

2. Study area

The eastern Gulf of Corinth has been selectedfor analysis because the Neogene sediments are

well exposed, due to the rapid uplift of the Pelo-ponnesus (Keraudren and Keraudren, 1987; Collieret al., 1992). Furthermore, the eastern termination

of the gulf is a structurally important area overthe whole Greek peninsula (Fig. 1b) because of itshigh earthquake activity (Fig. 1a) (Koukouvelas andDoutsos, 1996). The tectonic deformation of the area

is fairly well described (Roberts and Koukouvelas,1996). Active deformation in the Gulf of Corinth,which is prone to strong extensional earthquakes,is marked by large normal faults (Fig. 1c) that af-fect basin architecture, morphology and present-daybathymetry of the gulf (Doutsos and Piper, 1990).Morphotectonic characteristics of major boundaryfaults are defined by half dome geometry (footwallblock) and half spoon basins (Roberts and Koukou-velas, 1996; Roberts, 1996). Sequence stratigraphy,age determinations on marine terraces and tectonicsall suggest the critical role of fault activity for thebasin evolution that in turn is modified by sea levelfluctuations (Dia et al., 1997).

The Gulf of Corinth is composed of an Al-pidic calcareous basement and covered by PlioceneQuaternary lacustrine, marine and terrestrial sedi-mentary rocks. One of the most important featuresdeveloped during the Alpine orogeny over southernGreece was a west-verging nappe system (Temple,1968) that is now exposed as a roughly sinusoidalfold and thrust belt. Later faults striking NNWSSEand ENEWSW, combined with the effects of the

alpine nappe system, strongly influenced the fracturepattern of the Peloponnesus (Doutsos et al., 1988;Koukouvelas et al., 1996), that is now extending in aNS direction (Davies et al., 1997).

3. Data collection

The active faults on land (Fig. 2) were selectedinitially by interpretation of aerial photography on ascale of 1 : 33,000 supplemented by geological maps

(IGME maps Corinthos, Nemea, and Sofiko), andpreviously published syntheses (Doutsos and Piper,1990; Collier, 1990; Collier et al., 1992; Roberts andKoukouvelas, 1996; Armijo et al., 1996). However,the final detailed maps (Fig. 1c and Fig. 2) werecompiled by interpretation of aerial photography on ascale of 1 : 16,000. Geological interpretation of aerialphotographs has been most important for recognizingfaults. Data were interpreted separately by three indi-viduals to minimize any bias due to individual vari-


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I.K. Koukouvelas et al. / Tectonophysics 308 (1999) 263274 265

Fig. 1. (a) Map showing major normal faults in the Gulf of Corinth, basins and historical seismicity (from Koukouvelas and Doutsos,

1996, with modifications). (b) Map showing the position of the study area in respect to the Aegean province. Major grabens over the

entire peninsula following Doutsos and Piper (1990). (c) Simplified geological map of the east part of Gulf of Corinth showing the main

fault zones and sediment distribution. Rectangle is showing the location of Fig. 3 in the Sofiko Range.

ation. Finally, for the synthesis of the map in Fig. 3,we carried out detailed field mapping and mesoscopicanalysis on a scale of 1 : 5000. The certainty of a faultrefers to the reliability of both the reference plane(fault scarp) and the reference line (terrace edges or

lithofacies boundaries) (Fig. 2, cross-section). Faultsbeneath the sea were not used because the data uni-formity was not as reliable as that of the land faults.

Geometric and kinematic information on 142faults, defined as discrete structures with isolatedtips at both ends, was obtained by mapping at ascale of 1 : 5000 over the Sofiko Range (Fig. 1c) withestimated accuracy of our fault trace length measure-

ments of 25 m. For estimating throws we used bothfield outcrops and borehole data and we estimate thatthe accuracy of our throw measurements is 20 m.


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Fig. 2. The fault pattern of the east Gulf of Corinth. Cross-section shows the internal deformation of the graben while displacement on

each fault is also shown. Rectangle is showing the location of map in Fig. 3.

Maximum displacements on the mapped faults range

from 1 m to 602 m, and their trace lengths rangefrom 15 m to 9690 m. Faults in the Sofiko Range

are all segmented in geometric terms (dePolo et al.,1991) and enable us to recognize individual faultsand components. We define as individual faults por-tions of the fault including short faults with nearlyparallel strike, and as components the short faultsthat constitute the individual fault. We mapped com-ponent faults as continuous fault traces at the surface(Fig. 3). Faults in the Sofiko Range have separated

into 3 to 10 individual faults with corresponding

lengths ranging from 300 m to 1475 m, componentsegments trace ranges from hundred to ten meters inlength. Overlapping relationships of fault segmentsare of two types: those physically joined and thosewhose surface traces are kinematically but not phys-ically linked.

4. Fault geometry

Detailed mapping at a scale of 1 : 5000 enabled usto show that major north-dipping faults are often ac-companied by intersecting opposedly dipping faultsor fault arrays or conjugates (Fig. 3). We concen-trated our analysis on two examples exposed in thecentral part of the Sofiko Range (Fig. 1c and Fig. 2).There are two types of conjugates: those with X-typein map view and those with parallel fault strands.X-type conjugates can be physically joined or in-dicate a direct kinematic relationship between two

faults that are otherwise isolated on the map, demon-strating that one is the continuation of the other. Thistype of fault is termed a soft-linked fault (terminol-ogy by Walsh and Watterson, 1991). Parallel faultstrands with opposing dips border faults that interactin an antithetic interference zone (terminology ofGawthorpe and Hurst, 1993).


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Fig. 3. Detailed fault trace mapping of the fracture pattern in the Sofiko Range. In the figure is also shown detailed morphology of the

Nterias area as well as slip linear plots. Thick arrows on the map show the direction of extension in the area, stippled areas indicate

corresponds to Tripolitsa zone limestones.


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4.1. The Nterias faults zone

The Nterias fault zone consists of two intersect-ing ENE-striking faults with opposing dips that de-

fine two isolated basins (Fig. 3, basins I and II).These faults are typically X-shaped in map view andY-shaped in cross-section (Fig. 3, cross-section XX),and show asymmetry due to the displacement differ-ences on north-dipping faults (B1 and B2 in Fig. 3)compared with the south-dipping faults (A1 and A2in Fig. 3). The maximum throw (170 m) occurs nearthe eastern third of the north-dipping B2 fault (basinII), while the south-dipping fault has a maximumthrow (140 m) on the western third of the fault A1(basin I).

Faults are characterized by a 3- to 4-m-high faultscarp in limestone. A discontinuously present 3- to10-cm-high basal strip of fresh limestone indicatesrecent movement on the faults, suggesting episodicand=or long-term slip along these faults. Eroded faultscarps commonly range between 20 and 80 m high.Slickenside lineations on the fault planes indicate thatthe direction of the least compression, 3, is NNWSSE (slip linear plot in Fig. 3, plot a). Cataclasitesand flowstones up to 15 m thick were mapped at theeastern termination of the Nterias fault zone. The ex-istence of flowstones and the lacustrine marls in basin

II suggest a syntectonic evolution of the sedimentarybasin at the level of the phreatic horizon.

The intersection area where the Nterias faults A1,A2, B1 and B2 approach each other is characterizedby important tectonic and morphologic data (Fig. 3).Structurally the intersection is defined by the over-lapping tips of four faults that compose the Nteriasfault zone. The absence of sediments indicate thatthis area represents an intrabasin salience. The dis-tance between the tips of these faults is closer than

40 m and the faults A1, B1 and B2 are occasionally

joined. In this area the curvature of fault traces andthe displacement reduction toward the tip of eachfault towards the intrabasin salience (Fig. 3) indi-cates strong interaction of faults (see also Nicol etal., 1995).

The drainage pattern developed in the presence ofactive tectonic deformation and this is reflected in theaxial (basin parallel) and transverse (basin perpen-dicular) pattern of stream flows. The main transverserivers of the Sofiko Range are characterized by steep

gorges 120 m140 m deep, suggesting that the rect-angular pattern of rivers was incised through upliftedfootwalls (Fig. 3, inset). More careful analysis indi-cates that tilting of rivers is taking place near fault

tips of individual faults where the relief is reduced.In the same area, significant erosional retreat is pro-ceeding in an EW direction, reversing the axial flowof rivers and producing two wind gaps. Thus in thesalient area the displacement reduction is followedby erosion intensification (Fig. 3, point PJF).

All the above-mentioned structural and morpho-logical data of the linkage area suggest that north-and south-dipping faults typically appear to be partof a multisegmented soft-linked system. Thus weargue that both north- and south-dipping faults areactive synchronously on a geological time scale.

Quantitative and qualitative analysis of the inter-nal compartmentalization of these faults is furtheranalyzed since internal geometry is important for un-derstanding the evolution of the entire zone. Faultsin the Nterias area reveal a segmented trace geome-try in map view with individual faults stepping andoverlapping. A systematic distribution of short-com-ponent segments at the tip areas of individual faults(Fig. 3), with non-systematic distribution of longercomponents along the rest of the fault, suggests thatindividual faults interact at overlapping tips. In par-

ticular the north-dipping fault (B1, B2 in Fig. 3) thatis separated into 52 components, is organized intoten individual faults. The components are in generalleft-stepping, ranging in length from 10 m to 350 m.Furthermore, the south-dipping fault that is separatedinto 29 components is organized into four individualfaults, ranging in length from 15 to 300 m.

The populations of component faults in the Nte-rias area can be visualized with fault trace lengthpopulation plots. Fig. 4 shows that the Nterias faults(plots a and b) are characterized by a systematic

increase in the number of measured fault traces withdecreasing trace length. The central part of each plotdefines a straight line with steep slope, indicatinga power-law relationship between the trace lengthand cumulative number. The straight lines span overtwo orders of magnitude and have slopes between

1.00 and1.03 with R2 0.97 and 0.80, respectively

(Fig. 4a,b). The standard deviation (SD) of the A1,A2 fault components is 80.4 m (for location of faultssee Fig. 3, and Fig. 4a), and the SD of the B1, B2


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Fig. 4. Number of faults as a function of length for the Nterias (a, b) and Agios Ioannis (c, d) fault zones (for more details see text).

fault components is 98.2 m (for location of faultssee Fig. 3 and Fig. 4b). The slopes of the upper partof the distribution show a truncation effect (e.g.,Jackson and Sanderson, 1992) for faults with a small

length. That is an unavoidable sampling bias due

to slope-wash debris, alluvial deposits covering theoverlapping tips of the larger faults and vegetation.Furthermore, it is unlikely that faults with lengths


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The maximum throw on the north-dipping B3fault (360 m) occurs near the western third of thefault while the maximum throw on the south-dippingA3 fault (160 m) occurs near the eastern third

of the fault. Faults A3 and B3 are overlapping attheir tips in the center of the Agios Ioannis graben(Fig. 3). The overlap zone is 860 m long by 500m wide on the footwall of the faults A3 and B3,constituting an antithetic interference zone (Fig. 3,AIZ). Both basins IV and V progressively narrowtowards the interference zone.

The maximum thickness of sediments in thesebasins is observed close to the eastern third of faultA3 (80 m) and close to the western third of fault B3(60 m). Faults A3 and B3 are characterized by 2-to 15-m-high limestone scarps. Eroded fault scarpsin the Agios Ioannis fault zone range between 20 and140 m high. The basin architecture fits well with thestress analysis on the fault scarps with the directionof least compression 3, NNWSSE, determined byslickenside lineations on the fault planes (Fig. 3, slip

linear plot b). In addition, the existence of a 6- to10-cm-high basal strip of fresh limestone suggestsepisodic and=or long-term slip along these faults. Allthese data suggest that although basins IV and Vare isolated through geological time, they evolvedsynchronously.

Both faults are similar in terms of compartmen-talization with faults in the Nterias fault zone. In

particular the north-dipping B3 fault is divided into46 components organized into eight individual faults.These components range in length from 25 m to 500m. Furthermore, the south-dipping A3 fault is di-vided into 42 components ranging in length from 15m to 650 m, organized into three individual faults.

The western termination of the Agios Ioannisbasin is associated with three overlapping hanging-wall basins (Fig. 3, basins VI, VII and VIII). Each

of these basins exhibits a full graben form, withintergraben spacing diminishing towards the north-dipping B4 fault. The separation of the three basinsis important in selecting the data that are plotted onthe length population plots (Fig. 4c,d).

Trace length population plots of component seg-ments in the Agios Ioannis area (Fig. 4c,d) showsimilar geometry with plots in the Nterias area. Thusfrom the straight lines of both plots we calculateslopes of 1.13 to 1.02 with R2 0.87 and 0.9,

respectively. The standard deviation (SD) of the A3fault components is 113 m (for location of faultssee Fig. 3 and Fig. 4c), and the SD of the B3 faultcomponents is 110.2 m (for location of faults see

Fig. 3 and Fig. 4d). The upper and lower parts ofthe plots also show truncation and censoring effects,but larger maximum trace lengths equal to 650 msuggest a different characteristic scale than the scaleat Nterias. This is interpreted as a fundamental popu-lation characteristic comparable with the increase ofmaximum throw along the Agios Ioannis fault zone.

5. Ld relationships in the Sofiko range faults

The Sofiko range (Fig. 1) provides an excellentarea for analysis of a simple population L d dataset of maximum displacement .d/ and trace length.L/ for use in estimating the effect of segmenta-tion on the fault scaling properties (Fig. 5). Thedata on 142 extensional faults that can be definedas discrete structures with isolated tips at both endspresent a large compilation in a single area overwhich the lithological conditions are relatively uni-form. As mentioned above, the majority of the faultsare arranged as pairs of graben-bounding faults. Thepreservation of limestone fault scarps at the surface

is exceptionally good. The quality of the exposedfaults combined with excellent exposure of hanging-wall and footwall stratigraphy allow accurate deter-mination of fault throw to be made along strike.

The data set for 142 faults is plotted as a plotof maximum displacement .d/ vs. trace length .L/(Fig. 5a) and as a loglog plot (Fig. 5b). In the loglog plot, the data fit well to a straight line with a slopeof 1.092. The fitted line is similar to the slope of fittedlines published by Cowie and Scholz (1992); Dawersand Anders, 1995), and Clark and Cox (1996). Fur-

thermore, combining our plots with previously pub-lished data by Gillespie et al. (1992), and Cowie andScholz (1992) (Fig. 5b), the Sofiko Range faults areclustered (black diamonds on the plot of Fig. 5b)in the middle of the diagram on the line labeled

D 101 . is defined as the ratio of displace-ment to fault length [d=L], see Cowie and Scholz,

1992). Fig. 5a and c show also important scatter in dand L, that is expected in dL plots (see discussionin Marrett and Allmendinger, 1991). Further analy-


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Fig. 5. (a) Displacement against length plot of the Sofiko area. (b) Loglog plot of the displacement against length in relation with

universal data. Black diamonds correspond to our data, while the outline presents data by Cowie and Scholz (1992b) and Gillespie et al.

(1992). (c) Plot of ascending ordering of displacement vs. trace length. Note the systematically higher values of displacement in larger

faults than in shorter faults.

sis of scatter shows a general increase of d with L.

This increase can be described with a straight line

with a slope of 3.5 degrees and a line of the formd D 0:061L 19:13. The coefficient of correlationof the data with the straight line is 0.68 (Fig. 5c).

6. Strain in relation to fractal dimensions

The total strain accommodated by faults can becalculated between the length limits of the SofikoRange following the method of Scholz and Cowie

(1990). This allows the calculation of total strain

over the fault population from a power-law relation-

ship. The trace length population plot indicates thatthe fault of the Sofiko area obeys a power-law sizedistribution with:

N.L/ D cLD (1)

The integration of Eq. 1 over the distribution of

the fault population indicates the contribution of allfaults in the deformation:Z

d N.L/

d LD Ld L D

cD

1 DL1D (2)


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The sum of fault moment .Mg/ for small faults,that means faults with trace length smaller than thebrittle crust thickness .W/, L < W and d/ L is:

NXnD1

Mng D

cD

3 DL3D

(3)

Eq. 3 is valid for the Sofiko area since the faultstrace lengths are less than the 12 km thick seismo-genic layer of the east Gulf of Corinth (Jackson etal., 1982), and is equal to that predicted from Fig. 5b.Thus from the plot of Scholz and Cowie (1990: theirfig. 3) we estimate that 84% of the total strain isaccommodated on faults longer than 4 km.

7. Discussion

Extension within the Gulf of Corinth is accom-plished by a dense pattern of small faults (Fig. 2)and by major fault zones (Fig. 1b). However, majorfault zones are characterized by complex fault zonegeometry, while erosion and cultivation produce gen-tly dipping scarps obscuring the structure. Instead oftrying to study the major faults, we selected an areathat is excellently exposed with low vegetation andlimited cultivation. Active faults in the Sofiko Rangeconsist of echelon segments and offer excellent cases

for studying fault propagation models.Strain accommodation in the Sofiko Range is tak-

ing part in multisegmented conjugate normal faultsthat define active sedimentary basins. Trace lengthpopulation plots in the Sofiko Range indicate that ac-tive faults obey a power-law size-distribution. Basedon the estimation of D 1 we characterize all ana-lyzed faults acting as single faults. The estimation of

D 1 is both valid for main fault sets and conjugatefaults sets suggesting thus the synchronous evolutionof both fault sets.

As the fault population follows a power-law dis-tribution, we calculate that seventeen faults, largerthan 4 km in length, take up 84% of the strainaccommodated in that area. Furthermore, the frac-tal dimension of D 1 implies unstable criticalcoalescence of fault segments and suggests concen-tration of seismic activity on these faults (e.g., Main,1988, 1990). That these faults are seismically activeis supported strongly by the high seismicity in thearea (Delibasis, 1980) (Fig. 1a), the basal strip of

fresh limestone, the basin architecture and drainagepattern.

The maximum trace length of a fault segment ina fault is related with the maximum displacement

along this fault. In all cases, the ratio of segmentlength to maximum displacement is expressed by afactor of 2. This ratio indicates that fault segmentsin a fault maintain a degree of freedom, or in otherwords the entire fault is growing under a process ofindependent nucleation. This independent nucleationmodel has been used by Anders and Schlische (1994)for the analysis of large normal faults in the U.S.and on that basis the small faults that we havestudied may represent initial stages of large faults.This style of deformation is also detectable in theseismogenic fault ruptured during the 1995 Egionearthquakes (western Gulf of Corinth) where faultsegments maintained their characteristics althoughthe earthquake ruptured all segments. In addition,the concentration of maximum sediment thicknessin the area of maximum fault displacement, that isthe nucleation point of the fault (sensu Dawers andAnders, 1995), indicates that this area of the faultremains detectable over the entire fault life.

The slip-to-length ratio for 142 isolated faults overthe Sofiko Range can vary by a factor of 3.5 for thefault data observed. In Fig. 5c, short faults (250 m

1000 m) appear to have a systematically lower d=Lratio with less scatter than larger faults. We suggestthat this difference indicates that small faults of thearea, even segmented, grew as isolated fractures andthat larger faults are not characterized by a simpledisplacement pattern due to complex coalescence ofsegments. Another explanation is that large faults rup-ture stronger rock on average and thus displacementincreases are preferred (a similar explanation is alsoproposed by Cowie and Scholz, 1992).

The 10-cm-high basal strip zone on the 4- to 5-km-

long faults that we studied is of similar height as thatresulting from the Patras 1989 .ML D 5:0R/ earth-quakes (Doutsos and Poulimenos, 1992) where 4.8km of fault was ruptured, and from the Egion 1995.ML D 6:1R/ earthquakes (Koukouvelas and Dout-sos, 1996) where 12.1 km was ruptured. On the Sofikofaults events of ML 5:0R (Delibasis, 1980) are

well known (Fig. 1a). Based on these data, we spec-ulate that the analyzed Sofiko faults can host strongearthquakes (with a range of 5:0 < ML < 6:0/.


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8. Conclusions

The structural analysis of the Sofiko area is acase study for the estimation of the sensitivity of the

detailed mapping, the implication of faults segmen-tation and the importance of one-dimensional fractalanalysis over highly segmented faults.

(1) Fault fractal analysis in an active fault can beonly used if the fault length data base range fromthe limit of the mesoscopic analysis (i.e. length 10m) to the equivalent length in meters of twice themaximum throw of the fault.

(2) One-dimensional fractal analysis of active nor-mal faults can be used as a tool to estimate the ca-pability of a fault to host strong earthquakes in areascharacterized by the absence of historical seismicity.

(3) Short faults in the Gulf of Corinth (tracelength 1000 m) are characterized bycomplex coalescence of fault segments.

(4) Coalescence of fault segments in the Gulf ofCorinth is very important in terms of hazard analysis.Segment linkage organizes faults short in length ascapable to produce strong earthquakes.

Acknowledgements

We thank editing assistance of S. Pavlides, andincisive reviews by P. Dimitriou, D.J.W. Piper and ananonymous reviewer that greatly improved the paper.

References

Anders, M.H., Schlische, R.W., 1994. Overlapping faults, intra-

basin highs, and the growth of normal faults. J. Geol. 102,

165180.

Armijo, R., Meyer, B., King, G.C.P., Rigo, A., Papanastasiou,

D., 1996. Quaternary evolution of the Corinth Rift and itsimplications for the Late Cenozoic evolution of the Aegean.

Geophys. J. Int. 126, 1153.

Carter, K., Winter, C., 1995. Fractal nature and scaling of normal

faults in the Espanola Basin, Rio Grande rift, New Mexico:

implications for fault growth and brittle strain. J. Struct. Geol.

17, 863873.

Cartwright, J., Mansfield, C., Trudgill, B., 1996. The growth of

normal fault by segment linkage. In: Buchanan, P., Nieuwland,

D., (Eds.), Modern Developments in Structural Interpretation,

Validation and Modelling. Geol. Soc. London Spec. Publ. 99,

163177.

Childs, C., Walsh, J., Watterson, J., 1990. A method for esti-

mation of the density of fault displacements below the limits

of seismic resolution in reservoir formations. In: North Sea

Oil and Gas Reservoirs, II. Graham and Trotman, London, pp.

309318.Cladouhos, T.T., Marrett, R., 1996. Are fault growth and link-

age models consistent with power-law distributions of fault

lengths? J. Struct. Geol. 18, 281293.

Clark, R., Cox, S., 1996. A modern regression approach to

determining fault displacement-length scaling relationships. J.

Struct. Geol. 18, 147152.

Collier, R.E.L., 1990. Eustatic and tectonic controls upon Qua-

ternary coastal sedimentation in the Corinth Basin, Greece. J.

Geol. Soc. London 147, 301314.

Collier, R.E.L., Leeder, M.R., Rowe, P.J., Atkinson, T.C., 1992.

U-series dating and tectonic uplift of upper Pleistocene ma-

rine sediments from the Corinth and Megara Basins, Greece.

Tectonics 11 (6), 11591167.Cowie, P.A., Scholz, C.H., 1992. Displacementlength scaling

relationships for faults: data synthesis and discussion. J. Struct.

Geol. 14, 11491156.

Davies, R., England, P., Parsons, B., Billiris, H., Paradisis, D.,

Veis, G., 1997. Geodetic strain of Greece in the interval 1892

1992. J. Geophys. Res. 102 (B11), 2457124588.

Dawers, N.H., Anders, M.H., 1995. Displacementlength scaling

and fault linkage. J. Struct. Geol. 17, 607614.

Delibasis, N., 1980. A microearthquake activity in the Corinthian

region (Dec. 1976Jan. 1977) and its tectonic significance (in

Greek, with English abstr.) Greek Min. Metall. Ann. 9 (46),

2131.

dePolo, G., Clark, D., Slemmons, D., Ramelli, A., 1991. Histori-

cal surface faulting in the Basin and Range province, WesternNorth America: implication for fault segmentation. J. Struct.

Geol. 13, 123136.

Dia, A.N., Cohen, A.S., ONions, R.K., Jackson, J.A., 1997.

Rates of uplift investigated through 230Th dating in the Gulf of

Corinth (Greece). Chem. Geol. 138, 171184.

Doutsos, T., Koukouvelas, I., 1998. Fractal analysis of normal

faults in northwestern Aegean area, Greece. J. Geodyn. 26,

197216.

Doutsos, T., Piper, D.J.W., 1990. Listric faulting, sedimentation

and morphological evolution of the Quaternary eastern Corinth

rift, Greece: first stages of continental rifting. Bull. Geol. Soc.

Am. 102, 812829.

Doutsos, T., Poulimenos, G., 1992. Geometry and kinematics

of active faults and their seismotectonic significance in the

western CorinthPatras rift (Greece). J. Struct. Geol. 14, 689

699.

Doutsos, T., Kontopoulos, N., Poulimenos, G., 1988. The

CorinthPatras rift as the initial stage of continental frag-

mentation behind an active island arc (Greece). Basin Res. 1,

177190.

Gawthorpe, R.L., Hurst, J.M., 1993. Transfer zones in exten-

sional basins: their structural style and influence on drainage

development and stratigraphy. J. Geol. Soc. London 150,

11371152.


12/12


Gillespie, P.A., Walsh, J.J., Watterson, J., 1992. Limitations of

dimension and displacement data from single faults and the

consequences for data analysis and interpretation. J. Struct.

Geol. 14, 11571172.

IGME, Institute of Geological and Mineral Exploration, Geolog-

ical map sheets Korinthos, Sofiko, Nemea 1 : 50,000, Athens.Jackson, J.A., Sanderson, D.J., 1992. Scaling of fault displace-

ments from the BadajozCordoba shear zone, SW Spain.

Tectonophysics 210, 179190.

Jackson, J.A., Gagnepain, J., Houseman, G., King, G., Papadim-

itriou, P., Soufleris, C., Vireux, J., 1982. Seismicity and the ge-

omorphological development of the Gulf of Corinth (Greece):

the Corinth earthquakes of February and March 1981. Earth

Planet. Sci. Lett. 57, 377397.

Keraudren, B., Keraudren, D., 1987. The terraces of Corinth

(Greece) a detailed record of eustatic sea-level variations

during the last 500,000 years. Mar. Geol. 77, 99107.

Koukouvelas, I., Doutsos, T., 1996. Implication of structural

segmentation during earthquakes: the 1995 Egion earthquakes,

Gulf of Corinth, Greece. J. Struct. Geol. 18, 13811388.

Koukouvelas, I., Mpresiakas, A., Sokos, E., Doutsos, T., 1996.

The tectonic setting and earthquake ground hazards of the

1993 Pyrgos earthquake, Peloponnese, Greece. J. Geol. Soc.

London 152, 3949.

Main, I.G., 1988. Prediction of failure times in the earth for a

time-varying stress. Geophys. J. 92, 455464.

Main, I.G., 1990. Quasi-static modelling of stress histories dur-

ing the earthquake frequencymagnitude distribution. Geo-

phys. J. Int. 102, 195204.

Marrett, R., Allmendinger, R., 1991. Estimates of strain due to

brittle faulting: sampling of fault populations. J. Struct. Geol.

13, 735738.

Needham, D.T., Yielding, G., Fox, R., 1996. Fault population

description and prediction using examples from the offshore

U.K. J. Struct. Geol. 18, 155167.

Nicol, A., Walsh, J., Watterson, J., Bretan, P., 1995. Three-

dimensional geometry and growth of conjugate normal faults.J. Struct. Geol. 17, 847862.

Roberts, G.P., 1996. Noncharacteristic normal faulting surface

ruptures from the Gulf of Corinth, Greece. J. Geophys. Res.

101, 2525525267.

Roberts, G.P., Koukouvelas, I., 1996. Structural and seismo-

logical segmentation of the Gulf of Corinth fault system:

implications for models of fault growth. Ann. Geophys. 23,

619646.

Scholz, C.H., Cowie, P.A., 1990. Determination of total strain

from faulting using slip measurements. Nature 346, 837839.

Tchalenko, J.S., 1970. Similarities between shear zones of differ-

ent magnitudes. Bull. Geol. Soc. Am. 81, 16251640.

Temple, P.G., 1968. Mechanics of large-scale gravity sliding in

the Greek Peloponnesos. Bull. Geol. Soc. Am. 79, 687700.

Walsh, J., Watterson, J., 1991. Geometric and kinematic coher-

ence and scale effects in normal fault systems. In: Roberts, A.,

Yielding, G., Freeman, B. (Eds.), The Geometry of Normal

Faults. Geol. Soc. London Spec. Publ. 56, 193203.

Watterson, J., Walsh, J.J., Gillespie, P.A., Easton, S., 1996.

Scaling systematics of fault sizes on a large-scale range fault

map. J. Struct. Geol. 18, 199214.

Wojtal, S., 1996. Changes in fault displacement populations

correlated to linkage between faults. J. Struct. Geol. 18, 265

279.

Fractal characteristics of active normal faults

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