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Determination of lineaments in Hispaniola.

Introduction

Hispaniola is an island of approximately 77,914[km.sup.2], in the Greater Antilles chain (Figure 1). The Republic of Haiti and the Dominican Republic are situated on the island. From the neotectonic point of view it is a part of the Plate Boundary Zone [PBZ] of the Caribbean and North American Plates (Mann and Burke 1984, Mann et al. 1984, 1984a). Hispaniola can be considered at first glance a topographically emerged first-order morphostructure, with a differential rise (Cotilla et al., 2007, 1997). This structure underwent a change of the insular arc type starting in the Lower Cretaceous and contains metamorphic rocks [green schist, metavulcanites and serpentinised peridotites, and blue and serpentine schist in the northern mountains] (Lewis and Draper 1990, Bowin 1975, 1966; Bracey and Vogt 1970). Hispaniola also possesses volcanic and volcanoclastic rocks from the Upper Cretaceous with intrusions of granitoids from the Upper Cretaceous--Lower Tertiary (Pubellier et al. 1991; Butterlin 1958). In the extreme eastern section in the Dominican Republic there are large extensions of pelagic limestone deposited during the Palaeocene-Eocene (Mann et al. 1991; Bowin 1966). The southeast Bahamas banks have been colliding with Hispaniola Island along a restraining bend within the northern Caribbean PBZ since the Late Miocene (Mullins et al. 1992).

The Caribbean domain and Central America form a small lithospheric plate inserted between North America and South America plates that is moving eastward relative to North American plate (Molnar and Sykes 1969). The North American and Caribbean PBZ is an irregular seismogenic area of a 100-250km wide with left-lateral strike-slip deformation extending over 2,000km along the northern border of the Caribbean Sea (Mann et al. 1995). The main structural element in the PBZ is the Cayman trough, a submarine pull-apart basin of 1,100km of oceanic crust at the Mid-Cayman spreading centre, a 100km long-jog between left-lateral faults of the plate boundary (Pubellier et al. 2000; Rosencratz and Mann 1991). This spreading centre is active since the Middle Eocene and has a rate of 1.5cm/yr (Rosencratz et al. 1988). Farther to the east are situated Jamaica, Hispaniola [H] and the Puerto Rico Islands.

The Cayman strike-slip system is divided into two branches: a northern branch from the Cayman spreading centre to the Puerto Rico trench and a southern branch from Central America to Haiti. The western part of the southern branch, Walton--Plantain Garden--Enriquillo fault is clearly active and runs from Jamaica up to the Muertos trough (Rubio et al. 1994, Cotilla et al. 1991, Mann and Burke 1984). Within the North America--Caribbean PBZ two microplates Gonave and Hispaniola--Puerto Rico were defined (Masson and Scalon 1991, Rosencratz and Mann 1991; Byrne et al. 1985). A continuous, northern strike-slip fault bounding both Gonave and the Hispaniola-Puerto Rico microplates runs from the northern coast of Haiti, from the Bartlett-Cayman [Oriente] fault zone, (Dilon et al. 1992); Cibao valley of northern Hispaniola, northern fault zone (de Zoeten and Mann 1991) to Puerto Rico island slope and Puerto Rico trench (Masson and Scalon 1991). Figure 1 of McCann (2002) shows two other microplates, El Seibo [eastern Hispaniola] and Puerto Rico, with a great difference in speed, 17mm/yr and 2mm/yr, for the North America plate oblique subduction NE-SW [Puerto Rico trench] and the Caribbean plate in the Muertos trough subduction zone, respectively. Another important structure is the Beata Ridge [BR] (Figure 1). It extends 400km south from Beata Cape, Hispaniola, dividing the Caribbean into the Colombia and Venezuela basins. To the west, the ridge is bounded by a steep escarpment with a regional slope of 15[degrees]-25[degrees] which rises 2,500m above the Colombia abyssal plain. To the east, the ridge drops down to the centre of the Venezuela basin in a series of steps. BR is an oceanic plateau whose edges have been reactivated by differential motion between the two aforementioned structures. Hispaniola and Puerto Rico are separated from the Venezuela Basin by the Muertos trough.

At the present time, a group of geophysical studies are being carried out on Hispaniola to investigate its deep structure. To this end, the work has two major focuses: 1) morphotectonic study, and 2) geologic-geophysical study. It is well-known that many problems formulated by geologists have been resolved with the help of geophysics, but the best results are obtained when the contributions of these two fields are used in conjunction, and with other auxiliary methods in an integrated fashion (Alekseevskaya et al. 1977). It is clear that computer science has greatly facilitated investigative tasks. Hence, the objective of this work is to apply a computerized system, on a PC using a GIS (Cotilla and Cordoba 2004), for the digital treatment of the gravitatory field of Hispaniola Island. The ultimate aim is to discover the lineaments (Hobs 1912) that make up the main lines of tectonic weakness for their later application in morphostructural research. The methodology has already been exposed and applied in Central-Eastern Cuba (Cuevas 1994, Cuevas et al. 1995), Central Cuba (Pena et al. 2007) and on the Iberian Peninsula by Cotilla and Cordoba (2004).

[FIGURE 1 OMITTED]

Seismicity

In the northern Caribbean the most intense seismicity is located around restraining bends such as southern Cuba and northern Hispaniola (Calais et al. 1992). In particular, the seismicity of Hispaniola described by Russo and Villasenor (1995), McCann and Pennington (1990), Chuy and Alvarez (1988), Iniguez et al. (1975), Kelleher et al. (1973), Molnar and Sykes (1969), Robson (1964), Lynch and Bodle (1948), Taber (1922), Sherer (1912) is plainly justified by its geodynamic position, both with respect to frequency of occurrence and to the magnitude of the seismic events. So, in the catalogue of the 1502-1971 period (Chuy and Alvarez 1988), there appear 15 intensity VII, 12 intensity VIII and 10 intensity IX earthquakes, and 1 earthquake of X degrees of intensity [MSK scale], which the authors place in two independent bands to the north and the south of Hispaniola. On the other hand, Gonzalez and Vorobiova (1989) describe three bands of seismic activity, one to the north and two in a NW transversal direction, of which the one found in the southeastern section corresponds to deep earthquakes. This zone was studied and recognized much earlier by Sykes and Ewing (1965). Mann et al. (1991) describe eight active zones in the northeastern Caribbean. However, five of them do not have any associated with seismicity in the last 40 years (Cotilla et al. 1997a). On the basis of all this data and a statistical treatment Cotilla and Alvarez (1991) describe two seismogenetic bands two the north and the south, and one transversal band in a NW direction. Later, Cotilla et al. (1997a) define the seismic potential for the Cuba --Jamaica--Hispaniola sector, and determine that the strongest events [M=8.0] could occur in two sectors in the northern region, in Haiti and the Dominican Republic. Figure 2 shows some of the strongest earthquakes in the Caribbean area, all occurring within the PBZ.

[FIGURE 2 OMITTED]

The stress and strain distribution deduced from focal mechanisms analysis infers a small N-S to NE-SW convergent component associated with the major strike-slip motion of the Caribbean and North America plates (Cotilla 1998; Deng and Sykes 1995; Sykes et al. 1982). According with Calais and Mercier de Lepinay (1992) northern Hispaniola is under transpressional tectonic regime with the main compressive stress axis being subhorizontal and striking about N50[degrees].

Gravimetry

Data

Given the amount of points in the sampling, the data acquisition process and the reliability of the measurements, the gravimetric map of Bouguer anomalies for Hispaniola (Reblin 1973) was used by SYSMIN (1999) for studies of the gravimetric tomography in the Dominican Republic. Also, Cuevas et al. (2001) used it for their work in the Caribbean because the distribution data is uniform. For all these reasons, this Bouguer map was applied in our research. The map shows there are positive anomalies over almost the entire surface in a quiet regional field (Figure 3A). Three zones stand out, of successively parallel tendencies, with gravitational minimums oriented in an E-W to NW direction. The first zone of minimums is in the northern part and is made up of a set of relative minimums, occupying a small area and with a NW-SE direction. Their values are between -20 and -40mGal. This zone corresponds to the Cibao and the Vega Central Valleys. The morphological expression of this zone seems to be clearly bounded, in the north and south, by deep faults (Cotilla et al. 1997). To the south of this zone, in the central part of Hispaniola, is the second zone of minimums [-30 to -40 mGal], the largest, which corresponds to the San Juan and Artibonite Valleys. Its direction is also NW-SE. Meanwhile the third zone of minimums, with values of up to -20mGal, has a predominantly WNWESE direction and corresponds, entirely, to the Enriquillo depression. In this zone there are strong values for the gravimetric gradient. Here, we also judge there to be deep vertical faults (Cotilla et al. 2007).

The zones with maximum positive gravity are situated in the southeastern part of the Enriquillo depression; reaching values of 260mGal. Positive values of 100 to 160 mGal appear in the north and central parts of Hispaniola. The oldest rocks in the territory are found in all these zones (Butterlin 1958). These maximums are on an order similar to those in eastern Cuba (Cuevas et al. 1991) and are associated there with mountain chains of a NW direction, where the maximum neotectonic uplifts occur (Cotilla et al. 1991).

The following materials were used in our study: 1) Bouguer's maps of Anomalies, scale 1:500,000 (Reblin 1973); 2) map of Free Anomalies, scale 1:500,000 (Reblin 1973); 3) bathymetric maps, scale 1:500,000; 4) topographical maps, scale 1:50,000 (Direccion General de Mineria and Universidad de Santo Domingo 1989) and scale 1:250,000 (Instituto Geografico Universitario 2001).

Methods

The materials before mentioned were digitalized and the free anomalies converted to Total Bouguer Anomalies, which included the sea and land parts, to a density of 2.67g/[cm.sup.3], and a matrix of uniform distributed data was created. As the work has a regional character, these data were transformed by Rising Analytical Continuation Method. Thus, for the information, bi-dimensional, the scale was reduced to 1:1,000,000 so as to apply a set of mathematical transformations with image processing techniques such as: 1) descending analytical continuation; 2) maximum horizontal gradient; 3) radial spectrum of frequencies; 4) rising analytical continuation; 5) second derivatives from gravity; 6) standard total gradient; 7) tendency analysis; 8) variable direction interprofile correlation. Image processing was also applied (Castleman 1996, Cuevas et al. 1995, Marion 1991, Jain 1989, Pratt 1978), specifically the method of edges and lineaments. Digital filtering operations enable the spectral composition to be modified in accordance with a certain mathematical operator, fundamentally with two methods: 1) mobile averages; 2) convolution. The results of these methods accounted for in isolines and shaded relief maps for later qualitative interpretation. During the interpretation we considered the geological formations of the region in the surface and depth, thus as the density of rocks.

We present a summary of the methods used with the purpose of the best understanding of the reader. The details of all the methods and procedures are in Cuevas (1994), Cuevas et al. (1995) and Cotilla and Cordoba (2004).

Descending Analytical Continuation. Analogous to rising analytical continuation, but essentially inverse to it, descending analytical continuation highlights the details of the sources of the anomalies by the process of approaching nearer the anomalies. Local anomalies are accentuated.

Edges and lineaments. This type of data processing is directed at the detection of the edges [or the contacts] and lineaments that exist in the entry image. The exit image will be given by another image where these events, if they exist, will be reinforced. In other words, the intensity value will change in order to improve detection of the characteristics of the edge of the scene. The basis for this procedure is found in local characteristics which in general accompany the abrupt changes of the values of the image. Broadly speaking, it can be stated that when an image has an edge, the values of a wide area are relatively constant and are modified abruptly in the boundaries with adjacent zones. In the case of a lineament, the values at each point are practically constant throughout a narrow strip.

This method is applied in two stages. First the edge or lineament is amplified; next, the presence, or absence, of the event looked for is classified, on the basis of a previously selected threshold value. During the amplification process, various types of operators are used, three of which are: linear, non linear and statistical. Operators for different selected directions are used, according to the type of predominant structure in the area, in our case, E-W, NW, NE and N-S (Pratt 1978).

Maximum Horizontal Gradient. The method draws out the lateral variations in the gravimetric map of Bouguer anomalies which can be related with faults or contacts between the different types of structures that involve an anomalous horizontal gradient in the gravitatory field. The calculation process assumes a regular network of four points separated by a simple distance of .X starting from the initial point in the diagonal, and which is used in the following expression: GHM

(p) = (0.707/2 .X) x (R1 + R2);

where:

R1 = g (x1) - g (x3); R2 = g (x2) - g (x1); .X = sample pass (km)

Radial Spectrum of Frequencies. Pal et al. (1979) demonstrate the excellent results of this method in determining of the depth of localization of the geological bodies of this territory.

It is understood that on a graph of the logarithm of the amplitude of the spectrum of the potential and frequency (on a linear scale) the interval of frequencies can be found in which said logarithm of the amplitude can be represented as a linear function. To do this, the following expression is used: ln SP(k) = -2 k h; where: SP: spectrum of potential; k: number of waves; h: depth of the source Since our database is bidimensional, the matrix of the N x N elements leads from the spatial domain to that of frequencies with the help of the Fast Fourier Transform.

Rising Analytical Continuation. This is one of the most frequently applied in the literature, as it allows the separation of components into different orders. It is well-known that as the distance to the sources of the anomalies increases, the anomalies are differently accented depending on the dimensions and depth of mentioned sources. In this method, in the upper space, the regional anomalies stand out over the local ones. Here, five levels of recalculation were done for each 10km (Figure 3B).

Second Derivatives of Gravity. This method complements the total normalized gradient, as it determines the vertical contacts very well. The method also consists in determining, on the basis of the values for gravity of the map of Bouguer anomalies, the vertical second derivatives of gravity. Thus, it is possible to indicate the abrupt changes in gravity and separate the compound [those due to superimposing the effects of nearby masses]. The expression used is the following:

VZZZ = - 1/SP2 [4 VZ (0.0) - S VZi (SP)];

where: VZZZ: second vertical derivatives of gravity; VZi: Value for gravity; SP: spectrum of potential.

[FIGURE 3 OMITTED]

Standard Normalized Gradient.-Berezkin (1973, 1967) holds it is possible to transform the field with the following expression:

GN(x, z) = G (x, z)/G (z) - [V2ZZ (x, z) + V2XZ (x, z)]1/2/(1/n) [V2ZZ (x, z) + V2XZ (x, z)1/2]

where: n: number of points in the profile; (x, z): sample points; G(x, z): total gradient of gravity; G(z): Mean gradient for a given level; GN(x, z): total normalized gradient; VZZ (x, z) and VXZ (x, z): vertical and horizontal gradient of gravity, respectively.

This method allows the detection and evaluation of several geological factors that give rise to the anomalies, for example the faults (Eliseiva et al. 1986). It is necessary to draw profiles in the study zone and in each one calculate the GN(x, z) with a given sample interval, for example 3-5 km. The results appear in isolines for each harmonics, with a spacing of 0,1 and depth levels of 0-30km. This calculation is done for the lower semi-space and with a similar range [3-5km]. The amount of different harmonic in each profile is chosen according to the length of the profile (Table 1).

Tendency Analysis. With this method it was possible to establish the existence of a tendency in the behavior of the physical field with respect to distance. This calculation can be interpreted as a simple process of digital filtration [pass-band], as it always conserves the low frequencies and eliminates the high ones. In this way, the regional field associated with large structures can be studied.

Variable Direction Interprofile Correlation. In accord with Valdes (1978), the objective of this method is the detection, in the profiles set, of the direction of those events that present correspondence or correlation, producing additional accentuation of the noise. The basis of the method is the well-known supposition that noises are aleatory and appear in different profiles. Hence, noises are not correlatable, while anomalies are. In this way, it is possible to draw the true directions with minimal deformation.

Cuevas et al. (1995) found that a single method was not enough to clearly establish the existence of linear structures. Consequently they suggested a combination of methods to more reliably establish the lineaments. Cotilla and Cordoba (2004) indicated that with eight methods, such as those used here, the reliability is very high when five of them coincide.

With the results obtained from all the methods it is necessary to synthesize and integrate them into a map. This material allows the establishment of a set of lineaments for which a corresponding frequency of coincidence is detected. It is important to point out that in the gravitatory field the lineaments that can be faults are not only manifested in their gradient, through gravitational steps, since in faults there are different phenomena that deform and distort the field. These phenomena can be mineral bodies, variations in the density of rocks, etc. Also, the faults can be of different types and their expression in these intermediate results can not be appreciated in small inflections of isolines or the very weak variation of the indexes represented. It must be remembered the resulting map of these transformations is not aimed at elucidating the geological constitution of the territory, but rather to point out weak tectonic zones and consequently assist in the neotectonic interpretation. In other words, this application is always meant to be complementary to geological work.

In Figure 4 appear the relief and the main lineaments of Hispaniola. In this sense the showed lineaments are related to the strikes of the most significant structures. They correspond to NW and E-W (the largest) and NE. According to Cotilla et al. (2007) they are active faults associated to some earthquakes.

[FIGURE 4 OMITTED]

Results and discussion

The result of this computer application was the demarcation of 245 lineaments, 25 lineament zones [LZ] (Table 2), 9 main lineament zones [MLZ] (Table 3) and 8 MLZ knots [intersections] (Table 4). The equivalence between LZ and faults is discussed in Cotilla and Cordoba (2004). The LZs show that the predominant structural directions in Hispaniola are E-W and NW, while the directions N-S and NE are significantly fewer. The greatest longitudes correspond with the directions of the main geological structures. The selection of the LZ, according to their correspondence with well-known active structures, was limited to nine elements (Table 3), which are the MLZ, E-W and NW. In particular, MLZs 3 and 4 have strong northern and southern oriented gradients, respectively, from the first zone of minimums. MLZ 3 has a record of paleoseismicity (Prentice et al. 1993). Meanwhile, MLZ 4 is associated with tsunamis (Rubio 1982). This confirms the assertion of Brock (1972) that a lineament is defined briefly as a geological or topographical lineament too precise to be fortuitous. Table 3 shows a very high level of correspondence (>90% confidence) between the known faults and the MLZ detected.

On the map of the MLZ (Figure 5) we point out that No. 19, with a NE direction abruptly interrupts the remaining quasilatitudinal zones. This very clearly marked interruption appears to the east of the second gravimetric minimum. MLZ 19 is detected quite clearly with twelve identifications, in the Beata direction is known to follow and links up with important areas of active seismicity. To the east and to the west of this MLZ, the gravitatory field of Hispaniola can be distinguished without any ambiguity, such that this MLZ can be considered a morphotectonic boundary, since it corresponds to topographically very different zones. Also, this MLZ is found to occupy a range of negative values that divide the positive regions in the aeromagnetic map of Hispaniola (Compagnie Generale de Geophysique 1999).

One of the things the Standard total gradient method can do, on the basis of the regional profiles, is to confirm the existence of all the MLZ, including the depth to which they develop; MLZ 4 is the best detected in this regard [along with fourteen]. Furthermore, it is possible to establish the categorization of these zones on the basis of data of the two variants by looking at: 1) the interruption--deformation of other structures; 2) the extent of the MLZs. Thus, MLZ 19 interrupts and deforms MLZs 3 and 4, and interrupts MLZs 6 and 20. The most extensive MLZs are No. 6, 19 and 20. All these MLZs correspond to the recognized faults on the morphostructural maps of Hispaniola (Cotilla et al. 2007, 1997) (Table 3). Also it is possible to relate six MLZs to strong earthquakes showed in Figure 2 [1673 (MLZ20), 1770 (MLZ6), 1842 (MLZ22), 1897 (MLZ4), 1943 (MLZ23), 1946 (MLZ28)].

The amount of knots in the map (Figure 5) shows MLZs 3, 6 and 19 to have the greatest tectonic complexity on Hispaniola. Also, the set of lineaments and lineament zones shows that the crust of Hispaniola is much fractured. In this sense, it can be said that the island constitutes a large block [megablock] that is subdivided into two smaller units [Western and Eastern] by MLZ 19. They correspond to the Western and Eastern macroblocks of the Morphostructural map (Cotilla et al. 2007). At the same time, these units are subdivided into other structures of smaller dimension [blocks] and in general have a quasilatitudinal orientation. The western area shows a larger number of lineaments and blocks than the eastern section.

A brief comparison between our results (Figure 5) with the Figure 4 made possible to assure that there are a good correspondence. Particulary, six main lineament zones MLZ6, MLZ19, MLZ21, MLZ22, MLZ23, and MLZ24 are the best fixed and then should be considered as active faults.

[FIGURE 5 OMITTED]

As mentioned earlier, there are eight knots of MLZs, which are associated with areas of historic and instrumental seismicity. The presence of these knots leads to the conclusion that the seismogenic zones are segmented and consequently are smaller than the maximum longitudes and the magnitudes possible for the earthquakes (Machette et al. 1991). Also, the 1946 earthquake series in the northeastern part of the Dominican Republic, around the Samana Peninsula, approximately 1,000[km.sup.2] in area (Russo and Villasenor 1995), can be explained by the convergence of various MLZ there.

Table 5 presents the earthquake depths given for Hispaniola in the works of three different groups of authors (Calais et al. 1992, Cotilla and Alvarez 1991, Gonzalez and Vorobiova 1989) and three corresponding determinations, from the methods used here of the depth of localization of the lineament zones [Rising analytical continuation, Second derivative of the gravity, Standard total gradient]. These data show that there is a good fit between the gravimetric determinations and the focal depths. Furthermore, the slip depths determined with the methods applied for the LZ confirm the proposal of Cotilla et al. (2007, 1997) with respect to redoing, vertically, the neotectonic in the old faulting zones on Hispaniola.

It was also determined that the densest materials are at a depth of over 25km, in general. Similar values were obtained in SYSMIN (1999) for the Dominican Republic. This also accords with the findings of Cuevas et al. (1991) for Eastern Cuba. Four gravimetric zones were identified: 1) The northern, which includes the marine part and the adjacent insular part, and where the depth of those materials is less than 25km; 2) Central--Eastern, with depths of 30km [places: Monte Plata--La Mata Sabana Grande de Boya--Bayaguana--San Isidro--El Seibo--Santo Domingo]; 3) Southeastern at 30-45km [places: La Romana--San Rafael de Yuma--Isla Saona]; 4) Northeastern, corresponds to the Eastern Range, and the depths vary from 30 to 110km. This zone coincides with the area of deep earthquakes, mentioned above. Then, using the approach of Krestnikov (1987) is possible to estimate that the seismogenic layer has ~30km of depth.

Finally, in accord with the disposition and the configuration of the lineaments and the blocks, it is possible to assume, in a preliminary way that there is a directional movement relative to the blocks. Thus, the western and eastern blocks move in an opposite direction, clockwise and counter clockwise, respectively. This means there are rotations or turns that would explain the deformations of the MLZ and the seismicity in the region.

Conclusions

Hispaniola is a topographically emerged structure that is intensively fractured situated in the Plate Boundary Zone of the north Caribbean. In this area, it has been determined by studies and automated procedures and through digital treatment of images, and from gravitatory data, that there exist 245 lineaments, 25 lineament zones, 9 main lineament zones and 8 knots of main lineament zones. In this neotectonic framework, two large gravimetric zones or macroblocks are defined, Western and Eastern, limited by a zone of transversal--diagonal lineaments called Beata that shows moderate seismic activity. The main lineament zones in general correspond to zones of active faults cited by other authors. It was stated that the seismogenetic layer has up to 30km of depth.

Acknowledgements

This research was funded by the CTM2006-C02-02 and CCG07-UCM/AMB-2343 projects. We thank the Instituto Sismologico Universitario, of the Universidad Autonoma de Santo Domingo and the Direccion General de Mineria de la Republica Dominicana for their continued support in our research on Hispaniola.

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Mario Octavio Cotilla Rodriguez *

Diego Cordoba Barba *

* Departamento de Fisica de la Tierra y Astrofisica I, Facultad de Ciencias Fisicas, Universidad Complutense de Madrid, Ciudad Universitaria s/n, 28040, Madrid, correo electronico: macot@fis.ucm.es; dcordoba@fis.ucm.es
Table 1

Data of the profiles used in the Standard Total Gradient Method

Profile   Strike   Longitude (km)   Points   Harmonics

P1          NE          270           52         6
P2          NE          285           63         7
P3          NE          270           50         6
P4          NE          245           47         5
P5         ENE          490           97        12
P6         Ene          500          105        15
P7          Nw          320           83         9

Table 2

Lineaments detected

Methods

            I                   II   III   IV   V    VI

Lineamien   1    2    3    4

LZ1         --   D    D    D    D    --    --   --   --
LZ2         --   D    D    --   D    --    --   --   --
LZ3         D    D    D    D    D    D     --   D    D
LZ4         D    D    D    D    D    D     D    D    D
LZ5         --   D    --   D    D    --    --   D    --
LZ6         --   --   --   D    D    D     D    D    D
LZ7         --   D    D    --   D    --    --   D    D
LZ8         --   D    D    --   D    --    --   --   --
LZ9         D    D    D    D    D    --    --   --   --
LZ10        D    D    D    D    D    --    --   D    --
LZ11        --   D    D    --   D    --    --   --   --
LZ12        --   D    D    --   D    --    --   --   --
LZ13        D    D    D    D    D    --    --   --   --
LZ14        --   D    --   D    D    --    --   --   --
LZ15        --   D    --   D    D    --    --   --   --
LZ16        --   --   D    --   D    D     --   --   --
LZ17        --   --   D    --   D    D     --   D    --
LZ18        D    --   D    --   D    --    --   --   --
LZ19        --   D    D    D    D    D     D    D    D
LZ20        --   --   --   D    D    D     D    D    D
LZ21        D    --   D    D    D    --    D    --   D
LZ22        --   D    D    D    --   --    --   --   --
LZ23        D    D    D    D    --   --    D    D    D
LZ24        D    D    D    D    D    D     --   --   D
LZ25        --   --   D    --   --   D     D    D    D

Methods

            VII   VIII

Lineamien         1      2    3    4    [SIGMA]

LZ1         D     --     --   --   --   5
LZ2         D     --     --   --   --   4
LZ3         D     D      D    D    D    13
LZ4         D     D      D    D    D    14
LZ5         D     --     --   --   --   5
LZ6         D     D      D    D    --   10
LZ7         D     --     --   --   --   6
LZ8         D     --     --   --   --   4
LZ9         D     --     --   --   --   6
LZ10        D     --     --   --   --   7
LZ11        D     --     --   --   --   4
LZ12        D     --     --   --   --   4
LZ13        D     --     --   --   --   6
LZ14        D     --     --   --   --   4
LZ15        D     --     --   --   --   4
LZ16        D     --     --   --   --   4
LZ17        D     --     --   --   --   5
LZ18        D     --     --   --   --   4
LZ19        D     D      D    D    --   12
LZ20        D     D      D    D    --   10
LZ21        D     D      D    D    D    11
LZ22        D     --     --   --   --   4
LZ23        D     D      D    D    --   11
LZ24        D     D      D    D    --   11
LZ25        --    D      D    D    D    9

Legend: I: Edges and lineaments (1: NW-SE; 2: NE-SW;
3: N-S; 4: E-W); II: Fourier fast transform; III:
Interprofile correlation of variable direction; IV:
Maximum horizontal gradient; V: Tendency analysis;
VI: Standard Total gradient; VII: Qualitative analysis
of Bouguer map; VIII: Rising analytical continuation
(1:10km; 2:20km; 3:30km; 4:40km); D: detected;
--: no detected.

Table 3

Some characteristics of the main lineament zones

Lineament   Predominant   Detected   Rank        Knot
zone          strike

MLZ3        E-W/NW        13         1      N1, N6, N7, N8
MLZ4        E-W/NW        14         1      N1, N2
MLZ6        E-W/NW        10         3      N4, N5
MLZ19       NE            12         1      N2, N4, N3, N6
MLZ20       E-W/NW        10         2      N4
MLZ21       NE            11         2      N7
MLZ22       NW            4          2      N1
MLZ23       NW            11         2      N7
MLZ24       NE            11         2      N5, N8

Lineament            Correspond               Confidence (%)
zone                to the fault

MLZ3        Septentrional                   90
MLZ4        North Hispaniola                93.5
MLZ6        Enriquillo-Plantain Garden      92.7
MLZ19       Beata                           90 (southern part)
MLZ20       Muertos-Neiba                   90.3
MLZ21       Santo Domingo                   90.5
MLZ22       Oriente (Cuba)-Septentrional    92.5
MLZ23       Yuma                            93
MLZ24       Haiti                           93

Table 4

Short description of the knots of main lineament zones

Knot   Formed by the   Rank   Location
       lineaments

N1     MLZ3, MLZ4,     1      Haiti-Eastern
         MLZ22                Cuba
N2     MLZ4, MLZ19,    1      Bahamas
         MLZ28
N3     MLZ2, MLZ19     1      Beata
N4     MLZ6, MLZ19,    2      Neiba-Muertos
         MLZ20
N5     MLZ6, MLZ24     3      Puerto Principe
N6     MLZ3, MLZ19     2      Pimentel
N7     MLZ3, MLZ21,    2      Samana
         MLZ23
N8     MLZ3, MLZ24     3      La Esperanza

Knot        Seismicity

       Historic   Instrumental

N1       Yes          Yes

N2       Yes          Yes

N3       Yes          Yes
N4       Yes          Yes

N5       Yes          Yes
N6       Yes          Yes
N7       Yes          Yes

N8       Yes          Yes

Table 5

Depth of the main lineament zones

            Methods                           Focal deph (km)

Lineament   II   V     VI     VIII     VZZZ     C     CA   GV

MLZ3        D    D    35km   10-40km   40km   40      35   35
MLZ4        D    D    40km   10-40km   38km   45-50   35   45
MLZ6        D    D    32km   10-30km   29km   30      30   25
MLZ19       D    D    25km   10-30km   30km   40      30   30
MLZ20       D    D    30km   10-30km   28km   30      30   30
MLZ21       D    --   38km   10-40km   39km   55      40   40
MLZ22       --   --   --     --        --     50      25   40
MLZ23       --   D    30km   10-30km   28km   25      25   20
MLZ24       D    --   28km   10-40km   25km   30      20   20
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