Evaluación Paleosísmica Del Segmento San Felipe De La Falla De Boconó (Venezuela Noroccidental): ¿responsable Del Terremoto Del 26 De Marzo De 1812?

Chapter 12

“…An alternative explanation for this has been sought in the possible condition of fault creep along the short cut fault that has some supporting evidence in the common presence of fractures and cracks oriented perpendicular to the fault trace seen at surface and in buildings within the zone of fault shear along the western limit of the town of Algeciras. On the other hand, the morphotectonic expression of the main branch of Algeciras Fault compares with the Boconó Fault in Venezuela that has a well-established slip rate in the order of 10 Quaternary mm/y (Audemard, 2014(Audemard, , 2016Audemard et al, 2006;Pousse-Beltran et al, 2017). Likewise, fault slip rate data for faults of the Ecuadorian side of the transform system have yielded similar results (Alvarado et al, 2016;Baize et al, 2014;Tibaldi & Ferrari, 1991;Tibaldi et al, 2007).…”

“…This crustal block is in the process of tectonic escape to the NNE as first suggested by Pennington (1981) and later by others like Audemard (1993), Egbue & Kellogg (2010), Freymueller et al (1993, Kellogg & Vega, 1995, Taboada et al (2000, Tibaldi & Ferrari (1991), Trenkamp et al (2002), andWitt et al (2006). This escape movement has been demonstrated in the plots of Global Position System (GPS) velocity vectors established during the CASA project (Freymueller et al, 1993;Kellogg & Vega, 1995) and, more recently, has been corroborated by the densified network of permanent GPS/ GNSS stations of the GeoRED project, which firmly has established a NNE movement of 8.6 mm/y (Figure 3; Mora-Páez et al, 2002, 2016, 2019. The crustal block escape is the result of the interaction of the three major tectonic plates of Nazca, Caribbean, and South America, complemented by the collision of the Panamá-Baudó Arc (Figure 1).…”

“…Nevertheless, the up-to date pattern of velocity vectors established during the GeoRED project points universally to movement of the block in a NNE direction at a velocity of 8.6 mm/y (Figure 3; Mora-Páez et al, 2016, 2019. The Guaicáramo system runs along the foothills of the Eastern Cordillera and consists predominantly of east verging thrust and stacked thrust systems that are the mark of a foreland fold and thrust belt (Bayona et al, 2008;Diederix et al, 2010;García et al, 2011;Mora et al, 2010), but always maintains a dextral strike-slip component as has been observed in the field (Diederix et al, 2010) and is also evident in the pattern of GPS velocity vectors established during the GeoRED project (Figure 3; Mora-Páez et al, 2002, 2016, 2019. The Guaicáramo Fault System makes an abrupt double right angle bend north of the town of Tame in the northeast over a distance of 150 km to resume its NE strike at the town of Cúcuta and continues as the Boconó Fault that follows the length of the Mérida Andes in Venezuela (Audemard & Audemard, 2002;Audemard et al, 2005Audemard et al, , 2006.…”

“…The slightly more ENE orientation of the velocity field of GPS vectors that can be observed north of latitude 7° N, suggests the influence of a W-E push that add an E-W component to the NNE movement of the NAB (Figure 3; Mora-Páez et al, 2019). The consensus opinion is that the oblique Nazca Plate convergence with South America is the controlling factor for slip partitioning and the escape of the NAB and whatever the precise date for the beginning of the displacement of the NAB by means of movement of the fault system, a fact is that the AFS in all its morphological characteristics provides us with convincing evidence of recent and ongoing dextral strike-slip movement, that until now has not been possible to be quantified, but could well be in the range of 10 mm/y in analogy to the values for slip rate obtained of its trajectories in Ecuador (Alvarado et al, 2016;Baize et al, 2014;Ego et al, 1996;Nocquet et al, 2014; 1992; Tibaldi et al, 2007) and Venezuela (Audemard, 2014(Audemard, , 2016Pousse-Beltran et al, 2017).…”

“…Particularly in the sector between the village of Algeciras in the north and Pitalito in the south, most of the movement of the fault system is concentrated along this main branch. This has resulted in an outstanding morphological expression on the DEM imagery and also on aerial photos that compare with the well-known and well-studied Boconó Fault in Venezuela (e.g., Audemard, 2016;Audemard & Audemard, 2002;Audemard et al, 2005Audemard et al, , 2006Pousse-Beltran et al, 2017). The width of the fault belt of the AFS varies in this sector between 25 and 40 km.…”