Variations in elastic thickness and flexure of the Maracaibo block

Understanding Micropolar Theory in the Earth Sciences I: The Eigenfrequency $$\omega _r$$

“…In realistic 3D scenarios, the lithosphere responds to surface and subsurface loads by bending. In order to model the resulting flexure, the solution of the plate equation is appropriate only if the dimensions of the plate in the horizontal direction are much larger in the vertical direction (Burov, 2011;Ventsel et al, 2002;Arnaiz-Rodrı ´guez & Audemard, 2014;Van Wees & Cloetingh, 1994;Garcia et al, 2015;Sanford, 1959;Wessel, 1996;Braun et al, 2013;Stu ¨we, 2002;Judge & McNutt, 1991;Zhang et al, 2018;Manrı ´quez et al, 2014;Contreras-Reyes & Osses, 2010). However, in many situations, the distortion of the plate during the bending is limited by the extreme edges of the plate.…”

Chapter 13

“…However, recent work by Mora & Garcia (2006) mention that reprocessing and re-interpretation of existing subsurface seismic data has led to the confirmation of the existence of a vertical fault structure that follows the lineament of the projected central segment of the BF that crosses the Cesar valley, but they consider that it must be a strike-slip fault structure of low level activity. Moreover, as it is generally accepted that the MTB is in active tectonic escape to the NE with respect to the NAB, this movement must be facilitated by a continuous left lateral strike-slip fault and therefore the continuity of the fault across the Cesar valley is a necessity (Arnaiz- Rodríguez & Audemard, 2014;Laubscher, 1987). Related to this is the possibility of a clockwise rotation of the SNSM block during the Pliocene, as described by Montes et al (2010) and suggested by others before.…”

“…Julivert (1970) and Ward et al (1973) considered the BF to be a high angle reverse fault only, which has been responsible for the uplift in the order of 2000 m of the Santander Massif. However the general consensus is now that we deal certainly with a major strike-slip fault system that is also the western boundary of the MTB presently in a process of active tectonic escape to the northeast with respect to the NAB and the South American continent (Arnaiz- Rodríguez & Audemard, 2014).…”

“…GPS data of the GeoRED project have yielded velocity fields of displacement vectors that demonstrate that the NAB is moving to the NNE at a velocity of 8.6 mm/y (Mora-Páez et al, 2016, 2019Trenkamp et al, 2002). The MTB constitutes the northeastern corner of the NAB but moves semi-independently from it to the northeast (Arnaiz- Rodríguez & Audemard, 2014) while it shares the Boconó Fault in Venezuela as its southeastern boundary that has a displacement of ±11 mm/y. The displacement of the western boundary of the MTB along the SMBF relative to the NAB is 2.5 mm/y.…”

“…This northward movement of the NAB is facilitated by slip along the Eastern Andean Frontal Fault zone that runs all the way from the Gulf of Guayaquil to the Caribbean in Venezuela, a distance of approximately 2000 km and on the basis that it connects the Nazca and Caribbean Plates and perhaps also the Atlantic Plate, merits to be considered a transform fault belt (Audemard, 1993(Audemard, , 2014Audemard & Audemard, 2002;Audemard et al, 2005;Diederix et al 2020;Nocquet et al, 2014Nocquet et al, , 2016Pennington, 1981). Within the NAB and occupying its northeastern corner, sits the Maracaibo Tectonic Block (MTB), a smaller microplate that moves semi-independently from the NAB in a NE direction, along the NNW striking left lateral strike-slip SMBF that defines its western boundary and the northeast striking right lateral strike-slip Boconó Fault of the Merida Andes of Venezuela (Arnaiz- Rodríguez & Audemard, 2014;Audemard, 2014;Laubscher, 1987) that is part of the transform fault belt or Eastern Frontal Fault System as we prefer to call it. The northern margin of the MTB, is formed by the right lateral strike-slip Oca-Ancón Fault (Arnaiz-Rodríguez & Audemard, 2014;Laubscher, 1987).…”