Three major faults in northeastern Colombia (Sierra Nevada de Santa
Marta & Perija Range): seismotectonic model and scope of its seismic
hazard
Abstract
In the northeastern Colombia, the northernmost foothills of the Andes
are present, whose representatives are the Sierra Nevada de Santa Marta
(SNSM) and the Perija Range. This orogenic system is delimited by three
major faults that limit three large basins. In its order from west to
east are the Santa Marta Fault that limits the Sierra Nevada de Santa
Marta with the Lower Magdalena Basin. The Oca Fault that limits with the
low basin of the Rancheria River to the north in the south of Guajira
Peninsula, and toward the east the Perija – El Tigre Fault that limits
with the Maracaibo Basin. Each of these faults have a great size. Since
2008, when the National Seismological Network of Colombia (RSNC)
increased its number of seismological stations in this region of
Colombia, the recording of surface seismicity that is associated with
the tectonic mobility of this orogenic system began. The strong
earthquakes in this region do not exceed in magnitude M = 5.5,
emphasizing earthquakes with M ≈ 4.5 in average. The origin of the
tectonic mobility of this orogenic system obeys to the convergence
between the Caribbean Plate and the northwestern corner of South
America. As a historical antecedent in this region is the earthquake of
May 22, 1834 that destroyed the city of Santa Marta. Along the western
sector of the Oca fault, this is composed of parallel faults and towards
the east when it crosses the basin of the Ranchería River, present
evidences of neotectonics. This fault becomes a good candidate to
produce an earthquake with magnitudes greater than 5.0. For the Santa
Marta fault, the alteration of the landscape by anthropic effect has
erased evidence of active tectonics in its northern sector, while
towards SE it shows morphotectonics related to its fault plane, and the
Perijá - El Tigre fault due to inaccessible conditions Because it is a
jungle area, very large and lacking communication routes as well as
having a long history of armed conflict, it has been impossible to study
it in the field and it has only been verified from a morphotectonic
point of view with the help of remote sensors. To this fault is
attributed to the earthquake of September 11, 2014 with M = 4.1 and
inverse focal mechanism according to the report of the RSNC. In this
work a tectonic model is shown, the kinematic behavior of each fault,
and its probable seismic risk for this region of Colombia.