Boconó Fault

Boconó Fault
Name	Boconó Fault
Location	Venezuela, Andes
Length km	500
Type	Strike-slip
Plate	South American Plate
Status	Active

Boconó Fault is a major left-lateral strike-slip fault in the Venezuelan Andes that forms a key structural boundary within northern South America. It links crustal deformation associated with the interaction of the South American Plate, the Caribbean Plate, and nearby microplates, and it controls patterns of seismicity, topography, and drainage across the states of Táchira, Trujillo, and Mérida. The fault is central to studies that involve the Andes, the Cordillera de Mérida, the Venezuelan Basin, and regional tectonic frameworks developed by institutions such as the Servicio Geológico de Venezuela and international teams from the United States Geological Survey, Smithsonian Institution, and universities across Venezuela, Colombia, and United States.

Geology and Tectonic Setting

The Boconó Fault lies within the northern Andes orogenic system and accommodates oblique convergence between the South American Plate and the Caribbean Plate along with influence from the Nazca Plate interactions farther west. It traverses lithologies of the Merida Andes including Mesozoic sedimentary sequences, Cenozoic volcanic rocks, and metamorphic basement units juxtaposed against the Barinas Basin and the Llanos Basin. Regional tectonic models reference the fault in conjunction with the El Pilar Fault, the San Sebastián Fault, and the Oca-Ancón Fault System, and tie deformation to episodes recorded in the Cretaceous and Neogene stratigraphic columns. Geodynamic interpretations often cite work linked to the International Lithosphere Program, the Royal Society, and collaborative projects with the National Academy of Sciences.

Fault Geometry and Segmentation

Geophysical mapping, satellite imagery, and field mapping delineate a long, sinuous trace that segments into multiple strands with distinct geometries near morphotectonic features such as the Motatán River, Boconó Valley, and the Río Santo Domingo. Segmentation studies identify major fault segments often named after local towns and massifs, which correspond to structural offsets visible in topographic data from SRTM and deformation measured by GPS networks operated in collaboration with universities like the Universidad de Los Andes (Venezuela). Crosscutting relations with oblique thrusts related to the Boconó Range uplift, and step-overs near the Apure Plains influence rupture propagation, as demonstrated by comparisons with segment behavior on faults such as the San Andreas Fault and the North Anatolian Fault.

Seismic History and Paleoseismology

Instrumental seismic catalogs maintained by the Instituto Geofísico de Venezuela and historical compilations reference numerous earthquakes spatially associated with the fault, some correlated with macroseismic accounts from colonial-era records in cities like Valera and Trujillo. Paleoseismic trenches and radiocarbon dating performed by teams from Universidad Central de Venezuela and international partners reveal multiple Holocene surface-rupturing events, with stratigraphic offsets comparable to ruptures documented on the Peru–Chile Trench-related faults and the Altiplano. Correlations to regional seismic sequences such as the 1749 and 1834 events have been proposed in syntheses published alongside work by the International Seismological Centre and the Global Seismographic Network analyses.

Slip Rates and Kinematics

Kinematic studies using geodetic data from InSAR campaigns, continuous GNSS sites, and geological offsets indicate dominantly left-lateral slip with components of transpression producing uplift of the Cordillera de Mérida. Estimated long-term slip rates from geomorphic markers, river offsets, and trench measurements generally fall in the range of millimeters per year, and are compared against rates on regional strike-slip structures like the El Pilar Fault and the Boconó–San Juan transfer zone. Finite-element and block models developed in collaboration with researchers at the Massachusetts Institute of Technology, Imperial College London, and regional universities reconcile observed shortening in the Venezuelan Andes with strike-slip motion along the fault.

Hazard Assessment and Risk Mitigation

Because the fault traverses populated areas, hazard assessments undertaken by the Defensa Civil de Venezuela, municipal authorities in La Ceiba and Boconó, and international agencies calculate probabilistic seismic-hazard models that incorporate slip-rate, recurrence interval, and ground-motion prediction equations used by the Pacific Earthquake Engineering Research Center and the European Seismological Commission. Scenarios include multi-segment ruptures with the potential for strong ground shaking, surface rupture, secondary hazards like landslides in the Andes and slope failures affecting infrastructure on the Pan-American Highway. Risk mitigation measures advised by multidisciplinary teams include updated building codes referenced to standards from the International Building Code, retrofitting of critical facilities such as hospitals affiliated with the Hospital Central de Maracaibo, and public preparedness campaigns coordinated with the United Nations Office for Disaster Risk Reduction and regional NGOs.

Research and Monitoring Studies

Ongoing research integrates seismic monitoring by the Red Sísmica Nacional de Venezuela, dense temporary arrays installed by consortia including GEOSCOPE and academic partners, continuous GNSS observations linked to the SIRGAS reference frame, and geologic field campaigns led by the Universidad de Los Andes (Venezuela) and the Universidad Simón Bolívar. Recent studies employ high-resolution remote sensing from Landsat, Sentinel-1, and airborne LiDAR to map geomorphic fault scarps and paleochannels, while numerical modeling teams at the University of California, Berkeley and the Instituto de Geociencias (Venezuela) explore stress transfer, Coulomb failure simulations, and earthquake rupture scenarios. Collaborative publications and workshops sponsored by the Pan American Institute of Geography and History and the International Association for Seismology and Physics of the Earth’s Interior continue to refine the understanding of seismic hazard associated with the fault.

Category:Seismic faults of Venezuela