Tentative integration of paleoseismic data from lake sediments and from nearby trenches: the central section of the Boconó Fault (northern Venezuela). (June 2019)

• Record Type: Journal Article
• Authors: Beck, Christian; Carrillo, Eduardo; Audemard, Franck; van Welden, Aurélien; Disnar, Jean-Robert
• Is Part Of: Journal of South American earth sciences. Volume 92(2019)
• Page Start: 646
• Page End: 657
• Publication Date: 2019-06
• Subjects: Paleosismicity -- Lake sediments -- Trenches -- Last glacial maximum -- Holocene -- Mérida andes -- Boconó fault; Geology -- Latin America -- Periodicals; Earth sciences -- Latin America -- Periodicals; Geology -- Antarctica -- Periodicals; Earth sciences -- Antarctica -- Periodicals; Geology -- Caribbean Area -- Periodicals; Earth sciences -- Caribbean Area -- Periodicals; Géologie -- Amérique latine -- Périodiques; Sciences de la terre -- Amérique latine -- Périodiques; Géologie -- Antarctique -- Périodiques; Sciences de la terre -- Antarctique -- Périodiques; Géologie -- Caraïbes (Région) -- Périodiques; Sciences de la terre -- Caraïbes (Région) -- Périodiques; Earth sciences; Geology; Antarctica; Caribbean Area; Latin America; Periodicals; 550.5
• DOI: 10.1016/j.jsames.2019.03.028
• Languages: English
• ISSNs: 0895-9811

Abstract

Abstract: The right-lateral strike slip Boconó Fault (Mérida Andes, northern Venezuela) accommodates an important part of the South-American Plate northern transform boundary. Along its central portion, preserved post-LMG lake fills are intersected by two surface-reaching active traces which could be trenched just beside. Outcropping and cored lacustrine sedimentary archives are combined with trench data in order to achieve a Holocene paleoseismicity record for a 7 km-long segment. For lakes sediments, several types of sedimentary "events" were taken into account as co-seismic: mass wasting on deltaic foreset, liquefaction and slumping, reflected tsunami effects, re-suspension, abrupt change in sedimentary dynamics and sources, abrupt emptying and lake surface changes. Time coincidences between two lacustrine archives and two trenches can be proposed for the last 10 kyr BP. Among a total of 24 events, 13 events are detected in two sites, 3 events in 3 sites. 9 possible correlations concern separate traces while 4 concern the same trace; a relay between the activity of the two traces is also deduced. This combination of surveys both reinforces and completes the trenches results, leading to a better knowledge of local to regional seismic hazard. Nevertheless, the total information results probably incomplete and/or biased. The co-seismic origin of lacustrine fills disturbances evidenced but the associated archive is incomplete and/or biased due to: changing recording potential through time, possible impacts by strong distant earthquakes. Trenches data appear to fill lacustrine "gaps" but with a number of events possibly overestimated if all ruptures and associated 14 C data are considered as representing separated earthquakes. Highlights: Along the seismogenic strike slip Boconó Fault, NW Venezuela, a 7 km long strand permits to combine 2 lacustrine sedimentary records and 2 trenches for paleoseismic research. Along the seismogenic strike slip Boconó Fault, NW Venezuela, a 7 km long strand permits to combine 2 lacustrine sesites (1 or 2 lake fills and 1 or 2 trenches); 3 for 2 sites. A mean 400 yr return interval is deduced, longer than historical return period. Our correlation attempt points out two "opposite" biases: incomplete recording by sedimentation, and possible overestimation" of co-seismic rupturing events deduced from trench analysis.