Spatial and temporal distribution of deformation at the front of the Andean orogenic wedge in southern Bolivia

Weiss, Jonathan; Brooks, Benjamin A.; Arrowsmith, J Ramón; Vergani, Gustavo

doi:10.1002/2014jb011763

Cited by 17 publications

(37 citation statements)

References 113 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This is in contrast to the Bolivian sector of the foreland, between 17.5°S and 22°S, where Horton (1999) combined GPS data with estimates for long-term erosion rates in the Subandes to demonstrate that the orogenic wedge at those latitudes is likely critically tapered. The findings of Horton (1999) are consistent with the observation that the geodetically derived values for slip rate on the décollement in Bolivia agree well with geologically determined rates and that almost all of the Quaternary deformation there is being accommodated on structures near the thrust front (Weiss et al, 2016;Weiss et al, 2015). Although the geodetically derived dislocation model for the décollement reported here for the Santa Barbara system is similar to that inferred by Brooks et al (2011) and Weiss et al (2016) for the Bolivian section, we suspect that the inferred slip is not fully transmitted to the wedge front in our study area and therefore not recorded in the geologic slip rates on the thrust front at Lomas de Olmedo.…”

Section: Comparison Of Geodetically Derived Décollement Parameters Wisupporting

confidence: 83%

Rapid Geodetic Shortening Across the Eastern Cordillera of NW Argentina Observed by the Puna‐Andes GPS Array

et al. 2017

View full text Add to dashboard Cite

We present crustal velocities for 29 continuously recording GPS stations from the southern central Andes across the Puna, Eastern Cordillera, and Santa Barbara system for the period between the 27 February 2010 Maule and 1 April 2014 Iquique earthquakes in a South American frame. The velocity field exhibits a systematic decrease in magnitude from ~35 mm/yr near the trench to <1 mm/yr within the craton. We forward model loading on the Nazca‐South America (NZ‐SA) subduction interface using back slip on elastic dislocations to approximate a fully locked interface from 10 to 50 km depth. We generate an ensemble of models by iterating over the percentage of NZ‐SA convergence accommodated at the subduction interface. Velocity residuals calculated for each model demonstrate that locking on the NZ‐SA interface is insufficient to reproduce the observed velocities. We model deformation associated with a back‐arc décollement using an edge dislocation, estimating model parameters from the velocity residuals for each forward model of the subduction interface ensemble using a Bayesian approach. We realize our best fit to the thrust‐perpendicular velocity field with 70 ± 5% of NZ‐SA convergence accommodated at the subduction interface and a slip rate of 9.1 ± 0.9 mm/yr on the fold‐thrust belt décollement. We also estimate a locking depth of 14 ± 9 km, which places the downdip extent of the locked zone 135 ± 20 km from the thrust front. The thrust‐parallel component of velocity is fit by a constant shear strain rate of −19 × 10−9 yr−1, equivalent to clockwise rigid block rotation of the back arc at a rate of 1.1°/Myr.

show abstract

Section: Comparison Of Geodetically Derived Décollement Parameters Wisupporting

confidence: 83%

Rapid Geodetic Shortening Across the Eastern Cordillera of NW Argentina Observed by the Puna‐Andes GPS Array

et al. 2017

View full text Add to dashboard Cite

show abstract

“…Analogue and numerical models have shown that wedges evolve via distinct phases of widening, when new thrusts nucleate at the front of the wedge, and (Figure 11). The red curves are Quaternary shortening rate probability density functions (pdf) for the wedge-front Mandeyapecua thrust fault system (Figure 9) based on the analysis presented in Weiss et al [2015]. The pdfs were computed by summing the dip-slip rate pdfs from the profiles shown in Figure 8 of Weiss et al [2015] Profiles 1-5 were summed to create the Sucre profile pdf and profiles 7-8 were summed to create the Tarija profile pdf.…”

Section: Discussion Of Modeling Resultsmentioning

confidence: 99%

Isolating active orogenic wedge deformation in the southern Subandes of Bolivia

et al. 2016

Self Cite

View full text Add to dashboard Cite

A new GPS‐derived surface velocity field for the central Andean backarc permits an assessment of orogenic wedge deformation across the southern Subandes of Bolivia, where recent studies suggest that great earthquakes (>Mw 8) are possible. We find that the backarc is not isolated from the main plate boundary seismic cycle. Rather, signals from subduction zone earthquakes contaminate the velocity field at distances greater than 800 km from the Chile trench. Two new wedge‐crossing velocity profiles, corrected for seasonal and earthquake affects, reveal distinct regions that reflect (1) locking of the main plate boundary across the high Andes, (2) the location of and loading rate at the back of orogenic wedge, and (3) an east flank velocity gradient indicative of décollement locking beneath the Subandes. Modeling of the Subandean portions of the profiles indicates along‐strike variations in the décollement locked width (WL) and wedge loading rate; the northern wedge décollement has a WL of ~100 km while accumulating slip at a rate of ~14 mm/yr, whereas the southern wedge has a WL of ~61 km and a slip rate of ~7 mm/yr. When compared to Quaternary estimates of geologic shortening and evidence for Holocene internal wedge deformation, the new GPS‐derived wedge loading rates may indicate that the southern wedge is experiencing a phase of thickening via reactivation of preexisting internal structures. In contrast, we suspect that the northern wedge is undergoing an accretion or widening phase primarily via slip on relatively young thrust‐front faults.

show abstract

“…Most destructive, historic crustal earthquakes in Argentina ( M > 7.0) have been located at the Andean piedmont, between the cities of San Juan and Mendoza (Smalley & Isacks, , ; INPRES, ; Smalley et al, ; Alvarado et al, ; Figure ). The frontal deformation zone of the Andes thus constitutes an area prone to major crustal earthquakes (Brooks et al, ; Costa et al, ; Weiss et al, , ; Yepes et al, ). However, little is known at present about the Andean orogenic front in terms of surficial thrust geometries and rates of Quaternary fault activity.…”

Section: Introductionmentioning

confidence: 99%

Assessing Quaternary Shortening Rates at an Andean Frontal Thrust (32°30′S), Argentina

et al. 2019

Self Cite

View full text Add to dashboard Cite

At the latitude of 32–33°S, the orogenic front of the eastern flank of the Andes is located in the Southern Precordillera, where two major thrusts concentrate Quaternary deformation at the surface. We estimate the shortening rate for one of these, the Las Peñas thrust, for the last ~200 ka, at the site of one of the best exposures of Quaternary thrusting along the Andes. Shortening was estimated across two prominent splays of the deformation zone at the mouth of the Las Peñas River through balanced cross‐sections by using a terrace surface as a marker of cumulative deformation. Terrace ages were constrained through cosmogenic isotopes (10Be) analysis on quartz cobbles collected from the surface and three depth profiles. Results indicate a mean shortening rate across the Las Peñas thrust of 0.27 + 0.11 mm/a. Our results are lower than Holocene shortening rates (1.9–2.4 mm/a) obtained for individual splays of the Las Peñas thrust nearby. We discuss these discrepancies and implications for thrust evolution since the Late Pleistocene, in particular regarding along‐strike rate variations that highlight the complexity of the Quaternary‐active thrust deformation zone. We argue that ongoing stream incision rates largely prevail with respect to thrust activity at the study site. This observation might be connected with a recent (Holocene?) basinward shift of blind thrust activity.

show abstract

Spatial and temporal distribution of deformation at the front of the Andean orogenic wedge in southern Bolivia

Cited by 17 publications

References 113 publications

Rapid Geodetic Shortening Across the Eastern Cordillera of NW Argentina Observed by the Puna‐Andes GPS Array

Rapid Geodetic Shortening Across the Eastern Cordillera of NW Argentina Observed by the Puna‐Andes GPS Array

Isolating active orogenic wedge deformation in the southern Subandes of Bolivia

Assessing Quaternary Shortening Rates at an Andean Frontal Thrust (32°30′S), Argentina

Contact Info

Product

Resources

About