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

Jonathan R. Weiss, Benjamin A. Brooks, Ramon Arrowsmith, Gustavo Vergani

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

New observations from an active orogenic wedge help link the seismotectonic behavior of individual faults to wedge deformation rates and patterns over multiple timescales. We provide the first detailed constraints on the distribution and timing of deformation at the front of the Andean orogenic wedge in southern Bolivia, where a recent study suggests that great (Mw > 8) earthquakes could rupture the master fault underlying the wedge. We use stratigraphic relationships across fault-related folds and elastic dislocation modeling of seismic reflection horizons to obtain probabilistic estimates of wedge-front fault ages and slip rates. Our analyses reveal that at least half of the previously determined GPS-based wedge-loading and Quaternary whole-wedge shortening rates are absorbed across a 20-40 km wide wedge-front zone consisting of 1-4 en echelon and partially to fully overlapping faults and folds associated with blind thrust faults. The difference between our slip rates and the geodetic/geologic observations combined with evidence for activity across internal wedge structures supports the notion that nonsteady state mass balance conditions coupled with elevated erosional efficiency result in distributed wedge deformation. The orogenic wedge in southern Bolivia behaves in a similar fashion to the Taiwanese and Himalayan ranges; slip accumulates at downdip locations along the master fault and is released incrementally by earthquakes that rupture the wedge-front fault zone. The faults and folds comprising this zone pose a major source of seismic hazard. Accumulating slip is also released in the wedge interior and older, internal wedge faults must be considered in any future assessment of regional earthquake risk.

Original languageEnglish (US)
Pages (from-to)1909-1931
Number of pages23
JournalJournal of Geophysical Research: Solid Earth
Volume120
Issue number3
DOIs
StatePublished - Mar 1 2015
Externally publishedYes

Fingerprint

Bolivia
temporal distribution
earthquakes
wedges
Earthquakes
spatial distribution
geodesy
shortenings
Global positioning system
Hazards
slip rate
fold
slip
earthquake
support structure
earthquake rupture
seismotectonics
thrust fault
seismic hazard
dislocation

Keywords

  • Bolivia
  • orogenic wedge deformation
  • seismic hazard
  • sub-Andes

ASJC Scopus subject areas

  • Geophysics
  • Oceanography
  • Forestry
  • Ecology
  • Aquatic Science
  • Water Science and Technology
  • Soil Science
  • Geochemistry and Petrology
  • Earth-Surface Processes
  • Atmospheric Science
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science
  • Palaeontology

Cite this

Spatial and temporal distribution of deformation at the front of the Andean orogenic wedge in southern Bolivia. / Weiss, Jonathan R.; Brooks, Benjamin A.; Arrowsmith, Ramon; Vergani, Gustavo.

In: Journal of Geophysical Research: Solid Earth, Vol. 120, No. 3, 01.03.2015, p. 1909-1931.

Research output: Contribution to journalArticle

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