V. Sajama, Bolivia Kevin M. Ward, George Zandt, Susan L. Beck, Ryan C. Porter, Lara S. Wagner, Estela Minaya, Hernando Tavera
Central Andean Plateau (CAP) Average elevation ~4 km Max width ~300 km Total length ~2,000 km Abundant arc magmatism
Central Andean Plateau (CAP) Average elevation ~4 km Max width ~300 km Total length ~2,000 km Abundant arc magmatism Data from 315 broadband seismic stations Deployed piecemeal from May 1994 through August 2012
Ambient Noise Tomography Method
Ambient Noise Tomography Method Ambient Noise Source Lower periods ~ ocean waves against the shore Higher periods ~ atmospheric disturbances Not limited by event distribution
Ambient Noise Tomography Method Ambient Noise Source Lower periods ~ ocean waves against the shore Higher periods ~ atmospheric disturbances Not limited by event distribution Raw Waveform Processing Visually inspect waveforms 5 to 150 sec band-pass filter Spectral whitening and running absolute mean normalization
Ambient Noise Tomography Method Ambient Noise Source Lower periods ~ ocean waves against the shore Higher periods ~ atmospheric disturbances Not limited by event distribution Raw Waveform Processing Visually inspect waveforms 5 to 150 sec band-pass filter Spectral whitening and running absolute mean normalization Cross Correlations CC each station pair for each day 3,519,011 CCs Stack each CC station pairs to approximate the EGF
Ambient Noise Tomography Method Ambient Noise Source Lower periods ~ ocean waves against the shore Higher periods ~ atmospheric disturbances Not limited by event distribution Raw Waveform Processing Visually inspect waveforms 5 to 150 sec band-pass filter Spectral whitening and running absolute mean normalization Cross Correlations CC each station pair for each day 3,519,011 CCs Stack each CC station pairs to approximate the EGF Empirical Green s Function Approximates the seismic response of a Rayleigh wave traveling between stations Frequency-time analysis to extract dispersion curves
Rayleigh Wave Dispersion Curves
Rayleigh Wave Dispersion Curves
Phase Velocity Inversion Results
Phase Velocity Inversion Results
Phase Velocity Inversion Results
Shear Wave Inversion Results
Shear Wave Inversion Results
Shear Wave Inversion Results Low velocity zone is too shallow to represent a zone of crustal flow
Shear Wave Inversion Results Low velocity zone is too shallow to represent a zone of crustal flow
Shear Wave Inversion Results Low velocity zone is too shallow to represent a zone of crustal flow Resistivity studies indicate the low velocity zone is not a body of interconnected aqueous fluids
Shear Wave Inversion Results Low velocity zone is too shallow to represent a zone of crustal flow Resistivity studies indicate the low velocity zone is not a body of interconnected aqueous fluids Previous work in the Altiplano-Puna Volcanic Complex (APVC) and Cretaceous Sierra Nevada Batholith (CSNB) might provide answer
Model of Batholith Formation
Shear Wave Inversion Results
Shear Wave Inversion Results
Looking for the Batholith The 3.25 km/s velocity contour outlines the extent of the APVC
Looking for the Batholith The 3.25 km/s velocity contour outlines the extent of the APVC The 3.25 km/s velocity contour correlates well with known Neogene ignimbrite eruption centers
Looking for the Batholith The 3.25 km/s velocity contour outlines the extent of the APVC The 3.25 km/s velocity contour correlates well with known Neogene ignimbrite eruption centers The 3.25 km/s velocity contour agrees with low isostatic gravity anomalies
3D view of the Neogene Batholith
Concluding Remarks The 3.25 km/s velocity contour correlates well with known Neogene ignimbrite eruption centers and low isostatic gravity anomalies Our interpretation of a large Neogene batholith associated with active volcanism revisits the idea of magmatic addition as a contributing mechanism to the growth of the western portion of the CAP How much of a contributing mechanism?
Supplementary Material ~ PV Inversion
Supplementary Material ~ Vsv Inversion
Supplementary Material ~ Vsv Misfit