← Back to Sessions

Crustal Imaging of the Southern Central Andes by Seismic Autocorrelation of Nodal Seismic Data

Description: 

Autocorrelation of seismic waveform or ambient noise data recorded on individual seismic stations can reveal subsurface reflectivity underneath the station. In this study, to image the major subsurface boundaries, this processing method is implemented on the data collected by a dense array of three-component nodal seismometers at ~23-24˚S, deployed as part of the TransANdean Great Orogeny (TANGO) project. The array consists of 297 nodal stations with 2-3 km node spacing on an orogen perpendicular line across the Andes that extends from the coast of Chile to the Chaco Plain in Argentina covering ~700 km distance and crossing through major Andean tectonic units such as the Chilean forearc, main volcanic arc, Puna plateau, and Eastern Cordillera fold-and-thrust belt. For the autocorrelation with earthquake waves, vertically incident P-arrivals and their coda from teleseismic events and local deep events inside the Nazca slab are used. One minute of waveform data starting 10 seconds before the P-arrival is autocorrelated for each event and stacked together to obtain a stable reflection response. For the ambient noise autocorrelation, for each station in this array, hourly traces from ~5-6 months of data are autocorrelated and stacked together using a phase-weighted approach to amplify the most coherent signals. Temporal normalization is applied to remove the effects of any active or passive impulsive seismic sources. For both ambient noise and earthquake waves, spectral whitening is used to remove the effect of the zero-lag autocorrelation signal and to amplify the subsurface reflection signals. Additionally, the ambient noise autocorrelation is also performed with only the phase information, which avoids temporal normalization and spectral whitening and is independent of the amplitude. The resulting autocorrelation traces are used to identify major subsurface boundaries within the different tectonic units including the Moho, basal detachments in the Eastern Cordillera fold-and-thrust belt, and crustal magma bodies in the volcanic arc and the Puna plateau.

Session: Earth’s Structure from the Crust to the Core [Poster]

Type: Poster

Date: 4/16/2025

Presentation Time: 08:00 AM (local time)

Presenting Author: Sankha Subhra

Student Presenter: Yes

Invited Presentation: 

Poster Number: 100

Authors