Seismic interferometry by autocorrelation applied to fracture seismicity from Planchon-Peteroa Volcanic Complex, Argentina-Chile

Abstract

Seismic interferometry (SI) retrieves virtual seismic signals from measurements at two receivers from surrounding sources. Studies have demonstrated that SI can image subsurface reflectivity. Claerbout (1968) showed that the reflection response can be obtained by autocorrelating the transmission response assuming a 1-D acoustic medium. Migration techniques using primary and multiple reflections in the autocorrelogram effectively imaged the subsurface structure (Schuster et al., 2003; Yu et al., 2003). This research aims to contribute to the knowledge of the subsurface structure at Planchón-Peteroa Volcano Complex (PPVC) by using SI. Inspired by the theory and applications in Wapenaar (2003) and Ruigrok and Wapenaar (2012), this work applies SI to fracture seismicity originated at PPVC or in active geologic faults located nearby this volcanic complex. Autocorrelating an extracted time window for selected events, zero-offset reflection responses were retrieved for each station. This response is further used to image shallow subsurface reflectors underneath each station. This application uses seismic data recorded by stations deployed in Argentina and Chile. The Argentine data was recorded by a temporary array of six 2-Hz 3-component stations deployed in 2012 on the eastern flank of the volcano. The Chilean data is provided by OVDAS-SERNAGEOMIN (South Andes Volcanic Observatory, Chile). OVDAS has a permanent array of six 30-seconds 3-component stations. Three of these stations recorded data simultaneously with the Argentine stations and were used for this research. Very local seismicity is required for this study, therefore event selection procedure is of great importance. The two arrays were initially used independently to locate fracture events (Casas, 2014; RAV-SERNAGEOMIN, 2012). In order to obtain accurate locations, the two datasets were used together to relocate the detected events (Casas et al., 2016; Olivera Craig et al., 2016). This preprocessing step enhances the resolution of the subsurface images obtained by application of SI at PPVC since appropriate wave paths are selected for processing