Lithospheric Architecture of the Paranapanema Block and Adjacent Nuclei Using Multiple-Frequency P-Wave Seismic Tomography

We present a new P-wave seismic tomographic model for the region of the Paraná Basin and surroundings using a multiple-frequency approach, providing better resolution than previous regional studies. We processed a total of 62,692 cross-correlation delays for P, PKIKP, PcP, and PP phases distributed among 1,081 events using six different central frequencies (0.03, 0.06, 0.13, 0.25, 0.50, and 1 Hz). We merged our data with a previous multiple-frequency study of the Amazonian Craton to cover regions outside of the study area, obtaining a total of 75,187 cross-correlation delays. The data used are from the stations of the Brazilian Seismographic Network, and mainly from a temporary network (XC network) installed exclusively to study the region. The basement of the Paraná Basin is represented as a NE-SW trending P-wave high-velocity anomaly, extending from the northern limit of the basin to the southwestern border of Brazil, consistent with previous reports. The limit between this block and the São Francisco Craton is characterized by decreased amplitude of the P-wave high-velocity anomaly. Synthetic tests show that a narrow boundary between these two blocks displays the same behavior. At the southeastern portion of this anomaly, decreasing amplitude is consistent with the limit of the Luiz Alves Craton, which was also corroborated by synthetic tests. The northern portion of the Rio Apa Block agrees with a previous tomographic model, confirming that it does not extend under the Pantanal Basin, however, in our model this structure does not extend as far south.