The structural development of the Strike-Slip Água Bonita Basin – Brazil, using Receiver Function and the HVSR method

The horizontal-to-vertical spectral ratio (HVSR) is a passive seismic method that uses ambient noise to estimate impedance contrasts at shallow depths, such as sedimentary layers and faults. Its resolution depends on impedance contrast and geological context, decreasing with depth due to high-frequency attenuation. We conducted 58 measurements along five profiles in the Água Bonita Basin, a strike-slip basin in central-north Brazil, using short-period and broadband seismometers. The basin includes the Vereda Verde and Água Bonita Formations, deposited during the Ordovician-Silurian after reactivation of the Transbrasiliano Lineament. HVSR curves were calculated and inverted under the assumption of a diffuse field to constrain the basin structure. Additionally, continuous seismic data from a broadband station were analyzed with Receiver Functions, complemented by topographic and magnetic data. HVSR results indicate a maximum depth of 520 m, while Receiver Functions yield 435 m for the sedimentary package. Both estimates are shallower than previous models. A 3D geological model suggests two opposing half-grabens formed by transtensive sinistral reactivation of the Transbrasiliano Lineament. The Água Bonita Basin thus serves as an analogue for early Phanerozoic basin formation in Brazil and may represent a failed rift stage in the Early Ordovician.