Inversion of teleseismic receiver function and magnetotelluric sounding to determine basement depth in the Paraná Basin, SE Brazil

Flood basalts in the Paraná Basin make exploration of the deeper sedimentary sequence more difficult with seismic reflection methods. We present a new method to obtain information about sub-basalt layers by joint inversion of high-frequency Receiver Functions (RF) and Magnetotelluric (MT) data. Using genetic algorithm, which is more flexible to incorporate data variance in the objective function, we obtain 1D models of the main layers of the basin beneath three seismographic stations. We show that the joint inversion produces more stable models than inversion of RF or MT data alone. Thicknesses of the basalt layer were estimated at 1 km, and basement depth were found to range from 3.8 to 4.3 km, roughly consistent with expected values based on the sparse regional borehole data. Deep earthquakes in the nearby Nazca plate subduction zone are a good source of high frequency P-waves making the joint RF + MT inversion a promising method to study shallow intracratonic basins in Brazil, especially where the sedimentary structure can be represented by 1D models.