Ambient Noise Tomography with Short-Period Stations: Case Study in the Borborema Province

Abstract

The analysis of seismic ambient noise has been recently proven a viable alternative to the analysis of seismic waves generated by earthquakes. Although seismic ambient noise had traditionally been discarded from earthquake records, it has now been shown that the cross-correlation of the seismic ambient noise allows for the recovery of the Green’s function between the receivers. Furthermore, seismic noise has the ability to propagate continuously and independently of the occurrence of earthquakes, allowing for high-resolution tomographic studies in regions of low seismicity. Over the last two decades, the cross-correlation of continuous seismic noise recordings between pairs of stations has been widely utilized in surface-wave tomography studies. For the Northeast Brazil region, tomographic studies have been exclusively performed with seismic data from broadband stations; however, in addition to those stations, there exists a large volume of short-period data that might potentially improve the resolution of existing ambient noise tomographies. Thus, the goal of this work is to utilize, in addition to broadband data, short-period data recorded by 22 short-period stations in the Borborema Province. Through cross-correlation and stacking of ambient seismic noise, the emergence of the fundamental mode of the Rayleigh waves and their dispersive character was observed. Once the empirical Green's functions were retrieved, the accuracy of (phase and group) dispersion curves for periods up to 10 s and its tomographic inversion were assessed. Our results demonstrate that short-period dispersion measurements can be successfully integrated in regional tomographic studies for improved resolution.