Simultaneous retrieval of body and surface waves in the Dehdasht area, Iran, from the seismic ambient field and the observation of spurious artefacts

Abstract

Summary Recent developments in sensor technology have allowed for the low-cost deployment of dense seismic arrays which continuously record the seismic ambient noise field. Generally, the extraction of body waves from the seismic ambient noise field is more challenging than for surface waves, due to the dominant amplitude of the latter. In this study, we work with data from a dense seismic array deployment in the Dehdasht area, southwestern Iran. We show that by using the polarization properties of seismic waves, we can simultaneously retrieve both high frequency body waves and surface waves from the cross-correlated noise field. As a by-product of this study, we also observe high energy spurious artefacts, particularly those associated with the direct P-phases. Numerical simulations show that these artefacts are a consequence of an uneven distribution of noise sources, and are difficult to suppress during the simultaneous retrieval of body and surface waves.

3-D body-wave tomography from the seismic ambient noise recorded by a dense array in the Dehdasht area, Iran

“…Then, we separate surface and body waves (Section 2.2) and finally separate the first arriving P waves (Section 2.3). Riahi et al (2021) showed with beamforming analysis that the noise source distribution in the Deshdasht area is uneven for the frequencies of interest (around 0.7-1.2 Hz). The most dominant noise sources are the Persian Gulf, located approximately 80 km south of the area, and two concrete dams: the Maroun dam in the SW and the Koser dam in the SE in the vicinity of the array (Fig.…”

“…Only a handful of studies extracted diving P waves in local distances (e.g. Roux et al 2005;Zhang & Gerstoft 2014;Nakata et al 2015Nakata et al , 2016Riahi et al 2021) or reflected P waves (e.g. Draganov et al 2009;Dantas et al 2018) from the ambient wavefield; as well as in teleseismic distances (e.g.…”

“…Spidernano digitizers were used for all stations. Using part of this database, Riahi et al (2021) showed that body and surface waves could be simultaneously extracted using the polarization approach of Takagi et al (2014). With a summation of the ZR and RZ components, the P-wave contribution could be enhanced and the Rayleigh wave component eliminated.…”

“…In this study, we modify and expand the work of Riahi et al (2021) and perform 3-D seismic tomography of the Dehdasht area by inverting the time arrivals of the retrieved diving P wave. We first evaluate the noise source characteristics and describe the extraction of the P wave from the seismic ambient wavefield (Section 2) and outline the tomography (Section 3), before we discuss our results (Section 4).…”

Application of Full Waveform Inversion in passive seismic explorations: Some practical considerations

“…Using more than 8000 micro-earthquakes recorded by this network and a non-linear travel-time tomography technique, Shomali et al, (2018) developed a 3D V P and V P / V S velocity model for this area revealing velocity anomalies, low-angle thrust faults and synclines which attests for a tectonically complicated structure. Riahi et al, (2021) made the focus on the ambient noise part of this dataset. Using the polarization properties of the seismic waves, they were able to retrieve both high-frequency body and surface waves from cross-correlated noise elds.…”