Group B, Poster #040, Seismology

Preliminary study of precursor and scattered waves imaging of ambient noise cross-correlations from the Seal Beach dense array

Ettore Biondi, & Robert W. Clayton
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Poster Presentation

2022 SCEC Annual Meeting, Poster #040, SCEC Contribution #12268 VIEW PDF
Seismic noise cross-correlations (CCs) can provide important information about the subsurface; especially, when constructed using dense station arrays. In these virtual Green’s functions, multiple arrivals, such as direct arrivals, body waves, reflected and scattered events, can be commonly observed. When a non-uniform noise source distribution gives rise to the obtained CC functions, precursory energy preceding the direct arrivals is present within virtual shot gathers. Precursor and scattered arrivals can be used to characterize the geometry of subsurface structures as well as their physical properties (e.g., attenuation and seismic speed). Using synthetic tests, we compare images obtained... from a simple amplitude stacking procedure of direct scattered waves and precursor arrivals caused by the presence of subsurface structures (e.g., scatterers and fault lines). We discuss the advantages and limitations of each arrival-imaging technique and highlight potential applications. Finally, using the precursor-imaging technique on data recorded by a dense seismic array from the Seal Beach area (California), we provide evidence of the presence of the Garden Grove fault line, a blind fault with no surface expression that was identified using an active acquisition survey. This observation illustrates the potential of fault mapping using seismic noise recorded by dense station arrays in urban areas.