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Simulation of Core Phases From Coda Interferometry
Author(s) -
Wu Benjun,
Xia Han Hank,
Wang Tao,
Shi Xiaoqing
Publication year - 2018
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.983
H-Index - 232
eISSN - 2169-9356
pISSN - 2169-9313
DOI - 10.1029/2017jb015405
Subject(s) - coda , seismology , interferometry , geology , classification of discontinuities , seismic interferometry , inner core , seismogram , amplitude , attenuation , induced seismicity , waveform , phase (matter) , optics , physics , mathematical analysis , mathematics , quantum mechanics , voltage
The extraction of core phases through seismic interferometry is important for exploring the seismic structure of the Earth's inner core because it can provide an unprecedented data coverage. However, low signal‐to‐noise ratios and uncertainties in phase arrivals hinder the application of seismic interferometry. With three arrays from the China Regional Seismic Network, South America, and the western United States, we simulate coda interferometry using the one‐dimensional synthetic coda of large earthquakes (magnitude ≥ 7.0) from 2005 to 2012. Compared with the cross correlations of real coda (10,000–40,000 s after earthquakes), the similarities among the simulated waveforms of the core phases (PKIKP, PKIIKP, PKPab, PKIKP 2 , and PKIIKP 2 ) indicate that reverberations at first‐order discontinuities constitute the major source for coda interferometry. Relative to synthesized Green's functions, the core phases derived from coda interferometry provide reliable phase information but varying amplitudes. In particular, the slownesses are generally consistent with the theoretical calculations, thereby confirming the extracted phases. The simulations prefer the 15‐ to 50‐s period band and indicate that the earthquake distribution has an insignificant effect on the retrieval of core phases at small distances (0–8°). Coda interferometry is scarcely affected by white noise, but it is influenced by the attenuation of the inner core. Experiments on focal mechanisms further suggest that coda signals from dip‐slip earthquakes mainly contribute to the reconstruction of the core phases (except for the simulated PKPab).