[S-SS07] Environmental Seismology: from deep earth to surface process

[SSS07-P05] Intrinsic Uncertainty of noise cross-correlation functions and its implications to source properties

*Ying-Nien Chen¹ (1.Department of Earth and Environmental Sciences, National Chung Cheng University, Chia-yi County, Taiwan)

Keywords:Seismic interferometry, Microseisms, Fluctuation

We present a quantitative approach for evaluating the intrinsic uncertainty (IU) of the noise cross-correlation function (NCF) and apply it to realistic NCFs obtained from broadband seismic arrays in Taiwan. The evolution of the standard deviation of the NCF waveform with increasing correlation time aligns closely with theoretical predictions, confirming the validity of the method. The derived IU offers an objective metric for assessing NCF quality, particularly for coda waves, which is widely used in monitoring temporal structural variations. Through an analytic procedure applied to a synthetic experiment, we demonstrate that the distribution and excitation strength of noise sources strongly influence the IU. Consequently, combining IU estimates with NCF amplitudes derived from different normalization approaches enables a comprehensive assessment of ambient noise source characteristics. Using the proposed approach, we reveal the excitation mechanisms of short-period secondary microseisms, primary microseisms, and single-frequency microseisms.