Subsurface mapping by ambient noise tomography: Difference between revisions

Revision as of 14:38, 27 December 2023

Revision as of 02:00, 3 January 2024

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=== Nature of ambient noise ===

Ambient noise, as the rising star of the seismic source for seismic research other than [[earthquake]], accounts for the naturally and anthropogenically produced seismic vibration of the background.<ref>{{cite journal |last1=Oakley |first1=David O. S. |last2=Forsythe |first2=Brandon |last3=Gu |first3=Xin |last4=Nyblade |first4=Andrew A. |last5=Brantley |first5=Susan L. |title=Seismic Ambient Noise Analyses Reveal Changing Temperature and Water Signals to 10s of Meters Depth in the Critical Zone |journal=Journal of Geophysical Research: Earth Surface |date=2021-01-13 |volume=126 |issue=2 |doi=10.1029/2020JF005823 |bibcode=2021JGRF..12605823O |s2cid=234198739 |url=https://doi.org/10.1029/2020JF005823|doi-access=free }}</ref> This is different from the active seismic source created solely for seismic research or large seismic source from [[earthquake]]. [[Ocean]] is the most dominant natural origin of the ambient noise field.<ref name="tonyking4">{{cite journal |last1=Igel |first1=Jonas K. H. |last2=Bowden |first2=Daniel C. |last3=Fichtner |first3=Andreas |title=SANS: Publicly Available Daily Multi-Scale Seismic Ambient Noise Source Maps |journal=Journal of Geophysical Research: Solid Earth |date=2023 |volume=128 |issue=1 |doi=10.1029/2022JB025114 |bibcode=2023JGRB..12825114I |s2cid=255123230 |url=https://doi.org/10.1029/2022JB025114|doi-access=free |hdl=20.500.11850/591152 |hdl-access=free }}</ref>

Any seismic source is transmitted as either [[Body wave (seismology)|body wave]]s or [[surface waves]], where ambient noise is no exception. Summary of their properties are shown below.

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== Seismic velocity structure modelling ==

[[Seismic velocity structure]] modelling is the modelling technique showing the velocity difference of seismic waves across areas. The modelling process involves some steps, including [[cross-correlation]], [[Green's function]], and [[Seismic inversion|inversion]]. The usage of ambient noise as source of seismic velocity structure modelling rises from 2001 when seismologists tried to correlate the diffused ambient noise wave fields'<ref>{{cite journal |last1=Sager |first1=Korbinian |last2=Ermert |first2=Laura |last3=Boehm |first3=Christian |last4=Fichtner |first4=Andreas |title=Towards full waveform ambient noise inversion |journal=Geophysical Journal International |date=12 July 2021 |volume=212 |pages=566–590 |doi=10.1093/gji/ggx429|doi-access=free |hdl=20.500.11850/224948 |hdl-access=free }}</ref> Velocity structure modelling are complex and require multiple mathematical calculations.

=== Pre-processing of ambient noise data ===