Subsurface mapping by ambient noise tomography: Difference between revisions

Revision as of 03:53, 7 October 2023

Revision as of 16:29, 7 October 2023

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6. For less seismic region: Use of ambient noise: raising usage and thus attention

Draft 12

Most of the geological maps only show the superficial deposits and outcrops, which allows the public to discover the geological structures that are above the sea surface. For most of the geology related disciplines, such as geotechnical engineering, volcanology, geomorphology, civil engineering, exploration geology, however, understanding on the subsurface structures and to a small extent, lithology, is as important as those on surface. One of traditional method would be borehole drilling but it is invasive to the ground surface. Instead, geophysical survey is ana non-invasive alternative for subsurface exploration and thus subsurface mapping.

Major geophysical survey techniques include electrical resistivity, gravity anomaly and seismic. Seismic survey is particularly reliable on the detection of subsurface rock structures and even hydrocarbons. Seismologists attempt to correlate the velocity anomaly with the geological structure after the collection and further analysis of the seismic signals. The collection of seismic signals is easier for regions with frequent earthquakes. For Ambientsome noise,seismic oneinactive ofregions like Korea Peninsula, however, the seismic waves,signal analysis is themore backgrounddifficult<ref>{{cite noisejournal produced|last1=Kil by|first1=Dongwoo various|last2=Hong natural|first2=Tae-Kyung and|last3=Chung human|first3=Dongchan activities.|last4=Kim The|first4=Byeongwoo potential|last5=Lee |first5=Junhyung |last6=Park |first6=Seongjun |title=Ambient Noise Tomography of ambientUpper noiseCrustal onStructures subsurfaceand structureQuaternary mappingFaults isin discovered.the SubsurfaceSeoul mappingMetropolitan isArea anand importantIts skillGeological inImplications geological|journal=Earth mappingand becauseSpace itScience can|date=06 showNovember the2021 subsurface|volume=8 structure|issue=11 that|page=1 may|pages=27 affect|doi=https://doi.org/10.1029/2021EA001983}}</ref>. Instead of the stabilitycorrelation offrom infrastructure.strong Moreoverseismic sources like earthquake, wethe canpotential betterof understandambient thenoise structural,on sedimentarysubsurface andstructure volcanicmapping processesis discovered in arecent 3-dimensionalyears, which will be introduced mannerbelow.

Part 1: Source of Ambient Noise 700-800 words

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1.2 Frequency range of ambient noise

1.3 How do the ambient noise spread?

2. Nature of ambientseismic noise:source passive/background noise

2.1 Active/Artificial NoiseSource

2.2.1 Passive/NaturalAir Noisegun

2.2.2 Explosion

2.2 Natural Noise

2.2.1 Earthquake

2.2.2 Ocean

2.2.3 Urban

3. Variation of Ambient Noise

3.1 Cause of variation

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Draft 1

Subsurface mapping by geophysical survey can be conducted much easier in regions with frequent earthquake, that is, the regions along plate boundary or faults. When earthquake happens, the energy is released in all direction as body waves and thus surface waves. Geophysicists can collect the seismic data more easily since the seismic energy released from earthquake is much stronger. In contrast, geophysical survey would become more difficult for those seismic inactive regions if no artifical seismic source is provided. Compared with seismic source from earthquake, ambient noise is much weaker and has much lower frequency. Ambient noise was therefore much difficult to be detected in the past. Thanks to the technology advancement, geophysicists can now make use of ambient noise to generate velocity model such that correlation with subsurface structure is feasible.

Subsurface mapping by geophysical survey can be conducted much easier in regions with frequent earthquake, that is, the regions along plate boundary or faults. When earthquake happens, the energy is released in all direction as body waves and thus surface waves. Geophysicists can collect the seismic data more easily since the seismic energy released from earthquake is much stronger. In contrast, geophysicalGeophysical survey would become more difficult for those seismic inactive regions if no artificalartificial seismic source is provided. Compared with seismic source from earthquake, ambient noise is much weaker and has much lower frequency. Ambient noise was therefore much difficult to be detected in the past. Thanks to the technology advancement, geophysicists can now make use of ambient noise to generate velocity model such that correlation with subsurface structure is feasible.

Ambient noise is originated from almost everywhere, though most of the relevant research is about the ambient noise from the ocean. Since the ambient noise is much weaker than earthquake source, it is mostly transmitted as surface waves, including Rayleigh wave and love wave. P- and S-wave transmission is also possible. There are three ranges of ambient noise which have different origin, which will be introduced below.

Ambient noise, one of the seismic waves, is the background noise produced by various natural and human activities. Ambient noise is originated from almost everywhere, though most of the relevant research is about the ambient noise from the ocean. Since the ambient noise is much weaker than earthquake source, it is mostly transmitted as surface waves, including Rayleigh wave and love wave. P- and S-wave transmission is also possible. There are three ranges of ambient noise which have different origin, which will be introduced below.

Nature of Ambient Noise

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3.2.1 low-velocity zone

3.2.2 high-velocity zone

4. Factors affecting quality of resolution

Part 3: Application of Subsurface Mapping 700-800 words

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2. Volcano Monitoring

3. Landslide Monitoring

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