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| Titel |
Shear-wave velocity of marine sediments offshore Taiwan using ambient seismic noise |
| VerfasserIn |
Yu-Tse Lin, Jing-Yi Lin, Hao Kuo-Chen, Yi-Chin Yeh, Win-Bin Cheng |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250140889
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| Publikation (Nr.) |
 EGU/EGU2017-4340.pdf |
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| Zusammenfassung |
| Seismic ambient noise technology has many advantages over the traditional two-station
method. The most important one is that noise is happening all the time and it can be widely
and evenly distributed. Thus, the Green’s Function of any station pair can be obtained
through the data cross-correlation process. Many related studies have been performed
to estimate the velocity structures based on the inland area. Only a few studies
were reported for the marine area due to the relatively shorter recording time of
ocean bottom seismometers (OBS) deployment and the high cost of the marine
experiment. However, the understanding about the shear-wave velocity (Vs) of the marine
sediments is very crucial for the hazard assessment related to submarine landslides,
particularly with the growing of submarine resources exploration. In this study, we
applied the ambient noise technique to four OBS seismic networks located offshore
Taiwan in the aim of getting more information about the noise sources and having
the preliminary estimation for the Vs of the marine sediments. Two of the seismic
networks were deployed in the NE part of Taiwan, near the Ryukyu subduction system,
whereas the others were in the SW area, on the continental margin rich in gas hydrate.
Generally, ambient seismic noise could be associated with wind, ocean waves, rock
fracturing and anthropogenic activity. In the southwestern Taiwan, the cross-correlation
function obtained from two seismic networks indicate similar direction, suggestion
that the source from the south part of the network could be the origin of the noise.
However, the two networks in the northeastern Taiwan show various source direction,
which could be caused by the abrupt change of bathymetry or the volcanic degassing
effect frequently observed by the marine geophysical method in the area. The Vs
determined from the dispersion curve shows a relatively higher value for the networks
in the Okinawa Trough (OT) off NE Taiwan than that in the continental margin
offshore SW Taiwan. This observation could be linked to the presence of numerous
volcanic outcrops in the shallow marine sediments is the OT area. By comparing
the 1-D velocity shear-wave profile with the previous studies, we found that the
low Vs area could be associated with a sedimentary layer filled with gas in the
OT and the creeping area along the continental margin. The Vs range estimated
from our study also shows a good agreement with the velocity profile obtained
based on the OBS seismic refraction experiment, suggesting that this method could
be a more economical and effective way for the acquisition of the Vs parameters. |
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