Field and Synthetic Waveform Tests on Using Large‐Offset Seismic Streamer Data to Derive Shallow Seabed Shear‐Wave Velocity and Geotechnical Properties

Earth and Space Science

Wu‐Cheng Chi¹  Sebastian Wege¹  Pascal Kunath¹  Tan Kin Wang²  Cédric P. Legendre³  Char‐Shine Liu⁴ 

[1] Institute of Earth Sciences Academia Sinica Taipei Taiwan;Institute of Earth Sciences National Taiwan Ocean University Keelung Taiwan;Institute of Geophysics of the Czech Academy of Science Prague Czech Republic;Ocean Center National Taiwan University Taipei Taiwan;

关键词: Scholte wave;    shear‐wave velocity;    geotechnical properties;    large‐offset streamer data;    synthetic waveform;   

DOI  :  10.1029/2021EA002196

来源: DOAJ

【 摘 要 】

Abstract Characterizing properties of marine subsurface sediment helps with siting for offshore infrastructure. Shear‐wave velocity (Vs) provides information on the geotechnical properties of the seabed. We present our initial efforts to obtain a detailed two‐dimensional model of Vs for a large‐offset multi‐channel seismic (MCS) transect collected in shallow waters across the Taiwan Strait using surface waves excited by a large volume airgun. We derived the dispersion curves of the Scholte waves along the 37.5‐km‐long transect using the phase‐shift method and then conducted multimodal inversion to obtain a Vs model down to a depth of 150 m. To estimate the dynamic Poisson's ratio across the transect, we combined the Vs model with a compressional wave velocity model derived from the traditional MCS semblance velocity analysis. Lastly, we approximated the seismic attenuation of the profile. Our results show a large lateral variation in shear‐wave velocity. In the north, a low‐velocity zone with shear‐wave velocities of about 150 m/s was identified, while in the south, the shear‐wave velocity was found to be 300 m/s. With synthetic data, several sensitivity tests were performed to derive optimal parameters for offshore large‐offset streamer data. We particularly focused on the depth of the streamer and source and the water depth in combination with different seabed properties. Our results show that we can robustly derive the shear‐wave velocity, along with the Poisson's ratio, using large‐offset streamer data elsewhere based on the criteria we have tested using field and synthetic data sets.

【 授权许可】

Unknown